A Genomic Survey of Thirty Soybean-infecting Bean Common Mosaic Virus (BCMV) Isolates from China Pointed BCMV As a Potential Threat to Soybean Production

Widely known as a severe pathogen of bean plants, the bean common mosaic virus (BCMV) has been reported to infect soybeans only sporadically and the involved strains were all found in China regions. To explore variations among soybean-infecting BCMV strains, hundreds of soybean mosaic leave samples were collected throughout China, with a total of 30 BCMV isolates detected and their genomes sequenced. These newly obtained genomes, together with 16 other BCMV genomes available in GenBank were examined from multiple aspects to characterize BCMV evolutionary processes. Phylogenetic analysis showed that both soybean-infecting BCMVs (group I) and peanut-infecting BCMVs (group II) are distantly related to other BCMVs, suggesting ancestral differentiation and host adaptation. Genetic variation analysis showed that P1, P3 and 6K2 genes and the beginning portion of CP gene showed higher levels of variation relative to other genes. Moreover, selection analyses further confirmed that a number of sites within the P1 and P3 genes have suffered positive selection. These obtained BCMV sequences also exhibit high recombination frequencies, indicating a more dynamic evolutionary history. Finally, 12 different soybean cultivars were challenged with two BCMV isolates (DXH015 and HZZB011), with most of the cultivars successfully infected. These findings suggest that BCMV is indeed a potential threat to soybean production.