Begomoviruses have been considered as the most widespread group of whitefly-transmitted viruses causing diseases in tomato (leaf curl), okra (yellow vein), cotton (leaf curl), legumes (yellow mosaic), cassava (mosaic) and cucurbits (yellow mottle). These diseases are caused by a complex of begomovirus and satellite DNA molecules. The genomes of Begomoviruses possess either monopartiate (only DNA A) and or bipartiate (both DNA A & DNA B) with a size ~2.7–2.8 kb. DNA beta is ssDNA molecule approximately half the size (~1350 bp) of typical begomovirus genome, which is known to be essential for symptom induction. At Mahyco Research Center, Jalna, an attempt was made to identify, characterize & study the genetic diversity DNA beta in begomoviruses. We have successfully isolated, cloned and sequenced a number of full lengths DNA beta molecules associated with ToLCV, OYVMV and CLCuV from tomato, okra and cotton, respectively. In addition, sub-genomic DNA satellite molecules of size ~0.7–0.8 kb were also associated. Based on phylogenetic sequence analysis, the DNA beta molecules were grouped into three major clusters and identified nine, six and five distinct species associated with the begomoviruses infecting tomato, okra and cotton, respectively. New DNA beta molecules characterized from chilli and cucurbits were closely related to DNA beta from tomato cluster. Mixed infections of more than one beta DNA from the field isolates of CLCuV in cotton was also observed. The role of DNA beta molecules in begomovirus infections would elucidate to understand the functional aspects.
