Genetic variability of Phytophthora infestans isolates from south-western Colombia

Late blight caused by Phytophthora infestans is one of the most limiting diseases in solanaceous crops in the world. This pathogen is a main constraint in the highland Andes, where these plants are grown under high humidity conditions and continuous cropping. The aim of this research was to increase the available information on the biology of P infestans, specifically or its level of genetic variation in south-western Colombia, an area where various solanaceous crops susceptible to this pathogen converge. The study was carried out by using AFLP molecular markers with the restriction enzymes EcoRI and MseI and different primer combinations. Results indicated a low level of genetic variation among the 26 isolates evaluated, with only 18 polymorphic bands out of 135 amplicons obtained (13.43%), a Nei's genetic diversity index of 0.04, and a Shannon's information index of 0.06. The UPGMA dendrogram allowed dividing the population in two main groups, the first of them having the isolates collected from potato (Solanum tuberosum and Solanum phureja), while the second one included isolates obtained from tree tomato (Solarium betaceum). One of the isolates (C8) was located outside of these groups, although it shared a high level of similarity with them (0.86). The results support the hypothesis of population structure of P. infestans based on host; however, this situation needs to be verified with cross pathogenicity assays.