Genetic Diversity Analysis of Brassica Yellows Virus Causing Aberrant Color Symptoms in Oilseed Rape

The emergence of brassica yellow virus (BrYV) has increasingly damaged crucifer crops in China in recent years. In 2020, a large number of oilseed rape in Jiangsu showed aberrant leaf color. A combined RNA-seq and RT-PCR analysis identified BrYV as the major viral pathogen. A subsequent field survey showed that the average incidence of BrYV was 32.04%. In addition to BrYV, turnip mosaic virus (TuMV) was also frequently detected. As a result, two near full-length BrYV isolates, BrYV-814NJLH and BrYV-NJ13, were cloned. Based on the newly obtained sequences and the reported BrYV and turnip yellow virus (TuYV) isolates, a phylogenetic analysis was performed, and it was found that all BrYV isolates share a common root with TuYV. Pairwise amino acid identity analysis revealed that both P2 and P3 were conserved in BrYV. Additionally, recombination analysis revealed seven recombinant events in BrYV as TuYV. We also attempted to determine BrYV infection by quantitative leaf color index, but no significant correlation was found between the two. Systemic observations indicated that BrYV-infected plants had different symptoms, such as no symptom, purple stem base and red old leaves. Overall, our work proves that BrYV is closely related to TuYV and could be considered as an epidemic strain for oilseed rape in Jiangsu.

Automated summary

The emergence of brassica yellow virus (BrYV) has caused increasing damage to crucifer crops in China. A study in Jiangsu province found BrYV to be the major viral pathogen in oilseed rape plants with aberrant leaf color. Phylogenetic and amino acid identity analysis revealed close relationship between BrYV and turnip yellow virus (TuYV), with conserved regions in P2 and P3 of BrYV. Recombination analysis also showed associations between BrYV and TuYV. Overall, this research highlights the importance of BrYV as an epidemic strain in oilseed rape cultivation in Jiangsu.