The nematode effector calreticulin competes with the high mobility group protein OsHMGB1 for binding to the rice calmodulin-like protein OsCML31 to enhance rice susceptibility to Meloidogyne graminicola

The root-knot nematode Meloidogyne graminicola secretes effectors into rice tissues to modulate host immunity. Here, we characterised MgCRT1, a calreticulin protein of M. graminicola, and identified its target in the plant. In situ hybridisation showed MgCRT1 mRNA accumulating in the subventral oesophageal gland in J2 nematodes. Immunolocalization indicated MgCRT1 localises in the giant cells during parasitism. Host-induced gene silencing of MgCRT1 reduced the infection ability of M. graminicola, while over-expressing MgCRT1 enhanced rice susceptibility to M. graminicola. A yeast two-hybrid approach identified the calmodulin-like protein OsCML31 as an interactor of MgCRT1. OsCML31 interacts with the high mobility group protein OsHMGB1 which is a conserved DNA binding protein. Knockout of OsCML31 or overexpression of OsHMGB1 in rice results in enhanced susceptibility to M. graminicola. In contrast, overexpression of OsCML31 or knockout of OsHMGB1 in rice decreases susceptibility to M. graminicola. The GST-pulldown and luciferase complementation imaging assay showed that MgCRT1 decreases the interaction of OsCML31 and OsHMGB1 in a competitive manner. In conclusion, when M. graminicola infects rice and secretes MgCRT1 into rice, MgCRT1 interacts with OsCML31 and decreases the association of OsCML31 with OsHMGB1, resulting in the release of OsHMGB1 to enhance rice susceptibility.

Identification of Meloidogyne Species on Traditional Chinese Medicine Plants in the Qinling Mountain Area of China and Their Aggressiveness to Different Medicinal Herbs

Root-knot nematodes (Meloidogyne spp.) are plant-parasitic nematodes that cause serious damage worldwide. There are many species of traditional Chinese medicine (TCM) plants, but only a few have been reported to be infected by Meloidogyne species. From 2020 to 2022, a survey was conducted in the Qinling mountain area, which is the main production region of TCM plants in China. Obvious galling symptoms were observed on the root systems of 15 species of TCM plants. Females were collected from diverse diseased TCM plants and subsequently identified at morphological and molecular levels. Among the 20 diseased root samples collected, Meloidogyne hapla populations were identified in 12 samples (60%), and M. incognita populations were identified in eight samples (40%). Among the 15 species of diseased TCM plants, eight species, namely, Scutellaria baicalensis, Leonurus japonicus, Dioscorea zingiberensis, Cornus officinalis, Viola philippica, Achyranthes bidentata, Senecio scandens, and Plantago depressa, were reported to be infected by Meloidogyne species for the first time. The host status of five species of TCM plants for two M. hapla isolates and one M. incognita isolate from TCM plants in this study was then evaluated. Differences in TCM plants' response to nematode infection were apparent when susceptibility was evaluated by the egg counts per gram of fresh root and the reproduction factor of the nematodes. Among the five species of TCM plants tested, Salvia miltiorrhiza and Gynostemma pentaphyllum were the most susceptible, while S. baicalensis and V. philippica were not considered suitable hosts for M. hapla or M. incognita.

Morphological and Molecular Characterization of a New Root-Knot Nematode, Meloidogyne limonae n. sp. (Nematoda: Meloidogynidae), Parasitizing Lemon in China

Root-knot nematodes of the genus Meloidogyne parasitize the roots of thousands of plants and can cause severe damage and yield losses. Here, we report a new root-knot nematode, Meloidogyne limonae n. sp., parasitizing "lemon" (Citrus limon) in Hainan Province, South China. Lemon trees infected by the root-knot nematode showed poor-quality lemons, chlorosis of foliage, weak growth, and numerous root galls with white females and egg masses protruding outside. Phylogenetic trees of sequences within the ribosomal and mitochondrial DNA demonstrated that this species differs clearly from other previously described root-knot nematodes. Morphologically, the new species is characterized by an oval-shaped perineal pattern and the lateral field marked by a ridge of cuticle on one or both sides; the dorsal arch is low, with fine to coarse, smooth cuticle striae; the vulva slit is centrally located at the unstriated area; the spicules of males are arcuate and curved ventrally; the gubernaculum is distinct and curved; the labial disc of second-stage juveniles is prominent and dumbbell shaped; stylet knobs are oval and sloping backwardly; pharyngeal glands are not filling the body cavity and overlapping the intestine ventrally; and the conical tail is gradually tapering. Phylogenetic trees based on the ITS1-5.8S-ITS2, D2-D3 of the 28S rDNA, and COI and COII-16S rRNA genes of the mtDNA showed that M. limonae n. sp. belongs to an undescribed root-knot nematode lineage that is separated from other species with the resemblance in morphology, such as M. floridensis, M. hispanica, M. acronea, and M. paranaensis.

Brown planthopper infestation on rice reduces plant susceptibility to Meloidogyne graminicola by reducing root sugar allocation

Plants are simultaneously attacked by different pests that rely on sugars uptake from plants. An understanding of the role of plant sugar allocation in these multipartite interactions is limited. Here, we characterized the expression patterns of sucrose transporter genes and evaluated the impact of targeted transporter gene mutants and brown planthopper (BPH) phloem-feeding and oviposition on root sugar allocation and BPH-reduced rice susceptibility to Meloidogyne graminicola. We found that the sugar transporter genes OsSUT1 and OsSUT2 are induced at BPH oviposition sites. OsSUT2 mutants showed a higher resistance to gravid BPH than to nymph BPH, and this was correlated with callose deposition, as reflected in a different effect on M. graminicola infection. BPH phloem-feeding caused inhibition of callose deposition that was counteracted by BPH oviposition. Meanwhile, this pivotal role of sugar allocation in BPH-reduced rice susceptibility to M. graminicola was validated on rice cultivar RHT harbouring BPH resistance genes Bph3 and Bph17. In conclusion, we demonstrated that rice susceptibility to M. graminicola is regulated by BPH phloem-feeding and oviposition on rice through differences in plant sugar allocation.

Identification and biological characterization of a new cyst nematode, Heterodera glycines sbsp.n. tabacum, parasitizing tobacco in China

In an investigation of diseases from plant-parasitizing nematodes in Henan Province, a cyst nematode was found on tobacco roots and in rhizosphere soil. We identified this strain as a new cyst nematode subspecies, Heterodera glycines sbsp.n. tabacum. The cysts and second-stage juveniles (J2) parasitizing Henan tobacco were larger than those of Heterodera glycines. A single 345-bp fragment was amplified from H. glycines sbsp.n. tabacum, whereas the 345-bp and 181-bp fragments were amplified from the soybean cyst nematode. Thus, H. glycines sbsp.n. tabacum was different from that of H. glycines. There were base transversions at 504 sites and base transitions at 560, 858, 920 and 921 sites in the rDNA-ITS sequences of H. glycines sbsp.n. tabacum compared with H. glycines, and there were base transitions at 41, 275, 278, and 380 sites in the mtDNA-COI sequences. In the phylogenetic tree based on the rDNA-ITS and mtDNA-COI regions, H. glycines sbsp.n. tabacum plants were clustered on a single branch. Based on the RAPD technique, SCAR-PCR primers were designed. A single 1113-bp fragment was amplified by specific primers (HtF1/HtR1) from H. glycines sbsp.n. tabacum, while no fragments were obtained from H. glycines. The Heterodera glycines sbsp.n. tabacum can infect soybean plants but cannot complete its life cycle. Eleven tested tobacco cultivars were infected, with an average Rf of 9.74 and a maximum of 64.2 in K326. The cumulative egg hatching rate of H. glycines sbsp.n. tabacum plants in the presence of tobacco root exudates was 42.6% at 32 days posthatching, which was significantly greater than that in the presence of soybean root exudates (30.3%) and sterile water (33.1%). In summary, the cyst nematode population parasitizing Henan tobacco was identified as a new subspecies, H. glycines sbsp.n. tabacum.

Clarifying the functional role of serotonin in Meloidogyne graminicola host plant parasitism by immunolocalization and RNA interference

Serotonin (5-hydroxytryptamine, 5-HT) is an essential neurotransmitter involved in regulating various behaviors in plant-parasitic nematodes (PPNs), including locomotion, egg laying, feeding, and mating. However, the functional role of serotonin in root-knot nematode invasion of host plants and the molecular mechanisms underlying feeding behavior remain poorly understood. In this study, we tested the effects of exogenous serotonin and the pharmacological compounds fluoxetine and methiothepin on the feeding behaviors of Meloidogyne graminicola. Our results suggested that M. graminicola possesses an endogenous serotonin signaling pathway and that serotonin plays a crucial role in modulating feeding behaviors in M. graminicola second stage juveniles (J2). We also identified and cloned the serotonin synthesis enzyme tryptophan hydroxylase (Mg-tph-1) in M. graminicola and investigated the role of endogenous serotonin by generating RNA interference nematodes in Mg-tph-1. As a result, silencing Mg-tph-1 substantially reduced nematode invasion, development, and reproduction. According to the immunostaining results, we speculated that these serotonin immunoreactive cells near the nerve ring in M. graminicola are likely homologous to Caenorhabditis elegans ADFs, NSMs, and RIH serotonergic neurons. Furthermore, we investigated the impact of phytoserotonin on nematode invasion and development in rice by overexpressing OsTDC-3 or supplementing rice plants with tryptamine and found that an increase in phytoserotonin increases nematode pathogenicity. Overall, our study provides insights into the essential role of serotonin in M. graminicola host plant parasitism and proposes that the serotonergic signaling pathway could be a potential target for controlling PPNs.

A variant of the venom allergen-like protein, DdVAP2, is required for the migratory endoparasitic plant nematode Ditylenchus destructor parasitism of plants

The potato rot nematode, Ditylenchus destructor, poses a serious threat to numerous root and tuber crops, yet the functional characterization of effectors from this migratory endoparasitic plant nematode remains limited. Despite inhabiting distinct habitats, sedentary and migratory plant parasitic nematodes share the structurally conserved effectors, such as venom allergen-like proteins (VAPs). In this study, a variant of DdVAP2 was cloned from D. destructor. The transcription profile analysis revealed that DdVAP2 was higher expressed in D. destructor feeding on either potato or sweet potato compared to on fungus via qRT-PCR. And DdVAP2 was highly expressed at all life stages feeding on sweet potato, except for eggs. DdVAP2 was confirmed to be specifically expressed in the subventral esophageal glands of D. destructor through in situ hybridization assays. Combined with functional validation of the signal peptide of DdVAP2, it suggested that DdVAP2 could be secreted from nematode into host. Heterologous expression of DdVAP2 in Nicotiana benthamiana revealed that the protein localized in both cytosol and nuclei of plant cells. Knocking down DdVAP2 by RNAi in D. destructor resulted in infection and reproduction defects on plants. All the results suggest that DdVAP2 plays a crucial role in the interaction between D. destructor and plants by facilitating the nematode infection.

No Pairwise Interactions of GmSNAP18, GmSHMT08 and AtPR1 with Suppressed AtPR1 Expression Enhance the Susceptibility of Arabidopsis to Beet Cyst Nematode

GmSNAP18 and GmSHMT08 are two major genes conferring soybean cyst nematode (SCN) resistance in soybean. Overexpression of either of these two soybean genes would enhance the susceptibility of Arabidopsis to beet cyst nematode (BCN), while overexpression of either of their corresponding orthologs in Arabidopsis, AtSNAP2 and AtSHMT4, would suppress it. However, the mechanism by which these two pairs of orthologous genes boost or inhibit BCN susceptibility of Arabidopsis still remains elusive. In this study, Arabidopsis with simultaneously overexpressed GmSNAP18 and GmSHMT0 suppressed the growth of underground as well as above-ground parts of plants. Furthermore, Arabidopsis that simultaneously overexpressed GmSNAP18 and GmSHMT08 substantially stimulated BCN susceptibility and remarkably suppressed expression of AtPR1 in the salicylic acid signaling pathway. However, simultaneous overexpression of GmSNAP18 and GmSHMT08 did not impact the expression of AtJAR1 and AtHEL1 in the jasmonic acid and ethylene signaling pathways. GmSNAP18, GmSHMT08, and a pathogenesis-related (PR) protein, GmPR08-Bet VI, in soybean, and AtSNAP2, AtSHMT4, and AtPR1 in Arabidopsis could interact pair-wisely for mediating SCN and BCN resistance in soybean and Arabidopsis, respectively. Both AtSNAP2 and AtPR1 were localized on the plasma membrane, and AtSHMT4 was localized both on the plasma membrane and in the nucleus of cells. Nevertheless, after interactions, AtSNAP2 and AtPR1 could partially translocate into the cell nucleus. GmSNAP18 interacted with AtSHMT4, and GmSHMT4 interacted with AtSNAP2. However, neither GmSNAP18 nor GmSHMT08 interacted with AtPR1. Thus, no pairwise interactions among α-SNAPs, SHMTs, and AtPR1 occurred in Arabidopsis overexpressing either GmSNAP18 or GmSHMT08, or both of them. Transgenic Arabidopsis overexpressing either GmSNAP18 or GmSHMT08 substantially suppressed AtPR1 expression, while transgenic Arabidopsis overexpressing either AtSNAP2 or AtSHMT4 remarkably enhanced it. Taken together, no pairwise interactions of GmSNAP18, GmSHMT08, and AtPR1 with suppressed expression of AtPR1 enhanced BCN susceptibility in Arabidopsis. This study may provide a clue that nematode-resistant or -susceptible functions of plant genes likely depend on both hosts and nematode species.

Derivation and validation of a novel preoperative risk prediction model for surgical site infection in pancreaticoduodenectomy and comparison of preoperative antibiotics with different risk stratifications in retrospective cohort

BACKGROUND

Surgical site infections (SSIs) are common postoperative complications of pancreaticoduodenectomy.

AIM

To develop a model for preoperative identification of the risk of SSI that may improve outcomes and guide preoperative antibiotics.

METHODS

The prediction model was built by meta-analysis. After literature search and inclusion, data extraction, and quantitative synthesis, the prediction model was established based on the pooled odds ratio of predictors. A single-centre retrospective cohort was the validation cohort. Receiver operating characteristic curves and area under the curve were used to assess the model's ability. We also created a decision curve and a calibration plot to assess the nomogram. The effects of prophylactic antibiotics on SSI were compared between groups by multivariable logistic regression with different risk stratifications.

FINDINGS

Twenty-eight studies were included in the meta-analysis, 17 studies in the derivation cohort. Age, male gender, body mass index, pancreatic duct diameter, high-risk diagnosis, and preoperative biliary drainage were selected to build the prediction model. The model was validated in an external cohort. The cut-off value was 3.5 and area under the curve (AUC) was 0.76 in open pancreaticoduodenectomy (OPD). In laparoscopic pancreaticoduodenectomy, the cut-off value was 4.5 and AUC was 0.69. Decision curve and calibration plot showed good usability of the model, especially in OPD. Multivariable logistic regression did not indicate differences between broad- and narrow-spectrum antibiotics for SSI in different risk stratifications.

CONCLUSION

The model can identify patients with a high risk of SSI preoperatively. The choice of prophylactic antibiotics under different risk stratifications should be investigated further.

Self-Assembled Nanonematicide Induces Adverse Effects on Oxidative Stress, Succinate Dehydrogenase Activity, and ATP Generation

Long-term overuse of chemical nematicides has resulted in low control efficacy toward destructive root-knot nematodes, and continuous development in nanotechnology is supposed to enhance the utilization efficiency of nematicides to meet practical needs. Herein, a cationic star polymer (SPc) was constructed to load fluopyram (flu) and prepare a flu nanoagent. Hydrogen bonding and van der Waals forces facilitated the self-assembly of the flu nanoagent, leading to the breakdown of self-aggregated flu and reducing its particle size to 60 nm. The bioactivity of flu was remarkably improved, with the half lethal concentration 50 from 8.63 to 5.70 mg/L due to the help of SPc. Transcriptome analysis found that a large number of transport-related genes were upregulated in flu nanoagent-exposed nematodes, while the expression of many energy-related genes was disturbed, suggesting that the enhanced uptake of flu nanoagents by nematodes might lead to the disturbance of energy synthesis and metabolism. Subsequent experiments confirmed that exposure to flu nanoagents markedly increased the reactive oxygen species (ROS) level of nematodes. Compared to flu treatment alone, succinate dehydrogenase (SDH) activity was inhibited in flu nanoagent-exposed nematodes with an increase in the pIC50 from 8.81 to 11.04, which further interfered with adenosine triphosphate (ATP) biosynthesis. Furthermore, the persistence of SPc-loaded flu in soil was prolonged by 2.33 times at 50 days after application. The protective effects of flu nanoagents on eggplant seedlings were significantly improved in both greenhouse and field trials, and the root-knot number was consistently smaller in roots treated with flu nanoagents than in those treated with flu alone. Overall, this study successfully constructed a self-assembled flu nanoagent with amplified effects on oxidative stress, SDH activity, and ATP generation, leading to highly effective control of root-knot nematodes in the field.

MG1 interacts with a protease inhibitor and confers resistance to rice root-knot nematode

The rice root-knot nematode (Meloidogyne graminicola) is one of the most destructive pests threatening rice (Oryza sativa L.) production in Asia; however, no rice resistance genes have been cloned. Here, we demonstrate that M. GRAMINICOLA-RESISTANCE GENE 1 (MG1), an R gene highly expressed at the site of nematode invasion, determines resistance against the nematode in several rice varieties. Introgressing MG1 into susceptible varieties increases resistance comparable to resistant varieties, for which the leucine-rich repeat domain is critical for recognizing root-knot nematode invasion. We also report transcriptome and cytological changes that are correlated with a rapid and robust response during the incompatible interaction that occurs in resistant rice upon nematode invasion. Furthermore, we identified a putative protease inhibitor that directly interacts with MG1 during MG1-mediated resistance. Our findings provide insight into the molecular basis of nematode resistance as well as valuable resources for developing rice varieties with improved nematode resistance.

Recombinase Polymerase Amplification Coupled with CRISPR-Cas12a Technology for Rapid and Highly Sensitive Detection of Heterodera avenae and Heterodera filipjevi

The cereal cyst nematodes Heterodera avenae and Heterodera filipjevi are recognized as cyst nematodes that infect cereal crops and cause severe economic losses worldwide. Rapid, visual detection of cyst nematodes is essential for more effective control of this pest. In this study, recombinase polymerase amplification (RPA) combined with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a (formerly known as cpf1) was developed for the rapid detection of H. avenae and H. filipjevi from infested field samples. The RPA reaction was performed at a wide range of temperatures from 35 to 42°C within 15 min. There was no cross-reactivity between H. avenae, H. filipjevi, and the common closely related plant-parasitic nematodes, indicating the high specificity of this assay. The detection limit of RPA-Cas12a was as low as 10^-4 single second-stage juvenile (J2), 10^-5 single cyst, and 0.001 ng of genomic DNA, which is 10 times greater than that of RPA-lateral flow dipstick (LFD) detection. The RPA-Cas12a assay was able to detect 10^-1 single J2 of H. avenae and H. filipjevi in 10 g of soil. In addition, the RPA-LFD assay and RPA-Cas12a assays could both quickly detect H. avenae and H. filipjevi from naturally infested soil, and the entire detection process could be completed within 1 h. These results indicated that the RPA-Cas12a assay developed herein is a simple, rapid, specific, sensitive, and visual method that can be easily adapted for the quick detection of H. avenae and H. filipjevi in infested fields.

Association of Globodera rostochiensis (Nematoda) with Stunted and Chlorotic Potato Plants in Yunnan and Sichuan Provinces in China

On a global basis, potato cyst nematodes (Globodera spp. Skarbilovich 1959 [Behrens 1975]) are one of the most serious soilborne pathogens in potato (Solanum tuberosum L.) production. In 2019 to 2020, 188 soil samples were taken from rhizosphere soil associated with the roots of stunted and chlorotic potato plants in the main potato-growing areas of Yunnan and Sichuan Provinces of China. Globodera rostochiensis Wollenweber 1923 (Skarbilovich 1959) was recovered from 112 of the samples. Nematode identification was as confirmed by morphometric, light microscopy, electron microscopy, and molecular methodologies. Population densities of G. rostochiensis ranged from 47.0 to 69.0 eggs/g of soil. A BLASTn homology search program was used to compare the sequences of populations of G. rostrochienses from Yunnan and Sichuan Provinces with populations of other Heteroderinae spp. and populations of G. rostochiensis from other nations. Although potato has been grown in China for at least 400 years and the nation produces more potato than any other country, potato cyst nematodes were not reported in China until 2022.

First Record of Meloidogyne incognita on Maize (Zea mays) in Shaanxi Province of China

Meloidogyne incognita can severely infect and harm some crops in temperate zones under open field in some cases, even though it's more widespread and economically important in tropical and subtropical regions (Eisenback, 2020). In early June 2022, patches with poor growth maize plants were observed in Dali County (109.93E, 34.80N) of Shaanxi province, China. The infected maize plants were stunted with galled and small roots. Females, males, second-stage juveniles (J2s) and egg masses were extracted and collected from galled roots and soil for morphological identification. The perineal pattern of females had a dorsally high square arch lacking obvious lateral lines. Stylet knobs of females were rounded and set off. The excretory pores were at level of or posterior to stylet knobs, 10-20 annules behind head. The head cap of males was flat to centrally concave, the stylet shaft constricted slightly at the junction with the knobs, and stylet knobs were broadly elongate to round, set off, flat and the width usually greater than the height. Measurements of females (n=20) were: body length (L)= 734.63 ± 79.24 µm (642.15 µm to 788.48 µm); maximum body width (W)= 487.14 ± 50.79 µm (426.09 µm to 556.42 µm); stylet length (ST)= 14.78 ± 1.57 µm (13.17 µm to 16.56 µm); and distance from dorsal esophageal gland opening to the stylet knobs (DGO)= 3.55 ± 0.13 µm (3.17 µm to 3.90 µm). Measurements of males (n=10) were: L=1483.76 ± 134.81 µm (1174.39 µm to 1635.62 µm); W=44.37 ± 3.28 µm (39.76 µm to 50.26 µm); ST= 19.76 ± 1.05 µm (17.84 µm to 22.36 µm); and DGO= 3.48 ± 0.28 µm (3.08 µm to 3.87 µm). The morphological characteristics of this nematode were consistent with Meloidogyne incognita (Kofoid and White, 1919) Chitwood, 1949 (Williams, 1973; Eisenback and Hirschmann, 1981). Moreover, the identification was further confirmed by PCR using two pairs of primers, D2A/D3B and NAD5F/R, with DNA extracted from 20 individual females, respectively (Subbotin et al., 2006; Janssen et al., 2016). Both the D2-D3 region sequence (MZ665547) amplified by D2A/D3B and the 597 bp sequence (MZ665548) amplified by NAD5F/R showed >99% identity with sequences of other M. incognita isolates. Both morphological and molecular data identified the root-knot nematodes on maize as M. incognita. Then ten maize seedlings maintained in pots containing autoclaved sandy soil at 25°C were each inoculated with 2000 freshly hatched J2s of the original population of M. incognita. At 45 days after inoculation, all inoculated plants developed gall symptoms on the roots similar to those in the field. And five non-inoculated maize seedlings showed no symptoms. Females dissected from inoculated plants were identified to be M. incognita with species-specific primers IncK-14F/IncK-14R (Randig et al., 2002). According to consultation, in the same field root-knot nematode infected carrots were harvested in November last year, the field was left unploughed until March when maize was sowed. As Dali County locates in north temperate zone with a warm temperate climate, where the average annual temperature is 14.4°C, and the highest and lowest temperature was 18°C and -9°C in last winter, the overwintering rate of M. incognita in open field in such area needs further study.

Current advances in the identification of plant nematode diseases: From lab assays to in-field diagnostics

Plant parasitic nematodes (PPNs) cause an important class of diseases that occur in almost all types of crops, seriously affecting yield and quality and causing great economic losses. Accurate and rapid diagnosis of nematodes is the basis for their control. PPNs often have interspecific overlays and large intraspecific variations in morphology, therefore identification is difficult based on morphological characters alone. Instead, molecular approaches have been developed to complement morphology-based approaches and/or avoid these issues with various degrees of achievement. A large number of PPNs species have been successfully detected by biochemical and molecular techniques. Newly developed isothermal amplification technologies and remote sensing methods have been recently introduced to diagnose PPNs directly in the field. These methods have been useful because they are fast, accurate, and cost-effective, but the use of integrative diagnosis, which combines remote sensing and molecular methods, is more appropriate in the field. In this paper, we review the latest research advances and the status of diagnostic approaches and techniques for PPNs, with the goal of improving PPNs identification and detection.

Meloidogyne graminicola population structure in China suggests a south-to-north expansion

The distribution range of root-knot nematode Meloidogyne graminicola is rapidly expanding, posing a severe threat to rice production. In this study, the sequences of cytochrome oxidase subunit I (COI) genes of rice M. graminicola populations from all reported provinces in China were amplified and sequenced by PCR. The distribution pattern and phylogenetic tree showed that all 54 M. graminicola populations in China have distinct geographical distribution characteristics, specifically Cluster 1 (southern China), Cluster 2 (central south and southwest China), and Cluster 3 (central and eastern China). The high haplotype diversity (Hd = 0.646) and low nucleotide diversity (π= 0.00682), combined with the negative value of Tajima's D (-1.252) and Fu's FS (-3.06764) suggested that all nematode populations were expanding. The existence of high genetic differentiation (Fst = 0.5933) and low gene flow (Nm = 0.3333) indicated that there was a block of gene exchange between most populations. Mutation accumulation with population expansion might be directly responsible for the high genetic differentiation, so the tested nematode population showed high within-group genetic variation (96.30%). The haplotype Hap8 was located at the bottom of the network topology, with the widest distribution and the highest frequency (59.26%), indicating that it was the ancestral haplotype. The populations in Cluster 3 were newly invasive according to the lowest frequency of occurrence of Hap8, the highest number of endemic haplotypes and the highest total haplotype frequency (60%). On the contrary, Cluster 1 having the highest genetic diversity (Hd = 0.772, π = 0.01127) indicated that it was the most primitive. Interestingly, the highest gene flow (Nm > 1), lowest genetic differentiation (Fst ≤ 0.33), and closest genetic distance (0.000) only occurred between Guangdong / Hainan population and others, which suggested that there might be channels for gene exchange between them and long-distance dispersal occurred. This suggestion is further confirmed by the weak correlation between genetic distance and geographical distance. Based on these data, a hypothesis can be drawn that M. graminicola populations in China were spreading from south to north, specifically from Guangdong / Hainan provinces to other regions. Natural selection (including anthropogenic) and genetic drift were the main drivers of their evolution. Coincidentally, this hypothesis was consistent with the gradual warming trend and the chronological order of reporting these populations. The main factors, influencing current M. graminicola population expansion and distribution patterns, might be geography, climate, long-distance seedling transport, inter-regional operations of agricultural machinery, and rotation mode. It reminds human beings of the necessity to be vigilant about preventing nematode disease according to local conditions all year round.

First Report of Meloidogyne incognita on Daylily (Hemerocallis citrina) in Shaanxi, China

Daylilies (Hemerocallis citrina Baroni) are herbaceous perennials grown extensively as ornamental plants worldwide. In China, daylilies are important cash crops, which are used for their roots, leaves, and flowers as both food and medicine (Guo et al., 2022). Dali County, Shaanxi Province, is an important production region for the commercial cultivation of daylily in China. The daylily cultivation area of Dali County was 43.33 million m2 and the output reached 227 thousand kg, which worth more than 109.12 million dollars. In July 2021, numerous daylily plants (cv. Shayuan) showed chlorotic leaves and stunted growth in a field in Dali County. The area of daylily field we investigated was about 2000 m2, and the incidence of root-knot nematode disease was more than 90%. The inflorescences of diseased plants decreased by nearly 30%, which affected the yield seriously. The diseased plants exhibited obvious galling on the roots which were typical symptoms of infection by root-knot nematodes (RKNs). Population densities of second-stage juveniles (J2s) ranged from 300 to 350 in 100g soil layer of 10-20 cm. Nematodes were collected from root samples (n = 15) and were found in all of the diseased plant samples. Morphological and molecular analysis were conducted using females, males, and J2s. The perineal patterns of females (n = 20) showed a high dorsal arch, and with wavy striae, which mostly lacking obvious lateral lines. Morphological measurements of adult females (n = 20) include body length (BL) = 668.99 ± 24.56 (487.57-897.84) μm, body width (BW) = 433.73 ±12.84 (343.71-551.61) μm, stylet length = 15.64 ± 1.45 (10.86-28.26) μm, dorsal pharyngeal gland orifice to stylet base (DGO) = 2.57 ± 0.20 (1.41-3.68) μm, vulval slit length = 20.44 ± 0.91 (16.00-24.22) μm, and vulval slit to anus distance = 18.05 ± 1.06 (14.58-24.90) μm. The males showed a trapezoidal labial region, with a high head cap and concaved at the center of the top end in lateral view; and the stylet knobs were prominent, usually demarcated from the shaft. The morphological characters of males (n = 7) were as follows: BL = 1124.56 ± 53.97 (998.37-1336.52) μm, BW = 33.60 ± 0.79 (30.21-36.52) μm, stylet length = 23.63 ± 0.78 (20.14-26.37) μm, DGO = 3.04 ± 0.09 (2.69-3.38) μm, spicule length = 25.72 ± 0.57 (23.97-28.33) μm. The key morphometrics of J2s: BL = 439.13 ± 6.52 (398.32-481.33) μm, BW = 15.14 ± 0.26 (13.91-16.66) μm, stylet length = 13.44 ± 0.29 (10.96-14.60) μm, DGO = 2.13 ± 0.18 (1.22-3.10) μm, tail length = 57.46 ± 4.89 (38.85-101.33) μm, hyaline tail terminus = 16.93 ± 0.97 (11.45-22.54) μm. The morphological features of the females, males, and J2s match the original description of Meloidogyne incognita (Eisenback and Hirschmann, 1981). Eleven individual females were transferred to eleven different tubes for DNA extraction and the species-specific primers Mi2F4/Mi1R1 (ATGAAGCTAAGACTTTGGGCT/TCCCGCTACACCCTCAACTTC) were used for the identification of M. incognita (Kiewnick et al. 2013). A 300 bp target fragment was amplified by the primer pairs, confirming the RKNs collected from daylily plants were M. incognita. To confirm the result of species identification, the NADH dehydrogenase subunit 5 (nad5) from the mitochondrial DNA region was amplified using primers NAD5-F/R (TATTTTTTGTTTGAGATATATTAG/CGTGAATCTTGATTTTCCATTTTT) (Janssen et al. 2016). A fragment of 611 bp was obtained and the sequence (GenBank Accession No.OP115729) was 100% identical to the known sequence of M. incognita (GenBank Accession No. MT683461). The ITS region was amplified using the primers rDNA-F/R (TTGATTACGTCCCTGCCCTTT/TTTCACTCGCCGTTACTAAGG) (Vrain et al. 1992). The sequences from the ITS region were 768 bp (GenBank Accession No. OP095037) and showed 100% identical to the known sequence of M. incognita (GenBank Accession No. MH113856). An infection test was conducted in greenhouse conditions. Eighteen 5-weeks-old healthy daylily seedlings (cv. Shayuan) were individually cultured in 9 L pots filled with autoclaved-soil and each plant was inoculated with 3,000 J2s. Six non-inoculated daylily plants served as negative controls. After 60 days, all of the inoculated plant roots showed galling symptoms which were similar to those observed in the field, the nematodes were extracted from roots and were identified as M. incognita with the sequence-specificprimers Mi2F4/Mi1R1. No obvious symptoms were observed on control plants. An average of 9635 J2s were recovered from inoculated plants, (reproductive factor = 3.21), which confirmed the pathogenicity of M. incognita on daylily. Although it was reported that daylily was a host of M. incognita in Florida (Inserra et al. 1995), to our knowledge, this is the first evidence that M. incognita naturally infecting daylily in China. This root-knot disease leads to the yield reduction of daylily and may cause serious economic losses, so further studies should focus on the occurrence and effective control of this disease.

Circ_0124055 promotes the progression of thyroid cancer cells through the miR-486-3p/MTA1 axis

BACKGROUND

Thyroid cancer is one of the malignancy cancers. CircRNA, a non-coding RNA, plays an important role in the development of cancer. The relationship and roles of circ_0124055, miR-486-3p and MTA1 in thyroid cancer have not been reported.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) was performed to analyze the RNA levels of circ_0124055, miR-486-3p and MTA1. Western blot was conducted to analyze the protein levels of MTA1, Epithelial cadherin (E-cadherin) and Neuro cadherin (N-cadherin). Subcellular localization assay was used to analyze circ_0124055 location in thyroid cancer cells. Colony formation assay and 5-Ethynyl-2'-deoxyuridine (EdU) assay were carried out to analyze cell proliferation. Cell migration and invasion were analyzed by wound-healing assay and transwell assay. Flow cytometry assay was performed to investigate cell apoptosis. Dual-luciferase reporter assay and RIP assay were employed to analyze the interactions among circ_0124055, miR-486-3p and MTA1. Immunohistochemical (IHC) assay was performed to assess the expression of Ki67, MTA1 and E-cadherin in tumor tissues. Thyroid cancer tumor growth in vivo was evaluated by tumor xenograft mouse model assay.

RESULTS

The expression of circ_0124055 was up-regulated in tumor tissues and cells. Knockdown of circ_0124055 could inhibit thyroid cancer cell proliferation, migration and invasion and promote cell apoptosis, accompanied by the dysregulation of E-cadherin and N-cadherin expression. Circ_0124055 could target miR-486-3p, and miR-486-3p could target MTA1. MiR-486-3p inhibitor could restore the effect of circ_0124055 knockdown in the progression of thyroid cancer. Moreover, MTA1 overexpression weakened the inhibitory effects of miR-486-3p mimics on the progression of thyroid cancer. Further, circ_0124055 could influence tumor growth in vivo.

CONCLUSION

Circ_0124055 promoted the progression of thyroid cancer cells through the miR-486-3p /MTA1 axis.

The hidden power of secondary metabolites in plant-fungi interactions and sustainable phytoremediation

The global environment is dominated by various small exotic substances, known as secondary metabolites, produced by plants and microorganisms. Plants and fungi are particularly plentiful sources of these molecules, whose physiological functions, in many cases, remain a mystery. Fungal secondary metabolites (SM) are a diverse group of substances that exhibit a wide range of chemical properties and generally fall into one of four main family groups: Terpenoids, polyketides, non-ribosomal peptides, or a combination of the latter two. They are incredibly varied in their functions and are often related to the increased fitness of the respective fungus in its environment, often competing with other microbes or interacting with plant species. Several of these metabolites have essential roles in the biological control of plant diseases by various beneficial microorganisms used for crop protection and biofertilization worldwide. Besides direct toxic effects against phytopathogens, natural metabolites can promote root and shoot development and/or disease resistance by activating host systemic defenses. The ability of these microorganisms to synthesize and store biologically active metabolites that are a potent source of novel natural compounds beneficial for agriculture is becoming a top priority for SM fungi research. In this review, we will discuss fungal-plant secondary metabolites with antifungal properties and the role of signaling molecules in induced and acquired systemic resistance activities. Additionally, fungal secondary metabolites mimic plant promotion molecules such as auxins, gibberellins, and abscisic acid, which modulate plant growth under biotic stress. Moreover, we will present a new trend regarding phytoremediation applications using fungal secondary metabolites to achieve sustainable food production and microbial diversity in an eco-friendly environment.

Silicon Mediated Plant Immunity against Nematodes: Summarizing the Underline Defence Mechanisms in Plant Nematodes Interaction

Silicon (Si) is known to stimulate plant resistance against different phytopathogens, i.e., bacteria, fungi, and nematodes. It is an efficient plant growth regulator under various biotic and abiotic stresses. Silicon-containing compounds, including silicon dioxide, SiO₂ nanoparticles (NPs), nano-chelated silicon fertilizer (NCSF), sodium siliconate, and sodium metasilicate, are effective in damaging various nematodes that reduce their reproduction, galling, and disease severity. The defence mechanisms in plant-nematodes interaction may involve a physical barrier, plant defence-associated enzyme activity, synthesis of antimicrobial compounds, and transcriptional regulation of defence-related genes. In the current review, we focused on silicon and its compounds in controlling plant nematodes and regulating different defence mechanisms involved in plant-nematodes interaction. Furthermore, the review aims to evaluate the potential role of Si application in improving plant resistance against nematodes and highlight its need for efficient plant-nematodes disease management.

Opposite Beet Cyst Nematode Infection Phenotypes of Transgenic Arabidopsis Between Overexpressing GmSNAP18 and AtSNAP2 and Between Overexpressing GmSHMT08 and AtSHMT4

The rhg1-a GmSNAP18 (an α-SNAP) and Rhg4 GmSHMT08 are two major cloned genes conferring soybean cyst nematode resistance in Peking-type soybeans, but the application of α-SNAPs and SHMTs in cyst nematode management remains elusive. In this study, GmSNAP18 and GmSHMT08, together with their orthologs in Arabidopsis, AtSNAP2 (an α-SNAP) and AtSHMT4, were individually transformed into Arabidopsis Col-0 to generate the transgenic lines, and the growth of transgenic plants, beet cyst nematode (BCN) infection phenotypes, and AtSNAP2, AtSHMT4, and AtPR1 expression patterns were analyzed using Arabidopsis-BCN compatible interaction system, in addition with protein-protein interaction assay. Pulldown and BiFC assays revealed that GmSNAP18 and GmSHMT08 interacted with AtSHMT4 and AtSNAP2, respectively. Plant root growth was not impacted by overexpression of GmSNAP18 and AtSNAP2. However, overexpression of GmSHMT08 and AtSHMT4 both increased plant height, additionally, overexpression of GmSHMT08 decreased rosette leaf size. Overexpression of GmSNAP18 and GmSHMT08 both suppressed AtPR1 expression and significantly enhanced BCN susceptibility, while overexpression of AtSNAP2 and AtSHMT4 both substantially boosted AtPR1 expression and remarkably enhanced BCN resistance, in transgenic Arabidopsis. Overexpression of GmSNAP18 reduced, while overexpression of AtSNAP2 unaltered AtSHMT4 expression. Overexpression of GmSHMT08 and AtSHMT4 both suppressed AtSNAP2 expression in transgenic Arabidopsis. Thus, different expression patterns of AtPR1 and AtSHMT4 are likely associated with opposite BCN infection phenotypes of Arabidopsis between overexpressing GmSNAP18 and AtSNAP2, and between overexpressing GmSHMT08 and AtSHMT4; and boosted AtPR1 expression are required for enhanced BCN resistance in Arabidopsis. All these results establish a basis for extension of α-SNAPs and SHMTs in cyst nematode management.

Evaluation of commonly used nematicides with combined in in vitro and in planta bioassays

For efficient use of available synthesised nematicides, bioassay-guided analysis is required to understand the behaviours of nematicides. In this study, the key nematicides on the market, including avermectin B1a, avermectin B2a, emamectin benzoate, fluensulfone, fluopyram and fosthiazate, were evaluated by both in vitro and in planta approaches with optimised solvent and nematode inoculum. We found that acetone was the only one of the six solvents tested safe for both root-knot nematode (RKN) second-stage juveniles (J2) and cucumber at the tested concentration. The optimal numbers of RKN J2 for inoculation on cucumber seedlings in the glass-tube assay, cup assay and microplot experiment were 200, 700 and 1250, respectively. No obvious phytotoxicity symptoms were observed in the in planta assays for all nematicides selected at the tested concentration in the soil drench application. When the substrate changed from pure sand to matrix-sand, the EC50 and EC90 of all six nematicides increased. Among them, fluopyram rose the most. In the microplot experiment, avermectin B2a showed the lowest EC50 but the EC90 of avermectin B2a, fluensulfone, fluopyram and fosthiazate were similar. The results are useful as a guide to the application of commonly used nematicides in the field.

Origin and Phylogeography of Chinese Cereal Cyst Nematode Heterodera avenae Revealed by Mitochondrial COI Sequences

Heterodera avenae, a globally distributed plant-parasitic nematode, is one of the most significant pests on cereal crops. In China, it is widely distributed in cereal-growing areas of 16 provinces and causes serious yield losses. In the present study, a total of 98 populations of H. avenae were collected from major wheat-growing regions in China and six other countries. The mitochondrial COI genes were amplified and analyzed. Forty-one mitochondrial COI haplotypes were identified, suggesting a high genetic diversity and endemism level of H. avenae in China. Phylogenetic analysis showed that H. avenae populations in China were divided into four clades. Significant evolutionary and genetic differences were found between Chinese (except Hubei) and foreign populations. Hap1, the most widely distributed haplotype, was considered to be a separate evolutionary origin in China. The gene flow of H. avenae from the northwestern region to the north China region and Huang-Huai-Hai region was significant, so as the direction between north China and Huang-Huai-Hai region. We speculate that water flowing from the Yellow River and mechanical harvesters promoted gene exchange among these groups. A distance-based redundancy analysis showed that genetic distances observed among H. avenae populations were explained foremost not only by geographic distance but also by temperature and precipitation. This study provides theoretical support for the origin and spread of H. avenae populations in China and elsewhere in the world.

Phylogeography of Chinese cereal cyst nematodes sheds lights on their origin and dispersal

Reconstructing the dispersal routes of pathogens can help identify the key drivers of their evolution and provides a basis for disease control. The cereal cyst nematode Heterodera avenae is one of the major nematode pests on cereals that can cause 10%–90% crop yield losses worldwide. Through extensive sampling on wheat and grasses, the Chinese population of H. avenae is widely identified in virtually all wheat growing regions in China, with H1 being the predominant haplotype. The monoculture of wheat in north China might have been the key driver for the prevalence of H1 population, which should date no earlier than the Han Dynasty (202 BCE–220 CE). Molecular phylogenetic and biogeographic analyses of Chinese H. avenae suggest a Pleistocene northwest China origin and an ancestral host of grasses. We assume that the prosperity of Heterodera in this region is a result of their preference for cooler climate and various grass hosts, which only appeared after the uplift of Qinghai‐Tibetan Plateau and aridification of Inner Asia. Nematode samples from the current and historical floodplains show a significant role of the Yellow River in the distribution of Chinese H. avenae. Whereas mechanical harvesters that operate on an inter‐provincial basis suggest the importance in the transmission of this species in eastern China in recent times. This study highlights the role of environmental change, river dynamics, and anthropogenic factors in the origin and long‐distance dissemination of pathogens.

A Distinct Tobamovirus Associated With Trichosanthes kirilowii Mottle Mosaic Disease

Trichosanthes kirilowii is one of the most important perennial herbaceous vines that have been used in traditional Chinese medicine. In this study, a novel RNA virus was discovered in T. kirilowii plants showing leaf mottling and mosaic symptoms. The complete genome of this virus is 6,524 nucleotides long and encodes four open reading frames which are arranged in a manner typical of tobamoviruses. Phylogenetic analysis based on the complete genome sequence revealed that the virus was clustered into a branch with the tobamoviruses whose natural host are plants belonging to the family Cucurbitaceae. A full-length infectious cDNA clone was then constructed and demonstrated to establish a systemic infection with typical symptoms in Nicotiana benthamiana, T. kirilowii, and five other cucurbitaceous crops including Cucumis melo, C. lanatus, C. sativus, Luffa aegyptiaca, and Cucurbita pepo via agrobacterium-mediated infectivity assays. Further experiments provided evidence that the rod-shaped viral particles derived from the infectious clone could be mechanically transmitted and reproduce indistinguishable symptoms in the tested plants. Taken together, the mottle mosaic disease of T. kirilowii is caused by a distinct tobamovirus, for which the name Trichosanthes mottle mosaic virus (TrMMV) is proposed. As the infectious cDNA clone of TrMMV could also infect five other cucurbit crops, this distinct tobamovirus could be a potential threat to other cucurbitaceous crops.

First detection of the potato cyst nematode (Globodera rostochiensis) in a major potato production region of China

The potato cyst nematodes (PCN) Globodera rostochiensis and Globodera pallida are the very important quarantine nematode pests of potato [Stone 1973]. Both species cause serious potato tuber yield losses. These species are subjected to strict quarantine regulations in many countries (EPPO 2017). G. rostochiensis was detected in Sichuan and Yunnan province, China in 2022 (Jiang et al. 2022). A survey for cyst nematodes in potato fields was conducted in Guizhou Province from 2018 to 2020. A total of 200 samples, including roots and soil, were collected from 40 potato fields in Hezhang (N27 06.145, E104 39.153) and Weining (N26 50.541, E104 09.885) counties in Guizhou Province, China. The Cobb decanting and sieving method was used to isolate cysts and J2s from the soil samples (Southey 1986). The potato roots were stained with acid fusion to observe cyst development. Morphological and molecular analyses indicated that 27 (13.5%) of the samples contained G. rostochiensis. The cyst density ranged between 1-85 cysts per 100 cm3 of soil and a mean density was 15 cysts per 100 cm3 soil. The smoothly rounded cysts were in brown and golden color, and the terminal cone was absent and circumfenestrate. The key morphometrics of cysts (n=20) were 695 ± 26 (685-757) μm in length excluding neck and 690 ± 30 (668 to769) μm in width; the number of cuticular ridges between anus and vulval fenestra was 16.3 ±2.1 (14 to 18); fenestral length was 15.1 ± 2.1 μm (13.18 to 19.27); distance from anus to the edge of fenestra was 61.12 ± 8.9 (49.22 to76.27) μm; and Granek's ratio was 4.54 ± 0.8 (3.97-5.26). The key morphometrics of J2 (n = 20): 468.0 ± 20.1 (427 to - 521) μm in body length, 20.58 ± 0.7 (20.2 to 21.8) μm in stylet length, 43.9 ± 5.6 (40.3 to 53.9) μm in tail length, and 23.1 ± 1.8 (21.77 to 25.32) μm in hyaline region length. The cyst and J2 morphologies were consistent with those of G. rostochiensis (Subbotin et al. 2010, EPPO 2017). Genomic DNA was isolated from cysts (n=20). DNA extraction was performed in a volume of 20 μl containing 3 μl 10× PCR buffer, 3 μl Proteinase K (600 μg μl-1), 14 μl distilled water and a single cyst was added and ground in an ice bath as described by Ou et al. (2008). The internal transcribed spacer (ITS) regions were amplified using the universal primers: rDNA1 (5'-TTGATTACGTCCCTGCCCTTT-3') and rDNA2 (5'-TTTCACTCGCCGTTACTAAGG-3') (Fleming 1998 ), and the 28S rDNA-D2/D3 regions were amplified using the primers: D2A (5´-ACAAGTACCGTGAGGGAAAGTTG-3´) and D3B (5´-TCGGAAGGAACCAGCTACTA-3´) (Subbotin et al. 2006). After the brackets at the beginning and end of the sequences were closed-up, the ITS rDNA sequences (GenBank Accession No. MZ042367 and MZ042368) showed 99.66% - 99.92% identity to G. rostochiensis sequences available in GenBank (FJ212166.1, GQ294513, FJ212164.1 and KJ409617.1). Sequences from the 28S region (GenBank Accession No. MZ057597 and MZ057598) were 99.23% - 99.74% similar to those of G. rostochiensis isolate from Slovakia (KJ409625.1), Italy (KJ409631.1) and United Kingdom (KJ409633.1). We used species specific primers ITS5（5'-GGAAGTAAAAGTCGTAACAAGG-3'）and PITSr3 (5'AGCGCAGACATGCCGCAA-3') to amplify the product (Bulman & Marshall 1997; EPPO 2017). A single 434bp fragment was obtained from Hezhang and Weining populations. A host test for the Hezhang and Weining populations were performed by inoculating 1,000 eggs per plant of varieties Qingshu 9, Huize 2 and Hezuo 88 grown in the pots containing 800 cm3 of sterilized soil (soil: sand ratio was 3:1), and four replications were tested in greenhouse under 16 h light, 22°C in the day and 8 h dark in the night. At 90 days post inoculation, 32.6 ± 7, 31.2 ± 8, and 29.5 ± 8 females and cysts were extracted from the infected roots and soils of the varieties Qingshu 9, Huize 2 and Hezuo 88, respectively. No females and cysts were observed on the control plants. The trial indicated that potato cultivars Qingshu 9, Huize 2 and Hezuo 88 are hosts for the Hezhang and Weining populations of Globodera rostochiensis. To the best of our knowledge, this is the first detection of potato cyst nematode Globodera rostochiensis in Guizhou Province, China.

Breeding a Soybean Cultivar Heinong 531 with Peking-Type Cyst Nematode Resistance, Enhanced Yield, and High Seed-Oil Contents

Soybean cyst nematode (SCN) is a destructive threat to soybean production. It is economically important to develop a new SCN-resistant soybean cultivar with high yield and other good agronomic traits. In this study, a yellow-seed-coated and yellow-hilum-pigmented cultivar Heinong 531 belonging to maturity group I was developed by a pedigree breeding method through a test-cross between a female parental SCN-resistant soybean cultivar Pengdou 158 and a male parental line F1 (high-yield but SCN-susceptible Hefeng 55 × SCN-resistant Kangxian 12). Heinong 531 was evaluated for SCN resistance in both SCN-infested field and autoclaved soil inoculated with hatched second-stage juveniles of SCN HG Type 0. The results indicated that SCN development at all stages in Heinong 531 was suppressed and the female index was only 1.6 to 5.6%. Heinong 531 as well as Pengdou 158 and Kangxian 12 were identified as carrying the Peking-type resistance with both rhg1-a GmSNAP18 and Rhg4 GmSHMT08 genes. In the 2-year regional trials, the average yield of Heinong 531 reached 2805.0 kg/ha, and the 1-year production trial demonstrated an average yield of 2,751.5 kg/ha with yield increase of >12.0% when compared with the local cultivars. The average seed-fat (oil) contents of Heinong 531 reached up to 22.3%. The Peking-type SCN-resistant Heilong 531 with enhanced yield and high seed-oil contents was released in China in June 2021 with the certified number of 'Heishendou 20210004'. These agronomic traits make Heinong 531 a good prospect in a wide attempt to control SCN in the main soybean-producing areas of Northeast China.

First report of Meloidogyne hapla infecting Salvia miltiorrhiza in Shaanxi, China

Salvia miltiorrhiza is a perennial herbaceous plant for traditional Chinese medicine. It has been extensively applied for many hundred years to treat various diseases (Su et al. 2015). It is also a kind of important cash crop that is widely cultivated in southern Shaanxi province. In June of 2021, in a field in Luonan County, Shaanxi Province, some S. miltiorrhiza plants with stunting and leaf wilting symptoms were observed. The diseased plants exhibited a large number of globular galling on the secondary and tertiary roots. The symptoms were typical of infection by root-knot nematodes. Population densities of second-stage juveniles (J2s) ranged from 330 to 650 per 100 cm3. To identify the species of the root-knot nematodes, J2s and males were collected from the soil in the root zone, and females were isolated from diseased roots. The perineal patterns of females (n = 12) were round-shaped, with low dorsal arches, obvious lateral lines, and characteristic small punctations near anus. Morphological measurements of females (n = 20) included body length (L) = 565.25 ± 33.9 (503.35 - 632.47) μm, body width (BW) = 420.00 ± 21.28 (378.27 - 452.51) μm, stylet = 11.11 ± 0.73 (10.05-12.29) μm, dorsal pharyngeal gland orifice to stylet base (DGO) = 4.69 ± 0.45 (3.82-5.32) μm, vulval slit length = 21.1 ± 1.33 (18.38-22.96) μm, and vulval slit to anus distance = 15.76 ± 1.24 (13.38-17.45) μm. The morphological characters of males (n = 7): L = 1098.14 ± 82.99 (962.83-1193.87) μm, BW = 28.44 ± 1.18 (26.59-29.83) μm, stylet = 18.27 ± 0.97 (16.57-19.28) μm, DGO = 4.89 ± 0.62 (3.82-5.68) μm, and spicule length = 24.04 ± 1.80 (21.30-26.71) μm. The key morphometrics of J2s: L = 380.24 ± 18.24 (354.43-423.13) μm, BW = 13.94 ± 0.70 (12.88-15.34) μm, stylet = 11.82 ± 0.49 (10.96-12.61) μm, DGO = 3.68 ± 0.42 (3.09-4.56) μm, tail length = 55.42 ± 5.81 (46.97-67.03) μm, and hyaline tail terminus = 13.79 ± 1.24 (12.0-16.51) μm. These morphological characteristics are consistent with Meloidogyne hapla as described by Whitehead (1968). Ten individual females were transferred to ten different tubes for DNA extraction. The DNA extraction followed the method described by Htay et al. (2016). The species-specific primers JMV1 (5'-GGATGGCGTGCTTTCAAC-3') and JMV (5'-AAAAATCCCCTCGAAAAATCCACC-3') were used for the identification of M. hapla (Adam et al. 2007). A single 440 bp fragment was amplified by this pair of primers, confirming their identities as M. hapla. To confirm species identification, the ITS region was amplified using the primers 18S/26S (5'-TTGATTACGTCCCTGCCCTTT-3'/5'-TTTCACTCGCCGTTACTAAGG-3') (Vrain et al. 1992). The sequence from the ITS region was 768 bp (GenBank Accession No. OM049198) and was 100% identical to the sequences of M. hapla (GenBank Accession Nos. MT249016 and KJ572385). The mitochondrial DNA (mtDNA) region between COII and the lRNA gene was amplified using primers C2F3 (5'-GGTCAATGTTCAGAAATTTGTGG-3') and 1108 (5'-TACCTTTGACCAATCACGCT-3') (Powers and Harris, 1993). A fragment of 529 bp was obtained and the sequence (GenBank Accession No. OM055828) was 100% identical to the known sequence of M. hapla from Taiwan (GenBank Accession No. KJ598134). An infection test was conducted in greenhouse conditions. Six 2-month-old S. miltiorrhiza plants were individually maintained in 12-cm diameter, 10-cm deep plastic pots containing sterilized soil and each plant was inoculated with 3000 J2s hatched from egg masses of collected M. hapla samples. Two non-inoculated S. miltiorrhiza plants served as negative controls. After 60 days, inoculated plants exhibited galled roots similar to those observed in the field. Many galls (61.33 ± 8.52) and egg masses (26.17 ± 4.79) were found on each root system. The nematode reproduction factor (RF = final population/initial population) was 4.5. No symptoms were observed in control plants. The nematode was reisolated from root tissue and identified to be M. hapla with its sequence-specific primers JMV1/JMV. These results confirmed that the nematode population could infect S. miltiorrhiza. To our knowledge, this is the first time of natural infection of S. miltiorrhiza with M. hapla in China. Including S. miltiorrhiza, the medicinal ingredients of many traditional Chinese herbal medicines were extracted from the roots of the plants. The infection of root-knot nematode will cause a serious decline in the quality of Chinese medicinal materials. Therefore, it is necessary to identify the species of root-knot nematode in different Chinese herbal medicines.

Menopausal hormone therapy: what are the problems in the perception of Chinese physicians?

OBJECTIVE

This study aimed to investigate Chinese physicians' perception and attitudes toward menopausal hormone therapy (MHT).

METHODS

This nationwide online survey was conducted in China. Physicians registered in the WeChat groups of the Gynecological Endocrinology Committee of China's Maternal and Child Health Care Association received a message invitation to complete this anonymous online survey from April 2020 to July 2020. Physicians' knowledge of and attitudes toward MHT were surveyed.

RESULTS

In total, 4672 questionnaires were submitted; only completed questionnaires could be submitted. The message was sent to 6021 doctors, so the response rate was 77.6%. Overall, 77.9-92.9% of physicians knew the common indications and contraindications to MHT. Additionally, 90.6%, 85.4%, 80.7% and 37.5% of physicians thought that MHT would increase the risk of venous thrombosis, breast cancer, endometrial cancer and weight gain, respectively. In total, 58.1% of the physicians mistakenly believed that a sex hormone test was one of the necessary examinations to reassess MHT prescription during follow-up visits. We found that 68.5% of physicians would consider using MHT themselves or recommend MHT to their partners in the future, and 11.4% were currently using MHT.

CONCLUSIONS

Most Chinese physicians have basic knowledge of MHT. Their misunderstandings about MHT mainly centered on the risks of endometrial cancer, weight gain and the necessary examinations during follow-up visits. These misunderstandings need to be clarified in future professional training programs.

First Report of Southern Root-Knot Nematode (Meloidogyne incognita) on Gynostemma pentaphyllum in China

Gynostemma pentaphyllum, belonging to Cucurbitaceae, is a herbaceous climbing plant with multiple medicinal values (Li et al., 2019). It has been planted in Pingli County (109.35 E, 32.39 N), Ankang, Shaanxi province, China for a long history with more than 3000 ha per year. In April 2021, typical root-knot nematode disease symptoms, stunting and galled roots with massive egg masses, were observed on local G. pentaphyllum plants in several gardens. Meloidogyne females and egg masses were dissected from the infected roots. The female was spherical in body shape with a project neck; the excretory pore was at level of or posterior to stylet knobs, 10-20 annules behind head; the perineal pattern had a high dorsal arch, sometimes square or trapezoidal in shape, without obvious lateral lines. The male head was not offset with body, head cap was of stepped outline and concaved at center of top end in lateral view; stylet knobs were prominent, usually demarcated from shaft. Morphological measurements of females (n=20) were: body length (L)= 851.78 ± 83.55 µm (700.15 µm to 986.48 µm); maximum body width (W)= 633.11 ± 71.69 µm (453.09 µm to 746.31 µm); stylet length (ST)= 14.81 ± 0.69 µm (13.31 µm to 15.76 µm); stylet knob height (STKH)= 1.54 ± 0.09 µm (1.45 µm to 1.81 µm); stylet knob width (STKW)= 3.61 ± 0.11 µm (3.38 µm to 3.87 µm); and distance from dorsal esophageal gland opening to the stylet (DGO)= 3.56 ± 0.13 µm (3.28 µm to 4.90 µm). Measurements of males (n=20) were: L=1756.96 ± 67.81 µm (1643.58 µm to 1862.14 µm); W=55.37 ± 1.28 µm (53.46 µm to 57.66 µm); ST= 22.75 ± 1.05µm (19.14 µm to 24.88 µm); STKH= 2.59 ± 0.14 µm (2.45 µm to 2.72 µm); STKW= 3.66 ± 0.13 µm (3.27 µm to 3.91 µm); and DGO= 3.52 ± 0.18 µm (3.38 µm to 4.72 µm). Measurements of second-stage juveniles (J2) (n=20) were: L= 418.99 ± 22.04 µm (376.89 µm to 450.66 µm); W= 14.77 ± 1.15 µm (13.03 µm to 17.77 µm); ST= 12.84 ± 0.45µm (12.05 µm to 13.75 µm); STKH= 1.44 ± 0.13 µm (1.14 µm to 1.71 µm); STKW= 2.25 ± 0.23 µm (1.81 µm to 2.76 µm); and DGO= 1.81 ± 0.31 µm (0.38 µm to 2.56 µm). The morphological characteristics of this nematode were consistent with Meloidogyne incognita (Kofoid and White, 1919) Chitwood, 1949 (Williams, 1973; Eisenback and Hirschmann, 1981). Identification was further confirmed with DNA extracted from 20 individual females. Part of the rDNA spanning internal transcribed spacer (ITS) 1, 5.8S gene, and ITS2 was amplified with the pair of primers: rDNA-F/R (TTGATTACGTCCCTGCCCTTT/TTTCACTCGCCGTTACTAAGG) (Vrain et al., 1992). A 768 bp fragment (GenBank Accession No. MZ613806) was obtained, showing 100% identical (768 bp to 768 bp) to the known sequences of M. incognita (GenBank Accession Nos. MH113856, KC464469, and MT921010). Species identification was also confirmed by amplifying part of the NADH dehydrogenase subunit 5 (nad5) from mitochondrial DNA with primers: NAD5-F/R (TATTTTTTGTTTGAGATATATTAG/CGTGAATCTTGATTTTCCATTTTT) (Janssen et al., 2016). The resulting 611 bp fragment was deposited in GenBank with Accession No. MZ613807. The fragment showed a highest identity of 99.67% (601 bp out of 611 bp) with sequences from other M. incognita isolates (GenBank Accession Nos. MW759707, MW759706, MW759705). Based on both morphological and molecular data, the root-knot nematode from G. pentaphyllum was identified as M. incognita. A pathogenicity test was carried out by inoculating 1500 J2 hatched from the egg masses dissected from the diseased roots to a 4-weeks-old healthy G. pentaphyllum seedling cultured in sterilized sandy soil in pot, 15 plants were inoculated and 5 non-inoculated plants served as controls. After maintained at 25°C for 6 weeks, all of the inoculated plant roots showed galling symptoms which were similar to those observed in the field. Nematodes were collected from root and soil, and an average reproduction factor value of 3.51 was obtained. While no galls were observed on the control plants. For further confirmation, all egg masses dissected from inoculated plants were identified to be M. incognita with its sequence specific primers Mi-F/Mi-R (GGGCAAGTAAGGATGCTCTGAC/CTTTCATAGCCACGTCGCGATC) (Ray et al., 1994). In this study, G. pentaphyllum has been identified as a new host of M. incognita, hence the occurrence status and control of root-knot disease on G. pentaphyllum caused by this pathogen would be new problems in production and need further study.

Morphological characterization reveals new insights into giant cell development of Meloidogyne graminicola on rice

Three types of nematode-feeding sites (NFSs) caused by M. graminicola on rice were suggested, and the NFS polarized expansion stops before the full NFS maturation that occurs at adult female stage. Root-knot nematodes, Meloidogyne spp., secrete effectors and recruit host genes to establish their feeding sites giant cells, ensuring their nutrient acquisition. There is still a limited understanding of the mechanism underlying giant cell development. Here, the three-dimensional structures of M. graminicola-caused nematode-feeding sites (NFSs) on rice as well as changes in morphological features and cytoplasm density of the giant cells (GCs) during nematode parasitism were reconstructed and characterized by confocal microscopy and the Fiji software. Characterization of morphological features showed that three types of M. graminicola-caused NFSs, type I-III, were detected during parasitism at the second juvenile (J2), the third juvenile (J3), the fourth juvenile (J4) and adult female stages. Type I is the majority at all stages and type II develops into type I at J3 stage marked by its longitudinal growth. Meanwhile, NFSs underwent polarized expansion, where the lateral and longitudinal expansion ceased at later parasitic J2 stage and the non-feeding J4 stage, respectively. The investigation of giant cell cytoplasm density indicates that it reaches a peak at the midpoint of early parasitic J2 and adult female stages. Our data suggest the formation of three types of NFSs caused by M. graminicola on rice and the NFS polarized expansion stopping before full NFS maturation, which provides unprecedented spatio-temporal characterization of development of giant cells caused by a root-knot nematode.

Prevalence and Molecular Diversity of Plant-Parasitic Nematodes of Yam (Dioscorea spp.) in China, with Focus on Merlinius spp

Simple Summary

Plant nematodes (PPNs) have been documented as economically important pests of yam in different parts of the world with Pratylenchus spp. and Meloidogyne spp. being the most widespread and destructive pests in Asia, causing significant yield losses. The primary inspiration for this study is the scarcity of information about nematode pests of yam in China and the fact that no previous study has looked into the prevalence, diversity, and integrative taxonomy of PPNs species in China cropping systems, as well as their consequences on yam cultivation. Therefore, the objectives of this study were to conduct a nematode study in south-eastern China to (i) record the prevalence and diversity of PPNs of cultivated yam with emphasis on the five prominent genera identified, and (ii) characterized morphologically, morphometrically, and molecularly Merlinius spp. The high prevalence of the Merlinius spp. revealed that the species may be more important to yam than previously thought. Conclusively, this study provided useful baseline PPNs data for yam in China. Hence, future study should focus on; developing innovative, environmentally friendly, and cost-effective nematode management strategies to control this pest that damage farmers’ yam fields in China, and constantly updating information of PPNs species found to allow proactive measures in terms of their spread and management.

Abstract

There is little information about nematode pests associated with yam in China. Between 2020 and 2021, surveys of yam fields were conducted to investigate the abundance and prevalence of plant-parasitic nematodes in major yam growing areas. A total of 110 bulk soil samples from the yam rhizosphere and 48 yam tubers were collected from seven counties in Jiangxi and Shandong provinces. Standard protocols were used to extract nematodes from soil and tubers and identified at the genus level. In this study, 16 species and 13 nematode genera were recorded. The five most prominent species on the yam rhizosphere according to mean population densities were Pratylenchus coffeae (291/individuals), Meloidogyne (262/individuals), Rotylenchulus reniformis (225/individuals), Merlinius (224/individuals), and Helicotylenchus dihystera (171/individuals). In the tubers, the three most prominent species were Pratylenchus coffeae (415/individuals), Meloidogyne (331/individuals), and Rotylenchulus reniformis (115/individuals). These species were verified with appropriate molecular analysis. The high prevalence of the ectoparasite (Merlinius spp.) on the rhizosphere of yam also revealed that Merlinius spp. May be more important to yam than previously thought. Morphological and molecular analyses further confirmed the identity of the species as Merlinius brevidens and were characterized for the first time on yam in China. Minor morphometrical differences (slightly longer body and stylet) were observed in Chinese populations of M. brevidens compared to the original description. Additionally, this study reveals that M. brevidens isolated from China showed a higher nucleotide sequence in the ITS region compared to M. brevidens populations from India. This finding provides baseline information on the nematode pest occurrence on yam in China and calls for effective management.

Heterodera amaranthusiae n. sp. (Nematoda: Heteroderidae), a new cyst nematode parasitising Amaranthus retroflexus L. in China

A new species of cyst-forming nematode, Heterodera amaranthusiae n. sp., is described and illustrated from the weed, Amaranthus retroflexus, in a potato field in Yunnan Province, China. It is characterised by having canary to russet-brown and asymmetric lemon-shaped cyst, distinct neck, bifenestrate vulval cone, relatively short vulval slit of 29 (28-32) μm, bullae absent and underbridge absent or weak if present. Second-stage juveniles are characterised by a well-developed stylet of 23 (22-25) μm with robust shaft and basal knobs concave anteriorly, tail conoid, 51 (48-58) μm long and hyaline region comprising 48 (41-53)% of its length. Morphologically and morphometrically it most resembles H. vallicola in the Humuli group. The ITS, 28S and COI gene sequences of H. amaranthusiae n. sp. clearly differentiate it from other Heterodera species. For diagnostic purposes, restriction enzyme analysis of the ITS region and three restriction enzymes, AluI, BsuRI (HaeIII) and CfoI (HhaI), were selected, clearly distinguishing H. amaranthusiae n. sp. from representative species in the Humuli group. Phylogenetic relationships with other species of the genus, inferred from two ribosomal regions and the cytochrome oxidase c subunit 1 region, based on Bayesian analysis, consistently showed that H. amaranthusiae n. sp. clustered with high support with other Humuli group species but with separate species status.

Combining targeted metabolite analyses and transcriptomics to reveal the specific chemical composition and associated genes in the incompatible soybean variety PI437654 infected with soybean cyst nematode HG1.2.3.5.7

BACKGROUND

Soybean cyst nematode, Heterodera glycines, is one of the most devastating pathogens of soybean and causes severe annual yield losses worldwide. Different soybean varieties exhibit different responses to H. glycines infection at various levels, such as the genomic, transcriptional, proteomic and metabolomic levels. However, there have not yet been any reports of the differential responses of incompatible and compatible soybean varieties infected with H. glycines based on combined metabolomic and transcriptomic analyses.

RESULTS

In this study, the incompatible soybean variety PI437654 and three compatible soybean varieties, Williams 82, Zhonghuang 13 and Hefeng 47, were used to clarify the differences in metabolites and transcriptomics before and after the infection with HG1.2.3.5.7. A local metabolite-calibrated database was used to identify potentially differential metabolites, and the differences in metabolites and metabolic pathways were compared between the incompatible and compatible soybean varieties after inoculation with HG1.2.3.5.7. In total, 37 differential metabolites and 20 KEGG metabolic pathways were identified, which were divided into three categories: metabolites/pathways overlapped in the incompatible and compatible soybeans, and metabolites/pathways specific to either the incompatible or compatible soybean varieties. Twelve differential metabolites were found to be involved in predicted KEGG metabolite pathways. Moreover, 14 specific differential metabolites (such as significantly up-regulated nicotine and down-regulated D-aspartic acid) and their associated KEGG pathways (such as the tropane, piperidine and pyridine alkaloid biosynthesis, alanine, aspartate and glutamate metabolism, sphingolipid metabolism and arginine biosynthesis) were significantly altered and abundantly enriched in the incompatible soybean variety PI437654, and likely played pivotal roles in defending against HG1.2.3.5.7 infection. Three key metabolites (N-acetyltranexamic acid, nicotine and D,L-tryptophan) found to be significantly up-regulated in the incompatible soybean variety PI437654 infected by HG1.2.3.5.7 were classified into two types and used for combined analyses with the transcriptomic expression profiling. Associated genes were predicted, along with the likely corresponding biological processes, cellular components, molecular functions and pathways.

CONCLUSIONS

Our results not only identified potential novel metabolites and associated genes involved in the incompatible response of PI437654 to soybean cyst nematode HG1.2.3.5.7, but also provided new insights into the interactions between soybeans and soybean cyst nematodes.

First Report of Meloidogyne graminicola on Rice in Henan Province, China

Rice (Oryza sativa) is an important food crop in China and root-knot nematode Meloidogyne graminicola has been one of the most important diseases on rice in recently five years (Ju et al. 2020). In August 2020, rice plants were found to be maldeveloped, yellow leaves and hooked root tips in an irrigated paddy field of Yuanyang County, Xinxiang City, Henan Province. Fifty rice plants were randomly collected and 84.0 percent plants were infected with root-knot nematodes, with root-gall index of 56.0. Then nematodes from rice roots were isolated with 100-μm and 25-μm sieves. A large number of females, some third-stage juveniles (J3s), and a small number of males of Meloidogyne spp. were found in root galls of all samples after dissected, and then were identified and measured under the microscope. In females (n = 20), the perineal pattern was dorsoventrally oval with low and round dorsal arch, and the lateral field was not obvious or absent, striae are usually smooth, with occasional short and irregular striatal fragmentation. The morphological data of females are as follows: body length (BL) = 516.9 ± 72.5 μm (424.2 to 611.6 μm), body width (BW)= 328.4 ± 80.7 μm (232.1 to 437.4 μm), stylet length = 11.2 ± 1.3 μm (7.7 to 13.9 μm), dorsal pharyngeal gland orifice to stylet base (DGO) = 3.9 ± 0.5 μm (3.2 to 4.5 μm), vulval slit length = 24.3 ± 4.6 μm (15.2 to 31.4 μm), vulval slit to anus distance = 16.2 ± 2.5 μm (10.1 to 20.2 μm). Males are long cylindrical, wormlike, with a short round tail. Morphological measurements of males (n = 20) were BL = 1,218.0 ± 150.7μm (1,085.7 to 1,692.2 μm), BW = 34.2 ± 4.6 μm (28.5 to 39.7 μm), stylet = 17.4 ± 0.7 μm (15.9 to 19.3 μm), DGO = 3.6 ± 0.7 μm (2.5 to 4.5 μm), tail = 10.8 ± 2.1 μm (8.0 to 14.8 μm), spicule = 30.3 ± 2.6 μm (24.7 to 36.3 μm). The egg masses from the females were incubated at 28℃ for 48 hours. Measurements of J2s (n = 20) were BL = 444.2 ± 37.8 μm (315.7 to 547.5 μm), BW = 21.2 ± 2.7 μm (16.7 to 26.4 μm), stylet = 14.2 ± 0.3 μm (13.6 to 14.8 μm), DGO = 3.5 ± 0.5 μm (2.7 to 4.5 μm), tail = 70.8 ± 5.1 μm (61.3 to 80.8 μm), hyaline tail length = 21.0 ± 2.5 μm (16.3 to 26.1 μm). These morphological features are consistent with the original description by Golden and Birchfield (1965). DNA of a single female from each sample was extracted for molecular identification. Primer pairs D2A/D3B (5´-ACAAGTACCGTGAGGGAAAGTTG-3´/ 5´-TCGGAAGGAACCAGCTACTA-3´) (De Ley et al. 1999) and the species-specific primers Mg-F3/Mg-R2 (5'-TTATCGCATCATTTTATTTG-3'/ 5'-CGCTTTGTTAGAAAATGACCCT-3') (Htay et al. 2016) were used to amplify D2/D3 region of 28S RNA and the internal transcribed spacer (ITS) region, respectively. The amplified sequences of D2/D3 region (GenBank MW490724, 766 bp) shared 99.9% and 99.7% homology with the sequences of M. graminicola (MN647592, MT576694) isolated from Guangxi and Anhui Province (Ju et al. 2020), respectively, while ITS region sequences (MW487239, 369 bp) shared 100% and 99.7% homology to M. graminicola isolate GXL3 (MN636702) and FQJJ01 (MT159690), respectively. In order to verify the pathogenicity of nematodes, about 300 J2s were inoculated on ten 14-week-old rice (Oryza sativa cv. Nipponbare) planted in pots with sterilized sandy soil, respcectively, and maintained in a greenhouse at 28°C/26°C with a 16h/8h light/dark photoperiod and 75% relative humidity. At 14 days post inoculation, obvious symptoms of hook galls were observed on roots in all inoculated rice plants, and females and males in the same shape as the collected samples were found in the root galls under the stereoscopic microscope. No symptoms were observed on non-inoculated rice plants. After 28 days, the growth of the inoculated rice plants was significantly worse than that of uninoculated ones, with yellow leaves and short plants. These results confirmed the pathogenicity of M. graminicola on rice and it indicated that M. graminicola was already spread from the main rice-producing areas to the wheat and rice rotation areas. To our knowledge, this is the first report of M. graminicola in the Henan Province of China.

A new cyst-forming nematode, Cactodera tianzhuensis n. sp. (Nematoda:Heteroderinae) from Polygonum viviparum in China with a key to the Genus Cactodera

A new cyst-forming nematode, Cactodera tianzhuensis n. sp. was isolated from the rhizosphere soil of Polygonum viviparum L. in Tianzhu county, China. Morphologically, the new species is characterized by lemon-shaped or rounded cysts that have protruding necks and vulval cones. The vulval cone of the new species appeared to be circumfenestrate without bullae and underbridge, vulval denticle present and anus distinct. Second-stage juveniles are vermiform, stylet well-developed with the rounded stylet knobs to slightly concave anteriorly. Lateral field with four incisures. Tail gradually tapering to a finely rounded terminus with a length of ca 54 (47–59) µm, outline of hyaline portion is V-shaped or U-shaped. Egg shells without visible markings or punctations. The phylogenetic analyses based on ITS-rDNA, D2-D3 of 28S-rDNA clearly revealed that the new species formed a separate clade from other Cactodera species, which further support the unique status of C. tianzhuensis n. sp. Therefore, it is described herein as a new species of the genus Cactodera.

First report of Heterodera filipjevi on winter wheat from Hebei Province in North China

Three of the cereal cyst nematodes, Heterodera avenae, H. filipjevi and H. latipons are considered to be the most economically important cyst nematodes that affect cultivated cereals around the world. H. filipjevi was first detected in China from Xuchang, Henan Province in 2010 (Peng et al. 2010) and now has been recorded in the Central China of Henan, Shandong and Anhui provinces and the Northwest China of Xinjiang Uygur Autonomous Region (Cui et al. 2020). In June 2019, 42 samples consisting of roots and soil were collected from winter wheat fields in Hebei Province of North China. Cysts were detected in 37 soil samples with a mean of 6.4 ± 1.67 cysts per 100 ml of soil. Cysts and second-stage juveniles (J2s) were extracted from root and soil following Cobb's sieving gravity method. Morphological and molecular studies of J2s and cysts confirmed its identity with H. filipjevi in 5 samples from Handan (N36°10'052" and E114°35'056"; N36°37'054" and E114°22'052"), Xingtai (N36°53'060" and E114°30'011") and Shijiazhuang (N 37°26'048" and E 116°05'039") in Hebei Province, China. Morphologically, the cysts are lemon-shaped, light or dark brown in color. The vulval cone is bifenestrate with horseshoe-shaped semifenestrae, strongly globular bullae, and well-developed underbridge. Measurements (mean +_ sd (range)) of cysts (n=10), body length not including neck is 743.0 ± 36.1 μm (665 - 780 μm), body width is 559.0 ± 50.0 μm (455 - 639 μm), length / width ratio is 1.33 ± 0.07 (1.20 - 1.46); neck length is 99.3 ± 8.8 μm (85 - 122 μm); fenestrae length is 56.8 ± 5.0 μm (49 - 65 μm) and width is 25.5 ± 1.8 μm (21.1 - 27.8 μm); underbridge length is 84.0 ± 8.1 μm (62 - 93 μm); and vulval slit length is 8.6 ± 0.5 μm (7.2 - 9.1 μm). Measurements of J2s (n = 12), body length is 541 ± 11.4 μm (490 - 578 μm); stylet length is 22.3 ± 0.5 μm (22.0 - 25.0 μm) with anchor-shaped basal knobs; tail length is 57.7 ± 3.7 μm (52.7 - 65.2 μm), and hyaline tail terminal length is 36.5 ± 2.8 μm (32 - 39.8 μm). The tail had a sharp terminus. Morphology of the cysts and J2s were consistent with the record of H. filipjevi (Peng et al. 2010; Subbotin et al. 2010). The amplifications of rDNA-internal transcribed spacer (ITS) fragments were generated with a PCR fragment of 1054 bp from single cysts of each population, using primers TW81 and AB28 (Joyce et al. 1994). The PCR tests for each sample were repeated five times. The PCR product was purified and sequenced. All nucleotide sequences of ITS-rDNA were submitted to GenBank under accession numbers MW282843-6. Sequences from the ITS region were more than 99.5% identical to those of H. filipjevi from Egypt (KF225725), Turkey (KR704308, KR704293 and MN848333) and China (KT314234, MT254744 and KY448473). These results from ITS supported its identity as H. filipjevi. The results were also confirmed by species specific sequence characterized amplified region primers of H. filipjevi (Peng et al. 2013). Pathogenicity of the H. filipjevi was confirmed by infection of winter wheat (Triticum aestivum L cv. 'Aikang58') and examination of the nematode development and reproduction. Wheat seeds were germinated in petri dishes and then transplanted into five polyvinyl chloride tubs (3 cm in diameter, 25 cm in length) that contained 150 cm3 of a sterile soil mixture (loamy soil: sand = 1:1), each with 5 cysts (mean of 252.0 eggs/cyst). Plants were grown in an artificial climate box for one week at 14/18°C, two weeks at 16/20°C, five weeks at 18/25°C and two weeks at 22/30°C, under 8 h of darkness/16 h light and normal culturing practices (Cui et al. 2015). The parasitic J2s, third and fourth-stage juveniles, and adult females were observed in roots stained with acid fuchsin at 10, 20, 30, and 50 days after inoculation (DAI), and an average of 32.0 cysts per tubes were extracted 70 DAI. The new cyst' morphological and molecular characteristics were identical to the H. filipjevi cysts from the original soil samples. Three other tubes without cysts were set as control and there were no newly formed cysts. Heterodera avenae and H. filipjevi had been detected in a total of 16 wheat-producing provinces in China, which resulted in losses of 1.9 billion CNY year-1 (Cui et al. 2015). To our knowledge, this is the first report of H. filipjevi in Hebei Province of North China. Cereal cyst nematodes are easily transferred to non-infested areas by many avenues, resulting in increased species and pathotype complexity (Cui et al. 2020). Once H. filipjevi continues to spread in main wheat producing area of China, it could become be a new threat to cereals production. It is time to take effective control methods to prevent H. filipjevi further dispersal, especially through the farming machinery transmission. Hebei Province is one of the most important major grain-producing areas, our findings will be very beneficial for H. filipjevi management and further research on winter wheat in Hebei Province, North China.