Research carried out to assess the impact of open-pollinated Tomato leaf curl virus (ToLCV)-resistant tomatoes and hybrids on the livelihoods of resource-poor farmers in Southern India is described and discussed. Three high-yielding ToLCV-resistant tomato varieties were developed initially using conventional breeding and screening techniques involving inoculation by ToLCV-viruliferous whitefly, Bemisia tabaci. In 2003 and 2004, respectively, these varieties were released officially by the Karnataka State Seed Committee and the Indian Ministry of Agriculture through notification in the Gazette of India. From 2003 to 2005, eleven seed companies bought breeder seed of the ToLCV-resistant varieties and used them to begin breeding F1 hybrids from them. Socio-economic studies carried out to assess the benefits obtained from growing the ToLCV-resistant varieties found that farmers could gain up to 10 times the profit by growing the ToLCV-resistant varieties compared to the pre-existing ToLCV-susceptible varieties. Adoption of ToLCV-resistant tomatoes was also associated with reduced pesticide use. Extra income from tomato sales was prioritised by farmers to pay for children’s education, better nutrition and medicines. In a joint effort with the commercial seed sector in India, a promotional field day was organised in 2007. As well as the three ToLCV-resistant varieties, 62 ToLCV-resistant hybrid tomatoes were exhibited during a farmer-field day by 17 commercial seed companies and several public institutes. Tomatoes with ToLCV-resistance are now grown widely in South India and seeds of the three open-pollinated varieties have been distributed to more than 12 countries. In 2007, a conservative estimate of the financial-benefit to cost of the research ratio was already more than 837:1.

Bemisia tabaci adults from various host-plant species were collected from 31 regions across India. 266 B. tabaci samples were first screened by RAPD-PCR to examine molecular variability and to select individuals with different fingerprints. Host-plant and region of collection were then used to select 25 individuals for PCR amplification and sequencing of their partial mitochondrial cytochrome oxidase subunit one (mtCOI) genes. Pairwise comparisons with mtCOI consensus sequences showed that the majority of these samples had <3.5% sequence divergence from groups currently termed Asia I, Asia II-5, Asia II-7, and Asia II-8. The biotype-B B. tabaci from India clustered into the Middle East-Asia Minor 1 group. A new group of B. tabaci from Coimbatore, collected from pumpkin, was related most closely to the Asia I group (6.2% sequence divergence from the consensus Asia I sequence). To increase our understanding of the epidemiology of tomato leaf curl disease (ToLCD) and the key B. tabaci genetic groups involved in virus spread, the indigenous Asia I and the exotic biotype-B population from South India were used to carry out transmission experiments using Tomato leaf curl Bangalore virus (ToLCBV). The acquisition access periods (AAP), inoculation access periods (IAP), latent periods (LP), and ToLCBV transmission efficiencies of the two populations were compared and the biotype-B had the more efficient transmission characteristics. These results are discussed in relation to recent changes in the epidemiology of tomato leaf curl disease in South India.