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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. destructorwere 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. destructorwere 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. pilosulaand Angelica sinensiscompared 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. destructorwere 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. destructorpopulations on Chinese medicinal materials are very different from those on other hosts and this work provides a paradigm for relevant researches.

The cereal cyst nematode, Heterodera avenae, is one of the most economically important pathogens impacting the worldwide production of cereals and is widely distributed in more than 16 regions in China. The present study used the numbers of nematodes inside the plant roots to evaluate the resistance/susceptibility of different subpopulations of barley Hordeum vulgare(QH2R, QH6R and TB2R) to H. avenaeunder field and pot conditions. Nematode development in two highly resistant varieties was also evaluated by in vivoexperiment and microscopic observation. Analyses of 186 selected varieties showed the numbers of susceptible varieties identified with the number of females/cysts per plant (NFP) method were significantly higher than those identified with the Pf/Pi ratio (PPR) method, which indicated that the NFP method rather than the PPR method is more reliable to evaluate the resistance of barley. The field and pot experiment results indicated that the QH2R subpopulation had lower females/cysts numbers than QH6R and TB2R subpopulations, and eight HR varieties (Sunong 7617, Sunong 7635, Dongyuan 87-14, Rudong 14-46, Rudong 87-57, Rudong 87-8-45, Rudong 88-14-2, and Rudong 88-67-1) were identified in QH2R, with the NFP numbers below 4.2. Further microscopic observation of nematode development suggested that H. avenaeoften penetrated less into highly resistant varieties (Sunong 7635 and Dongyuan 87-14) and more frequently failed to develop into females than the susceptible barleys. The promising resistant varieties identified in the present research might be helpful for breeders to develop CCN-resistant cultivars and control H. avenaepopulations effectively at low costs.