Virology Unit, Division of Plant Pathology, Indian Agriculture Research Institute, New Delhi-110012, India.
Citrus mosaic virus (CMBV) is a bacilliform double stranded DNA virus belonging to genus Badanvirus of Caulimoviridae. The virus causes yellow mosaic disease in Sathgudi sweet orange in Andhra Pradesh. Its natural occurrence on other citrus varieties has also been reported and the symptoms of the disease may vary from mild to bright yellow mottling in different species of citrus. Full genome of the CMBV associated with acid lime, Rangpur lime and Sathgudi sweet orange has been cloned and sequenced. The size of CMBV genome was ∼7.5 kb. Deletions of nucleotide were observed at several points in the viral genome of these isolates. The ORF 3 contains domains homologous to those of aspartic protease, reverse transcriptase and RNase H, which are conserved among all the plant pararetroviruses. In order to determine the variability in CMBV associated with different citrus species, part of ORF 3 and intergenic region of 6 isolates were amplified, cloned and sequenced. There was high variability in 3’ intergenic region (4–20%) while 5’ intergenic region was comparatively conserved (1.7–12.2%). The variability in nucleotide and amino acid sequence in the putative RNase H and reverse transcriptase region of ORF 3 was up to 10% and 5% respectively. The phylogenetic studies have been carried out based on intergenic region and part of ORF3 and have been discussed in this paper.
