Abstract:

In order to understand the occurrence of sorghum mosaic virus (SrMV), one of pathogenic virus causing sugarcane mosaic disease in south China, sugarcane leaf samples with mosaic symptom were collected from commercial growing fields in Guangzhou, Wengyuan, Boluo of Guangdong province and Nanning of Guangxi province. The virus was detected by one-step RT-PCR with SrMV specific primers P1 (5′-ACAGCAGAWGCAACRGCACAAGC-3′) and P2 (5′-CTCWCCGACATTCCCATCCAAGCC-3′, Y=C/T, W=T/A, K=G/T, R=A/G) based on the viral coat protein (CP) gene. The results showed that 48% samples were infected with SrMV. Ten amplified cDNA products were chosen based on host and geographic origin for direct sequencing. BLAST analysis revealed that they were all homologous to reported SrMV CP gene. To investigate the genetic diversity within the species SrMV, multiple alignment analysis of CP gene nucleotide sequences of the 10 SrMV isolates, together with all 18 SrMV isolates documented in GenBank up to date, was perfermed using Clustal W algorithm. It was showed that 28 SrMV isolates were clustered into two groups, namely hybrid sugarcane (HS) group and noble sugarcane (NS) group. The average CP gene nucleotide identities were 80% between groups, and 87% and 90% between isolates within HS and NS groups, respectively. Coincidently, most isolates in HS group were from hybrid sugarcane, whereas most isolates in NS group from noble sugarcane. This implies that SrMV has evolved under host selection. Hence, not only different pathogens and host types, but also the virus genetic diversity should be taken into consideration in sugarcane mosaic disease controlling and virus-resistance breeding.

Key words: Sugarcane mosaic disease, Sorghum mosaic virus, Genetic diversity