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POSTERS: Population biology and genetics

Phenotypic and genotypic characterization of recent isolates of Phytophthora infestans on Solanum lycopersicum crops in Colombia
Mauricio Soto-Suárez - Corporación colombiana de investigación agropecuaria - AGROSAVIA. Maria Florencia Lucca- Instituto Nacional de Tecnologia Agropecuaria (INTA), William Fry- Cornell University, Giovanna Danies- Universidad de los Andes, Silvia Restrepo- Universidad de los Andes, Kevin Myers- Cornell University, Andrea Olave-Achury- Unive

Late blight disease caused by the plant pathogen Phytophthora infestans, is one of the major threats for tomato crops in Colombia. All tomatoes grown in Colombia are susceptible to this disease and control requires a high input of fungicides. Knowledge on the population structure of P. infestans is important to determine if there are changes in the sensitivity to fungicides and aggressiveness on the host. Here, we characterized the genotypic and phenotypic diversity of 22 isolates of P. infestans. Isolates were collected in 2017 and 2018 on tomato crops in the departments of Cundinamarca, Boyacá, Antioquia, and Caldas. The genotypic diversity for this isolates was assessed using microsatellite markers and mitochondrial haplotyping. Furthermore, sensitivity to three systemic fungicides (mefenoxam, cymoxanil, and fluopicolide) and pathogen aggressiveness on three tomato cultivars was evaluated. Mitochondrial haplotyping showed that in Colombia, isolates of P. infestans collected on tomato are Ia and Ib, while isolates collected on potatoes are IIa. Furthermore, differences in sensitivity to fungicides were observed. Ninety percent of the P. infestans isolates were resistant to mefenoxam with an EC50 greater than 10 µg ml-1, response to cymoxanil were intermediate with 54% of the isolates with an EC50 between 1 to 10 µg ml-1, while 91% of the isolates were sensitive to fluopicolide with an EC50 less than 1 µg ml-1. The information obtained in this study will help establish the actual state of P. infestans populations associated to tomato crops in Colombia.