Diversity and Phylogeny of Begomovirus Populations and their Management

Begomoviruses are plant-infecting viruses, which are transmitted by the whitefly vector Bemisia tabaci and have been known to cause extreme yield reduction in a number of economically important vegetables around the world. They are abundant in tropical and subtropical environments, where insects that transmit these viruses are abundant. Identification of plant viruses, monitoring for new viral diseases, understanding the vectors that transmit viruses, and determining viral and vector impacts on the growth and development of crop cultivars and lines is vital to managing and controlling these diseases. In addition to damaging crops and causing yield losses, plant viruses interact with vectors and other diseases to increase the damage from the diseases/pests. The crops and weeds growing close to the crop fields are potential reservoirs of begomoviruses, but it is not known whether the same viruses infect several host species or co-infect any of the hosts. This increases the difficulty of controlling both the plant virus and the interacting pathogen or vector. In a survey carried out in 2011-14 we observed several cultivated crops, ornamental plants and weeds with leaf curling, vein yellowing and growth stunting - typical symptoms of begomovirus. The DNA was isolated from the infected samples and the presence of begomovirus was confirmed by PCR using component specific primers. Further, rolling circular amplification (RCA) was performed to get the full-length sequence of the isolates. The full length sequence showed genome arrangement typical of monopartite/ bipartite begomovirus. Some of the infected samples showed association of a betasatellite responsible for the epidemic diseases in the case of monopartite. Phylogenetic analysis confirmed the diversity of begomovirus in India. Our result also indicates that begomovirus has broaden its host range by recombination process. Expression of various full length or truncated or defective proteins of the virus has been effective in accomplishing pathogen-derived resistance. We analyzed the recombination parmeters of begomovirus strains and developed the RNAi strategy for the disease management.