Function of the natural variation of CP in their infectivity of WYMV and CWMV

The soil-borne viral disease, caused by Wheat yellow mosaic virus (WYMV) and Chinese wheat mosaic virus (CWMV), is one of the most destructive diseases of wheat in China. Considering the large wheat growing area in China, the genetic diversity of WYMV and CWMV could be high in the country. However, studies on genetic variabilities of WYMV and CWMV in China are limited, making it difficult to prevent and control viral diseases in wheat. During 2021-2022, the wheat leaves with typical yellow mosaic virus symptoms were randomly collected from wheat fields in seven provinces. Nine WYMV and one CWMV isolates were identified in the samples using small RNA sequencing and RACE technology. Sequence alignment showed that several amino acid substitutions were occurred in the CP (coat protein) from these isolates. Moreover, we replaced the CP of WYMV and CWMV infectious clones with CP of newly identified isolates and found that natural variation of CP is involved in the infectivity of WYMV. Moreover, the WYMV infectious clones containing CP of the WYMV isolates from Junan at Shandong Province or Yangzhou at Jiangsu Province have enhanced WYMV infection in several local wheat resistance cultivars. Taken together, our findings suggested that the distribution of WYMV and CWMV in wheat growing areas has expanded in these years and the natural variation of viral genome was involved in pathogenicity of WYMV. Our results also provided a theoretical basis to explain the real distribution of wheat viral resistance varieties in China.