Division of Molecular Virology, Mahyco Research Center, Dawalwadi, Jalna.
Abstracts of Research Papers Presented during the National Symposium of Indian Virological Society at Unit of Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110 012, October 14–1.
Leaf curl is one of the major constraint in tomato cultivation across the country. An extensive survey has been conducted in the major tomato growing regions of India and collected representative leaf curl virus isolates for biological and molecular characterization. In the present study we have analyzed over 100 tomato leaf curl virus ((ToLCV) isolates collected during 1999–2004. It has been observed that there are two distinct type of symptoms associated in tomato viz., common leaf curl and yellow mottle type. The common leaf curl virus isolates are widely prevalent across the country with varied levels of severity, whereas the yellow mottle type of symptoms were highly confined to Central and Northern India. Further, it has been observed that the yellow mottle types were generally associated with the bipartite genome of DNA-A and DNA-B. In order to understand the sequence diversity across the country, nearly one foruth (∼700 bp) of DNA-A component among the ToLCV isolates were PCR amplified, cloned and sequenced. The sequences were analyzed using vector NTI software Version 5.5. Phylogenetic analysis of nucleotide sequences indicated the existence of more than 13 tentative ToLCV species among the common leaf curl and yellow mottle virus isolates in India. Out of 13 ToLCV species, eight species/clusters are belonging to a distinct yellow mottle type and mixed infections. In the present study, the results of phylogenetic analysis among ToLCV nucleotide sequences were discussed. Nucleotide sequence analysis revealed that mixed infections and recombinations in the ToLCV genome were frequently encountered among tomato isolates. In some of the cases, recombination between ToLCV and Okra yellow vein mosaic virus has been observed. Geminviruses shares nucleotide sequences/fragments of its genome with other species or a strain establishing that recombination is an essential event for virus evolution.
In addition to complex sequence diversity, association of DNA beta molecules were commonly encountered in ToLCV isolates collected from different regions. It has been observed that ∼ 1300 bp and satellite DNA molecules of ∼ 650 bp were also reported. DNA beta interaction with monopartite and bipartite ToLCV are yet to be understood.
