Development of tomato hybrids resistant to tomato leaf curl virus disease in South India

Resistance to tomato leaf curl virus disease (ToLCVD) in tomato (Solanum lycopersicum) is scarce but was developed recently in three open pollinated (OP) varieties (Sankranthi, Nandi and Vybhav), which are now available for cultivation in South India. Hybrids with superior yield capabilities, however, are a preferred choice of cultivation by farmers but hybrids are highly susceptible to ToLCVD. In order to develop virus resistant tomato hybrids, the three OPs were crossed with 12 tomato genotypes with superior agronomic characteristics. From the crosses, 20 hybrids were selected (named BLRH-1 to BLRH-20, Bangalore leaf curl virus-resistant hybrid) and evaluated for their resistance to ToLCVD at the University of Agricultural Sciences, Bengaluru, South India, both through whitefly-mediated inoculations in the glasshouse and natural infection in the field during summer 2005. Their growth and fruit yield parameters were compared against the popularly grown hybrids and OPs. Differences occurred between hybrids in disease incidence, spread, symptom severity and fruit yield. Of the 20 hybrids evaluated, 11 were found resistant to ToLCVD in the field, but only three (BLRH-3, BLRH-9 and BLRH-16) remained resistant when challenged with high virus inoculum pressure in the glasshouse through whitefly-mediated inoculations. None of the six commercially available hybrids tested was found resistant to ToLCVD. An examination of the extent of heterosis in resistant hybrids for both quantitative and qualitative characters over the popularly grown hybrid, US-618, indicated a major improvement in virus resistance, yield and fruit quality. All the twenty hybrids yielded significantly more than US-618, and of these, BLRH-3 and BLRH-16 were considered the best with yields over ca. 60 t/ha and resistant to virus both in the glasshouse and field.