Genetic characterization of late blight resistance in Solanum pimpinellifolium accession PI 270442

Abstract

One of the most destructive foliar diseases of the cultivated tomato (Solanum lycopersicum) is late blight (LB), caused by the oomycete Phytophthora infestans. Due to the limited number of commercial tomato cultivars with resistance to this disease, control is mainly through cultural practices and heavy use of fungicides. The appearance of fungicide-resistant P. infestans genotypes, however, necessitates identification of new genetic sources of host resistance to the disease and subsequent breeding of new resistant cultivars. Several new sources of resistance to tomato LB were identified in a recent screening of the tomato related wild species S. pimpinellifolium. In the present study, we examined the genetic basis of LB resistance in accession PI 270442, through parent-offspring correlation analysis, generation means analysis, and analysis of response to selection, using populations derived from crosses with a LB-susceptible tomato breeding line. 14 Matthew T. Sullenberger and Majid R. Foolad Across experiments, estimates of heritability (h) for LB resistance ranged from 0.56 – 0.86, suggesting the heritable nature of this resistance and possibility of effectively transferring LB resistance from PI 270442 to the cultivated tomato genetic background through phenotypic selection and traditional backcross breeding. Genetic mapping studies are currently underway to identify the associated molecular markers for LB resistance in PI 270442.