Tomato Leaf Curl Viruses from India

Abstract

Leaf curl disease of tomato (ToLCD) caused by tomato leaf curl viruses (ToLCVs) is one of the major constraints for successful cultivation of this crop throughout India. Intensive agricultural practices necessitated by the ever-increasing demands of rapidly growing population and the introduction of new genotypes and cropping pattern have further aggravated the situation. Whitefly (Bemisia tabaci Genn.) can successfully transmit the causal virus under natural conditions. Several crop as well as weed species are known to harbor ToLCVs in India. Maximum temperature and rainfall play an important role for spread of the disease in southern India, while minimum temperature and minimum relative humidity influence the whitefly population in the north. Five distinct species of the genus Begomovirus (Tomato leaf curl Bangalore virus, Tomato leaf curl Karnataka virus, Tomato leaf curl Gujarat virus, Tomato leaf curl Pune virus, and Tomato leaf curl New Delhi virus) are known to be associated with ToLCD in India. Satellite DNA-β's associated with ToLCVs are highly diverse and share a much lower degree of nucleotide identity among themselves. Mixed begomovirus infections, a prerequisite for recombination, are also observed which lead to synergistic interaction and virulent pseudo-recombination. Extensive research on conventional breeding has led to development of resistant genotypes from which resistant gene has also been mapped.