First Report of Anthracnose Caused by Colletotrichum plurivorum on Passion fruit in Guangxi, China

Passion fruit (Passiflora edulis Sims.) is popular for its rich taste and nutritional value. The planting area of passion fruit in Guangxi has reached 24,300 ha, with an annual output of 380,000 t (Qian 2023). In March 2023, leave spots on more than half of the plants (cv. Qinmi "NO.9"). Moreover, the incidence of disease on the leaves was approximately 20% in Shabu Town, Qinnan District, Qinzhou City, Guangxi, China (N20˚54'-22˚41', E107˚27'-109˚56'). Leaf diseases were orbicular or irregular in shape, white, whitish-grey, yellowish, or gray in color. When leaves were severely affected, larger blotches were formed with yellow halos. For pathogen isolation, three diseased leaf samples were collected from three gardens, respectively, and 5×5 mm tissues were cut from infected margins, surface-disinfected in 75% ethanol for 15 s, followed by 2% sodium hypochlorite for 1 min, rinsed three times with sterile water, and incubated on PDA at 25°C under 12/12 h light/darkness. After 5 days, ninety cultures were isolated, sixty isolates with similar morphology were retained, and three representative isolates BY-1, BY-2, and BY-4 were randomly selected for further study. On PDA, colonies of the three isolates displayed white or grayish-white. Conidia were single-celled, hyaline, and cylindrical, measuring 17.3±1.5 × 6.3±0.7 μm, 17.8±1.7 × 6.0±0.6 μm, and 16.3±1.4 × 6.4±0.6 μm (n=90) for BY-1, BY-2, and BY-4, respectively. Appressoria were single, brown or black, and irregular in shape, measuring 10.2±1.1×6.5±0.5 μm, 10.5±1.3×7.3±0.6, and 10.9±0.8×7.0±0.8 (n=90) for BY-1, BY-2, and BY-4, respectively. These morphological characteristics were similar to Colletotrichum spp. as previously described (Damm et al. 2019). The isolates were further identified by sequencing the internal transcribed spacer (ITS-ITS1/ITS4), glyceraldehyde-3-phosphate dehydrogenase (GAPDH-GDF/GDR), actin (ACT-512F/783R), partial sequences of the chitin synthase 1 (CHS-1-79F/354R), and beta-tubulin 2 (TUB2-T1/Bt2b) (Zhang et al. 2023). All sequences were deposited in GenBank (ITS: OR741759 to OR741761, GAPDH: OR767654 to OR767656, ACT: OR767657 to OR767659, CHS-1: OR767660 to OR767662, TUB2: OR767651 to OR767653). A phylogenetic tree was built with RAxML version 8.2.10 based on concatenated sequences of ITS-GAPDH-ACT-CHS-1-TUB2. The results revealed that the three isolates clustered with C. plurivorum. To confirm the pathogenicity of the three isolates, attached leaves of healthy 5-month-old passion fruit plants were injured in the middle region with sterile toothpicks and inoculated with 20 μL of spore suspension (106 conidia/mL), and the noninoculated control received 0.05% Tween-20 (6 leaves/plant, 3 plants/treatment). The inoculated plants were kept in a greenhouse at 25°C and covered with plastic bags to maintain high humidity. After 9 days, all inoculated leaves were symptomatic, whereas no symptoms were observed in the control. C. plurivorum was reisolated from infected leaves, confirming Koch's postulates. C. plurivorum has been reported to infect Abelmoschus esculentus (Batista et al. 2020) and Carya illinoinensis in China (Zhang et al. 2023). However, this is the first report of anthracnose caused by C. plurivorum on passion fruit in China. The results can provide a robust basis for scientific prevention and control of anthracnose.

Recovery of Alternaria brassicicola from Chopped, Bagged Kale (Brassica oleracea var. acephala)

Alternaria brassicicola was found on pieces of chopped, bagged kale held 1 week beyond the typical postharvest storage period. Three of 11 Alternaria isolates were identified as A. brassicicola based on species-specific primers and multilocus genotyping with the translation elongation factor 1-alpha (tef1), RNA polymerase second largest subunit (rpb2), and glyceraldehyde-3-phosphate dehydrogenase (gapdh) gene regions. Two isolates of A. alternata, two isolates of A. tenuissima, and four isolates comprising two unidentified species also were found. A. brassicicola also was found in a production field on the same farm. In the greenhouse, only A. brassicicola isolates caused disease on inoculated kale plants. As previously reported, A. brassicicola isolates had larger colony diameters on semi-selective CW medium than the non-pathogenic isolates. Black spot caused by A. brassicicola on kale leaves in the field can lead to black spot on harvested kale.

First report of leaf spot disease caused by Pseudopithomyces chartarum on Lonicera caerulea L. in Heilongjiang Province, China

Blue honeysuckle (Lonicera caerulea L.) cultivation has gradually expanded in China but continues to be limited by challenges such as leaf spot disease. Between September 2022 and September 2023, a leaf spot disease was observed on approximately 30% of 'Lanjingling' blue honeysuckles grown in a 2.66 ha field (a total of about 11,000 plants) in Jiamusi city (130.47°E, 46.16°N), Heilongjiang Province, China. Affected plants displayed brown necrotic lesions on their leaves that gradually expanded in area until the leaves fell off the plant entirely. Small, 3 to 4 mm segments of infected tissue from 50 randomly selected leaves were surface sterilized with 75% ethanol for 30 s and 5% sodium hypochlorite (NaOCl) for 3 min, rinsed three times with sterile distilled water, dried on paper towels, and plated in 9 cm Petri dishes containing potato dextrose agar (PDA) (Yan et al. 2022). Five pathogens (LD-232, LD-233, LD-234, LD-235, and LD-236) were isolated on PDA and displayed a conidia morphology consistent with Pseudopithomyces spp. (Perelló et al. 2017). The fungal colonies on PDA were villiform, white, and whorled and had sparse aerial mycelium on the surface with black conidiomata. The conidia were obpyriform and dark brown, had 0 to 3 transverse and 0 to 1 longitudinal septa, and measured 9.00 to 15.30 μm × 5.70 to 9.30 μm in size (n = 50). Genomic DNA was extracted from a representative isolate, LD-232, for molecular verification and PCR amplification was performed with ITS1/ITS4 (White et al. 1990), LROR/LR7 (Carbone and Kohn 1999), and RPB2-5F2/RPB2-7CR (Liu et al. 1999) primers. Sequences of LD-232 ITS (OR835654), LSU (OR835652), and RPB2 (OR859769) revealed 99.8% (530/531 nt), 98.8% (639/647 nt), and 99.8% (1015/1017 nt) shared identity with Pseudopithomyces chartarum sequences (OP269600, OP237014, and MK434892), respectively (Wu et al. 2023). Bayesian inference (BI) was used to construct the phylogenies using Mr. Bayes v. 3.2.7 to confirm the identity of the isolates (Ariyawansa et al. 2015). Phylogenetic trees cannot be constructed based on the genes' concatenated sequences because selective strains do not have complete rDNA-ITS, LSU, and RPB2 sequences. Therefore, based on the morphological characteristics and molecular phylogeny, LD-232 was identified as P. chartarum (Perelló et al. 2017; Wu et al. 2023). A pathogenicity test was performed with six healthy, two-year-old 'Lanjingling' blue honeysuckle plants. Three plants were inoculated by spraying the LD-232 conidial suspension (1 × 106 spores/ml) or clean water as an experimental control condition (Wu et al. 2023; Yan et al. 2023). All plants were cultured in a greenhouse at 28℃ under a 12-h light/dark cycle, and each experiment was replicated three times. Typical leaf spot symptoms were observed on inoculated leaves after 10 days. The same pathogens were reisolated from infected leaves, displayed the same morphological and molecular traits, and were again identified as P. chartarum, confirming Koch's postulate. P. chartarum previously caused leaf spot disease on Tetrapanax papyrifer in China (Wu et al. 2023). To our knowledge, this is the first report of blue honeysuckle leaf spot caused by P. chartarum in China. Identification of P. chartarum as a disease agent on blue honeysuckle will help guide future management of leaf diseases for this economically important small fruit tree.

First Report of Agroathelia rolfsii Causing Southern Blight on Lippia (Phyla canescens) in Guangzhou, China

Lippia (Phyla canescens) is a fast-growing, mat-forming, and prostrate perennial plant well adapted to infertile, high-saline, and drought environments (Leigh, et al. 2004). It arrived in China from Japan as a flowering ground cover in 2001 (Cai, et al. 2004). In June 2022, southern blight appeared in our nursery of the Floriculture Research Institute of Guangdong Academy of Agricultural Sciences. High temperature and damp environment are major factors for this disease. The symptoms of top-layer plants were not easily detected, but they were slightly yellowed. A yellowish-brown water-soak lesion appeared on the stems and lowest leaves exposed to soil. White mycelium appeared in the middle stage. Finally, the surface plants showed water-soak decay, and a mass of beige to black-brown rapeseed-shaped sclerotia appeared on the residue and surrounding soil; these plants died. Sclerotia and mycelia were collected from disease tissue, and after surface sterilization, sclerotia was cultured on potato dextrose agar (PDA) at 28±2°C in an incubator without light. Eight fungal isolates with similar colony morphologies were consistently isolated by purifying from different sampling areas. The isolates exhibited obvious septa and a clamp connection structure within the white mycelium. The average growth rate was 26.86±0.06 mm/day. Numerous white granular sclerotia were produced on the mycelium 6 days later. The sclerotia with a diameter of 1.24±0.07mm (n=189) gradually changed from diage to yellow to brown. A typical strain B1 was selected for further identification, targeting its 18S rRNA and LSU rRNA sequences (Yang, et al. 2011; Xue, et al. 2019). Its 18S rRNA sequence (GenBank Accession No. OR517233, 1626 bp) is 99.63% and 99.57% identical to Athelia rolfsii (AY665774, 1179bp; KC670714, 1775bp; JF819726, 1781bp). Its LSU rRNA sequence (OR539570, 757 bp) is 99.87% identical to Agroathelia rolfsii (OR526537, 904 bp). For Athelia rolfsii, a synonym of Agroathelia rolfsii, by combining the morphological characteristics and molecular identification, the isolate pathogen B1 was confirmed to be Agroathelia rolfsii (the teleomorph of Sclerotium rolfsii). To fullfill Koch's postulates, we inoculated the mycelial plugs to healthy lippia stems and leaves which has grown for one year, with PDA plugs free of mycelium as the control. All the plants were kept in a greenhouse at 28±2°C with a 14-h photoperiod and 80% relative humidity. Each treatment was repeated thrice and vaccinated with 6 points. At 7 d following inoculation, all plants inoculated with B1 showed typical symptoms, but the control group was asymptomatic, and sclerotia appeared 17d after inoculation. Using the same protocol mentioned above, pathogenic fungal was reisolated only from treated groups, but not from the control group. Chose three of the pathogens for 18S rRNA and LSU rRNA sequencing, the results showed 100% identity to B1, the same as its microstructure. There are few reports about the disease on P. canescens. Sosa (2007) investigated the pathogens on P. canescens in Argentina, 16 fungi were found but no A. rolfsii. Sclerotium rolfsii were identified on P. nodiflora or P. lanceolata (Michaux) Greene in America (Farr, et al. 1989). To our knowledge, this is the first report in China. Because this pathogen has wide-ranging hosts and causes serious damage, the results from this study will offer guidance for the prevention and treatment of this disease.

Occurrence and distribution of Meloidogyne spp. in fields rotated with sweetpotato and host range of a North Carolina population of Meloidogyne enterolobii

Root-knot nematodes (RKN, Meloidogyne spp.) are some of the most economically important and common plant parasitic nematodes in North Carolina (NC) cropping systems. Soil samples collected from fields planted with crops rotated with sweetpotato [Ipomoea batatas (L.) Lam.] in 39 NC counties in 2015-2018 were processed at the NC Nematode Assay Laboratory. The occurrence of second-stage juvenile (J2) RKN populations was examined based on collection year, month, county, and previous planted crop. The highest number of RKN positive samples originated from Cumberland (53%), Sampson (48%), and Johnston (48%) counties. The highest average RKN population density was detected in Sampson (147 J2/500 cm3 soil) and Nash (135 J2/500 cm3 soil) counties, while Wayne (7 J2/500 cm3 soil) and Greene (11 J2/500 cm3 soil) counties had the lowest average RKN population density. Meloidogyne enterolobii is a new invasive species that is impacting sweetpotato growers of NC. The host status of a NC population of M. enterolobii, the guava-root knot nematode, was determined by examining eggs per gram of fresh root (ER) and the final nematode egg population divided by the initial population egg count (reproductive factor, RF) in greenhouse experiments. This included eighteen vegetable, field, cover crops and weed species. The tomato 'Rutgers' was used as a susceptible control. Cabbage 'Stonehead', pepper 'Red bull', and watermelon 'Charleston gray' and 'Fascination' were hosts and had similar mean ER values to the positive control, ranging from 64 to 18,717. Among field crops, cotton, soybean 'P5018RX', and tobacco were hosts with ER values that ranged from 185 to 706. Members of the Poaceae family such as sweet corn (Zea mays) and sudangrass (Sorghum x drummondii) were non-hosts to M. enterolobii and the mean ER values ranged from 1.85 to 7. The peanut 'Tifguard' and winter wheat (Triticum aestivum) also had lower ER values than the vegetable hosts. Growers should consider planting less susceptible or non-hosts such as peanut, sudangrass, sweet corn, and winter wheat in 2-3 year crop rotations to lower populations of this invasive nematode.

First report of pepper chlorosis-associated virus infecting tobacco (Nicotiana tabacum) plants in Sichuan Province in China

Tobacco (Nicotiana tabacum) is an economically important crop in China, and more than 30 viruses have been reported to infect tobacco (Yin et al. 2022). In July 2022, we observed interveinal necrosis on tobacco leaves in fields in Sichuan Province (N 27.9172, E 105.6662) (Fig. 1). Total RNA was isolated from multiple leaves of one plant using an RNAprep Pure Polysaccharide Polyphenol Plant Total RNA Extraction Kit (TIANGEN, Beijing, China). Total RNAs were pooled, and a TruSeq Stranded Total RNA with RiboZero Gold Kit (Illumina, San Diego, CA, USA) was used to eliminate ribosomal RNA. An RNA-Seq library was constructed using VAHTS Universal V6 RNA-seq Library Prep (Nanjing Vazyme, China). High-throughput sequencing was performed on the Illumina DNBseq platform (BGI-ShenZhen, China), which yielded 20,102,087 reads with an average length of 150 nt (total size >6 Gb). Unaligned reads were assembled de novo using SPAdes (Bankevich et al. 2012). Contigs with length ≥200 nt were subjected to local BLASTn and BLASTx analyses against the GenBank nt and nr databases, respectively (Wang et al. 2022). A total of 23 contigs were identified through BLASTx (e-value cut-off = 10 -3), ranging from 631 to 1555 bp long, with 82% to 96% coverage to partial genomic sequences of pepper chlorosis-associated virus (PepCaV-Higashitsuno_2021; Accessions: LC719619 to LC719621) and one contig (6459 bp) with 99% similarity to tobacco mosaic virus (Accession: OP525281) isolate DSMZ PV-0109 from Germany. The complete genome sequence of PepCaV was obtained using primers based on the assembled contigs. The 5'- and 3'-terminal regions of the RNA genome were obtained by 5'- and 3'-rapid amplification of cDNA ends. These amplicons were cloned using the pEASY-Blunt Zero Cloning Kit (TRANSGEN, Nangjing, China) and sequenced by Sanger sequencing. Complete genome sequences of tripartite PepCaV from tobacco samples were 7697, 1808, and 1557 nucleotides long (Accession: OR451987 to OR451989) and showed genome organization typical of the genus Ophiovirus in the family Aspiviridae. The complete sequences of RNA1, RNA2 and RNA3 genome segments shared 92.36%, 90.43%, and 95.24%, nucleotide sequence identities, respectively, with the isolate PepCaV-Higashitsuno_2021 pepper isolate (Accession: LC719619 to LC719621) (Shimomoto et al. 2023), but PepCaV has not been reported to infect N. tabacum. In June 2023, 10 plants collected from each place of Macheng (N 27.9094, E 105.6740), Xiangyang (N 28.0936, E 105.6249) and Moni (N 27.8899, E 105.5936) showing interveinal necrosis symptoms were tested using RT-PCR using PepCaV-MP610-F (5'-TGTTCTCTGCTATGCGGTTG -3') and PepCaV-MP610-R (5'-AGCAATCTCGCACCTGAAGT-3') to product 610bp amplicon. Twenty-five tobacco plants were positive for PepCaV. Single sequence from each location was submitted to GenBank (Accession: PP728631 to PP728633). Sap extracts from the original field leaf samples collected from Sichuan Province were used to mechanically inoculate tobacco plants (10 plants) at the four-leaf stage. After 7 days, leaf samples were tested using RT-PCR assay specific to PepCaV and TMV while samples were positive only for TMV but failed to transmit PepCaV by mechanical inoculation. According to previous literature, ophioviruses may be transmitted though soilborne fungus (Jeong et al. 2014). Further research is needed to understand the transmission, epidemiology, and pathological properties of the PepCaV. To our knowledge, this is the first report documenting natural PepCaV infection of tobacco plants in China, providing a scientific basis for PepCaV infection control in tobacco plantations.

Quantitative insights into grapevine anthracnose (Elsinoë ampelina) epidemiology: impact of temperature and leaf age on incubation, lesion development, and sporulation

Grapevine anthracnose, caused by Elsinoe ampelina, is one of the most devastating diseases for wine and table grapes, particularly in hot, humid regions. This study explores how temperature and leaf age affect incubation and how temperature affects lesion development and sporulation. The influence of temperature and leaf age on incubation period (days) was tested under controlled conditions. Leaves from 1 to 8 days old were inoculated and maintained at temperatures of 5, 10, 15, 20, 25, and 30°C. The time elapsed between inoculation and the emergence of initial lesions was recorded. The effect of temperature on lesion development and sporulation was investigated under vineyard conditions. This was achieved through artificial inoculations, with 17, 11, and 11 inoculations conducted in 2016, 2017, and 2018, respectively. The average incubation period, considering all leaf ages, was 27.50 days at 5°C, 15.10 days at 10°C, 9.70 days at 15°C, 5.90 days at 20°C, 3.70 days at 25°C, and 2.26 days at 30°C. Regardless of temperature, the average incubation period was 3.6, 5.9, 8.3, 9.8, 11.9, 13.4, 15.6, and 17.1 days for leaves 1, 2, 3, 4, 5, 6, 7, and 8 days old respectively. The exponential decay model accurately describes the incubation period as a function of both temperature and leaf age. On average, the relative lesion development (RLD) were 0.00, 0.00, 0.23, 0.47, 0.72, 0.93 0.92, 0.90, 0.94, and 1.0 at 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 days after inoculation, respectively. The average relative sporulation (RSPO) was 0.03, 0.36, 0.82, 0.96, and 1.0 at 5, 10, 15, 20, and 25 days after inoculation, respectively. Both RDL and RSPO as a function of degree-days (Tbase= 0°C) since inoculation were well described by the logistic function. The rates of change in relative lesion development and relative sporulation were 0.055 and 0.032, respectively. The results of this study provide new quantitative insights into three important stages (monocyclic processes) in the development of grapevine anthracnose caused by E. ampelina.

Discovery of Fusarium pseudograminearum Causing Crown Rot of Winter Wheat in Xinjiang Uygur Autonomous Region, China

Fusarium pseudograminearum is an important plant pathogen that invades many crops (Zhang et al. 2018). Since it was first discovered in Australia in 1951, F. pseudograminearum has been reported in many countries and regions and caused huge economic losses (Burgess et al. 2001). In 2012, crown rot of wheat caused by F. pseudograminearum was discovered for the first time in Henan Province, China (Li et al. 2012). Wheat (Triticum aestivum L.) is one of the most important food crops in Xinjiang Uygur Autonomous Region (XUAR), with 1.07 million hectares cultivated in 2020. In June 2023, a survey of crown rot disease was carried out in winter wheat cv. Xindong 20 in Hotan area, XUAR, China (80.148907°E, 37.051474°N). About 5% of wheat plants showed symptoms of crown rot such as browning of the stem base and white head. The disease was observed in 85% of wheat fields. In order to identify the pathogens, 36 pieces of diseased stem basal tissue, 0.5 cm in length, were collected and sterilized with 75% alcohol for 30s and 5% NaOCl solution for 2 min, then rinsed three times with sterile water and placed on potato dextrose agar (PDA) medium at 25°C. A total of 27 isolates with consistent morphological characteristics were obtained using single-spore technique (Leslie and Summerell. 2006), and the isolation rate was 75%. The isolates grew rapidly on PDA, produced large numbers of fluffy white hyphae, and pink pigment accumulated in the medium. The isolates were grown on 2% mung bean flour medium and identified by morphological and molecular methods. Macroconidia were abundant, relatively slender, curved to almost straight, commonly two to seven septate, and averaged 22 to 72 × 1.8 to 4.9 μm. Microconidia were not observed. The morphological characters are consistent with Fusarium (Aoki and O'Donnell. 1999). Two isolates (LP-1 and LP-3) were selected for molecular identification. Primers EF1/EF2 (5'-ATGGGTAAGGARGACAAGAC-3'/5'-GGARGTACCAGTSATCATG-3') were used to amplify a portion of the EF-1α gene (O'Donnell et al. 1998). The two 696 bp PCR products were sequenced and submitted to GenBank. The EF-1α gene sequences (GenBank Accession No: PP062794 and PP062795) shared 99.9% identity (695/696) with published F.pseudograminearum sequences (e.g., OP105187, OP105184, OP105179, OP105173). The identification was further confirmed by F. pseudograminearum species-specific PCR primers Fp1-1/Fp1-2 (Aoki and O'Donnell. 1999). The expected PCR products of 518 bp were produced only in F. pseudograminearum. Pathogenicity tests of LP-1 and LP-3 isolates were performed on 7-day-old seedlings of winter wheat cv. Xindong 20 using the drip inoculation method with a 10-μl of a 106 macroconidia ml-1 suspension near the stem base (Xu et al. 2017). The experiment was repeated five times in a 20 to 25°C greenhouse. Control seedlings were treated with sterile water. After 4 weeks, wheat seedling death and crown browning occurred in the inoculated plants with over 90% incidence. No symptoms were observed in the control plants. The pathogen was reisolated from the inoculated plants by the method described above and identified by morphological and PCR amplification using F. pseudograminearum species-specific primers Fp1-1/Fp1-2. No F. pseudograminearum was isolated from the control plants, fulfilling Koch's postulates. To our knowledge, this is the first report of F. pseudograminearum causing crown rot of winter wheat in XUAR of China. Since F. pseudograminearum can cause great damage to wheat, one of the most important food crops in China, necessary measures should be taken to prevent the spread of F. pseudograminearum to other regions.

First Report of Fusarium pernambucanum Causing Fruit Rot of Melon in China

In May of 2020, November of 2021 and May of 2022, a preharvest fruit rot with white mycelia was observed inside and outside of the fruits of thick skin muskmelon (Cucumis melo L.) growing in about ten greenhouses (each greenhouse had about 320 muskmelons) with disease incidence of 70% in Ningbo, Zhejiang Province of China. In order to identify the causal agent, plant tissues from the margin of the symptomatic tissue were sterilized for 1 min with 1% sodium hypochlorite (NaClO), 2 min with 75% ethyl alcohol, rinsed in sterile distilled water three times (Zhou et al 2019), and then placed on potato dextrose agar (PDA) plates containing streptomycin sulfate (100 μg/mL) at 25℃ for 4 days. Only Fusarium colonies were isolated from all the plant tissues. The growing hyphae were transferred to new PDA plates using the hyphal tip method, putative Fusarium colonies were purified by single-sporing. Six fungal isolates (Fi-1~6) were obtained. The average radial mycelial growth rate of Fusarium isolate Fi-3 was 4.6 mm/day at 25℃ in the dark on PDA, and like other five isolates. The colonies are abnormal, producing lots of aerial hyphae, each isolate was white to light orange. Isolate Fi-3 produced macroconidia with 4 to 6 septa, tapered with pronounced dorsiventral curvature and measured 21 to 30 μm long 4 to 5 μm wide on Spezieller Nährstoffarmer Agar (SNA) medium at 25℃ for 10 days (Leslie and Summerell 2006), but polyphialides and chlamydospores were still not available for 30 days. The pathogen species was further identified by translation elongation factor-1 alpha (EF-1α) sequencing. The EF-1α of six isolates were sequenced, and their EF-1α sequences were 100% identical to each other, and the sequence of strain Fi-3 was deposited in GenBank with accession no. OL782040 and was also compared with sequences in the FUSARIUM-ID database (Geiser et al. 2004), which indicated that it was 100% identical to those of F. pernambucanum strain NRRL 32864 (GenBank accession GQ505613), F. pernambucanum strain LC7040 (GenBank accession MK289626), and F. pernambucanum strain LC12149 (GenBank accession MK289588) within the Fusarium incarnatum - F. equiseti species complex 17 (FIESC17). Two phylogenetic trees were established based on the TEF1-α sequences of Fi-1~6 and other Fusarium spp., Fi-1~6 was clustered with the sequences of F. pernambucanum within the FIESC17. Thus, both morphological and molecular criteria supported identification of the strain as F. pernambucanum. A pathogenicity test was conducted to verify Koch's postulates, mycelium agar plugs (6 mm in diameter) were removed from the colony margin of a 3-day-old culture of strain Fi-3, healthy melon fruits were surface-sterilized with 70% ethanol and rinsed twice with sterile-distilled water. Then, the melons were wounded using a sterile inoculating needle to stab and inoculated by a mycelium agar plug of strain Fi-3 on the wound sites. 5 fruits were inoculated in each treatment, and a mycelium-free PDA plug was used as a negative control, repeated 3 times, at 25℃ with high relative humidity for 10 days. The results show disease symptoms similar to those naturally infected fruits on all inoculated melon fruits. The fungus re-isolated from the diseased fruits, showed the same colony morphology as the original isolate. Koch's postulates were repeated three times with the same results. Strain Fi-3 inoculated fruits without wounding remained healthy. To our knowledge, this is the first report of fruit rot of melon caused by F. pernambucanum in China.

Bisifusarium lunatum causing cladode soft rot in pear cactus (Nopalea cochenillifera L. Salm-Dyck) in Brazil

Cactus pear var. miúda (Nopalea cochenillifera L. Salm-Dyck) is an important crop for the Northeast region of Brazil, composing one of the main sources of animal feed. By April 2021, cladode rot caused death of several cactus pear plants in a production area located in Itaporanga, Paraíba state, Brazil (7°21'55.35" S and 38°11'38.68" W). The infected cladodes showed brown circular necrotic spots, and soft rot with perforations that extended throughout the cladode, followed by tipping over and death of the infected plants. The incidence of the disease ranged from 10 to 30% of the plants. Bisifusarium strains were isolated and cultured on potato dextrose agar (PDA) and syntetic-nutrient-poor-agar (SNA). The colonies showed purple color on PDA. On SNA, macroconidia (n = 100) were abundant, hyaline, slightly falcate, three-septate, measuring 11.0-23.1 x 2.3-4.1 μm. Microconidia (n = 100) were oval, generally aseptate, measuring 4.1-8.7 x 2.3-3.0 μm. Conidiogenic cells formed into short monophialides. Chlamydospores were not observed. According to these morphological features, the pathogen was initially identified as Bisifusarium lunatum (Gryzenhoutm et al. 2017). For further confirmation of the identification, the partial sequences of translation elongation factor 1-alpha (TEF1-α) and the second largest subunit of RNA polymerase II (RPB2) genes were sequenced for a representative isolate (CMA 34: GenBank accession no: TEF1-α: OR536502; and RPB2: OR553509) and compared to other Bisifusarium species from GenBank database. Subsequently, it was subjected to a phylogenetic analysis of maximum likelihood including previously published sequences. According to BLAST searches, the TEF1-α and RPB2 sequences were 99% (637/640 nt) and 100% (312/312 nt) similar to B. lunatum (COUFAL0213: TEF1-α (MK640219), and RPB2 (MK301291)), respectively. The isolate was also clustered in a clade containing the ex-type of B. lunatum with 100% support (SH-aLRT and UFboot), being confidently assigned to this species. The pathogenicity test was performed after Medeiros et al. (2015), by using healthy two months old cactus pear seedlings (n = 10) cultivated in a greenhouse. Sterile toothpicks were distributed over colonies of the representative isolate grown on PDA at 25 ± 2 °C for seven days. Seedling cladodes were stuck with the toothpicks, moistened with sterile water and covered with transparent plastic bags for 24h, thus simulating a humid chamber. Following three months, all control plants (stuck with sterile toothpicks) remained healthy, while those inoculated with the representative isolate exhibited rot symptoms. This test was performed twice. B. lunatum was reisolated from symptomatic cladodes and identified as previously described, thus fulfilling the Koch's postulates. To our best knowledge, this is the first report of B. lunatum causing soft rot on N. cochenillifera in Brazil. Besides N. cochenillifera, this species was also reported on Opuntia ficus-indica in India (Gryzenhoutm et al., 2017), which raises concern regarding its ability to infect other forage sources for cattle feed in Brazilian semiarid regions. The present study highlights that the precise identification of B. lunatum is a key factor to adjust control strategies and management of the disease to prevent the spread of this disease to prevent its spread to other crops.

First Report of Pectobacterium polaris Causing Soft Rot on Broccoli in China

In April 2023, soft rot symptoms were observed in broccoli (Brassica oleracea L. var. italica) commercial fields in Songming County, Yunnan province, China (103°12'E, 25°31'N). The disease incidence in these fields (6 ha in size) was high, exceeding 50%, and it caused significant yield loss. The affected plants displayed characteristic symptoms, with the roots and stems of broccoli becoming soft, yellowish-brown, rotten, and emitting a foul odor. To identify the causal agent, soft rot symptomatic stems were surface sterilized by dipping them in 75% ethanol for 30 seconds, followed by three successive rinses with sterile distilled water. Tissue specimens were then plated onto nutrient agar (NA) plates and incubated at 28°C for 24 hours. (Wang et al. 2022). Three representative bacterial isolates HYC22041801-HYC22041803 from broccoli were selected for further analysis. The colonies on NA plates appeared as white, small, round, and translucent with smooth edges. Physiological and biochemical tests were performed, along with 96 phenotypic screenings using the BIOLOG GENIII microplate system (Biolog, Hayward, CA, USA). Three isolates were negative for D-arabitol, maltose, and sorbitol, but were positive for cellobiose, α-D-glucose, sucrose, glycerol and gentiobiose tests, which are consistent with the reported type strain P. polaris NIBIO1006T (Chen et al. 2021). Total genomic DNA was extracted from three bacterial isolates using the QIAamp DNA Mini Kit (QIAGEN, USA). The 16S rRNA region and nine housekeeping genes (gapA, icdA, mdh, mtlD, pel, pgi, pmrA, proA and rpoS) were amplified with universal primers 27F/1492R (Monciardini et al., 2006) and designed specific primers (Xie et al., 2018), respectively. All amplicons were sequenced and deposited in GenBank with accession numbers ON723841-ON723843 and ON723846-ON723872. The BLASTn analysis of the 16S rRNA amplicons confirmed that the isolates HYC22041801-HYC22041803 belonged to the genus Pectobacterium. Phylogenetic trees based on 16S rRNA gene sequences and multilocus sequence analysis of other nine housekeeping genes of the three isolates were constructed and the results revealed that three isolates clustered with P. polaris type strain NIBIO1006T, which was previously isolated from potato (Dees et al., 2017). To confirm the pathogenicity, nine broccoli seedlings were stab inoculated with a bacterial suspension (108 CFU·ml-1), while sterile distilled liquid LB medium was used as a negative control. The seedlings were kept at 80% relative humidity and 28°C in a growth chamber. Three trials were conducted per isolate (HYC22041801-HYC22041803). After 3 days, the inoculated petioles showed soft rot symptoms similar to those observed initially in the field, while control plants remained asymptomatic. All three isolates were re-isolated successfully from symptomatic tissues to complete Koch's postulates. P. polaris has been previously reported as the causative agent of blackleg in potato in several countries, including Norway, Poland, Russia, and China (Handique et al. 2022; Wang et al. 2022). Additionally, it was reported to cause soft rot in Chinese cabbage in China (Chen et al. 2021). However, this is the first report of P. polaris causing soft rot disease in broccoli in China. This discovery is of great importance for vegetable growers because this bacterium is well established on Cruciferous vegetables in the local area, and effective measures are needed to manage this disease.

First report of Colletotrichum incanum causing leaf spots on common bean in Europe (Slovenia)

A Phaseolus vulgaris L. leaf showing necrotic spots was collected in an experimental bean field in central Slovenia in August 2021. The field contained diverse common bean lines sourced from genebank collections, with each line represented by 10 plants. While symptomatic leaves were seen across various lines, the reported species derived exclusively from a Huasca Huallaga Colorado plant (single-seed descent, USDA accession PI153714, doi: 10.18730/H7P9N), a Peruvian landrace. After incubating the leaf for 2 d at ambient temperature in a moist chamber, setose acervuli developed producing curved, distally tapering and proximately truncated conidia. Single-spore cultures developed equally-shaped conidia measuring 14.5-21.5 (avg. 18.5) × 3-4 (avg. 3.5) μm (n=60) on corn meal agar when mounted in lactic acid. Obtained morphological characters and sequences of the partial actin (GenBank accession, OR208162), beta-tubulin (OR208164), and histone 3 (OR208165) gene identified the isolate as Colletotrichum incanum H.-C. Yang, J.S. Haudenshield & G.L. Hartman. Sequences were identical to those from CBS 133485 (= NRRL 62592, IL6A), ex-type strain of C. incanum (KC110823, KC110814, and KC110796). Partial sequences of the chitin synthase (CHS) gene (OR208163), not available for the ex-type strain, was identical to sequences of other C. incanum strains reported from China (KP145539, ON189040, and OQ613679-OQ613686) or differed in two nucleotide positions (OL471268 and OL471269). The strain from Slovenia was deposited in the CBS biobanks of the Westerdijk Fungal Biodiversity Institute (Utrecht, The Netherlands) as CBS 150848. Pathogenicity of the strain was tested by spraying ca. 3×105 conidia as a watery spore suspension onto each leaf of 6 greenhouse-grown and 3 wk-old common bean plantlets (cv. KIS Amand). Nonsterile commercial substrate (Potgrond H, AGRO-FertiCrop) was used and natural light conditions at ambient temperatures (18-23°C) applied. Sterile water was sprayed on 6, equally grown negative control plants. Treated plants showed small brownish spots after 3 wks similar to those described by Yang et al. (2014) on soybean. Setose acervuli formed within 5 days after detached leaves were incubated in moist chambers. No acervuli formed on negative control plants. Conidia re-isolated from these acervuli and obtained cultures were morphologically identical to originally obtained conidia and cultures and those used for performing the pathogenicity test. Anthracnose is an important disease of common bean attributed to various races of C. lindemuthianum (Sacc. & Magnus) Briosi & Cavara (Nunes et al. 2021). Reporting an additional agent potentially able to cause diseases in common bean and so far not known to occur in Europe is of high relevance as the various genetic bean lines used in Europe may show alternative susceptibility levels to it. However, symptoms caused by C. incanum seem to be less severe as those caused by C. lindemuthianum and the species belongs to the C. spaethianum species complex, whose members have so far not been considered as pathogens of economic importance (Talhinhas & Baroncelli 2021). Yang et al. (2014) based C. incanum on isolates from soybean petioles (USA) and associated it with common bean by re-identifying strain ATCC 64682 obtained by Tu (1990) in Canada. Database queries revealed that it was encountered also on sugar beet (USA; Hanson et al. 2023) and on various crop hosts in China (e.g., chili; Diao et al. 2017), but not in Europe. The work was funded by the Ministry of Agriculture, Forestry and Food and conducted as part of research programs P4-0072 and P4-0431, financed by the Slovenian Research and Innovation Agency ARIS, and the Horizon 2020 project INCREASE funded by the European Union.

First Report of Colletotrichum scovillei Causing Anthracnose Fruit Rot on Pepper in Ontario, Canada

Anthracnose fruit rot affecting field peppers (Capsicum annuum L.) has been reported in Ontario, Canada, leading to significant crop losses of up to 80% over the past three years. Ten symptomatic fruits per field, exhibiting one or more soft, sunken lesions covered with salmon-colored spore masses (Fig. S1), were collected from one and two Banana pepper fields in August 2022 and 2023, respectively, all located in southwestern Ontario. Small sections of diseased tissue (0.5 cm in length) from lesion edges underwent surface sterilization and plated on 2% potato dextrose agar (PDA, Difco) supplemented with kanamycin (50 mg liter-1), neomycin sulfate (12 mg liter-1) and streptomycin sulfate (100 mg liter-1), and incubated at 22°C for 7 days in the dark. Fifteen fungal colonies were isolated and purified using the hyphal tipping method. All fungal isolates showed a pale gray colony morphology with a faint salmon tint on PDA (Fig. S1). Conidia, produced on PDA after incubating the 15 isolates at 22°C for 17 days in the dark, were hyaline, aseptate, smooth-walled, cylindrical with obtuse ends (Fig. S1), and measured 9.4 to 15.0 × 2.7 to 4.8 µm (mean ± standard deviation of 145 conidia = 11.3 ± 1.2 μm × 3.7 ± 0.5 μm), the typical morphology of Colletotrichum species (Damm et al. 2012). Internal transcribed spacer (ITS), actin (ACT), chitin synthase 1 (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glutamine synthetase (GS), histone H3 (HIS3) and beta-tubulin 2 (TUB2) gene regions of all isolates were amplified and sequenced with primers ITS1/ITS4, ACT-512F/ACT-783R, CHS-79F/CHS-345R, GDF1/GDR1, GSF1/GSR1, CYLH3F/CYLH3R and Bt2a/Bt2b and deposited in GenBank (Accession Nos. ITS: PP060584 to PP060596; ACT, CHS-1, GAPDH, GS, HIS3 and TUB2: PP085919 to PP086005), respectively. The sequences were 100% identical to Colletotrichum scovillei strains from different hosts and countries (ITS: PP079643; ACT: MN718468; CHS-1: MN718466, GAPDH: MN718465.1, HIS3: MT592502, TUB2: MK462971). The maximum likelihood-based phylogenetic analysis of ITS, ACT, CHS-1, GAPDH, GS, HIS3, and TUB2 concatenated sequences was conducted using IQ-TREE 2.2.2.7 (Minh et al. 2020). All isolates from this study were grouped with high bootstrap support values with the holotype C. scovillei CBS 126529 (Fig. S2). Living cultures of these isolates were deposited in the Canadian Collection of Fungal Cultures (DAOMC 252833 to 252847). Pathogenicity was tested by inoculating 4 Banana (cv. Jumbo Stuff) and 4 Bell (cv. Archimedes) pepper fruits with 10 μl droplet of a 1 × 105 conidia ml-1 suspension of each isolate onto a wound made with a sterile pipette tip. Eight control fruits were mock-inoculated with sterilized water. Nine days post-inoculation, necrotic lesions measuring 24.7 ± 0.3 mm on Bell and 27.9 ± 0.2 mm on Banana peppers were observed. Colletotrichum scovillei was re-isolated from all symptomatic fruits, and its species identity was confirmed through morphology, fulfilling Koch's postulates. Control fruits remained symptom-free, and no fungi were isolated from them. This is the first report of C. scovillei in Canada. Previously identified as a pathogen causing anthracnose on peppers in eastern Asia, the United States, Brazil, and Kosovo (Farr and Rossman 2024; Xhemali et al. 2023), its emergence in Ontario raises significant concerns for pepper crops. Additional research is essential to better understand the epidemiology of the disease and develop effective phytosanitary strategies for control.

First Report of Powdery Mildew Caused by Podosphaera xanthii on Youngia japonica subsp. elstonii in Hainan Province, China

Youngia japonica (L.) DC. is a polymorphic annual herb of the Asteraceae family. Although this plant originated in Asia, it is now world-widely distributed. In China, Y. japonica is used for edible or folk medicine to treat viral infections and various kinds of inflammation (Yu et al. 2021). As a traditional Chinese medicinal herb, Y. japonica used for the treatment of inflammatory diseases, such as angina, leucorrhea, mastitis, conjunctivitis, and rheumatoid arthritis (Chen et al. 2006). During the spring of 2023, powdery mildew symptoms were observed on 60% of Y. japonica subsp. elstonii plants in a greenhouse on the Hainan Medical University campus (19° 58' 53″ N; 110° 19' 47″ E) in Haikou, Hainan Province, China. Powdery mildew colonies covered the leaf surfaces and stems of affected plants, causing discoloration and defoliation. Mycelia were superficial and hyphal appressoria were nipple-shaped. Conidiophores (n =30) were unbranched, cylindrical, 99 to 166 × 11 to 16 µm, and produced three to five immature conidia in chains with a crenate outline. Foot cells (n =30) were cylindrical, straight or sometimes curved at the base, and 35 to 61 µm long. Conidia (n =100) were ellipsoid-ovoid to doliiform, 21 to 40 ×13 to 21 µm (length/width ratio = 1.4 to 2.3), with well-developed fibrosin bodies, and produced germ tubes from the lateral position. Based on these morphological characteristics, the pathogen was provisionally identified as Podosphaera xanthii (Braun and Cook 2012). The teleomorph was not observed. A specimen was deposited in the Hainan Medical University Plant Pathology Herbarium as HMYJ-23. To confirm the genus identification and ascertain a putative species, genomic DNA was extracted from mycelium, conidiophores, and conidia using a fungal DNA kit (Omega Bio-Tek, USA). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1/ITS4 (White et al. 1990) and sequenced directly. The resulting 575-bp sequence was deposited in GenBank (accession no. OR229712). A BLASTn search in GenBank of this sequence showed 99% similarity with the ITS sequences of P. xanthii isolates from China (MT260063, OP765400, MW422608, and MT739423), Thailand (LC270778, LC270779, and LC270780), and Argentina (AB525914). Additionally, the 613-bp 28S rDNA region was amplified using the primer pairs NL1 and NL4 (O'Donnell 1993; accession no. OR240257). This region shared 100% similarity with P. xanthii isolates (MK357436, LC371333, LC270780, OP765401, and AB936277) as well. To confirm pathogenicity, five healthy potted plants of Y. japonica subsp. elstonii were inoculated by gently pressing a powdery mildew-infected leaf onto the young leaves. Five non-inoculated plants served as controls. All plants were maintained in a greenhouse at 24 to 30°C, 70% relative humidity, with a 16-h photoperiod. After 7 days, inoculated leaves showed powdery mildew symptoms whereas no symptoms were observed on control plants. The fungal colonies observed on inoculated plants were morphologically identical to those found on the originally infected leaves collected from Hainan Province. Based on the morphological characteristics and molecular identification, the fungus was identified as P. xanthii. To our knowledge, this is the first record of P. xanthii infecting Y. japonica subsp. elstonii in Hainan province, China. We are concerned that the pathogen could become a threat to the widespread planting of Y. japonica subsp. elstonii in the future.

First Report of Alternaria alternata Causing Leaf Spot on Smooth Bromegrass (Bromus inermis Leyss.) in China

Smooth bromegrass (Bromus inermis Leyss.) is an important forage crop in northern China. In July 2021, leaf spot symptoms were observed on smooth bromegrass in Ewenki Banner, Hulunbuir, Inner Mongolia. In an area of approximately 0.12 hectares, 95% disease incidence was observed. Ten diseased plants were collected for pathogen isolation. Leaf tissues near the lesions were cut into 5 × 5 mm pieces, surface-disinfested in 75% ethanol for 3 min, and rinsed with sterile distilled water. The pieces were placed on water agar in petri plates and incubated at 25℃ for three days. The resulting colonies were flushed with sterile water and a spore suspension was serially diluted and plated on potato dextrose agar (PDA). A single-spore colony was obtained. Ten isolates were obtained and designated HE1 to HE10. The colony morphology was identical for all isolates, grayish white in color on the upper surface and light black on the underside. The mycelia were light gray and velvety. Conidia were light brown to brown in color and oblate, oblong or oval. The conidial dimensions were typically between 15 to 43 μm by 8 to 9 μm in size. The conidia possessed one to six transverse septa, with slight to distinct constrictions at each division, and zero to two longitudinal septa. These morphological characteristics resembled Alternaria alternata (Fr.) Keissl.. DNA was extracted from three isolates, HE3, HE4 and HE5, using the CTAB method. Polymerase chain reaction (PCR) was performed on the extracted DNA with a set of primers ITS1/ITS4, H31a/H31b, gpd1/gpd2, TEF1-728F/TEF1-986R, and RPB2-5F2/fRPB2-7cR. The amplicon sequences from the three isolates were analyzed using the BLAST in GenBank (https://www.ncbi.nlm.nih.gov/). The results showed a high sequence identity, ranging from 99 to 100%, with the A. alternata strain YTMZ-20-2 across all the genetic markers tested. The strong match reinforced the identification of the strains as A. alternata. The sequences were deposited in GenBank (Table S1). The three fungal isolates were identified as A. alternata based on their morphological and genetic data. To conduct Koch's postulates, the representative isolate HE4 was used. Smooth bromegrass seed was soaked in water for four days and sown in potting soil contained in plastic pots (10 cm diameter × 15 cm height, five seeds/pot) in a greenhouse under a 16-h photoperiod at temperatures between 20 to 25°C and 60% relative humidity. When the plants reached a height of approximately 20 cm, the plants in three pots (replicates) were sprayed with a spore suspension (106 conidial/ml) at 10 ml/pot, and three pots were sprayed with sterile water for control. Five days after inoculation, the plants exhibited leaf spot symptoms similar to those previously described, while the control plants remained unaffected. The causative fungus was successfully re-isolated from the diseased plants and confirmed morphologically and molecularly on its identity as described above. This experiment was independently conducted three times. This is the first report of A. alternata causing leaf spot on smooth bromegrass in China. Since there is risk that the disease could seriously reduce the yield of the forage crop smooth bromegrass, further research is needed.

Biocontrol potential of Cladosporium sphaerospermum against the wheat powdery mildew fungus Blumeria graminis f. sp. tritici

Cladosporium spp. are known to be mycoparasites and inhibit phytopathogenic fungi. However, so far, little information is available on the impacts of Cladosporium spp. on powdery mildews. Based on the morphological characteristics and molecular analysis, C. sphaerospermum was identified as a mycoparasite on the wheat powdery mildew fungus (Blumeria graminis f. sp. tritici, Bgt, recently named as B. graminis s. str.). C. sphaerospermum was capable of preventing colony formation and conidial distribution of Bgt. The biomasses of Bgt notably decreased by 1.3, 2.2, 3.6 and 3.8 times at 2 dpi, 4 dpi, 6 dpi and 8 dpi, respectively. In addition, biomasses of C. sphaerospermum at 2 dpi, 4 dpi, 6 dpi and 8 dpi significantly increased to 5.6, 13.9, 18.2 and 67.3 times, respectively. In vitro, C. sphaerospermum exudates significantly impaired appressorial formation of Bgt. Thus, C. sphaerospermum acts as a potential biological control agent by suppressing the formation, distribution and development of Bgt conidia and is a viable alternative for managing the wheat powdery mildew. These results suggest that C. sphaerospermum is an antagonistic parasite of the wheat powdery mildew fungus, and hence, provide new knowledge about the biological control of phytopathogenic fungi.

Root rot of spinach caused by Pythium myriotylum and P. aphanidermatum in Taiwan

Spinach (Spinacia oleracea) is a commonly used green vegetable. During September and October in both 2022 and 2023, a vegetable nursery company located among paddy rice fields in Taichung City, Taiwan, reported significant failures in spinach seedling production in net-houses with mean outdoor temperatures of 28.7℃. Abnormal growth was observed in approximately 30% of the spinach seedlings in each batch (n = 2,000 to 3,000), with aboveground tissues showing stunting, yellowing, and wilt, and underground tissues displaying root rot. The symptoms resembled the spinach damping-off documented in Taiwan in extension articles but which lacked complete pathogen identification. A total of 110 plants from two batches were used for pathogen isolation by placing roots on water agar incubated at 25℃ or were examined for the presence of oospores in diseased roots. Eighty-one percent of these plants were associated with Pythium. Nine Pythium isolates were used in subsequent analyses. Genomic DNA from these isolates was subjected to amplification of ITS, β-tubulin gene (TUB2), and cytochrome C oxidase subunit Ⅱ (COXII) gene with primer pairs ITS1 / ITS4, BT5 / BT6, and FM58 / FM66 (Villa et al. 2006). Sequences of ITS (PP209187-PP209195), TUB2 (PP212864-PP212872), and COXII (PP212855-PP212863) were deposited in GenBank. Four isolates (sp01, sp02, sp03, and sp04) were 100% identical to the neotype strain (CBS 118.80) of Pythium aphanidermatum (Edson) Fitzp. for the ITS (761 bp), TUB2 (583 bp), and COXII (547 bp). Five isolates (2sp, 3sp, ND2-4sp, D3-4sp, and ND3-3sp) were 99.87%, 100%, and 99% identical to the reference strain (CBS 254.70) of Pythium myriotylum Drechsler for the ITS (762 bp), TUB2 (602 bp), and COXII (556 bp), respectively. Phylogenetic analysis of Pythium isolates inferred from concatenated sequences of the three genes (LéVesque and De Cock 2004; Villa et al. 2006) revealed that the same four isolates grouped with the neotype strain of P. aphanidermatum, and the five isolates clustered with the reference strain of P. myriotylum, each with a 100% bootstrap support. Morphological features of isolates ND3-3sp and sp01 were used for identification. Isolate ND3-3sp produced inflated lobulate sporangia and aplerotic and smooth oospores (16.3 to 25.1 um; n = 30) attached with three to five antheridia, consistent with identification as P. myriotylum. Isolate sp01 produced inflated lobulate sporangia and aplerotic and smooth oospores (17.0 to 24.0 um; n= 30) attached with a single intercalary antheridium, agreeing with the morphology of P. aphanidermatum (Van der Plaats-Niterink 1981). To investigate the pathogenicity of the nine Pythium isolates on spinach, 20 mycelial agar discs (4 mm in diameter) from a 2-day-old V8 culture of each isolate were used to induce sporangia and zoospores in 20 ml sterilized water at 25℃ with a 12 h light / dark regime. A 1.5 ml zoospore suspension (6 × 103 zoospores / ml) was dropped into BVB growth substrate of two spinach seedlings in 2-week-old at 25℃ with 12 h light / dark regime, resulting in symptoms resembling those observed in commercial nurseries at 7 days post-inoculation (dpi). Each Pythium isolate inoculated 20 seedlings in 10 cells of a planting tray. At 14 dpi, disease incidences were 95 to 100% for P. myriotylum isolates and 60 to 85% for P. aphanidermatum isolates, while control plants treated with water showed no symptoms. Re-isolated pathogens from the inoculated plants were morphologically identical to the inoculated isolates, completing Koch's postulates. Results of the pathogenicity assay, along with molecular and morphological identification, conclude that the root rot of spinach was caused by P. myriotylum and P. aphanidermatum. The two oomycetes were not formally documented to cause spinach diseases in Taiwan. Although P. myriotylum has been isolated from spinach (Wang et al. 2003), its pathogenicity to spinach was not documented worldwide. Root rot of spinach caused by P. aphanidermatum has been reported in the United States (Bates and Stanghellini 1984), Korea (Cho and Shin 2004), and Italy (Garibaldi et al. 2015). These pathogens thrive in humid and hot weather (Littrell and McCarter, 1970). Producing spinach in cooler weather or in a temperature-controlled environment may help prevent severe occurrence of the disease.

First Report of Powdery Mildew Caused by Podosphaera xanthii on Sphagneticola trilobata in Hainan Province, China

Sphagneticola trilobata (L.) Pruski is a perennial creeping herb of the Asteraceae family, which is native to South America. It was introduced into Southern China as a groundcover in the 1970s (Zhang et al. 2023). Now it is mainly used for folk medicine to treat various kinds of inflammatory, incuding joint pain, rheumatic diseases, arthritis, in addition to treating persistent wounds, ulcers, and edemas (Gonçalves et al. 2022). In February and November 2023, powdery mildew symptoms were observed on 60% of S. trilobata plants on the Hainan Medical University campus (19° 58' 53″ N; 110° 19' 47″ E) in Haikou, Hainan Province, China. Powdery mildew colonies covered the leaf surfaces and stems of affected plants, causing discoloration and defoliation. Mycelia were superficial and hyphal appressoria were nipple-shaped. Conidiophores (n =30) were unbranched, cylindrical, 74 to 161 × 10 to 14 µm, and produced three to five immature conidia in chains with a crenate outline. Foot cells (n =30) were cylindrical, straight or sometimes curved at the base, and 27 to 56 µm long. Conidia (n =100) were ellipsoid-ovoid to doliiform, 17 to 30 ×14 to 28 µm (length/width ratio = 1.1 to 1.9), with well-developed fibrosin bodies, and produced germ tubes from the lateral position. Based on these morphological characteristics, the pathogen was provisionally identified as Podosphaera xanthii (Braun and Cook 2012). The teleomorph was not observed. A specimen was deposited in the Hainan Medical University Plant Pathology Herbarium as HMST-23. To confirm the genus identification and ascertain a putative species, genomic DNA was extracted from mycelium, conidiophores, and conidia using a fungal DNA kit (Omega Bio-Tek, USA). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1/ITS4 (White et al. 1990) and sequenced directly. The resulting 577-bp sequence was deposited in GenBank (accession no. OR784549). A BLASTn search in GenBank of this sequence showed 100% similarity with the ITS sequences of P. xanthii isolates from China (MT260063, MN203658, OP765400, and MT739423), Thailand (LC270780), and Vietnam (KM260731, KM260730, and KR779870). Additionally, the 28S rDNA region was amplified using the primer pairs NL1 and NL4 (O´Donnell 1993; accession no. OR784550). This region shared 100% similarity with P. xanthii isolates (LC371334, LC270782, AB936277, and OP765401) as well. Powdery mildew from Hainan sample belonged to the P. xanthii group with strong bootstrap values support 99% in maximum likelihood phylogenetic tree based on ITS and 28S gene sequences. To confirm pathogenicity, five healthy potted plants of S. trilobata were inoculated by gently pressing a powdery mildew-infected leaf onto 15 young leaves. Five non-inoculated plants served as controls. All plants were maintained in a greenhouse at 24 to 30°C, 70% relative humidity, with a 16-h photoperiod. After 7 days, inoculated leaves showed powdery mildew symptoms whereas no symptoms were observed on control plants. The fungal colonies observed on inoculated plants were morphologically identical to those found on the originally infected leaves collected from Hainan Province. Based on the morphological characteristics and molecular identification, the fungus was identified as P. xanthii. In different countries and regions, P. xanthii has been previously reported on S. trilobata in Taiwan (Yeh et al. 2021). To our knowledge, this is the first record of P. xanthii infecting S. trilobata in Hainan Province, China. S. trilobata is often planted as an ornamental plant on both sides of the road, and we are concerned that it may serve as a new host, spreading this pathogen to other economic crops.

Leptodelphax maculigera (Hemiptera: Delphacidae) harbors the corn stunt complex pathogens

The African planthopper Leptodelphax maculigera (Hemiptera: Delphacidae) has been recently reported in many places in Brazil in association with maize. Its occurrence in maize production fields in Brazil has brought concerns to the corn production chain regarding the possibility of this planthopper to be a vector for maize bushy stunt phytoplasma (MBSP), corn stunt spiroplasma (Spiroplasma kunkelii), maize rayado fino virus (MRFV) and maize striate mosaic virus (MSMV). The phytoplasma and spiroplasma, that are bacteria belonging to the Class Mollicutes, and the two viruses are associated with the corn stunt disease complex. Given the presence of the African planthopper species and the corn stunt disease complex in Brazil, we further investigated the abundance of this planthopper species in Santa Catarina state, Brazil, and whether the planthopper can carry the four pathogens. We inspected 12 maize production fields in different municipalities in the state for 20 weeks, using two yellow sticky traps for each maize field. The sticky traps were replaced weekly. A total of 130 specimens of L. maculigera were captured, with a great discrepancy in quantity among locations and weeks. We detected the mollicute MBSP, and the viruses MRFV and MSMV in L. maculigera, whereas S. kunkelii was absent in the assessed African planthopper samples. The molecular detection of the phytoplasma and the viruses in field-collected African planthoppers is a strong evidence that this insect species has the ability of acquiring those pathogens through feeding from phloem of diseased maize plants. Nonetheless, transmission capacity needs to be experimentally proven to assert L. maculigera as a vector for the corn stunting pathogens.

No Common Candidate Genes for Resistance to Fusarium graminearum, F. proliferatum, F. sporotrichioides, and F. subglutanins in Soybean (Glycine max L.) Accessions from Maturity Groups 0 and I: Findings from Genome-Wide Association Mapping

Seedling diseases and root rot, caused by species of Fusarium, can limit soybean (Glycine max L.) production in the United States. Currently, there are few commercially available cultivars resistant to Fusarium. This study was conducted to assess the resistance of soybean maturity group (MG) accessions from 0 and I to Fusarium proliferatum, F. sporotrichioides, and F. subglutinans, as well as to identify common quantitative trait loci (QTL) for resistance to these pathogens, in addition to F. graminearum, using a genome-wide association study (GWAS). A total of 155, 91, and 48 accessions from the USDA soybean germplasm collection from maturity groups 0 and I were screened with a single isolate each of F. proliferatum, F. sporotrichioides, and F. subglutinans, respectively, using the inoculum layer inoculation method in the greenhouse. The disease severity was assessed 21 days post-inoculation and analyzed using non-parametric statistics to determine the relative treatment effects (RTE). Eleven and seven accessions showed significantly lower RTEs when inoculated with F. proliferatum and F. subglutinans, respectively, compared to the susceptible cultivar 'Williams 82'. One accession was significantly less susceptible to both F. proliferatum and F. subglutinans. The GWAS conducted with 41,985 single-nucleotide markers identified one QTL associated with resistance to both F. proliferatum and F. sporotrichioides, as well as another QTL for resistance to both F. subglutinans and F. graminearum. However, no common QTLs were identified for the four pathogens. The USDA accessions and QTLs identified in this study can be utilized to selectively breed resistance to multiple species of Fusarium.

First Report of Alternaria alternata Causing Leaf Spot on Catalpa bungei in China

Catalpa bungei originates from China. It is fast-growing and possesses a vertically aligned trunk, rendering it a commendable construction material and a significant economic species. In July 2022, a serious leaf spot occurred in the LanLake farm (surveyed area of about 700 acres) in Nanyang (33°3'23" N, 112°28'50" E), Henan Province, China. The incidence rate of leaf disease reached 54% (n=100). The disease initially manifested as irregular round spots with a yellowish-brown hue, subsequently extending in all directions. Later, the lesion periphery exhibited a darkening effect, leading to yellowing. Twenty diseased leaves were randomly collected and cut into small pieces at the interfaces between infected and healthy tissues. The tissues were sterilized in a solution of 75% ethanol and 1% NaClO for 30 seconds and 1 minute, respectively. After rinsing in sterile water, the pieces were placed on potato dextrose agar (PDA) plates and incubated at 25°C for 5 days. A total of 29 purified fungal strains were acquired, exhibiting comparable phenotypes in terms of morphological characteristics. Three strains (QS1-1, QS1-2, and QS1-3) were isolated for subsequent investigations. The colony exhibited abundant aerial mycelium with shades ranging from dark green to grey-brown on the reverse side. To analyze the morphological characteristics of conidia, potato carrot agar (PCA) was used as the culture medium and incubated at 25°C with a 12-hour light/dark cycle. Conidia were obclavate or spheroidal, dark brown, with 3 to 5 transverse septa, and 1 to 4 longitudinal septa, measuring 12.4 to 36.7 × 4.4 to 9.0 μm (n=100), with conical beak lengths ranging from 0 to 4.3 μm. These morphological traits suggested that the pathogen shares similarities with the Alternaria species. The rDNA internal transcribed spacer (ITS), translation elongation factor 1-alpha gene (tef1), glyceraldehyde 3-phosphate dehydrogenase gene (gapdh), and RNA polymerase II second largest subunit (rpb2) were amplified for further molecular identification. The resultant sequences were submitted to GenBank with the following accession numbers: OR733559, OR742124, OR761873 (ITS), OR939796, OR939797, OR939798 (tef1), OR939801, OR939802, OR939803 (gapdh), and PP054846, PP054847, PP054848 (rpb2). A Phylogenetic tree was constructed of combined genes (ITS, tef1, gapdh, and rpb2) of sequences, alongside the sequences of the type strains by the neighbor-joining method. The three strains formed a clade with the strains CBS 121456 of Alternaria alternata in phylogenetic trees, being separated from other Alternaria spp. The morphological features and molecular analyses supported the strains as members of Alternaria alternata (Woudenberg et al. 2015). To validate pathogenicity, a conidial suspension (106 conidia ml-1) of all three strains was inoculated onto three healthy leaves of five seedlings, with 50 μl of inoculum absorbed with cotton balls. Another group of five plants received sterile water as a control. All plants were incubated in a climate chamber at 28°C and 90% relative humidity. Four days post-inoculation, lesions resembling natural phenomena were observed, whereas control plants showed no symptoms. Subsequent reisolation produced cultures that were morphologically and molecularly identical to the original strains, fulfilling Koch's postulates. Stem canker of C. bungei caused by Phytophthora nicotianae has been reported in China (Chang et al. 2022). This is the first report of A. alternata causing leaf spots on C. bungei in China. Further research is required on management options to control this disease and the host range still needs to be clarified for accurate disease management.

First Report of Globisporangium (Pythium) mastophorum causing Damping-off / Root Rot on Parsley in Slovenia

Pythium-like species cause damping-off symptoms of various hosts, including umbelliferous crops. In April 2023, parsley plantlets (Petroselinum crispum), showing stunted growth, yellowing, decayed roots and damping-off, were obtained from a nursery in central Slovenia, where parsley was grown in polystyrene trays in a greenhouse. Nearly 30% of plants were symptomatic. Sampled roots of ten plants contained ornamented oogonia (avg. 33.3 ± 1.4 µm in diam) with conical projections (5.2 ± 0.5 µm long) (Figure S1 A, B) in microscopically analyzed squash mounts. The pathogen was isolated from root pieces treated for surface disinfection with 0.5% sodium hypochlorite for 30 s, and washed with sterile water. Four 1-2 mm root pieces were taken from each of 10 plants, plated on the selective medium P5ARP, and incubated at 21 °C. Mycelia emerging from root pieces were transferred to carrot piece agar (CPA). Twenty-two equally looking oomycetous colonies were obtained; all sampled plants were infested. Oogonia formed by all colonies were similar to those observed on decayed roots and suggested that Globisporangium (Pythium) mastophorum is the causal disease agent. Analyses of partial β-tubulin (Kroon et al. 2004) and mitochondrial cytochrome c oxidase I (COI) gene sequences (Robideau et al. 2011) confirmed the identification. Obtained COI (Genbank accession number OR725417) sequence was 100% identical to that from G. mastophorum strain CBS 375.72 (EU350523), whereas the β-tubulin sequence (OR725416) corresponded to 99.6 % pairwise identity (KJ595502). Further, pathogenicity of an obtained isolate was tested on 4 wk-old curly leaf (cv. Petra F1) parsley. Half of a 7 d-old CPA culture, consisting of mycelium and oogonia, was finely cut and mixed with ca 50 ml of nonsterile commercial substrate (Potgrond H, AGRO-FertiCrop) in each of six 400 ml pots. Pots were filled with ca 300 ml additional substrate, into which 5 parsley seedlings were planted. Control plants were treated equally but with sterile CPA. Plantlets were watered with sterile tap water and held at ambient light conditions and temperature (night 18 °C - day 23 °C). After 14 d, inoculated plants started wilting and yellowing and showed stunted growth. After 21 d, roots were severely decayed and the seedlings damped-off (Figure S1 C). Four pieces each from 10 decayed roots were plated. Thirty-one pieces revealed pythium-like colonies. Obtained isolates were morphologically identical to the strain used for inoculation and identified as G. mastophorum. Control plants developed no foliar or root symptoms and no pythium-like species was obtained. Agricultural advisors observed occurrence of parsley damping-off also in other nurseries in Slovenia what may lead to spreading the pathogen to parsley in production fields and private gardens. The case emphasizes the need for implementing phytosanitary measures in order to eliminate primary inoculum. Reports from field-infected plants showed that G. mastophorum is a pathogen of parsley in Australia (Petkowski et al. 2013) and the USA (Tsuchida et al. 2018), and celery in the Czech Republic (Šafránková and Holková 2017). Others isolated G. mastophorum from parsley in The Netherlands (online database of the Westerdijk Fungal Biodiversity Institute, strain CBS 243.86). However, the here described case is, to the best of our knowledge, one of the rare documentations of damping-off due to G. mastophorum in Europe (Šafránková and Holková 2017) and the first in Slovenia. Funding: The work was funded by the Ministry of Agriculture, Forestry and Food of Slovenia, and Slovenian Research and Innovation Agency (ARIS Programs P4-0431 and P4-0072).

First Report of powdery mildew of Quercus guyavifolia (Fagaceae) Caused by Erysiphe quercicola

Oaks are the most abundant trees in naturally regenerated forests in China, play a crucial role in preventing soil erosion and maintaining ecological stability (Du et al. 2022). Quercus guyavifolia H. Léveillé (Fagaceae family, Subgenus Cerris, section Ilex), is endemic in China, distributed in the southeastern boundary of the Qinghai-Tibet Plateau, with elevations from 2, 000 - 4, 500 m a.s.l. (Denk et al. 2018; Sun et al. 2016). Powdery mildew is a prevalent disease of oaks with up to 60% of foliage infection, which can induce leaf necrosis or deformation and might contribute to oak decline (Marçais and Desprez-Loustau 2014). In September 2023, we found leaves of Q. guyavifolia near Yunnan Baima Snow Mountain covered with white fungal colonies. Diseased Q. guyavifolia plants were transplanted into a greenhouse at Yunnan University for pathogenicity tests. Conidia from diseased plants were blown into twenty healthy Q. guyavifolia seedlings by cold air blower and five non-inoculated healthy seedlings were used as control. The inoculated seedlings developed powdery mildew symptoms within ten days on both sides of the leaves. Trypan blue staining was used to identify the pathogen that infects Q. guyavifolia (Xiao et al. 2017). Microscopic examination revealed abundant conidia and extensive branched hyphae on leaves, similar to the characteristics of powdery mildew fungi. The mean length and width of conidia were 29.06 ± 3.96 × 9.52 ± 1.36 μm (n = 50). We collected fungi (YNBAIMAXS01) and extracted genomic DNA from five diseased plants (from the same location) using the CTAB method. We amplified and sequenced the ITS (Gardes and Bruns, 1993), MS294, and MS447 (two nuclear protein-encoding genes; Feau et al. 2011; GenBank numbers: PP079015, PP083693, PP083694). BLAST analysis revealed 100% identity of above three sequences with the ITS of Erysiphe quercicola isolate DACA010 (GenBank accession MT569439), MS294 of E. quercicola isolate GEM09_11_FRTB1 (GenBank accession KY348509), and MS447 of E. quercicola isolate A1I1.5 (GenBank accession KY466619). Therefore, the isolate YNBAIMAXS01 was identified as E. quercicola based on its morphological and molecular characteristics. Sequences from the above three regions for YNBAIMAXS01 and five Erysiphe species were used to construct a Maximum likelihood (ML) tree. In addition, we constructed a ML tree using only the ITS region of YNBAIMAXS01 and eight Erysiphe species from GenBank to better distinguish E. quercicola from these species. Both trees were constructed using MEGA X with K2 + G as best model. The ML trees confirmed the powdery mildew fungi isolated from Q. guyavifolia is closely related to E. alphitoides. To date, thirty-four powdery mildew species belonging to genus Erysiphe have been found affecting Quercus and nine oak species can be infected by E. quercicola (https://fungi.ars.usda.gov/). To our knowledge, this is the first report of powdery mildew caused by E. quercicola on Q. guyavifolia, thus the development of control strategies and disease management is urgently needed.

First report of sweepoviruses infecting Ipomeas batatas L. cultivars and landraces in Trinidad

Root crops, referred to as ground provisions in the Caribbean, are traditional staples in Trinidad. One widely consumed example is sweet potato (Ipomeas batatas L.). The crop is mainly produced by subsistence farming which together with imports from neighboring Caribbean countries meet domestic demand (Singh et al. 2008). The Central Experiment Station, situated in the eastern part of Trinidad, maintains a sweet potato germplasm collection comprising both imported and locally-sourced landraces for cultivar development and distribution of propagules. In May 2017 chlorosis and leaf curling symptoms, typically associated with sweepoviruses, were observed on imported cultivars, Centennial, Jewel, 86 BM 31, TIB 313, TIB 8 21 1, and S128, and the landraces, Kick Up Jenny, John, and Carrot. Leaf samples from these nine symptomatic plants were collected for analysis, along with samples from the asymptomatic landrace, Chickenfoot. Total nucleic acids were extracted (Sharma et al. 2008) and the samples were assayed by PCR using degenerate primers SPG1 and SPG2 (Li et al. 2004) that target the replication associated protein gene (ORF C1), a highly conserved region of sweepoviruses. Amplicons of 912-bp were obtained from two of the nine symptomatic plants (TIB 8 21 1, Kick Up Jenny), but not from the asymptomatic Chickenfoot. The same samples were assayed by PCR amplification using primers SpvF and SpvR (Avelar 2015) which are specific to a highly conserved 632-bp region of the coat protein gene (ORF V1) of sweet potato leaf curl virus (SPLCV). All 10 samples tested positive for SPLCV, including the asymptomatic landrace, Chickenfoot. The ORF V1 PCR products from three of the 10 samples, namely Chickenfoot, TIB 8 21 1, and Kick Up Jenny, were cloned and sequenced (two clones per sample). Comparison of the sequences (GenBank accession nos. OR882007 [Chickenfoot], OR913125 [TIB 8 21 1] and OR913126 [Kick Up Jenny]) identified up to 4% nt sequence variability between samples. In BLASTn analysis, they were most closely related to the SPLCV isolate China:Sichuan (GenBank accession no. KJ013557), sharing 94 to 98% nt identity. Total nucleic extracts from one representative sample (TIB 8 21 1) was used as template for rolling circle amplification (RCA, TempliPhi Amplification Kit, GE Healthcare Life Sciences, Piscataway, NJ, USA). Digestion of the RCA product with StuI (Thermo Scientific, MA, USA) yielded ~2.8 kb DNA fragments indicative of monomeric full length genomes. Digested fragments were cloned, completely sequenced and deposited in GenBank under the accession nos. OR866202 (2,821 nts) and OR866203 (2,828 nts). Two species of sweepoviruses were detected. In BLASTn analysis, OR866202 showed 95% nt identity with sweet potato golden vein associated virus (SPGVaV) US:MS:1B-3 (GenBank accession no. HQ333143.1) which is a recombinant virus comprised of SPLCV and sweet potato leaf curl Georgia virus (SPLCGV) (Zhang and Ling 2011) and in BLASTx analysis OR866202 was most similar (92-99%) to SPLCV isolates from Brazil (GenBank accession nos. ACI23475.1, AGW16179.1, ACY79479.1), Peru (GenBank accession no. ACY79466.1) and China (GenBank accession nos. ACY79439.1). OR866203 shared 96% nt identity with SPLCV China:Henan25(8):2012 (GenBank accession no. KF040465.1) in BLASTn analysis and BLASTx analysis revealed ≥ 94% aa sequence identity with SPLCV from Brazil (GenBank accession nos. ACI23475.1, AGW16179.1, ADZ96559.1), Peru (GenBank accession no. ACY79479.1), China (GenBank accession no. ACY79466.1). and Spain (GenBank accession no. QWQ56365.1). Both Trinidad isolates also showed 90-96% nt identity with SPLCV from Korea (GenBank accession no.s KT992061.1, KT992064.1, unpublished). This is the first detection of sweepoviruses in Trinidad. SPGVaV has been reported in Brazil, the United States and Korea (Kil et al. 2014), while SPLCV has been described in other Caribbean islands, including Cuba, Jamaica, Puerto Rico, St. Vincent (Cuellar et al. 2015), and Barbados (Alleyne et al. 2019), as well as several countries in South America. Although Koch's postulates were not completed, our findings suggest that sweet potato crops in Trinidad harbor sweepoviruses, notwithstanding efforts to distribute pathogen-free materials and, in some instances, the apparent absence of visible symptoms on infected plants. Further studies on the management and impact of these viruses are necessary, including their prevalence in the sweet potato production regions of Trinidad.

First Report of Paramyrothecium breviseta Causing Target Spot on Amorphophallus muelleri in Yunnan, China

Amorphophallus muelleri is an Araceae plant with perennial tuber, widely used in food, pharmaceutical and chemical industry due to its richness in glucomannan. In April 2022, an outbreak of a target spot on A. muelleri plantlets was observed in a nursery in Ruili, Yunnan, China. The leafstalks of the diseased plantlets in the nursery turned brown and decayed (Fig.1 A-B), then gradually some water-soaked spots on the true leaves developed along the veins (Fig.1 A). Subquencely, the spots on the true leaves turned dark green to white-grayish in the center, which formed light to dark brown concentric rings with a target-like appearance surrounded by a yellow halo (Fig.1 C). When the temperature was 20-34℃ and the relatively humidity was 25-80%, dark-green to black sporodochia with white hypha appeared on the lower and upper leaf surfaces. Finally, 5-8% of the plants surveyed on 800 m2 of one-year-old plantlets in the nursery showed the symptoms and some plants with infected leafstalks would be death. Similar symptoms were also observed on about 10% of the transplanted plants surveyed on 12000 m2 (1.2 ha) of two-year-old plantlets in the field. Five diseased leaves from five distinct plantlets in the nursery were collected for pathogen isolation. Leaf pieces(5 x 5 mm) were cut from the edge of necrotic lesions, and surface-sterilized with 2.5% sodium hypochlorite for 1 min, 75% ethanol for 30 s, then rinsed 5 times by sterilized distilled water, finally put the leaf pieces on sterilized filter paper for 3-5 minutes to dry them and transferred onto potato dextrose agar (PDA) in petri dishes at 25℃ for three days. Five pure cultures identical to colony and conidial characteristics were isolated from five individual plants. The representative pure culture (M1) was grayish-white and circular colonies were 7.50 cm in diamter after 15 days at 25℃, with dark green concentric rings of sporodochia, the dorsal view of the colonies were yellowish. Conidia were aseptate, smooth, cylindrical, 5.00-6.25 (5.71) x 1.25-1.67 (1.63) µm (n = 20) rounded at both ends. A spore suspension (1 x 106 spores/ml) was prepared by harvesting spores from 15-day-old cultures grown in the dark at 25℃, then a thirty-ml of spore suspension was sprayed on the healthy leaves of 10 two-year-old plantlets. Thirty-ml of sterile water was sprayed on the healthy leaves of another 10 seedlings and used as the control. All seedlings were placed in a nursery at 20 to 34℃ and a relative humidity of 25 to 80%. Similar symptoms (Fig.1 D-F) to those observed in the nursery and field developed on all the 10 seedlings inoculated with M1 after two days, but not on the control leaves. The pathogenicity tests were repeated for three times. Fungal cultures reisolated from the infected leaves were identical to the original colonies and conidia, completing Koch's postulates. The internal transcribed spacer (ITS, primers ITS1 and ITS4) region of ribosomal DNA (OQ553785), calmodulin (cmdA, primers CAL-228F and CAL2Rd)(OQ559103), RNA polymerase II second largest subunit (rpb2, primers RPB2-5F2 and RPB2-7cR) (OQ559104) and β-tubulin (tub2, primers Bt2a and Bt2b) (OQ559105) of M1 had 100%, 98.52%, 98.98% and 98.98% identity with the sequences of Paramyrothecium breviseta CBS544.75 (KU846289 for ITS, KU846262 for cmdA, KU846351 for rpb2, and KU846406 for tub2), respectively. In the phylogenic tree based on ITS, cmdA, rpb2 and tub2 gene sequences, the pure culture M1 clustered with P. breviseta CBS544.75, SDBR-CMU387, DRL4 and DRL3, which has been reported as the pathogen of leaf spot of Coffea arabica in China, C. canephora in China and Thailand (Wu et al. 2021; Withee et al. 2022). Molecular and morphological observations showed the pure culture M1 were P. breviseta (Withee et al. 2022), in addition the disease was named as target spot dueing to the typical target symptom on the leaves. To our knowledge, this is the first report of P. breviseta on A. muelleri from Yunnan, China, as well as worldwide. This disease can caused serious economic losses of A. muelleri dueing to that it can result 5-8% death of the plants in the nursery.

Host range characterization of Phytophthora sansomeana across corn, soybean, wheat, winter cereal rye, dry bean and oats, and an in vitro assessment of seed treatment sensitivity

Formally described in 2009, Phytophthora sansomeana is a pathogen of increasing interest in native, agricultural, and horticulturally important plant species. The objective of this study was to elucidate the symptomatic and asymptomatic host range of P. sansomeana on six agricultural crop species commonly used in field crop rotations in Michigan. In addition, sensitivity to oomicides commonly used in seed treatments including, oxathiapiprolin, mefenoxam, ethaboxam, and pyraclostrobin was performed to aid in disease management recommendations. Plant biomass, quantity of P. sansomeana DNA in roots, and reisolations were used to assess pathogenicity and virulence of eighteen isolates of P. sansomeana on each plant species using an inoculated seedling growth chamber assay. Isolates displayed varying levels of virulence to the hosts tested. Reisolations were completed for each plant species tested, and varying quantities of P. sansomeana DNA were found within all plant species root samples. Corn, wheat, soybean, dry bean, and winter cereal rye plants were symptomatic hosts with significant reduction observed in total plant biomass. No significant reduction in total plant biomass was observed in oats, and oat roots harbored the least amount of P. sansomeana DNA. No P. sansomeana isolates were insensitive to the oomicide compounds tested with mean absolute EC50 values of 7.8 x 10-2 µg/ml for mefenoxam, 1.13 x 10-1 µg/ml for ethaboxam, 2.6 x 10-2 µg/ml for oxathiapiprolin, and 3.04 x 10-1 µg/ml for pyraclostrobin. These results suggest that common crop rotations in Michigan may not be a viable option to reduce soilborne inoculum accumulation and oomicide seed treatments should be considered for early season management of P. sansomeana.

Detection of Beet curly top virus in Solanum jamesii, Artemisia tridentata, Helianthus annuus, and Cannabis sativa in Utah

Historically, beet curly top virus (BCTV; Geminiviridae, Curtovirus) is known for destroying the sugar beet industry in Utah and has been a persistent problem in the state since then (Ball, 1917). Starting in June of 2022, we began identifying plants in San Juan County, Utah with chlorosis and leaf curling. Of note, Solanum jamesii, the Four Corners potato, Artemisia tridentata, big sagebrush, and Helianthus annuus, common sunflower, were found with general chlorosis, severe leaf curling and in the case of the sage brush, completely lacking in smell whereas nearby sage plants without the yellowing were intensely fragrant. In August 2023, Cannabis sativa plants for hemp production were found with severe leaf curling in Juab County, Utah. Samples were collected and stored at -80°C for future work. DNA was extracted using the IBI Genomic Plant DNA kit (IBI Scientific, Dubuque, IA) and subjected to rolling circle amplification using Phi29 polymerase (NEB, Ipswich, MA). The primer set BCTV2 (Strausbaugh et al. 2008) for BCTV detection was then used on a subset of the RCA-positive samples for either one (A. tridentata, H. annus, and S. jamesii) or two (C. sativa) plants displaying classic BCTV symptoms, to amplify a 518 bp region. This amplicon was then sequenced by the Sanger method to a 4x coverage. The resulting sequences (accession nos. OR698900 to OR698904) share 98.94 to 99.80% nucleotide identity to the Worland strain (accession no. KU892789.1) for all samples. To confirm the detection, a triple antibody sandwich ELISA kit from Nano Diagnostics (San Jose, CA) was used on these, and other plants of similar species and symptoms from across the state. Samples that tested positive include 3/3 symptomatic H. annuus plants, 1/1 symptomatic S. jamesii, 3/3 symptomatic A. tridentata. The A. tridentata samples were collected from Juab, San Juan, and Utah Counties. None of three asymptomatic A. tridentata plants tested were ELISA positive. Of the C. sativa plants tested by ELISA, 9/9 of the plants displaying classic BCTV symptoms in that host were positive and 6/6 of the plants without classic BCTV symptoms were ELISA positive. The findings of these novel hosts indicate the need for increased testing and analysis of economically relevant crops and native flora across the state. These findings represent a concern for conservation in the case of S. jamesii and a potential threat to the growing hemp industry in the state due to the severity of BCTV symptoms on these plants. Additionally, the finding of A. tridentata as a host may represent a significant finding for the epidemiology of BCTV in the Mountain West region as A. tridentata is distributed from Mexico to Canada along the Rocky Mountain range and is found in much of the Western US in arid regions. This is the first report, to our knowledge, of S. jamesii and A. tridentata as hosts for BCTV and the first peer reviewed reports for H. annuus and C. sativa as hosts for BCTV in Utah.

Molecular-Phylogenetic Characterization of Xanthomonas hortorum pv. pelargonii Strains Causing Leaf Spot of Geraniums in Iran

Bacterial blight and leaf spot of geraniums is a destructive disease of cultivated Pelargonium species around the world. During 2020-2021, surveys were conducted in seven geranium-growing provinces of Iran to monitor the status of bacterial blight and leaf spot disease. The disease was observed in six surveyed provinces varying in the extent of occurrence and severity. Twenty-two Gram-negative pale-yellow bacterial strains resembling members of Xanthomonas were isolated from symptomatic leaves and stems. Pathogenicity and host range assays showed that the bacterial strains were pathogenic on Pelargonium grandiflorum, P. graveolens, P. peltatum, and P. zonale. All strains were positive for PCR test using the primer pair XcpM1/XcpM2 which is specific for Xanthomonas hortorum pv. pelargonii. Phylogenetic analysis using the sequences of gyrB and lepA genes showed that the 22 strains clustered in a clade among the sequences of X. hortorum pv. pelargonii strains retrieved from the GenBank, while distinct from the other pathovars of X. hortorum. BOX-PCR-based fingerprinting using BOX-A1R primer revealed that the strains isolated in this study were grouped into two clusters while no distinct correlation was observed between the host/area of isolation and BOX-PCR fingerprinting. None of the strains obtained in this study nor reference strain of the pathogen did produce bacteriocin against each other. Results obtained in this study shed light on the geographic distribution, taxonomic status and host range of the bacterial blight and leaf spot pathogen of geraniums in Iran, paving the path of further research on disease management.

First Report of Powdery Mildew Caused by Podosphaera xanthii on Acalypha indica in China

Acalypha indica L. is an annual erect herb of the Euphorbiaceae family. This plant is found widely in the tropics and parts of Africa and Asia (Chakraborty et al. 2023). In China, A. indica is a vegetable and also used as a folk medicine due to its antipyretic and hemostatic, antibacterial and anti-inflammatory properties. In February 2022 and 2023, powdery mildew symptoms were observed on 70% of A. indica plants on the Hainan Medical University campus (19° 58' 53″ N; 110° 19' 47″ E) in Haikou, Hainan Province, China. Powdery mildew colonies covered the leaf surfaces and stems of affected plants, causing discoloration and defoliation. Mycelia were superficial and hyphal appressoria were nipple-shaped. Conidiophores (n =30) were unbranched, cylindrical, 66 to 150 × 10 to 15 µm, and produced three to five immature conidia in chains with a crenate outline. Foot cells (n =30) were cylindrical, straight or sometimes curved at the base, and 31 to 59 µm long. Conidia (n =100) were ellipsoid-ovoid to doliiform, 20 to 33 ×12 to 20 µm (length/width ratio = 1.3 to 2.4), with well-developed fibrosin bodies, and produced germ tubes from the lateral position. Based on these morphological characteristics, the pathogen was provisionally identified as Podosphaera xanthii (Braun and Cook 2012). The teleomorph was not observed. A specimen was deposited in the Hainan Medical University Plant Pathology Herbarium as HMAI-23. To confirm the genus identification and ascertain a putative species, genomic DNA was extracted from mycelium, conidiophores, and conidia using a fungal DNA kit (Omega Bio-Tek, USA). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1/ITS4 (White et al. 1990) and sequenced directly. The resulting 575-bp sequence was deposited in GenBank (accession no. OR775733). A BLASTn search in GenBank of this sequence showed 99% similarity with the ITS sequences of P. xanthii on plants of Fabaceae, Malvaceae and Cucurbitaceae family from China (MH143485, MT242593, MK439611 and MH143483), Thailand (LC270779 and LC270778), Korea (MG754404), Vietnam (KM260704), and Puerto Rico (OP882310). Additionally, the 28S rDNA region was amplified using the primer pairs NL1 and NL4 (O´Donnell 1993; accession no. OR784547). This region shared 99% similarity with P. xanthii isolates (LC371333, LC270780, AB936277, and OP765401) as well. To confirm pathogenicity, five healthy potted plants of A. indica were inoculated by gently pressing a powdery mildew-infected leaf onto 15 young leaves. Five non-inoculated plants served as controls. All plants were maintained in a greenhouse at 24 to 30°C, 70% relative humidity, with a 16-h photoperiod. After 7 days, inoculated leaves showed powdery mildew symptoms whereas no symptoms were observed on control plants. The fungal colonies observed on inoculated plants were morphologically identical to those found on the originally infected leaves collected from Hainan Province. Based on the morphological characteristics and molecular identification, the fungus was identified as P. xanthii. In different countries and regions, P. xanthii has been previously reported on A. indica from Sudan and India (Amano 1986). To our knowledge, this is the first record of P. xanthii infecting A. indica in China. We are concerned that the pathogen could become a threat to the widespread planting of A. indica in the future.

First report of leaf blight caused by Stemphylium lycopersici on Salvia splendens in China

Salvia splendens is a popular ornamental plant in China with extensive potentials, including value in traditional Chinese medicine and in environmental restoration function (Li et al. 2008). In September 2019, leaf blight disease was observed on road side plants of S. splendens in Bayi park, Nanchang city, Jiangxi province, China. The typical symptoms appeared as irregular necrotic spots or leaf blight, accompanied by extensive scorch necrosis or ultimately defoliation. Small segments cut from diseased leaves were surface sterilized in a 2% sodium hypochlorite solution for 2 min and rinsed three times with sterile distilled water. Then, the samples were placed on potato dextrose agar (PDA) plates incubated at 25°C in darkness. Pure cultures were obtained by the hyphal tip method. Morphologically, all 11 colonies were identical to each other on PDA. Two strains, YZU 191468 and YZU 191481, were selected for further study and deposited in the Fungal Herbarium of Yangtze University (YZU), Jingzhou, Hubei, China. The 7-day-old colonies were circular, 53 to 56 mm in diameter, and consisted of white mycelium with a buff margin, and were cinnamon colored in the center of the reverse side. To examine conidial morphology, the mycelium was transferred onto potato carrot agar (PCA) and incubated at 23°C with a period of 8 h light/16 h dark for 7 days. Conidia were normally solitary or two in a chain, ellipsoid or long ellipsoid, beakless, 10 to 23×30 to 60 µm in size (n=50). Based on morphology, the isolates were consistent with Stemphylium lycopersici (Yamamoto 1960). To confirm the identification, genomic DNA was extracted from both isolates and used to amplify the internal transcribed spacer rDNA region (ITS), glyceraldehydes-3-phosphate dehydrogenase (GAPDH) and calmodulin (CAL) genes with primer pairs ITS5/ITS4, gpd1/gpd2, and CALDF1/CALDR2, respectively (Woudenberg et al. 2017). Sequences were deposited in GenBank with accession numbers OP564983 and OP564984 (ITS), OP892529 and OP892530 (GAPDH), OP584970 and OP584971 (CAL). A neighbor-joining tree was constructed with Mega 7.0 based on the combined dataset with 1,000 bootstrap replicates. The resulting phylogenetic tree showed that the strains from S. splendens clustered with S. lycopersici (CBS 122639 and CBS 124980) supported with 100% bootstrap values. The molecular analyses confirmed that the species causing leaf blight symptoms was S. lycopersici. To test pathogenicity, healthy leaves of S. splendens were surface sterilized and inoculated by mycelium blocks (6 mm in diameter) and spore suspension (1×106 spore/mL) of representative strains YZU 191468 and YZU 191481, respectively. Controls were inoculated with blocks of PDA and sterile water. Each strain was inoculated on three leaves of a plant. One clean plant was used as control. The test was replicated three times. After inoculation, the plants were covered with plastic bags and incubated in a greenhouse (25℃, 80 % relative humidity, 8 h light/16 h dark). After 5 days, the inoculated leaves exhibited dark brown spots with white mycelium, followed by withering of necrotic tissues. There were no symptoms observed on the controls. The fungal isolates inoculated leaves had the same morphological characteristics as the strains used for inoculation. S. lycopersici has been found on eggplant and Zinnia elegans in China (He et al. 2019; Yang et al. 2017). To the best of our knowledge, this is the first report of S. lycopersici causing leaf blight on S. splendens in China. This finding offers a new reference for the management and control of S. splendens leaf diseases in China.

First Report of Anthracnose on Euonymus japonicus Thunb. Caused by a Provisionally Novel Species of Colletotrichum in the Magnum Complex in South Korea

Euonymus japonicus Thunb., also known as the evergreen spindle tree, is an evergreen tree, which is widely planted as a hedge plant along streets in South Korea. In April 2022, severe anthracnose symptoms were observed on the leaves of this tree in Jangsu in the Jeonbuk Province of the country (35°43'49.44″N, 127°34'53.7″E). About 80% of the leaves of each affected tree within a 0.03-ha area showed incidence of the disease on approximately 30 trees were planted along the roadside (~30 m). These symptoms typically included circular or irregularly shaped whitish-gray lesions with a diameter of 2.0 to 3.0 cm. In cases where some leaves were severely affected, larger blotches formed. To isolate the pathogen, about ten leaves showing anthracnose symptoms on each tree were randomly selected and brought to the laboratory. Fungal isolations were made from acervuli filled with conidial masses on infected evergreen tissues, followed by plating onto 2% potato dextrose agar (PDA) as well as incubated at 25℃. On the PDA, colonies were circular, raised, green-grey or dark grey, and had a distinct white margin. The conidia were single-celled, transparent, cylindrical with rounded ends, had smooth walls, with a length ranging from 12 μm to 16.7 μm and a width raging from 4 μm to 6.5 μm (av. = 14.1 X 5.0 μm, n=40). Of those that were successfully recovered with approximately 90% frequency, two monoconidial isolates were deposited to the culture collection at Chungnam National University in South Korea (Accession number: CDH059-060). To ensure the identity of the fungus, genomic DNAs were extracted from the selected isolates, CDH059-060, and were sequenced. This was achieved based on partial sequences of the internal transcribed spacer (ITS), actin and beta-tubulin (TUB2) gene regions which were amplified using ITS1F / ITS4 (Gardes and Bruns 1993; White et al. 1990), ACT-512F / ACT-783R (Carbone and Kohn 1999), and T1 / Bt2b (O'Donnell and Cigelnik 1997; Glass and Donaldson 1995) primer pairs, respectively. The resulting sequences were deposited to GenBank (OR984424-425) for ITS, (OR996289-290) for actin, and (OR996291-292) for TUB2. For a phylogenetic analysis, sequences from different gene regions (ITS, actin and TUB2) retrieved from GenBank were aligned, concatenated, and analyzed as a single dataset based on a maximum likelihood analysis. The phylogenetic result revealed that the fungus isolated in this study was positioned in a clearly distinct lineage, provisionally representing an undetermined species of Colletotrichum, which is most closely related to Colletotrichum liaoningense (Y.Z. Diao, C. Zhang, L. Cai & X.L. Liu, CGMCC3.17616 (KP890104 for ITS, KP890097 for actin, and KP890111 for TUB, Diao et al. 2017). Sequence comparisons revealed that this pathogen differed from C. liaoningense at 20 of 494 characters (∼4.0%) in the ITS and 2 of 251 (∼1.0%) in the actin sequences. For pathogenicity tests, three seedlings of E. japonicus were used. The leaves for each tree were treated with 10 ml of a conidial suspension by spraying (1x10⁶ conidia ml-1 of the isolate, CDH059), while the three seedlings were treated with distilled water as control. After sprayed, the treated areas were sealed with plastic bags for a day to maintain humidity. Anthracnose symptoms identical to those observed in the field appeared seven days after inoculations, while no symptoms were observed in the control. Re-isolations were successfully achieved from the treatments, fulfilling Koch's postulates. Anthracnose associated with the provisionally novel species of Colletotrichum sp. on E. japonicus has not been recorded elsewhere, and in this regard, this is the first report of anthracnose caused by Colletotrichum sp. on E. japonicus in Korea. To effectively control the disease, more attention should be paid to the host range of the pathogen and other regions where the disease caused by the pathogen might occur in the country.

First report of Pseudomonas cichorii causing bacterial leaf blight of pocketbook plant (Calceolaria hybrida) in Taiwan

Pocketbook plants (Calceolaria spp.) are flowering ornamentals often grown as potted plants (Poesch 1937). In December 2022, leaf blight symptoms were observed on 2-mo-old plants of C. hybrida F1 'Dainty'. The disease was found in a nursery in Ren'ai Township, Nantou, and about 20% of the plants exhibited symptoms. Symptomatic plants had brown or gray necrotic lesions of different sizes and shapes, mostly around leaf margins. Lower leaf wilting was also observed (Fig. S1, A and B). Three plants were sampled. Leaf lesions were surface-disinfected with 75% ethanol and cut into smaller pieces in 10 mM MgCl2. After observing bacterial streaming under a microscope, the bacteria were streaked onto nutrient agar (NA). Following 2 days at 28°C, a type of round, creamy white colony predominated on all the plates. Three strains (Calc-A, Calc-B, and Calc-C) were obtained, one from each plant. The strains produced fluorescent pigments on King's B medium and were tested Gram-negative. The strains were characterized with the LOPAT scheme (Schaad et al. 2001). They did not exhibit activities of pectic enzymes, arginine dihydrolase and levan sucrase, but produced oxidase and induced the hypersensitive response in tobacco. DNA was extracted from the strains for PCR amplification of the 16S rDNA with primer pair 27f/1492r as described by Lane (1991). The 16S rDNA sequences were compared with entries in the GenBank database. The sequences obtained (GenBank accession no. OR824302) matched that of Pseudomonas cichorii MAFF 301158 (accession no. AB724288; 1,403/1,403 bp) and were 99% identical to that of DSM 50259T (accession no. CP074349; 1,391/1,405 bp). The strains were also tested with the species-specific primers hrp1a and hrp2a (Cottyn et al. 2011). The amplicons were sequenced and a BLASTn search showed that the sequences (accession no. OR827305) shared the highest identity (99.3%) with that of P. cichorii strain 83-1 (accession no. DQ168848; 848/854 bp) and were 97.3% identical to the sequence of DSM 50259T (accession no. CP074349; 831/854 bp). Calc-A was selected as a representative strain and deposited in the Bioresource Collection and Research Center, Taiwan (reference no. BCRC 81432). Koch's postulates were fulfilled by spray-inoculating a suspension of Calc-A on three 2-mo-old C. hybrida F1 'Dainty' plants. The inoculum was prepared by suspending NA-grown cells in 10 mM MgCl2 including 0.02% Silwet L-77 (OD600 = 0.3; 1.5 x 108 CFU/ml). For the controls, three plants were sprayed with bacteria-free solution. The plants were bagged throughout the experiment and kept in a growth chamber (14/10 h light/dark; 26/24°C day/night). Leaf blight and wilting symptoms developed on all leaves of the inoculated plants after 30 h, but not the controls (Fig. S1, C and D). The pathogen was reisolated from the treatment group, and colony PCR with hrp1a/hrp2a showed that the reisolated strain shared the same sequence with Calc-A to Calc-C. Repeating the inoculation assay produced consistent results. This is the first report of P. cichorii affecting Calceolaria in Taiwan. The bacterium has been reported infecting diverse crops in Taiwan, such as tomato and lettuce (Tsai et al. 2014). Expanding the understanding of the pathogen's potential hosts could help prevent its spread across important crops.

First report of Candidatus Phytoplasma australasia (16SrII- subgroup D) associated with virescence of Chia (Salvia hispanica L.) from India

Chia (Salvia hispanica L., Lamiaceae) is an important commercial and medicinal crop recently popularized in India and widely cultivated in Karnataka (Joy et al., 2022). During the field survey of chia crop diseases, characteristic virescence like symptoms were observed at Main Agricultural Research Station, UAS, Raichur as well as at Mysuru and HD Kote region. The incidence was ranged from 2 - 4 per cent in an area of 30 hectares. Typical symptoms associated with chia are malformed shoot and/or inflorescence axis with reduced floral parts with greenish florets. The stem axis become thick, flattened, leaves are reduced towards terminal region. A total of five phytoplasma suspected samples and five suspected healthy samples were used for identification purpose. The Plant Genomic DNA Miniprep Kit (Sigma Aldrich, USA) was used to extract the DNA from five symptomatic and five asymptomatic samples and the DNA was used as template to amplify the phytoplasma-specific 16S rDNA gene using P1/P7 primers (Deng and Hiruki, 1991; Schneider et al., 1995) followed by nested PCR using R16F2n/R16R2 primers (Gundersen and Lee 1996). The expected 1.25-kb amplicon was detected from the suspected symptomatic samples. Nested PCR products were purified and sequenced from both the directions using ABIX370 Genetic Analyzer (Applied Biosystems, Waltham, MA). The analysis revealed that all five sequences shared 100 per cent identity with Candidatus Phytoplasma aurantifolia (OM649850, ON975012) and Tomato big bud phytoplasma (EF193359). The in-silico RFLP pattern of F2n/R2 primed region of 16S rDNA gene analyzed by using iPhyClassifier (Zhao et al. 2009) revealed that the sequence shared 98.72 per cent nucleotide sequence similarity with coefficient value of 1.00 to the reference strain RFLP pattern of 16Sr group II, subgroup D (witches'-broom disease of lime; U15442). Based on 16SrDNA sequences and in-silico RFLP analysis, the phytoplasma associated with the chia virescence was identified as a member of 16SrII-D group. Further, SecA gene was also amplified from the samples using SecAfor1/SecArev3 primer pair (Hodgetts et al., 2008). All samples produced ~400 bp products and sequenced as detailed above. Sequence analysis by nBLAST revealed 100 per cent similarity to Ca. P. australasia (MW020545) and Ca. P. aurantifolia isolate Idukki Kerala 1 (MK726369) both representing 16SrII-D group phytoplasma. The representative sequence (16Sr: PP359693, PP359694; secA:PP386558, PP386559) were deposited in GenBank. Chia virescence phytoplasma belonging to Ca. phytoplasma australasia has not been reported anywhere. The phytopathological studies associated with chia crop are very limited. Joy et al. (2022) reported the occurrence of foot rot disease caused by Athelia rolfsii. Several hosts are recorded to be associated with 16SrII D phytoplasma which includes china aster, eggplant and crotalaria (Mahadevakumar et al., 2017, Yadav et al., 2016a, b). Now the wide occurrence of the phytoplasma in the area might have transmitted by vectors. The occurrence of virescence is of great importance as it affects the overall yield which reduces the market value. To our knowledge, this is the first report of a group 16SrII-D phytoplasma associated with chia virescence in India.

First Report of White Mold Caused by Sclerotinia sclerotiorum on Echeveria gigantea in Mexico

Echeveria gigantea, native of Mexico (Reyes et al. 2011), holds economic importance as it is marketed as a potted plant and cut flower due to its drought-tolerant capabilities and aesthetic appeal. In September 2023, a field sampling was conducted at the Research Center in Horticulture and Native Plants (18°55'56.6" N, 98°24'01.5" W) of UPAEP University. Echeveria gigantea cv. Quilpalli plants with white mold symptoms were found in an area of 0.5 ha, with an incidence of 40% and severity of 50% on severely affected stems. The symptoms included chlorosis of older foliage, necrosis at the base of the stem, and soft rot with abundant white to gray mycelium and abundant production of irregular sclerotia resulting in wilted plants. The fungus was isolated from 30 symptomatic plants. Sclerotia were collected, sterilized in 3% NaOCl, rinsed with sterile distilled water (SDW), and plated on Potato Dextrose Agar (PDA) with sterile forceps. Subsequently, a dissecting needle was used to place fragments of mycelium directly on PDA. Plates were incubated at 23 °C in darkness. A total of 30 isolates were obtained using the hyphal-tip method, one from each diseased plant (15 isolates from sclerotia and 15 from mycelium). After 6 days, colonies had fast-growing, dense, cottony-white aerial mycelium forming irregular sclerotia of 3.67 ± 1.13 mm (n=100). Each Petri dish produced 32.47 ± 7.5 sclerotia (n=30), after 12 days. The sclerotia were initially white and gradually turned black. The isolates were tentatively identified as Sclerotinia sclerotiorum based on morphological characteristics (Saharan and Mehta 2008). Two isolates were selected for molecular identification. Genomic DNA was extracted using the CTAB protocol. The ITS region and the glyceraldehyde 3-phosphate dehydrogenase (G3PDH) gene were sequenced for two randomly selected isolates (White et al. 1990; Staats et al. 2005). The ITS and G3PDH sequences of the SsEg9 isolate were deposited in GenBank (ITS-OR816006; G3PDH-OR879212). BLAST analysis of the partial ITS (510 bp) and G3PDH (915 bp) sequences showed 100% and 99.78% similarity to S. sclerotiorum isolates (GenBank: MT101751 and MW082601). Pathogenicity was confirmed by inoculating 30 120-day-old E. gigantea cv. Quilpalli plants grown in pots with sterile soil. Ten sclerotia were deposited at the base of the stem, 10 mm below the soil surface. As control treatment, SDW was applied to 10 plants. The plants were placed in a greenhouse at 23 °C and 90% relative humidity. After 16 days, all inoculated plants displayed symptoms similar to those observed in the field. Control plants did not display any symptoms. The fungus was reisolated from the inoculated stems, fulfilling Koch's postulates. The pathogenicity tests were repeated three times. Recently S. sclerotiorum has been reported causing white mold on cabbage in the state of Puebla, Mexico (Terrones-Salgado et al. 2023). To the best of our knowledge, this is the first report of S. sclerotiorum causing white mold on E. gigantea in Mexico. Information about diseases affecting this plant is very limited, so this research is crucial for designing integrated management strategies and preventing spread to other production areas.

First Report of Stem and Foliage Blight of Chrysanthemum morifolium cv. Fubaiju Caused by Stagonosporopsis chrysanthemi in China

Chrysanthemum (Chrysanthemum morifolium cv. Fubaiju) is used as medicinal herb (Chen et al. 2020). In October 2021, a leaf spot disease was observed on leaves of C. morifolium in Huanggang, Hubei province. Disease incidence was approximately 40%. Leaf lesions manifested as necrotic spots, coalesced, and expanded to form brown-black spots, leading to wilting of the leaves. On stems, the lesions manifested as dark brown necrotic spots. To identify the pathogen, 29 pieces (5 × 5 mm) from lesion margins were surface sterilized in 1% NaOCl and rinsed three times with sterile water. The pieces were transferred onto potato dextrose agar (PDA) for incubation at 25℃ for 3 d in the dark. Fifteen fungal colonies were successfully isolated. The colony morphology with flat wavy edge, sparse aerial mycelia, and surface olivaceous black were observed at 7 days post incubation. Subglobular pycnidia were brown with a short beak, and pycnidia diameters were thick (212 to 265 × 189 to 363 µm, n = 20). Ovoid conidia were aseptate and hyaline, conidia diameters were thick (4.0 to 9.8 × 1.8 to 4.7 µm, n = 100). The morphological characters of these isolates were consistent with those of Stagonosporopsis chrysanthemi (Zhao et al. 2021). Pure culture of representative HGNU2021-18 isolated from the diseased leaves subjected to molecular identification. Sequences of the rDNA internal transcribed spacer (ITS) region, 28S large subunit ribosomal RNA (LSU), β-tubulin (TUB2), actin (ACT), and partial RNA polymerase II largest subunit (RPB2) genes were amplified from genomic DNA of isolate HGNU2021-18 using the following primer pairs: ITS1/ITS4 (White et al. 1990), LR0R/LR5 (Rehner et al. 1994), Btub2Fd/Btub4Rd (Woudenberg et al. 2009), ACT512F/ACT783R (Carbone et al.1999), and RPB2-5F2 (Sung et al. 2007)/fRPB2-7cR (Liu et al. 1999), respectively. The PCR products were purified and then sequenced by Sangon Biotech (China). Nucleotide sequences of ITS (544 bp, OM346748), LSU (905 bp, OM758418), TUB2 (563 bp, OM945724), ACT (294 bp, OM793715), and RPB2 (957 bp, OM793716) amplified from the isolate HGNU2021-18 were subjected to BLASTn analysis. The results showed that ITS, LSU, TUB2, ACT, and RPB2 shared 100.00%, 99.45%, 99.20%, 100.00%, and 100.00% sequence identity to the five published sequences (MW810272.1, MH869953.1, MW815129.1, JN251973.1, and MT018012.1, respectively) of the S. chrysanthemi isolate CBS 500.63. Phylogenetic analysis of the multilocus sequences of ITS, LSU, RPB2, ACT, and TUB2 belonging to different Stagonosporopsis species was performed in MEGA 7.0 (Chen et al. 2015). Isolate HGNU2021-18 was placed in a clade with S. chrysanthemi with 99% bootstrap support. Thus, the results of morphological and molecular analyses indicated that the disease symptoms on chrysanthemum plants were caused by S. chrysanthemi. Under conditions of 25°C and 85% relative humidity, pathogenicity test was performed on 2-month-old healthy plants using isolate HGNU2021-18. The leaves were inoculated with 5 mm diameter mycelial plugs or with sterile agar plugs (control). Six plants were used in each treatment. Disease symptoms were observed on treated plants at 2 weeks post inoculation which were those previously observed in the field, while the control plants remained symptomless. The pathogen was re-isolated from the diseased plants, and S. chrysanthemi was confirmed as the causal pathogen. This is the first report of S. chrysanthemi causing stem and foliage blight of chrysanthemum in China.

First report of soybean root rot caused by Fusarium falciforme in the Republic of Korea

Phytopathogenic Fusarium species causing root and stem rot diseases in susceptible soybean (Glycine max (L.) Merrill) are a major threat to soybean production worldwide. Several Fusarium species have been reported to infect soybean plants in the Republic of Korea, including F. solani, F. oxysporum, F. fujikuroi, and F. graminearum (Cho et al., 2004; Choi et al., 2019; Kang et al., 2020). During the nationwide survey of soybean diseases in 2015, soybean plants showing symptoms of leaf chlorosis, wilting, and shoot death were found in soybean fields in Seosan, Chungnam. Fusarium isolates were obtained from the margins of sterilized necrotic symptomatic and asymptomatic regions of the stem tissues of diseased samples by culturing on potato dextrose agar (PDA). To examine the morphological characteristics, isolates were cultured on PDA at 25°C in the darkness for 10 days. Colonies produced white aerial mycelia with apricot pigments in the medium. Macroconidia were hyaline, slightly curved in shape with 3 or 4 septa, and their average length and width were 34.6± 0.56 μm (31.4 to 37.8 μm) and 4.7±0.16 μm (4.1 to 5.8 μm), respectively (n = 20). Microconidia were elongated, oval with 0 or 1 septum, and their average length and width were 11.4±0.87 and 5.2±0.32 μm, respectively (n = 20). The colonies and conidia exhibited morphological similarities to those of F. falciforme (Xu et al., 2022). Using the primers described by O'Donnell et al. (2008), identity of a representative strain '15-110' was further confirmed by sequencing portions of two genes, the translation elongation factor 1-alpha (EF-1α) and the second largest subunit of RNA polymerase II (RPB2). The two sequences (GenBank accession No. OQ992718 and OR060664) of 15-110 were 99% similar to those of two F. falciforme strains, 21BeanYC6-14 (GenBank accession nos. ON375419 and ON331931), and 21BeanYC6-16 (GenBank accession nos. ON697187 and ON331933). To test the pathogenicity, a single-spore isolate was cultured on carnation leaf agar (CLA) at 25℃ for 10 days. Pathogenicity test was performed by root-cutting assays using 14-day-old soybean seedlings of 'Daewon' and 'Taekwang'. Ten-day-old mycelia of 15-110 were collected from the CLA plates by scraping with distilled water, and the spore suspension was filtered and diluted to 1 × 106 conidia/mL. The roots of the soybean seedlings were partially cut and inoculated by soaking in the diluted spore suspension for two hours. The seedlings were then transplanted into 12 cm plastic pots (11 cm in height) and grown in a growth chamber at 25°C, 14h light/10h dark for 2 weeks. The infected plants exhibited wilting, observed brown discoloration on the root, and eventually died within 2 weeks, whereas the control plants inoculated with sterile water remained healthy. F. falciforme 15-110 was reisolated from infected plants, but not from the uninoculated controls. The morphology of the re-isolated fungus on PDA and its target gene sequences were identical to those of the original colony. To the best of our knowledge, this is the first report of root rot in soybean caused by F. falciforme in the Republic of Korea. Fusarium spp. induce a range of diseases in soybean plants, including root rot, damping-off, and wilt. Given the variable aggressiveness and susceptibility to fungicides among different Fusarium species, it is imperative to identify the Fusarium species posing a threat to soybean production. This understanding is crucial for developing a targeted and tailored disease management strategy to control Fusarium diseases.

Comparing RT-PCR of individual samples with high throughput sequencing of pooled plant samples for field-level surveillance of viruses in blackberry and wild Rubus

Blackberry production is increasing in the southeastern U.S. with the availability of new cultivars. In addition to high production costs, growers are challenged by virus diseases. Blackberry yellow vein disease (BVYD) significantly limits blackberry production. BYVD is associated with the crinivirus blackberry yellow vein-associated virus (BYVaV) in mixed infections with other viruses. The specific disease etiology and ecological factors underlying BYVD are not well understood and rely on the effective diagnosis of several viruses involved in the complex. In 2021, we collected samples from blackberry plants showing BYVD symptoms, asymptomatic blackberry plants, and wild Rosaceae spp. from nine farms across South Carolina, for a total of 372 individual plant samples. RNA from individual samples was isolated and pooled into sample groups (i.e., symptomatic, asymptomatic, and wild) from each farm for a total of 24 pooled samples. We sequenced the pooled RNA using Illumina and analyzed sequence profiles using the Virtool bioinformatics application. We also tested each plant for six viruses by RT-PCR or RT-qPCR and compared plant (PCR)-level and field (high throughput sequencing (HTS))-level data. Virtool detected 17 known viruses in the pooled samples, including 11 blackberry viruses. PCR testing was mostly consistent with HTS, with some notable disagreements for specific viruses. Our study demonstrates that HTS could be used as an efficient tool to detect viruses in bulked samples in blackberry fields, though limitations to using HTS for field-level surveillance are also discussed here.

Genetic Diversity Analysis of Anisogramma anomala in the Pacific Northwest and New Jersey

Anisogramma anomala, a biotrophic ascomycete, causes eastern filbert blight (EFB) of hazelnuts (Corylus spp.). EFB is endemic in eastern North America, preventing the commercial production of European hazelnut (C. avellana L.). In contrast, the historic absence of A. anomala in the Pacific Northwest (PNW) supported the development of a robust hazelnut industry. Circa 1960, A. anomala was inadvertently introduced into southwestern Washington causing orchard devastation. Distribution of the pathogen in the PNW has been hypothesized to be the result of a single-point introduction. This study aimed to investigate the single-point introduction hypothesis of A. anomala by comparing the genetic diversity of A. anomala samples from the PNW and New Jersey (NJ). Specimens from the main PNW production region [n=60] and an area within the pathogen's native range, NJ [n=151], were genotyped using 15 simple sequence repeat (SSR) markers. The following were used to assess genetic diversity and population structure: allelic summary statistics, discriminant analysis of principal components, network median-joining tree, analysis of multilocus genotypes, and allelic population diversity analysis. Analyses separated the samples into one cluster containing all the PNW isolates, and five clusters of NJ isolates. The PNW samples were nearly genetically uniform, and the NJ isolates were diverse. These findings support the hypothesis that A. anomala in the PNW was derived from a single-point introduction and corroborate previous studies that have shown A. anomala is very diverse in NJ. This indicates that maintaining restrictions on the movement of Corylus into the PNW is important to prevent the introduction of new populations of A. anomala, thus protecting the PNW hazelnut industry.

First Report of Anthracnose Caused by Colletotrichum siamense on Machilus thunbergii Siebold & Zucc. in South Korea

Machilus thunbergii Siebold & Zucc., known as Japanese bay tree, is an evergreen tree distributed widely in East Asia, including South Korea, where the species is of ecological importance. Machilus thunbergii provides habitat for wildlife species and is a common urban tree. In September 2022, anthracnose symptoms on leaves were observed in Jeju (33°26'02.4"N, 126°19'48.8"E) and Tongyeong (34°49'27.1"N, 128°24'01.8"E) in South Korea. Disease incidence on leaves of each affected tree, naturally growing in an urban forest area covering approximately 0.5 ha was approximately ~ 70 % in each study area. Anthracnose symptoms that were observed on 70 to 80% leaves per tree in each study area included orbicular or irregular, whitish-grey spots on leaves that were 1.5 to 3.0 cm in diam. In some cases where leaves were severely affected, larger blotches were formed, leading to bleaching symptoms and eventually defoliation. For pathogen isolation, two or three leaves showing anthracnose symptoms from each of the 15 trees were randomly selected and brought to the laboratory. Fungal isolations were then directly made by transferring spores from acervuli that developed on diseased leaves onto potato dextrose agar (PDA) media. Cushion shaped acervuli filled with salmon to orange-colored conidial masses were produced on media approximately two weeks after the incubation at 25 ± 1°C with a photoperiod of 12 h. Conidia were single celled, hyaline, cylindrical with rounded ends, smooth walls, 13.7 to 18.1 μm long and 3.1 to 4.5 μm wide (n=30). Among 15 cultures that were successfully isolated, 10 isolates were retained based on culture characteristics, and two randomly selected monoconidial cultures were deposited in the culture collection (CDH) of the Chungnam National University, Republic of Korea (Accession No. CDH057-58). Two isolates selected, CDH057 and CDH058, were subjected to identification, and this was achieved based on multiplesequence comparisons using on internal transcribed spacer regions of rDNA (ITS1 and ITS2), partial sequences of actin (ACT) and β-tubulin (TUB2) gene regions amplified using ITS1F / ITS4, ACT-512F / ACT-783R and T1 / Bt2b, respectively (Weir et al. 2012). The representative sequence data were deposited in GenBank under the accession numbers OR473277 and OR473278 for the ITS, OR480772 and OR480773 for ACT, and OR480774 and OR480775 for TUB2. The resulting sequences were further used for a phylogenetic analysis based on the maximum likelihood method using a concatenated dataset of the ITS, ACT and TUB2 gene sequences for Colletotrichum species in the C. gloeosporioides clade. The results showed that the pathogen isolated in this study clustered with Colletotrichum siamense (Vouchered specimens: MFLU 090230, COUFPI291, and COUFPI294) (Prihastuti et al. 2009). Sequence comparisons revealed that the isolates obtained in this study differed from the type species of C. siamense (MFLU 090230; FJ972613 for ITS, FJ 907423 for ACT, FJ907438 for TUB2) at 2 of 258 bp (∼0.8%) and 6 of 387 bp (∼1.6%) in the ACT and TUB2 sequences, respectively, while the ITS was identical to the type species. For pathogenicity tests, a total of ten three-year-old seedlings of M. thunbergii were used. The leaves of each tree were sprayed with 5 ml of conidial suspension (105 conidia/ml, isolate CDH057). Three control plants were sprayed with sterile water. After being sprayed, treated areas were sealed with a plastic bag for 24 hours to preserve humidity. Anthracnose symptoms, identical to those observed in the field, appeared five to seven days after the inoculations, while no symptoms were observed on control plants. The isolates used in the pathogenicity test were reisolated from 90% of lesions, and their identity was confirmed based on sequence comparisons, thus fulfilling Koch's postulates. Species of the C. gloeosporioides species complex include important plant pathogens, particularly C. siamense, which cause significant losses of economic and ecological relevance on a wide range of hosts (~ 100 hosts) (Talhinhas and Baroncelli 2021). Although C. fioriniae in the C. acutatum species complex, was found on M. thunbergii in South Korea (Thao et al. 2023), anthracnose associated with C. siamense on M. thunbergii has not been reported in the country. In this regard, this is the first report of anthracnose caused by C. siamense on M. thunbergii in South Korea. To effectively control the disease, more attention should be paid on the host range of the pathogen and other regions where the disease caused by the pathogen might occur in the country.

Southern blight of water lily: The first host record of Agroathelia rolfsii on Nelumbo nucifera discovered in Florida, USA

Nelumbo nucifera Gaertn. (Nelumbonaceae, Eudicots), also known as water lily or sacred lotus, is a nonnative and invasive plant commonly found in artificial ponds and natural lakes throughout Florida (UF-IFAS 2023; Wunderlin et al. 2023). In August 2020, a single sample of water lily plants showing large leaf spots were collected at a residence in Dunnellon, Marion County, Florida (80% disease prevalence with 40% leaf coverage). Symptoms and signs of the disease were necrotized adaxial leaf spots only, bordered by whitish mycelia and hyphae with clamp connections, and whitish to light brown sclerotia formed in the center (<0.7 mm diameter). Symptomatic tissue was plated on acid potato dextrose agar (APDA) amended with chloramphenicol (100 mg/L) and ampicillin (30mg/L), and incubated at 20 °C for one week. Data supporting the molecular identification of this putative pathogen were gathered by PCR amplification and Sanger sequencing of the complete internal transcribed spacer (ITS) and a fragment of the large subunit (LSU) of the rRNA gene (~1.5 kb) using primers ITS1F and LR5 (FDACS-DPI PPST 2020-105211, GenBank OR492009) (White et al. 1990). The identification of the host was confirmed by Sanger sequencing of three plant barcode fragments: ITS2 (ITS2-S2F/ITS4, OR492008), ribulose 1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) (rbcLa-F/rbcLa-R, GenBank OR502388), and Maturase K (matK) (matK-KIM1R/matK-KIM3F, GenBank OR502389) (Fazekas et al. 2012). MegaBLAST queries of the ITS/LSU sequence obtained here recovered a 99.61% match to the fungal pathogen Agroathelia (=Athelia) rolfsii (Sacc.) Redhead & Mullineux. (Redhead and Mullineux 2023) (Amylocorticiaceae, Agaricomycotina) strain GP3 (GenBank JABRWF010000005) (Yan et al. 2021). MegaBLAST queries of three host plant DNA barcodes recovered matches of greater than 99.62% similarity to N. nucifera sequences. After diagnosis, symptomatic dried leaf samples were deposited at Plant Industry Herbarium Gainesville (PIHG 17807) and an axenic culture was deposited at the Agricultural Research Services Culture Collection (NRRL 66964). Koch's postulates were fulfilled by the inoculation of sclerotia (as in Terrones-Salgado et al. 2022) on adaxial leaf surface of four-week- old water lily transplants obtained from an artificial pond on campus (two plants with five leaves each). One additional transplant was not inoculated and served as a control; this plant remained asymptomatic during the experimentation period. Each transplant was kept in a 27-gallon plastic container (21W × 30L × 14H in) filled with tap water containing one tablespoon of 20-20-20 all-purpose-water-soluble plant fertilizer (VPG, TX, USA) in a plant biosafety level 2 greenhouse (23 °C, >50% relative humidity, and a 12-h/12-h photoperiod). All inoculated leaves showed necrotized areas after one week and new sclerotia were observed floating on the water surface after three weeks. Fungal pathogen was reisolated and reidentified subsequently. Agroathelia rolfsii is the causal agent of southern blight, also known as grey rot, and is reported from at least in 260 plant genera, including specialty crops such as citrus, cucumber, pepper, peanuts, pumpkin, and strawberry (Farr and Rossman 2018). Agroathelia rolfsii usually causes lower stem, crown, and root rots; consequently, leaf spots are a noteworthy presentation of symptoms for this fungus.

First Report of the Rust Fungus Melampsora ferrinii on Salix babylonica in China and a New Spermogonial and Aecial Host, Corydalis bungeana

The occurrence of rust fungi on Corydalis bungeana Turcz. and Salix babylonica L. were found in same area of Hebei Province, China from 2022 to 2023. The life cycle connection of these rust fungi was suspected because Peng et al. (2022) reported the life cycle of Melampsora ferrinii Toome & Aime by inoculations, producing spermogonia and aecia on Corydalis species, and uredinia on S. babylonica. The morphology of the uredinial and telial stages on S. babylonica collected in the field was identical with the description of M. ferrinii by Toome and Aime (2015), and its identity was confirmed by phylogenetic analyses using the method of Ji et al. (2020) (LSU-PP087777, ITS-PP091274; Similarity with M. ferrinii: LSU-100%, ITS-99.85%). To confirm the life cycle of this rust fungus, inoculations were conducted on C. bungeana with basidiospores obtained from the teliospores on fallen leaves of Salix babylonica. The fallen leaves producing basidiospores were cut into small pieces (ca. 5 mm2) and placed on healthy leaves of C. bungeana. The inoculated plants were kept in a moist plastic box in darkness at 15-20℃ for 2 days and then transferred to the floor near windows at about 15-20℃ for observations. Ten days after inoculations small yellow spots of spermogonia appeared on the upper surface of the leaves of C. bungeana. About 7 days later, pale yellow aecia with aeciospores were produced mainly on the under surface of the leaves and petioles. The morphology of rust fungus on C. bungeana collected from the fields and obtained by inoculations was identical with the description by Peng et al. (2022). Phylogenetic analyses also showed that a specimen on C. bungeana collected from the field (LSU-OR607838, ITS-OR612063) were included into the same clade of M. ferrinii (Similarity: LSU-100 %, ITS-99.85). Based on morphology, inoculations and DNA sequence analyses, the rust fungi on C. bungeana and S. babylonica are identified as different stages of life cycle of M. ferrinii. This rust fungus has been reported to produce spermogonia and aecia on C. acuminata Franch., C. edulis Maxim. and C. racemosa (Thunb.) Pers. in China (Peng et al. 2022), and uredinia and telia on S. babylonica in USA, Argentina and Iran (Toome and Aime 2015, Abbasi et al. 2024), and on Salix sp. in Chile (Zapata 2016). Therefore, C. bungeana is a new host for M. ferrinii, and its field occurrence on S. babylonica is reported for the first time in China although Peng et al. (2022) reported successful results in its inoculations to S. babylonica in China. This report contributes to the control of rust diseases caused by this species. Specimens used in this experiment were deposited in the Fungal Herbarium of the Jilin Agricultural University, Changchun, China (HMJAU) and sequences newly analyzed were deposited in GenBank.

Aggressive Alternaria brassicicola with reduced fungicide sensitivity can be associated with naturally infested broccoli seeds

Alternaria brassicicola is a part of Alternaria complex that causes leaf blight and head rot (ABHR) in brassica crops. Infested broccoli seeds can play an important role in introducing A. brassicicola in transplant houses and production fields. However, characterization of natural seed infestation and seed-to-seedling transmission of A. brassicicola in broccoli is yet to be demonstrated. In this research we characterized Alternaria spp. isolates from commercial broccoli seedlots for their species identity, pathogenicity and aggressiveness on broccoli and their sensitivity to Quinone-outside inhibitor (QoI) fungicide (azoxystrobin). Two hundred commercial seedlots from two broccoli cultivars; Cultivar 1 (EC; n=100 seedlots) and Cultivar 2 (ED; n=100 seedlots) were evaluated for the presence of A. brassicicola under in-vitro conditions using a seedling grow-out assay. Alternaria spp. was detected in 31 and 28% of the commercial seedlots of Cultivar 1 and Cultivar 2, respectively. The seed-to-seedling transmission (%) varied considerably within each positive infested seedlot, which ranged from 1.3 to 17.3%. Subsequent molecular identification of single spore cultures (n=138) was made by sequencing four housekeeping genes; actin, the major allergen (Alta1), plasma membrane ATPase and Glyceraldehyde-3-phosphate dehydrogenase (GPD), and later the sequences were concatenated and compared for the phylogenetic distance with diverse Alternaria species. Ninety-six percent (n=133) of the isolates formed a cluster with a known A. brassicicola based on multigene phylogeny, which were later confirmed as A. brassicicola using a species-specific PCR assay. One hundred percent of the A. brassicicola seed isolates (n=133) were either highly- or moderately- aggressive on broccoli (cv. Emerald Crown) based on a detached leaf assay. Sensitivity of representative A. brassicicola isolates (n=58) to azoxystrobin was evaluated using a spore germination assay and the EC50 values (effective fungicide concentration (ppm) at which germination of conidia of isolates were reduced by 50% compared to control) for each isolate was determined. A. brassicicola isolates from naturally infested commercial broccoli seeds were sensitive to azoxystrobin with considerably low EC50 values in the range of <0.0001 ppm to 0.33 ppm; however, there were a few isolates (14%), which showed 100-fold reduced sensitivity from the most sensitive isolate (EC50 =0.0001 ppm). Our results confirm that commercial broccoli seedlots can be naturally contaminated with pathogenic and aggressive A. brassicicola. We also provide evidence for potential presence of A. brassicicola isolates with reduced azoxystrobin-sensitivity in naturally infested commercial broccoli seedlots, which has never been reported before. Together, these findings may have implications in considerations for seed-health testing, seed treatments and greenhouse scouting to limit introduction of infested seedlots in commercial broccoli fields.

Spongospora subterranea f. sp. subterranea (Sss) affects plant susceptibility to subsequent pathogen infections under controlled environment conditions

Spongospora subterranea f. sp. subterranea (Sss) is a soilborne potato pathogen responsible for causing powdery scab on tubers and galls on roots, reducing root water uptake through colonizing root hairs, and vectoring of Potato mop-top virus (PMTV). However, effects of Sss on overall plant susceptibilities against subsequent infections of potato pathogens above ground have not been previously reported. This study aimed to investigate the effects of Sss on root and tuber disease expression, yield, and susceptibilities to subsequent late blight and white mold infections across six potato varieties. Sss-infected Silverton plants had 28.3% less total tuber yield and 29% fewer tubers compared to non-infected Silverton plants. We did not find a correlation across the varieties between root colonization and root gall formation. Sss-infected Silverton plants were more susceptible to hemibiotrophic late blight and less susceptible to necrotrophic white mold. Sss infection also increased susceptibilities of Goldrush and Atlantic plants to white mold. We also evaluated prevalence of asymptomatic Sss infections across the six varieties. Between 50% to 92% of the asymptomatic tubers tested positive for Sss DNA, depending on the variety. Further research is required to understand the possibility and extent of these asymptomatic infections to the spread of Sss in the field. These findings highlight the complexity of Sss-host interactions and gives precedence that the lack of disease expression does not necessarily indicate resistance of a variety to Sss.

Fungicide sensitivity of Phytophthora isolates from the Washington red raspberry industry

Phytophthora rubi is an important pathogen causing Phytophthora root rot of red raspberries worldwide. Management of this disease is partially achieved with fungicides, but efficacy has been low and growers are concerned about fungicide resistance. To determine whether fungicide resistance is developing, Phytophthora species were isolated from 26 raspberry fields with root rot, identified, and evaluated for sensitivity to four fungicides: mefenoxam, phosphorous acid, oxathiapiprolin, and dimethomorph. The majority of the recovered 152 Phytophthora isolates were P. rubi (143 isolates, 25 fields), with P. megasperma (8 isolates, 2 fields) and P. gonapodyides (1 isolate, 1 field) being found much less frequently. These results confirm P. rubi as the dominant species affecting the Washington red raspberry industry. Almost all tested isolates were sensitive to all four fungicide chemistries, although three isolates were less sensitive to mefenoxam with EC50 values ranging from 3.53 to 100 µg ai/ml. No resistance was detected against current fungicide label rates. However, other reasons were identified for why fungicides have been ineffective. Label rates vary widely by brand and most fungicides are applied in the fall when P. rubi is inactive. In addition, some phosphorous acid products are only labeled for foliar applications, which have been shown to be less effective than soil applications in other agricultural systems. Efficacy trials are needed to compare foliar and soil fungicide applications at different times of the year for their ability to control Phytophthora root rot in red raspberry production fields.

Biological Control of Rapeseed Clubroot (Plasmodiophora brassicae) using the Endophytic Fungus Didymella macrostoma P2

Didymella macrostoma P2 was isolated from rapeseed (Brassica napus), and it is an endophyte of rapeseed and an antagonist of three rapeseed pathogens, Botrytis cinerea, Leptosphaeria biglobosa and Sclerotinia sclerotiorum. However, whether or not P2 has a suppressive effect on infection of rapeseed by the clubroot pathogen Plasmodiophora brassicae remains unknown. This study was conducted to detect production of antimicrobials by P2 and to determine efficacy of the antimicrobials and P2 pycnidiospores in suppression of rapeseed clubroot. Results showed that cultural filtrates (CF) of P2 in potato dextrose broth and the substances in pycnidiospore mucilages exuded from P2 pycnidia were inhibitory to P. brassicae. In the indoor experiment, seeds of the susceptible rapeseed cultivar Zhongshuang No.9 treated with P2 CF and the P2 spore suspension (P2 SS, 1 × 107 spores/ml) reduced clubroot severity by 31% to 70% on the 30-day-old seedlings compared to the control (seeds treated with water). P2 was re-isolated from the roots of the seedlings in the treatment of P2 SS, the average isolation frequency in the healthy roots (26%) was much higher than that (5%) in the diseased roots. In the field experiment, seeds of another susceptible rapeseed cultivar Huayouza 50 (HYZ50) treated with P2 CF, P2 CE (chloroform extract of P2 CF, 30 µg/ml) and P2 SS reduced clubroot severity by 29% to 48% on 60-day-old seedlings and by 28% to 59% on adult plants (220 days old) compared to the control treatment. The three P2 treatments on HYZ50 produced significantly (P < 0.05) higher seed yield than the control treatment on this rapeseed cultivar, and they even generated seed yield similar to that produced by the resistant rapeseed cultivar Shengguang 165R in one of the two seasons. These results suggest that D. macrostoma P2 is an effective biocontrol agent against rapeseed clubroot.

Prevalence of FRAC group 11 fungicide resistance in Stemphylium vesicarium isolates, but not S. beticola isolates, causing Stemphylium leaf spot of spinach (Spinacia oleracea)

Stemphylium leaf spot of spinach, caused by Stemphylium beticola and S. vesicarium, is a disease of economic importance in fresh market, processing, and seed production. There have been increasing reports of difficulty managing the disease in the southern United States using fungicides in Fungicide Resistance Action Committee (FRAC) group 11. Isolates of S. beticola and S. vesicarium from spinach leaves and seed from 2001 to 2020 were screened for resistance to azoxystrobin and pyraclostrobin in vitro, in vivo, and using PCR assays to detect mutations in cytochrome b associated with resistance in other fungi (F129L, G137R, and G143A). EC50 values for mycelial growth and conidial germination of S. beticola isolates in vitro were significantly lower (mean of 0.35 μg/ml) than that of S. vesicarium (mean of 14.17 μg/ml) with both fungicides. All isolates were slightly more sensitive to pyraclostrobin than azoxystrobin in both assays. In vivo assays of plants inoculated with the isolates of S. vesicarium demonstrated poor efficacy of fungicides with each of the two active ingredients. Only the G143A mutation was detected of the three mutations. The mutation was detected in all spinach isolates of S. vesicarium, including an isolate of S. vesicarium collected in 2003, and 82.9% of isolates from spinach seed lots harvested from crops grown in or after 2017 in Europe, New Zealand, and the United States. The in vitro, in vivo, and DNA mutation assays suggest FRAC group 11 fungicide resistance is widespread in spinach isolates of S. vesicarium, but not S. beticola.

First Report of Lingonberry Stunted Yellows Disease of Vaccinium vitis-idaea L. associated with 'Candidatus Phytoplasma trifolii'-Related Phytoplasma Strain in Lithuania

Lingonberries (Vaccinium vitis-idaea L.) are low-growing, evergreen shrubs of cooler, northern regions of North America and Europe. These plants produce berries that are unique in flavor, bear high economic significance, and play a vital role in maintaining the diversity of the northern ecosystems (Kowalska, 2021). In October 2023 diseased plants of lingonberry were discovered in Labanoras Forest (55°14'N 25°42'E) (Lithuania). The plants expressed symptoms of stunting, yellowing, little leaf, shortened internodes, and stem distortions. Samples (leaves) were collected and tested from ten asymptomatic and ten symptomatic lingonberry plants. Total genomic DNAs of all samples were extracted by a CTAB protocol. Extracted DNAs were used as a template in direct and nested PCRs using the universal primer pairs P1/P7 and R16F2n/R2, respectively, to amplify phytoplasma 16S rRNA gene 1.2 kb fragments (Lee et al. 1998). The primer pairs SecAFor1/SecARev3 and SecAFor2/SecARev3 were used in direct and semi-nested PCRs, respectively, to amplify phytoplasma secA genes 0.5 kb fragment (Dickinson and Hodgetts, 2013). PCR amplicons of the 16S rRNA and secA genes specific for the phytoplasmas were only obtained from all sampled symptomatic plants. Three R16F2n/R2 and three SecAFor2/SecARev3 amplicons were cloned and submitted for Sanger sequencing (Nature Research Centre, Vilnius, Lithuania by 3500 Genetic Analyser). The three 16S rDNAs as well as the three secA gene fragments were identical. The BLAST analysis (NCBI) of the obtained sequences showed a similarity percentage, ranging from 99.75% to 100% (1247-1250 bp from 1250 bp) for 16SrRNA, and 98.13% to 99,15% (473-478 bp from 482 bp) for secA amplicons, with numerous strains of 'Candidatus (Ca.) Phytoplasma (P.) trifolii' (first hit MT674293 and KR906724, respectively). Additionally, 16S rDNA sequences by using iPhyClassifier were used to create virtual RFLP pattern (Zhao et al. 2009). The generated pattern was identical (similarity coefficient 1.00) to the reference pattern of 16Sr group VI, subgroup A. The phytoplasma strain detected in lingonberries was designated as lingonberry stunted yellows, LingbSY. Furthermore, the enzymatic RFLP analysis was performed with the 14 restriction enzymes (Lee et al., 1998), and obtained profiles were compared with virtually generated using iPhyClassifier. This yielded the same classification of detected phytoplasma to the 16SrVI-A phytoplasma subgroup. The phylogenetic analysis of both marker gene sequences revealed the same LingbSY phytoplasma classification. Selected sequences were deposited in GenBank (NCBI) with Accession No: PP237769 (16S rRNA gene) and No: PP238489 (secA gene). Phytoplasmas of 16SrI phytoplasma group were identified in lingonberries in Canada (Brochu et al. 2022). Strains of 16SrVI phytoplasma group were reported in Vaccinium myrtillus in Austria (Fernandez et al. 2007). This is the first report of 'Ca. P. trifolii' strain belonging to 16SrVI-A phytoplasma subgroup infecting lingonberry worldwide. Also, this is the first report of 16SrVI phytoplasma group in Lithuania. The presence of this phytoplasma poses a threat to the natural ecosystem and could eventually spread into agricultural settings in our country. Therefore, it's crucial to conduct surveillance for insect vectors, and assess effective control methods. Without proactive action, long term sustainability of lingonberries and their ecosystems may be jeopardized.

First report of Cryptostroma corticale causing sooty bark disease in California and first worldwide report of silver maple as a host

In November 2022 and February 2023, CAL FIRE tree health experts examined four maples (Acer spp.) planted decades earlier in a residential setting in Elk Grove, Sacramento Co., California (USA). Three of the trees were silver maples (Acer saccharinum ) and one was a Norway maple (A. platanoides); both species are exotic to California. The trees were in an irreversible state of decline, with the canopy substantially thinned and browning. Extensive bark cankers elongating longitudinally along the stem were visible on all trees (Fig. S1). Cankers were filled by fungal stromata protruding through the bark and producing masses of elliptical dark brown conidia (Fig. S2), approximately 5.5 x 3.7 um in size, giving the cankers a sooty appearance. The cankered bark could be peeled off easily, revealing dark and discrete lesions in the phloem and xylem. Samples from the three trees were shipped to the U.C. Berkeley Forest Pathology and Mycology Laboratory and to the CDFA PPDC in Sacramento, CA. In the laboratories, small wood chips were taken from the margins of the lesions, surface sterilized by dipping them for 30 seconds in 70% Ethanol, rinsed for 30 seconds in sterile water and plated onto 2.5% Malt Extract Agar amended with 0.3g/L Streptomycin or onto one-half strength acidified potato dextrose agar (APDA). Two morphologically identical cultures were obtained, one (T2) from a silver maple and one (T6) from the Norway maple. Cultures were then grown in liquid 2.5% malt extract broth and, after one week, DNA was extracted using the Qiagen Plant DNeasy DNA extraction kit. The ITS sequences are diagnostic for this fungus (Li et al. 2021) and those of the two cultures (GB OR064033 and OR933565) were 100% homologous to GenBank sequences of Cryptostroma corticale ( e.g. GB OP474010-11). The RPB2 sequence of T2 ( GB OR992132) was 100% homologous to that of C. corticale (GB HG934116.1). The isolate obtained from silver maple was inoculated in four potted silver maples by removing a bark disk 50 mm in diameter with a cork borer in three spots staggered at different heights and sides on the stem, placing a colonized agar plug of C. corticale in contact with the phloem, replacing the bark disk and wrapping with parafilm. Two control trees were mock inoculated using sterile agar plugs. Trees were in 57 L pots, had an average stem caliper of 2.7 cm, an average height of 3.5 m and were kept in a lath house at average high temperatures of 18-24 degrees C. After ten weeks, average lesion length was 15.4 cm (SE= 4.6) and 4.3 cm (SE=2.3) in the fungus-inoculated and control trees, respectively. An ANOVA test, nesting lesions sizes within tree, determined lesions lengths were different between inoculated and mock trees (P= 0.04). The fungus was reisolated from all points in all inoculated trees but never from control trees. C. corticale was first described in the UK from sycamore maple (Acer pseudoplatanus) (Gregory et al. 1949) and is an emerging problem in Europe (Muller et al. 2023). In North America, it has been reported from A. negundo, A. campestre, A. macrophyllum and Cornus nuttallii (Worral 2020), and it appears to be present in the Pacific Northwest (Brooks et al. 2023, Goree 1969). Norway maple is included in the European Plant Protection Organization list of hosts for C. corticale (EPPO 2023), however our finding of C. corticale on silver maple is a first report of this host worldwide and of this pathogen in California. This report is noteworthy, given that C. corticale is also a human pathogen infecting the respiratory system (Braun et al. 2021).

Elaborate Report of Allium sativum Clove Brown Rot Caused by Fusarium solani in China

In September 2023, brown rot disease was observed on cloves of garlic (Allium sativum) variety "Zipi-1" (purple skin) collected from Jinxiang County, China during scientific research at the Beijing Academy of Agricultural and Forestry Sciences after being planted in nutrient soil for approximately 2 weeks in a growth chamber maintaining 22℃, 60% relative humidity, and 16 hours of light. Out of the 90 garlic cloves investigated, 18 showed signs of decay, characterized by a brown color and rot, with the surface covered in blue and white mold layers. Six symptomatic cloves were collected for isolating the pathogen using the method described in a previous study (Wu et al. 2021). After 2 d of incubation, individual spores were harvested from the fungal colonies and recultured. Single-spore cultures growing on PDA medium appeared white and flocculent when viewed from the top, and yellowish-brown when viewed from the bottom. After 5 d of cultivation, the colonies had a diameter of approximately 5.8 cm and microscopic examination revealed that the mycelium had a diameter of about 9-13 µm (Fig. S1a, b and c). Isolate As1 produced three types of spores: oval-shaped chlamydospores with a diameter of approximately 6 µm, while spindle-shaped microconidia and sickle-shaped macroconidia measuring approximately 6-7 × 20-30 µm and 8 × 50 µm, respectively (Fig. S1d and e). The mycelial characteristics and reproductive structures of the isolates fit the morphological description of Fusarium solani (Xie et al. 2022). To confirm the identification, TEF1, RPB1 and RPB2 regions of the genome were amplified from three separate isolates (As1, As2, and As3) using EF1/EF2, RPB1-Fa/G2R, RPB2-5F2/7cR, and RPB2-7cF/11aR primer pairs (O'Donnell et al. 2022). The results indicated that the sequences of the three isolates were completely identical. Furthermore, the BLASTn comparison results of the TEF1 (OR916018, 710bp, 100%), RPB1 (OR916019, 1797bp, 99.8%), and RPB2 (OR916020, 1874bp, 100%) sequences in the FUSARIUM-ID v.3.0 database revealed that As1 was identified as F. solani species complex 5 (O'Donnell et al. 2022). To assess the pathogenicity of As1, the surface of healthy garlic cloves (n = 30) was spread with 106 microconidia/mL As1 suspension, while a control group (n = 30) was inoculated with sterile water. All inoculated cloves were placed in an artificial climate chamber under same conditions described above. After 10 d, all inoculated cloves exhibited rot symptoms consistent with those of the initially infected cloves identified in September 2023, while the control plant cloves remained asymptomatic (Fig. S2). Based on morphological and molecular characters (TEF1, RPB1, and RPB2), the reisolated pathogen from diseased plants was identical to the As1 isolate used for inoculation, and the disease assays were repeated twice. Fusarium spp. has been reported as the causal agent of garlic rot disease in several countries such as Mexico, America, and Russia (Gálvez and Palmero 2022). Tai (1979) previously published a report on the presence of F. solani in garlic; however, the content in the book is rather basic, lacking detailed information on the isolation, identification, and the potential for causing garlic diseases, whether postharvest or during growth. Our research can be considered a supplement and improvement to the study by Tai (1979) and lays the groundwork for future studies on management strategies to combat plant diseases caused by F. solani.

First report of Cassava Bacterial Blight caused by Xanthomonas phaseoli pv. manihotis in the Amazonian forest of Ecuador

Xanthomonas phaseoli pv. manihotis (Xpm) is a plant pathogenic bacterium known as the causal agent of cassava bacterial blight (CBB). CBB is the most limiting bacterial disease affecting cassava (Manihot esculenta Crantz), characterized by diverse symptoms including angular water-soaked leaf lesions, blight, wilting, stem exudates, stem cankers and dieback. CBB has been reported in most cassava-growing regions around the world, and, under conducive conditions, crop yield losses can reach up to 100% (Zárate-Chaves et al. 2021). While Xpm genetic diversity is remarkably high in South America (Bart et al. 2012) and cassava originates and was domesticated in the Amazon basin (Allem 2002), reports of CBB in the Amazonian region are missing. To fill this gap, in October 2018 we surveyed for CBB symptoms in cassava fields of the Orellana Province, located in the Amazon forest of the Republic of Ecuador. Adult cassava plants exhibiting typical angular, water-soaked leaf lesions were found in polyculture plots, i.e. intercrops of cassava with other species such as plantains and fruit trees (a.k.a. chakras). After surface disinfection with 5% sodium hypochlorite followed by 70% ethanol, white Xpm-like colonies were isolated from diseased leaf tissues of four plants on YPGA medium (yeast extract, 5 g/l; peptone, 5 g/l; glucose, 5 g/l; agar-agar, 15 g/l) supplemented with cephalexin (40 mg/l) and cycloheximide (50 mg/l). Pathogenicity tests were performed on peat-potted, 2-month-old cassava plants of the cultivar 60444. Bacterial suspensions were adjusted to an OD600 of 0.2 (2 × 108 CFU/ml) in sterile 10-mM MgCl2 and syringe infiltrated in fully-expanded leaves. In parallel, 20 µl of each bacterial suspension adjusted to an OD600 of 0.02 (2 × 107 CFU/ml) were inoculated on stems inside a hole previously punched with a sterile needle in the junction of the third-top petiole. Sterile 10-mM MgCl2 was used for mock inoculations in both leaves and stems, and experiments were replicated in three plants. Plants were incubated in a greenhouse at 28 ± 1°C with a 12-h photoperiod. Infiltrated leaves developed watersoaking 3 days post inoculation, while wilted leaves, stem exudates, and dieback were observed 21 days after stem inoculation. Control plants remained symptomless. White Xpm-like colonies were re-isolated from symptomatic leaves (Fig S1). One colony of each of the four Xpm isolates (before and after re-isolation) was assessed using diagnostic PCRs (Bernal-Galeano et al. 2018; Flores et al. 2019), using strain Xam668 as positive control. All four candidates were positive for both diagnostic tools. The sequences of the housekeeping genes atpD, dnaK, efp, glnA, gyrB and rpoD of our isolates were extracted from full genome sequences obtained through Oxford Nanopore Technologies (ONT) (GenBank OR288194 to OR288217) and compared to their homologs in four close Xanthomonas species and a reference Xpm strain (Table S1). The sequences of the tested strains aligned with that of Xpm CIO151 (GCA_004025275.1) (Arrieta-Ortiz et al. 2013) with nucleotide identity above 99.92% (Fig S2). The four strains were named CIX4169, CIX4170, CIX4171 and CIX4172, stored in the IRD Collection of Xanthomonas, where they are available upon request. To our knowledge, this is the first report of CBB in the Amazonian region and in Ecuador, where cassava is a central element for local culture and economy. Further surveys will be necessary to evaluate the distribution and prevalence of CBB in other ecozones of Ecuador where cassava is cultivated.