Biological and molecular characterization of Zucchini yellow mosaic virus isolates infecting melon in Xinjiang, China

Zucchini yellow mosaic virus (ZYMV) causes one of the most destructive diseases of cucurbits worldwide. Although the virus has been present in China for more than 25 years, there is little information about biological and molecular traits of ZYMV isolates from China. This study aimed to characterize 26 ZYMV isolates from Xinjiang, China based on pathotypes, molecular variability and host range. Phylogenetic analysis of the complete sequences of the coat protein gene revealed three distinct groups (A, B and C), with four subgroups in A (I–IV). All isolates from Xinjiang were placed in group C and subgroups A–I and A–II. To test for differences in host range among different phylogenetic groups from Xinjiang, 13 isolates were mechanically inoculated onto 14 plant species in five families and their pathotypes were also identified based on the reaction of a resistant melon accession PI414723. Overall, the results showed that there were no correlations of host responses to inoculation with ZYMV isolates from different phylogenetic groups. However, on Cucurbita pepo, differences in host responses to inoculation with the ZYMV isolates from different phylogenetic groups were observed. Although the host range of the 13 isolates tested was similar, their biological properties on different hosts were slightly different from the ZYMV isolates characterized in other countries. The results of the pathotype test showed that the 13 ZYMV isolates were classified as pathotype 0. The information obtained is important in breeding for resistant varieties.