Marker assisted selection of Ty - 2 and Ty - 3 carrying tomato lines and their implications in breeding tomato leaf curl disease resistant hybrids

Tomato leaf curl virus disease caused by whitefly-transmitted begomoviruses is a serious tomato production constraint in tropical and subtropical regions of the world. Use of genetic resistance for diseases caused by begomoviruses is an important component of sustainable disease management approaches. To date, six introgressions ( Ty genes) derived from different tomato wild species that confer resistance to tomato leaf curl disease have been identified. Among these, dominant Ty - 2 and partially dominant Ty - 3 are important for the development of resistant hybrids because of their gene action. In the present study we report marker assisted selection of tomato lines carrying Ty - 2 and Ty - 3 genes and the effect of combining these in tomato hybrids using agroinoculation. The response of lines and hybrids with the Ty - 2 gene indicated ineffectiveness of Ty - 2 to infection by a bipartite tomato leaf curl virus. The Ty - 3 gene showed dosage effect with partial resistance in heterozygous state. However, the level of resistance in hybrids with the combination of Ty - 2 and Ty - 3 genes was higher and similar to homozygous Ty - 3 plants. The Ty - 2 gene in either homozygous or heterozygous state enhanced the level of resistance of plants with heterozygous Ty - 3 . Thus, tomato hybrid breeding programs can be benefited by using tomato lines carrying Ty - 2 and Ty - 3 resistance genes. The combined results of evaluation of horticultural performance, field resistance and agroinoculation tests demonstrated that the set of tomato lines developed in this study could be useful resources for achieving higher level of resistance in tomato hybrids.