Genetic analysis of late blight resistance in Solanum pimpinellifolium accession PI 270441: Heritability and response to selection

Late blight (LB), caused by Phytophthora infestans, is a destructive disease of tomato (Solanum lycopersicum) worldwide. Currently, there are few commercial cultivars of tomato with resistance to LB, and the disease is mainly controlled by heavy use of fungicides. Due to the emergence of fungicide-resistant pathogen isolates, there is a concerted effort to identify new genetic sources of resistance and breed new resistant cultivars. A recent screening identified several new tomato accessions with strong resistance to LB. Here, we report on the genetic basis of LB resistance in S. pimpinellifolium accession PI 270441, as determined by generation means analysis and analysis of response to selection, using populations derived from crosses with LB-susceptible breeding line Fla. 8059. Heritability of LB resistance ranged from 0.76 to 0.78, and the minimum number of genes was estimated 1—few. These results suggest that transfer of LB resistance from PI 270441 to the cultivated tomato should be feasible via a traditional backcross breeding approach. Genetic mapping studies are underway to identify molecular markers associated with resistance in this accession.