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Inheritance of Tomato yellow leaf curl virus Resistance Derived from Solanum pimpinellifolium UPV16991

Resistance to tomato yellow leaf curl disease (TYLCD) in accession UPV16991 Solanum pimpinellifolium has been previously reported by our group. A breeding program was developed from an initial S. lycopersicum × S. pimpinellifolium UPV16991 cross. This first cross was followed by several selfing generations. Selection for resistance to Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) was carried out for plants of each generation. One partially resistant F₆ plant (L102) was chosen to form the family to study the genetic control of resistance to TYLCV. Crosses between four breeding lines susceptible to TYLCD and L102 were also performed to study the dominance of the resistance in S. lycopersicum genetic backgrounds. Response to TYLCV infection of P₁, P₂, F₁, F₂, BC₁, and BC₂ generations fitted, for this line, a monogenic control with partial recessiveness and incomplete penetrance. The percentage of homozygotic plants with partial resistance was 72.75. Among the four hybrids developed, the highest levels of resistance were found in the hybrid formed from the most vigorous S. lycopersicum line. These results must be considered for breeding purposes. Partial resistance derived from UPV16991 will be useful in homozygosis or combined with resistance genes from other sources.