Indian Phytopath. 57 (4) : 396-407 (2004) Current status of begomoviruses in the Indian subcontinent NARAYAN RISHI Department of Plant Pathology, CCS Haryana Agricultural University, Hisar 125 004 INTRODUCTION Some of the now known ssDNA containing geminivirus diseases date back to the end of the 19 th century and early or mid 20 th century. They are cassava mosaic in Africa in 1894, maize streak in South Africa in 1901, curly top of sugar beet and other crops in United States of America and Mediterranean in 1900s, tobacco leaf curl in Indonesia in 1912 and then in Africa (Storey, 1931) and India (Pal and Tandon, 1937) and cotton leaf curl disease in 1931 in Angola and Egyptian Sudan (Tarr, 1951). In India earlier recorded geminivirus diseases are leaf curl of Zinnia elegans (Mathur, 1933), papaya (Nariani, 1956), chilli (Mishra et al., 1963), tomato (Vasudeva and Sam Raj, 1948) and mungbean yellow mosaic disease in 1955 (Nariani, 1960). The losses caused by some of these geminivirus diseases (Varma et al., 1992, Harrison and Robinson, 1999) are enormous to the world economy and food security. In India the yield losses per annum due to yellow mosaic diseases in mungbean, blackgram and soybean combined together was estimated to be US$ 300 million (Varma et al., 1992). Tomato leaf curl and tomato yellow leaf curl diseases are wide spread in more than 20 countries, it caused heavy yield losses and wiped out tomato crops in some areas (Green and Kalloo, 1994, Czosnek and Laterrot, 1997). Saikia and Muniyappa (1989) reported more than 90% fruit yield loss due to tomato leaf curl disease when infection occurred within four weeks of transplanting. In the very recent past, cotton leaf curl disease (CLCuD) emerged as a serious threat to cotton crops in Pakistan and India (Hameed et al., 1994, Rishi and Chauhan, 1994, Narula et al., 1999). During five years (1992-1997) losses to Pakistan economy due to CLCuD was calculated to be US$ 5 billion (Briddon and Markham, 2000). The aetiology of all these diseases and others, predominantly known in the tropics and sub-tropics proved to be elusive till 1977, when circular ssDNA containing Geminiviruses were reported (Harrison et al., 1977). Geminiviruses are bisegmented (geminate) in shape and 30x20 nm in size. In 1978 International Committee on Taxonomy of Viruses (ICTV) recognized Geminiviruses as a separate group on the basis of geminate morphology of the virus particles and circular ssDNA as their genomic component. ICTV in its meeting in the XI International Congress of Virology, held in 1999. Sydney raised geminivirus group to the status of family Geminiviridae. The criteria for demarcation of species of the members of family Geminiviridae were revised and accordingly now instead of three, there are four genera distinguished (Table 1) on the basis of genome organization, distinguished insect vector and host range (Fauquet et al., 2003). Begomovirus is the most diverse and world wide distributed genus in the family Geminiviridae. The geographical distribution of begomoviruses parallels to that of whitefly (Bemisia tabaci Gennadius) (Brown et al., 1995). It covers almost entire tropical and parts of subtropical areas in the Americas, Africa, Europe, Asia and Australia. To meet the ever growing demand of agricultural commodities, intensive and extensive agriculture were widely followed, introducing high yielding varieties in the last three or four decades of 20 th century. This led to wide spread appearance of begomoviruses and its vector whitefly in additional crops/weeds and also in the newer areas. The economic importance of begomoviruses was thus realized and it gave impetus to concerted studies on these economically important geminivirus diseases in several laboratories in world. In the recent past, investigations of academic and applied value have been carried out on economically important diseases in Indian subcontinent, which are reviewed here in the present address. S.N. Dasgupta Memorial Lecture Award (2003)