Coniella vitis sp. nov. Is the Common Pathogen of White Rot in Chinese Vineyards

The cysteine-rich receptor-like kinase CRK10 targeted by Coniella diplodiella effector CdE1 contributes to white rot resistance in grapevine

Grape white rot is a devastating fungal disease caused by Coniella diplodiella. The pathogen delivers effectors into the host cell that target crucial immune components to facilitate its infection. Here, we examined a secreted effector of C. diplodiella, known as CdE1, which has been found to inhibit Bax-triggered cell death in Nicotiana benthamiana plants. The expression of CdE1 was induced at 12-48 h after inoculation with C. diplodiella, and the transient overexpression of CdE1 led to increased susceptibility of grapevine to the fungus. Subsequent experiments revealed an interaction between CdE1 and Vitis davidii cysteine-rich receptor-like kinase 10 (VdCRK10) and suppression of VdCRK10-mediated immunity against C. diplodiella, partially by decreasing the accumulation of VdCRK10 protein. Furthermore, our investigation revealed that CRK10 expression was significantly higher and was up-regulated in the resistant wild grapevine V. davidii during C. diplodiella infection. The activity of the VdCRK10 promoter is induced by C. diplodiella and is higher than that of Vitis vitifera VvCRK10, indicating the involvement of transcriptional regulation in CRK10 gene expression. Taken together, our results highlight the potential of VdCRK10 as a resistant gene for enhancing white rot resistance in grapevine.

Temporal Dynamics and Dispersal Patterns of the Primary Inoculum of Coniella diplodiella, the Causal Agent of Grape White Rot

Grape white rot can cause considerable yield losses in viticulture areas worldwide and is principally caused by Coniella diplodiella. The fungus overwinters in berry mummies on the soil surface or on the trellis and produces pycnidia and conidia that serve as primary inoculum. However, little is known about the temporal dynamics and dispersal pattern of C. diplodiella conidia. In this study, we investigated the production and dispersal of C. diplodiella conidia from a primary inoculum source, namely, affected mummified berries that overwintered in two vineyards in northern Italy in 2021 and 2022. Conidia of C. diplodiella were repeatedly produced in berry mummies from the budburst of vines to harvesting, with approximately 50 and 75% of the total conidia in a season being produced before fruit set and véraison, respectively. The production dynamics of C. diplodiella conidia over time were described by a Weibull equation in which the thermal time is the independent variable, with a concordance correlation coefficient of ≥0.964. A rainfall cutoff of ≥0.2 mm provided an overall accuracy of ≥0.86 in predicting conidial dispersal through rain splashes from berry mummies on the soil surface, with the number of dispersed conidia increasing with the amount of rainfall. The dispersal of conidia from mummies on the trellis by washing with rain required at least 6.1 mm of rain. The proposed mathematical equations and rain cutoffs can be used to predict periods with a high dispersal risk of C. diplodiella.

Additional four species of Tatraea (Leotiomycetes, Helotiales) in Yunnan Province, China

During the investigations of discomycetes in Yunnan, China, five species of Tatraea were discovered on decayed, decorticated oak trees or unidentified wood. All species have typical disc-like, large fruiting bodies with grey, brown or greyish-green colors. The ITS sequence analysis showed that they belong to Tatraea (Helotiaceae, Helotiales) and the LSU and ITS combination revealed a different topology within the genus. Four species, T.clepsydriformis, T.griseoturcoisina, T.yunnanensis and T.yuxiensis were established as new species, and T.aseptata was collected and described on oak woods. The pairwise homoplasy index (PHI) test results indicated that there is no significant genetic recombination (Φw = 1.0) between all related species pairs. All the species described here are supported by descriptions, illustrations and multi-gene analyses.

Taxonomic analysis reveals host preference of rare fungi in endophytes of Vitis vinifera from the Czech Republic

This paper represents the results of screening a diversity of fungal endophytes associated with Vitis vinifera leaves and canes in the Czech Republic. The characterization of strains is based on morphological and phylogenetic analyses of ITS, EF1α and TUB2 sequence data. Our strain selection covers 16 species and seven orders belonging to Ascomycota and Basidiomycota. Together with ubiquitous fungi, we report on several poorly known plant-associated fungi, Angustimassarina quercicola (= A. coryli, a synonym proposed in this study) and Pleurophoma pleurospora. Other species, such as Didymella negriana, D. variabilis, Neosetophoma sp. (species identical or sister to N. rosae), Phragmocamarosporium qujingensis and Sporocadus rosigena, have so far been little known and rarely found, but are frequent on V. vinifera in different parts of the world and obviously belong to a microbiota with a strong preference for this plant. Detailed taxonomical identification allowed us to identify species with apparent stable associations with V. vinifera, for which further interactions with V. vinifera can be expected. Our study is the first to focus on V. vinifera endophytes in Central Europe and expands the knowledge about their taxonomy, ecology and geography.

Appressoria-Producing Sordariomycetes Taxa Associated with Jasminum Species

Appressoria are specialized structures formed by certain phytopathogenic fungi during the early stages of the infection process. Over the years, significant advancements have been made in understanding the formation, types, and functions of appressoria. Besides being formed primarily by fungal pathogens, many studies have reported their occurrence in other life modes such as endophytes, epiphytes, and saprobes. In this study, we observed the formation of appressoria in fungal genera that have been found associated with leaf spots and, interestingly, by a saprobic species. We used morphological descriptions and illustrations, molecular phylogeny, coalescent-based Poisson tree processes (PTP) model, inter- and intra-species genetic distances based on their respective DNA markers, and Genealogical Concordance Phylogenetic Species Recognition Analysis (GCPSR) to establish a new species (Pseudoplagiostoma jasmini), a Ciliochorella sp., and a new host record (Coniella malaysiana). The Ciliochorella sp. is reported as a saprobe, while Pseudoplagiostoma jasmini and Coniella malaysiana were found to be associated with leaf spots of Jasminum species. All three taxa produce appressoria, and this is the first study that reports the formation of appressoria by a Ciliochorella sp. and a Pseudoplagiostoma sp.

QTL detection and candidate gene analysis of grape white rot resistance by interspecific grape (Vitis vinifera L. × Vitis davidii Foex.) crossing

Grape white rot, a devastating disease of grapevines caused by Coniella diplodiella (Speg.) Sacc., leads to significant yield losses in grape. Breeding grape cultivars resistant to white rot is essential to reduce the regular use of chemical treatments. In recent years, Chinese grape species have gained more attention for grape breeding due to their high tolerance to various biotic and abiotic factors along with changing climatic conditions. In this study, we employed whole-genome resequencing (WGR) to genotype the parents of 'Manicure Finger' (Vitis vinifera, female) and '0940' (Vitis davidii, male), along with 101 F₁ mapping population individuals, thereby constructing a linkage genetic map. The linkage map contained 9337 single-nucleotide polymorphism (SNP) markers with an average marker distance of 0.3 cM. After 3 years of phenotypic evaluation of the progeny for white rot resistance, we confirmed one stable quantitative trait locus (QTL) for white rot resistance on chromosome 3, explaining up to 17.9% of the phenotypic variation. For this locus, we used RNA-seq to detect candidate gene expression and identified PR1 as a candidate gene involved in white rot resistance. Finally, we demonstrated that recombinant PR1 protein could inhibit the growth of C. diplodiella and that overexpression of PR1 in susceptible V. vinifera increased grape resistance to the pathogen.

First Report of Root Rot caused by Coniella fragariae on Paeoniae radix Rubra in China

Paeoniae radix Rubra is a traditional Chinese herbal medicine, which has the effect of clearing heat and cooling blood, activating blood and removing stasis. It has become popular in the Chinese market in recent years due to its extremely high medicinal value and showy flower color. In May 2021, typical symptoms of root rot were observed in a field (35°7'12″ N, 103°58'48″ E) in Dingxi, Gansu province, China. Approximately 10% of the plants in the field had typical root rot symptoms, and the root of each affected plant is at least 5% severe. The roots of the naturally infected plants in the field discolored and decayed with black brown spots on the surface of the root bark, the root bark detached from the phloem，and some leaves were chlorosis, shrunken and smaller, and the branches were dead and underdeveloped. In the transverse section, the xylem was black diffusion and abnormal odor. Three diseased plants with typical symptoms were chosen at random and brought back to the lab. Small pieces cut from the margins of lesions were surface disinfested with 75% ethanol for 15 s, and 0.5% NaClO solution for 30 s, rinsed three times in sterile distilled water, dried on sterile filter paper, plaed onto potato dextrose agar (PDA), and incubated at 25 ± 1℃ for 7 days in the dark. The pure cultures were obtained by single-spore isolation. All isolates produced wavy on the surface, radial from the inside out, initially white or milky white to orange colonies with abundant black brown oily conidiomata pycnidia on PDA at 25 ± 1℃ after 15 days in the dark. The conidiomata pycnidia is spherical to irregularly spherical, 231.5 to 512.4 μm, initially transparent with age turning brown, with a dark brown internal conidial mass inside, and with a 13.1 to 45.4 μ m wide ostiole central. Young conidia (n=100) developed from conidiogenous cells, which were simple, tapering, hyaline, smooth, and 12.3 to 18.0 × 2.5 to 4.6 μm, 1.0 to 1.5 µm wide at apex. Mature conidia (n=100) were ellipsoid, apices tapering, subobtusely rounded, brown, and 6.5 to 11.0 × 4.1 to 7.5 µm. The morphological characteristics of the isolates were consistent with previous descriptions of the genus Coniella (Crous et al., 2014). A representation isolate CS-1 was deposited in the Institute of Plant Protection, Gansu Academy of Agricultural Sciences and used for further studies. To confirm the identity of the causal fungus, the internal transcribed spacer (ITS), 28S large subunit of nuclear ribosomal RNA (LSU) and partial translation elongation factor 1-alpha (TEF1-α) gene of the representative isolate CS-1 were amplified and sequenced using primers ITS1/ITS4 (White et al., 1990), LROR/LR7 (Chethan et al., 2017) and EF1-728F/EF1-986R (Carbone and Kohn, 1999), respectively, and deposited on GenBank with accession numbers OP824764 (ITS), OP824767 (LSU)/span>and OP903926 (TEF1-α). Blastn analysis of all sequences resulted in E-value of 0.0 (ITS and LSU) and nearly 0.0 (TEF1-α), with Query cover values of 90% to 99% identity with C. fragariae, confirming the hypothesis based on morphological features examination. To conduct a pathogenicity test, three root segments of healthy plants were wounded using sterilized needles and inoculated by pipetting 10 μL of conidial suspension (1×107 conidia/mL) onto each wound, and controls were inoculated with 10 μL sterile distilled water. These root segments were kept in a moist chamber at 25°C in the dark. The experiment was repeated three times. After 14 days, root rot symptoms were observed on all of the inoculated root segments and identical to those observed in the field, whereas control root segments did not develop symptoms. The pathogen was re-isolated from the lesions of inoculated root segments, fulfilling Koch's postulates. To the best of our knowledge, this is the first report of C. fragariae causing root rot on P. radix Rubra in China. This identification can aid in the selection of appropriate management measures for this disease.

First report of Coniella vitis causing white rot on Virginia creeper (Parthenocissus quinquefolia [L.] Planch.) in China

Virginia creeper (Parthenocissus quinquefolia [L.] Planch.) belongs to the genus of Parthenocissus and Vitaceae family, which is very common in vineyards and where wild grape occurs (Bergh et al., 2011). In September of 2021, a severe white rot disease was observed on Virginia creeper around the vineyard of wine grapevine (Cabernet Sauvignon) located in Penglai city (37º 75'38" N, 120º 84'28" E), Shandong province of China. The disease incidence was about 75%, and infected leaf of Virginia creeper exhibited irregular necrotic lesion with brown center, and most lesion occurred on leaf margin, black pycnidia were also observed on the infected leaf at the late stage of infection. To determine the causal agent, symptomatic leaves with typical lesions were cut into small pieces (5 mm × 3 mm), surface sterilized with 75% ethanol for 1 min, followed by three times rinsed in sterile water. Leaf sections were plated onto potato dextrose agar (PDA) medium and incubated at 28°C for 3 days. Totally, five isolates (referred to as JD01, JD07, JD09, JD12 and JD16) were collected and transferred on to fresh PDA medium for incubation at 28°C. Seven days later, colonies on PDA plates had crenulated edges with concentric rings, the upper surface of colonies was mostly flat and white with many pycnidia. The conidia were hyaline at immature and became brown later, spherical or ellipsoid, aseptate, and 7.92 ± 1.20 μm × 5.18 ± 0.61 μm (n=50), length : width ratio is nearly 2. Morphologically, the isolates were identified as Coniella vitis (Chethana et al., 2017). Further to confirm the fungal species, the internal transcribed spacer region (ITS) of the ribosomal RNA gene, large subunit rRNA gene (LSU) and the translation elongation factor 1-alpaha gene (TEF1-α) were amplified using primers ITS1/ ITS4, LR7/ LROR, and TEF1- 728F/ TEF1- 986R (Chethana et al., 2017; Raudabaugh et al., 2018). The amplification products were sequenced and deposited in GenBank database. The sequences were compared to type sequences in GenBank. The results showed that ITS (GenBank accession numbers ON329769, ON329770, ON329771, ON329772 and ON329773), LSU (ON358423，ON358424, ON358425, ON358426 and ON358427) and TEF (ON297671, ON229071, ON229072, ON229073 and ON297672) sequences of the five isolates were 99.66%, 96.90% and 98.79% identical with the sequences data from C. vitis isolates in GeneBank (MFLUCC 18-0093, JZB3700020 and MFLUCC 18-0093, respectively). Furthermore, concatenated sequences of the three genes (ITS, LSU and TEF) were used to conduct a phylogenetic tree using maximum likehood MEGA-X (Raudabaugh et al., 2018). The phylogenetic analysis showed that the five isolates (JD01, JD07, JD09, JD12 and JD16) belong to C. vitis clade among the 41strains of Coniella spp. In the pathogenicity tests, detached leaves of Virginia creeper (1-year-old) were inoculated with mycelia plugs (5 mm diameter) (form 3-day-old of isolate JD07 culture), and control were inoculated with PDA plugs (5 mm diameter). Virginia creeper live plants (1-year-old) were inoculated with conidial suspension (2.5×106 spores/ml) of the isolate JD07 of one week old, and control plants were inoculated with sterile water. All treated Virginia creeper plants (detached leaves) were placed in a greenhouse maintained at 28°C and 95% relative humidity. Virginia creeper plants (detached leaves) inoculated with the conidial suspension (fungal mycelia) had brown lesion on leaves, the disease symptoms were similar to those observed in field. No such symptoms were observed on control plants (detached leaves). The pathogen was reisolated from inoculated Virginia creeper plants and re-identified, thus fulfilling Koch's postulates. C. vitis had been reported to cause grape white rot in China (Chethana et al., 2017). Virginia creeper, as an excellent host of C. vitis, will increase the transmission risk of the pathogens. To our knowledge, this is the first report of C. vitis causing white rot on Virginia creeper, and this finding will provide useful information for developing effective control strategies for white rot disease.

Comparative genomic and functional analyses of Paenibacillus peoriae ZBSF16 with biocontrol potential against grapevine diseases, provide insights into its genes related to plant growth-promoting and biocontrol mechanisms

Paenibacillus peoriae is a plant growth-promoting rhizobacteria (PGPR) widely distributed in various environments. P. peoriae ZBFS16 was isolated from the wheat rhizosphere and significantly suppressed grape white rot disease caused by Coniella vitis. Here, we present the complete genome sequence of P. peoriae ZBFS16, which consists of a 5.83 Mb circular chromosome with an average G + C content of 45.62%. Phylogenetic analyses showed that ZBFS16 belongs to the genus P. peoriae and was similar to P. peoriae ZF390, P. peoriae HS311 and P. peoriae HJ-2. Comparative analysis with three closely related sequenced strains of P. peoriae identified the conservation of genes involved in indole-3-acetic acid production, phosphate solubilization, nitrogen fixation, biofilm formation, flagella and chemotaxis, quorum-sensing systems, two-component systems, antimicrobial substances and resistance inducers. Meanwhile, in vitro experiments were also performed to confirm these functions. In addition, the strong colonization ability of P. peoriae ZBFS16 was observed in soil, which provides it with great potential for use in agriculture as a PGPR. This study will be helpful for further studies of P. peoriae on the mechanisms of plant growth promotion and biocontrol.

Current Insight into Traditional and Modern Methods in Fungal Diversity Estimates

Fungi are an important and diverse component in various ecosystems. The methods to identify different fungi are an important step in any mycological study. Classical methods of fungal identification, which rely mainly on morphological characteristics and modern use of DNA based molecular techniques, have proven to be very helpful to explore their taxonomic identity. In the present compilation, we provide detailed information on estimates of fungi provided by different mycologistsover time. Along with this, a comprehensive analysis of the importance of classical and molecular methods is also presented. In orderto understand the utility of genus and species specific markers in fungal identification, a polyphasic approach to investigate various fungi is also presented in this paper. An account of the study of various fungi based on culture-based and cultureindependent methods is also provided here to understand the development and significance of both approaches. The available information on classical and modern methods compiled in this study revealed that the DNA based molecular studies are still scant, and more studies are required to achieve the accurate estimation of fungi present on earth.

Suppression of Grape White Rot Caused by Coniella vitis Using the Potential Biocontrol Agent Bacillus velezensis GSBZ09

Grape white rot caused by Coniella vitis is prevalent in almost all grapevines worldwide and results in a yield loss of 10–20% annually. Bacillus velezensis is a reputable plant growth-promoting bacterial. Strain GSBZ09 was isolated from grapevine cv. Red Globe (Vitis vinifera) and identified as B. velezensis according to morphological, physiological, biochemical characteristics and a multilocus gene sequence analysis (MLSA) based on six housekeeping genes (16S rRNA, gyrB, rpoD, atpD, rho and pgk). B. velezensis GSBZ09 was screened for antifungal activity against C. vitis under in vitro and in vivo conditions. GSBZ09 presented broad spectrum antifungal activity and produced many extracellular enzymes that remarkably inhibited the mycelial growth and spore germination of C. vitis. Furthermore, GSBZ09 had a high capacity for indole-3-acetic acid (IAA) production, siderophore production, and mineral phosphate solubilization. Pot experiments showed that the application of GSBZ09 significantly decreased the disease index of the grape white rot, directly promoted the growth of grapes, and upregulated defense-related enzymes. Overall, the features of B. velezensis GSBZ09 make it a potential strain for application as a biological control agent against C. vitis.

Effects of Temperature and Wetness Duration on Infection by Coniella diplodiella, the Fungus Causing White Rot of Grape Berries

Grapevine white rot, caused by Coniella diplodiella, can severely damage berries during ripening. The effects of temperature and wetness duration on the infection severity of C. diplodiella were investigated by artificially inoculating grape berries through via infection pathways (uninjured and injured berries, and through pedicels). The effect of temperature on incubation was also studied, as was that of inoculum dose. Injured berries were affected sooner than uninjured berries, even though 100% of the berries inoculated with C. diplodiella conidia became rotted whether injured or not; infection through pedicels was less severe. On injured berries, the disease increased as the inoculum dose increased. Irrespective of the infection pathway, 1 h of wetness was sufficient to cause infection at any temperature tested (10–35 °C); with the optimal temperature being 23.8 °C. The length of incubation was shorter for injured berries than for uninjured ones, and was shorter at 25–35 °C than at lower temperatures; the shortest incubation period was 14 h for injured berries at 30 °C. Mathematical equations were developed that fit the data, with R² = 0.93 for infection through any infection pathway, and R² = 0.98 for incubation on injured berries, which could be used to predict infection period and, therefore, to schedule fungicide applications.

Molecular and Morphological Assessment of Septoria Species Associated with Ornamental Plants in Yunnan Province, China

The Karst landform is the main geographic characteristic in South China. Such areas are rich in vegetation and especially suitable for growth of shrubs and herbaceous plants. In this study, 11 Septoria strains were obtained from different plants’ leaves collected in the Kunming Botanical Garden, Yunnan Province, China. Based on single-gene and multi-gene analyses of five gene loci (tef1, rpb2, tub2, ITS, and LSU) and four gene regions (without LSU), these strains were found to belong to three independent phylogenetic lineages representing five species, including four novel taxa, and one new record for China. Five single gene trees were also provided to evaluate the effectiveness of each gene for discriminating the species, as a result of which tub2 was found to have the most suitable DNA barcode for rapid identification. Morphological descriptions, illustrations, and comparisons are provided for a more comprehensive assessment. Genealogical Concordance Phylogenetic Species Recognition (GCPSR) with a pairwise homoplasy index (PHI) test was used to evaluate the conclusions of the phylogenetic analyses.

Genome Assembly and Transcriptome Analysis of the Fungus Coniella diplodiella During Infection on Grapevine (Vitis vinifera L.)

Grape white rot caused by Coniella diplodiella (Speg.) affects the production and quality of grapevine in China and other grapevine-growing countries. Despite the importance of C. diplodiella as a serious disease-causing agent in grape, the genome information and molecular mechanisms underlying its pathogenicity are poorly understood. To bridge this gap, 40.93 Mbp of C. diplodiella strain WR01 was de novo assembled. A total of 9,403 putative protein-coding genes were predicted. Among these, 608 and 248 genes are potentially secreted proteins and candidate effector proteins (CEPs), respectively. Additionally, the transcriptome of C. diplodiella was analyzed after feeding with crude grapevine leaf homogenates, which reveals the transcriptional expression of 9,115 genes. Gene ontology enrichment analysis indicated that the highly enriched genes are related with carbohydrate metabolism and secondary metabolite synthesis. Forty-three putative effectors were cloned from C. diplodiella, and applied for further functional analysis. Among them, one protein exhibited strong effect in the suppression of BCL2-associated X (BAX)-induced hypersensitive response after transiently expressed in Nicotiana benthamiana leaves. This work facilitates valuable genetic basis for understanding the molecular mechanism underlying C. diplodiella-grapevine interaction.

Genome Sequence Resource of Coniella vitis, a Fungal Pathogen Causing Grape White Rot Disease

Several fungal pathogens cause grape white rot disease and Coniella vitis is a predominant pathogen in Chinese vineyards. The disease occurs on leaves, vines, and fruit berries, leading to considerable yield losses and even to total destruction of vineyards. Here, we present the first Pacbio and Illumina-sequenced draft genome assembly of C. vitis QNYT13637 and its annotation. This genome sequence provides a unique resource that will be a powerful foundation for future research on exploring virulence-related genes, investigating the pathogenicity mechanism of the pathogen, and, finally, improvement of white rot disease management strategies.

Candidate genes for grape white rot resistance based on SMRT and Illumina sequencing

BACKGROUND

White rot is one of the most dangerous fungal diseases and can considerably affect grape berry production and quality. However, few studies have focused on this disease, and thus, finding candidate white rot resistance genes is of great importance for breeding resistant grapevine cultivars. Based on field observations and indoor experiments, the cultivars "Victoria" and "Zhuosexiang" showed significant differences in white rot resistance. For understanding the molecular mechanisms behind it, different phenotypes of grapevine leaves were used for RNA sequencing via Illumina and single-molecule real-time (SMRT) sequencing technology.

RESULTS

A transcript library containing 53,906 reads, including known and novel transcripts, was constructed following the full-length transcriptome sequencing of the two grapevine cultivars. Genes involved in salicylic acid (SA) and jasmonic acid (JA) synthesis pathways showed different expression levels. Furthermore, four key transcription factors (TFs), NPR1, TGA4, Pti6, and MYC2, all involved in the SA and JA signal pathways were identified, and the expression profile revealed the different regulation of the pathogenesis related protein1 (PR1) resistance gene, as mediated by the four TFs.

CONCLUSIONS

Full-length transcript sequencing can substantially improve the accuracy and integrity of gene prediction and gene function research in grapevine. Our results contribute to identify candidate resistance genes and improve our understanding of the genes and regulatory mechanisms involved in grapevine resistance to white rot.