Molecular characterisation of cereal cyst nematodes in winter wheat on the Huang-Huai floodplain of China using RFLP and rDNA-ITS sequence analyses

In response to the recent discovery of Heterodera filipjevi central Henan and the uncertain taxonomic status of Heterodera avenae more widely in China, heteroderid specimens from winter wheat at 21 locations in Henan and adjacent provinces were subjected to RFLP and rDNA-ITS sequence analysis. H. filipjevi was found in six locations in Henan, including two mixed with H. avenae; H. avenae being found at all other locations. A new RFLP profile type was found for H. filipjevi, three new types for H. avenae and the Australian type (Heterodera australis) were found for the first time in China (at two locations). Otherwise, H. avenae and H. filipjevi were of RFLP types previously reported in China. Phylogenic analysis of the rDNA sequences showed H. filipjevi in China was less diverse than H. avenae, with greatest similarity to specimens from Italy and the USA, which is consistent with a more recent introduction. In contrast, H. avenae in China was clearly distinct from H. avenae found elsewhere, except for the discovery of the Australian types. Although the Australian types clustered together, this fell within the variation found for the remainder of the specimens from China, which may represent a single species. These data reveal additional genetic diversity within the two cereal cyst nematode species in China, which is likely to have implications for the development of their control by host resistance.