GENETIC VARIATIONS IN RICE GRASSY STUNT VIRUS STRAINS ISOLATED FROM CUU LONG RIVER DELTA PROVINCES

Abstract

Rice Grassy Stunt Virus (RGSV), Rice Ragged Stunt Virus (RRSV) and Rice Tungro Spherical Virus (RTSV) are members in the genus TenuivinJs. causing destructive disease of rice (Ory=a sativa, L.). The common properties of the viruses in the genus family are virions filamentous, single-stranded ambisense RNAs in the genome. Recently, the disease has spreaded out and resulted in a drastical decrease of rice yield in Cuu Long river delta (CLRD) provinces. We collected viral-infected rice samples in several CLRD provinces aiming to investigate genetic diversity of the viruses. To amplify gene encoding viral coat protein (CP), primers were designed based on the viral nucleotide sequences in GenBank. In this paper, we cloned and sequenced the CP gene ofRGSV but not RRSV and RTSV due to in part the low infection of these viruses. The CP genes of ROSY in various rice samples were similar to each other from 97% to 99.8% at the nucleotide level and from 91.5% to 99.7% at the amino acid level. The phylogenetic tree showed that Vietnamese CP sequences and the others in GenBank belong to two separated groups. Taken together, we conclude that ROSY might be the main destructive factor in rice in CLRD provinces and the CP gene sequences are well conserved among these ROSV strains