Quantitative trait loci determining resistance to bacterial wilt in tomato cultivar Hawaii7996

Several loci governing resistance to bacterial wilt, a disease caused by Ralstonia solanacearum, have been mapped in tomato (Lycopersicon esculentum). An F2 population derived from a cross between a highly resistant cultivar, Hawaii7996, and a very susceptible line of L. pimpinellifolium, WVa700, was used to develop a map of molecular markers. The parental lines were screened for polymorphism using 462 RFLP probes with 14 restriction enzymes. Genetic mapping revealed that the distribution of polymorphisms was very uneven. Nevertheless, the extensive screening permitted development of a map covering much of the genome. Nine independent resistance tests were done on cuttings from plants of this population in a controlled environment culture chamber. In addition to the most important QTL detected on chromosome 6, analyses of our data using either nonparametric or interval mapping tests suggest the presence of another QTL on chromosome 4 (2 QTL) and weaker putative QTL at other map positions. Together these loci, all derived from the resistant parent Hawaii7996, account for 30 to 56% of the phenotypic variation observed.