Differences in cultivar response and complete sequence analysis of two isolates of wheat yellow mosaic bymovirus in China

Seeds of selected European and Japanese winter wheat cultivars were grown at two experimental sites in China, namely Yaan, Sichuan province (YA), and Yangzhou, Jiangsu province (YZ), where wheat yellow mosaic bymovirus (WYMV) was severe. There were some differential responses of the cultivars to the virus isolates present at the two sites. The complete nucleotide sequence of both RNAs of both virus isolates was determined. Their genome organization was identical to that reported for a Japanese isolate and the sizes were very similar. Nucleotide comparisons demonstrated that parts of the CI and NIa coding regions on RNA1 and the N-terminal part of the P2 coding region on RNA2 were particularly variable, while substantially conserved regions occurred in the 3' UTR of RNA2, the 7K, one part of the CI and parts of the NIb and coat protein. It seems unlikely that differences in the 7K and NIa-VPg proteins are responsible for virulence differences and the CI and NIb regions were considered the most promising for further study.