GENETIC VARIABILITY OF THE REPLICASE (NIb) GENE OF PAPAYA RINGSPOT VIRUS IN NORTHERN INDIA INDICATES COMMON ANCESTRY WITH ISOLATES FROM CHINA AND TAIWAN

The purpose of the present study was to investigate the genetic variability and phylogeny of Papaya ringspot virus (PRSV) on the basis of NIb (replicase) gene. The NIb and coat protein (CP) regions of about 2.5 kb of seven PRSV isolates from North India were cloned and sequenced. The North Indian isolates R2R and R5R have higher and lower sequence similarity with other PRSV isolates, respectively. Sequence comparison of NIb gene of 42 PRSV isolates, revealed that the average evolutionary divergence of all sequence pairs were 10.6% and 11.2% at amino acid and nucleotide level, respectively. Transitions were more frequent than transversions in the analyzed sequences. Maximum likelihood phylogenetic tree of combined NIb and CP regions indicated the common ancestry of North Indian isolates with Chinese and Taiwanese isolates. One potential recombination breakpoint in isolate R5R, together with its higher sequence identity and common ancestry with Chinese PRSV isolates, suggest the possible import of the former from the Chinese subcontinent.