Exploiting Partial Resistance to Tomato yellow leaf curl virus Derived from Solanum pimpinellifolium UPV16991

Tomato yellow leaf curl disease (TYLCD) causes great economic losses in tomato crops worldwide. Despite efforts undertaken by different research groups, there are no immune commercial plant materials available. Recently, our group reported partial resistance to TYLCD in line L102, derived from Solanum pimpinellifolium UPV16991. Resistance in this line is monogenic, with partial recessiveness and incomplete penetrance. Even though the resistance gene in L102 is not dominant, we also proved that levels of resistance were high in hybrids with different tomato lines. The objective of this work was to evaluate the level of resistance in plants which combined UPV16991-derived resistance and the Ty-1 gene, both in heterozygosis. Most of the hybrids between S. pimpinellifolium- and S. chilense-derived resistant lines exhibited milder symptoms than heterozygotes for either S. pimpinellifolium- or S. chilense-derived resistance. In some of the hybrids, viral accumulation was also lower than in respective heterozygotes. Our results support the utility of resistance derived from UPV16991 combined with the Ty-1 gene in increasing levels of resistance to TYLCD in tomato hybrids. This is the most practical approach to exploiting resistance derived from UPV16991, because it allows the development of hybrids without the need of fixing the resistance gene in both parents.