Poster Session: Population Genetics-Oomycetes

512-P

Pathogenicity and aggressiveness of isolates belonging to a new Phytophthora infestans sensu lato population in Colombia.
M. F. MIDEROS (1), J. Bastidas (2), Y. V. Castillo (2), L. E. Lagos (2), A. Bernal (1), S. Restrepo (1)
(1) Universidad de Los Andes, Bogotá, Colombia; (2) Universidad de Nariño, Pasto, Colombia

New populations of Phytophthtora infestans sensu lato have been characterized in South America, and most of them have been found causing diseases in native hosts of the tropical region. Recently in Colombia, we have found a new population of this pathogen associated with tree tomato (Solanum betaceum). Unlike isolates previously reported in the Andean Region, this new population is highly virulent on its host and shows different morphological and genetic characteristics. To understand the impact of pathogenicity features on the epidemiology and evolution of Phytophthora in the North Andean highlands, we obtained 40 isolates collected from different cultivars of tree tomato in Colombia and 10 isolates from potato. Isolates were morphologically and molecularly characterized. Additionally, nine aggressiveness components were evaluated in a detached leaf assay on four cultivars of tree tomato and two cultivars of potato (Solanum tuberosum). Results indicated that Phytophthora infestans sensu lato in tree tomato is highly diverse. Morphological features and some molecular markers revealed unique patterns among these isolates. There were significantly high levels of aggressiveness among the isolates evaluated. Using hierarchical clustering principal component analysis (HCPC), three clusters were identified according to the aggressiveness components. A significant correlation was obtained between the aggressiveness component and genotypes. Interestingly, only three isolates were able to infect a susceptible cultivar of potato indicating that there exists a high level of host specificity. Result of this study can be used to understand the evolutionary history and strategies of adaptation to new hosts of Phytophthora infestans population in South America, especially when strong events of hybridization are occurring to increase the possibility of modification of the initial host range.