Ana Pérez de Castro

Identification of a CAPS marker tightly linked to the Tomato yellow leaf curl disease resistance gene Ty-1 in tomato

During the process of breeding programmes, several resistance genes have been introgressed into tomato (Solanum lycopersicum) cultivars from different wild tomato relatives. A number of these resistance genes have been mapped to chromosome 6. Among them, Ty-1 and Mi, which confer resistance to Tomato yellow leaf curl disease and to Meloidogyne spp., respectively, are in most cases incorporated in commercial hybrids. Several molecular markers tightly linked to Mi have been identified. This study was conducted in order to find an informative molecular marker linked to Ty-1. Six markers mapped in the same region as Ty-1 were analysed in plant material carrying different combinations of Ty-1 and Mi alleles. Three of the six markers revealed polymorphism among the assayed accessions. One allele of JB-1 marker showed association with Ty-1. Furthermore, the presence of Mi did not interfere with the results. The analysis of several accessions of wild tomato relatives with the three polymorphic markers allowed the establishment of the origin of the alleles found in cultivated plant material, showing that introgressions from S. lycopersicum, S. pimpinellifolium and S. habrochaites will not interfere with the results of this marker which tags Ty-1. Furthermore this analysis enabled the location of CT21, the RFLP marker from which JB-1 was designed.

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.

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.

Evaluación de la competencia transversal "Responsabilidad ética, medioambiental y profesional" a través de una e-rúbrica en el laboratorio.

Este trabajo ha sido financiado por un Proyecto de Innovacion y Mejora Educativa concedido por el Vicerrectorado de Estudios, Calidad y Acreditacion de la Universitat Politecnica de Valencia.