Preliminary results of resistance of tomato accessions to late blight (Phytophthora infestans (Mont.) de Bary)

Late blight (LB) caused by Phytophthora infestans (Mont) de Bary is a highly destructive disease of tomato and appears worldwide. The losses caused by late blight depend on several factors, but main are weather conditions, genotype and amount of inoculum. The aim of this paper was to determine the reaction to the late blight in ten tomato genotypes under conditions of natural infection and to detect the potential sources of resistance. These genotypes are from tomato seed collection of Institute of Field and Vegetable Crops. Two wild Solanum species (S. pimpinellifolium and S. habrochaites), four varieties, two lines and one population were included in the trial. Weather conditions in Serbia in 2014 were very favourable for the disease development. Six assessments of LB intensity were performed from the end of June until the beginning of September. Per each genotype twenty four plants were evaluated according to 0-9 scale. Obtained data were transformed to percent and analysed by Kruskal-Wallis test. Intensity of LB symptoms on tomato plants in the second and third assessment in July was very low, up to 10%. In the following evaluations, the level of the infection increased and in the final assessment, wild species and local population grouped as less susceptible to the disease. However, the intensity of late blight, under extremely favourable weather conditions, was also high, 50% on wild species S. pimpinellifolium and S. habrochaites and 70% on local population Volovsko srce.