In recent years, Meloidogyne enterolobii has emerged as a major parasitic nematode infesting many plants in tropical or subtropical areas. However, the regions of potential distribution and the main contributing environmental variables for this nematode are unclear. Under the current climate scenario, we predicted the potential geographic distributions of M. enterolobii worldwide and in China using a Maximum Entropy (MaxEnt) model with the occurrence data of this species. Furthermore, the potential distributions of M. enterolobii were projected under three future climate scenarios (BCC-CSM2-MR, CanESM5 and CNRM-CM6-1) for the periods 2050s and 2090s. Changes in the potential distribution were also predicted under different climate conditions. The results showed that highly suitable regions for M. enterolobii were concentrated in Africa, South America, Asia, and North America between latitudes 30° S to 30° N. Bio16 (precipitation of the wettest quarter), bio10 (mean temperature of the warmest quarter), and bio11 (mean temperature of the coldest quarter) were the variables contributing most in predicting potential distributions of M. enterolobii. In addition, the potential suitable areas for M. enterolobii will shift toward higher latitudes under future climate scenarios. This study provides a theoretical basis for controlling and managing this nematode.
Diagnosis and characterization of the ribosomal DNA-ITS of potato rot nematode (Ditylenchus destructor) populations from Chinese medicinal herbs
The potato rot nematode (Ditylenchus destructor) is a very economically important nematode in agronomic and horticultural plants worldwide. In this study, 43 populations of D. destructor were collected from different hosts across China, including 37 populations from Chinese herbal medicine plants. Obtained sequences of ITS-rDNA and D2–D3 of 28S-rDNA genes of D. destructor were compared and analyzed. Nine types of significant length variations in ITS sequences were observed among all populations. The differences in ITS1 length were mainly caused by the presence of repetitive elements with substantial base substitutions. Reconstructions of ITS1 secondary structures showed that the minisatellites formed a stem structure. Ten haplotypes were observed in all populations based on mutations and variations of helix H9. Among them, 3 known haplotypes (A–C) were found in 7 populations isolated from potato, sweet potato, and Codonopsis pilosula, and 7 unique haplotypes were found in other 36 populations collected from C. pilosula and Angelica sinensis compared with 7 haplotypes (A–G) according to Subbotin’ system. These unique haplotypes were different from haplotypes A–G, and we named them as haplotypes H–N. The present results showed that a total of 14 haplotypes (A–N) of ITS-rDNA have been found in D. destructor. Phylogenetic analyses of ITS-rDNA and D2–D3 showed that all populations of D. destructor were clustered into two major clades: one clade only containing haplotype A from sweet potato and the other containing haplotypes B–N from other plants. For further verification, PCR-ITS-RFLP profiles were conducted on 7 new haplotypes. Collectively, our study suggests that D. destructor populations on Chinese medicinal materials are very different from those on other hosts and this work provides a paradigm for relevant researches.
were inoculated with 2 000 eggs, and cultured in an incubator at 23°C/20°C with a 16 h/8 h light/dark photoperiod. After three months inoculation, 36±7.2 cysts and females were extracted from the infested potato roots, no females and cysts were observed on control plants.
This is the first report of potato golden cyst nematode G. rostochiensis in China.
Potassium (K), an important nutrient element, can improve the stress resistance/tolerance of crops. The application of K in resisting plant-parasitic nematodes shows that the K treatment can reduce the occurrence of nematode diseases and increase crop yield. However, data on K2SO4 induced rice resistance against the root-knot nematode Meloidogyne graminicola are still lacking. In this work, K2SO4 treatment reduced galls and nematodes in rice plants and delayed the development of nematodes. Rather than affecting the attractiveness of roots to nematodes and the morphological phenotype of giant cells at feeding sites, such an effect is achieved by rapidly priming hydrogen peroxide (H2O2) accumulation and increasing callose deposition. Meanwhile, galls and nematodes in rice roots were more in the potassium channel OsAKT1 and transporter OsHAK5 gene-deficient plants than in wild-type, while the K2SO4-induced resistance showed weaker in the defective plants. In addition, during the process of nematode infection, the expression of jasmonic acid (JA)/ethylene (ET)/brassinolide (BR) signaling pathway-related genes and pathogenesis-related (PR) genes OsPR1a/OsPR1b was up-regulated in rice after K2SO4 treatment. In conclusion, K2SO4 induced rice resistance against M. graminicola. The mechanism of inducing resistance was to prime the basal defense and required the participation of the K+ channel and transporter in rice. These laid a foundation for further study on the mechanism of rice defense against nematodes and the rational use of potassium fertilizer on improving rice resistance against nematodes in the field.
Soybean cyst nematode (SCN) Heterodera glycines is considered as the major constraint to soybean production. GmSHMT08 at Rhg4 locus on chromosome 08, encoding a serine hydroxylmethyltransferase, is a major gene underlying resistance against H. glycines in Peking-type soybeans. However, the molecular mechanism underpinning this resistance is less well characterized, and whether GmSHMT08 could interact with proteins in H. glycines remains unclear. In this study, yeast two-hybrid screening was conducted using GmSHMT08 as a bait protein, and a fragment of a 70-kDa heat shock protein (HgHSP70) was screened from H. glycines that exhibited interaction with GmSHMT08. This interaction was verified by both GST pull-down and bimolecular fluorescence complementation assays. Our finding reveals HgHSP70 could be applied as a potential candidate gene for further exploring the mechanism on GmSHMT08-mediated resistance against SCN H. glycines.