Genetic diversity of viruses associated with sugarcane mosaic disease of sugarcane inter-specific hybrids in China

Abstract

In this study, we investigated 78 sugarcane samples with severe mosaic symptoms collected from four provinces of southern China: Guangxi, Yunnan, Hainan, and Guangdong, which cover nearly 85 % of commercial sugarcane planting zones in China. Using RT-PCR, sequencing and phylogenetic analysis, we identified 72 hybrid sugarcane samples containing causal agents of sugarcane mosaic disease. Among these, 66 virus isolates were identified as Sorghum mosaic virus (SrMV) (84.6 %), four were identified as Sugarcane streak mosaic virus (SCSMV) (5.1 %), and two were identified as Sugarcane mosaic virus (SCMV) (2.6 %). The isolates of SrMV were classified into three subgroups: I, II, and III with a 95 % similarity level. The two largest subgroups, SrMV I containing 36 sugarcane mosaic diseases isolates (46.2 %), and SrMV III containing 20 isolates (25.6 %), were prevalent in Guangdong and Guangxi provinces; however, SrMV II containing five isolates (6.4 %) did not exhibit any close association with geographical distribution. The popular sugarcane cultivar, ROC22, was found to be infected with all the three subgroup types of SrMV. According to our knowledge, this is the first reported detection of the co-infection of SrMV and SCSMV in Saccharum hybrid (YN-bs-9). Recombination analysis indicated recombination between different isolates mostly occurring in Yunnan and Guangxi provinces among the SrMV I group. This study provides insight into the species diversity and geographical distribution of causal agents of sugarcane mosaic disease, and provides the basis for its identification, prevention, and future control efforts.