Potato Late Blight is the main pathogen, which affect potatoes. Due to unavailability of effective chemical control methods and the intensive use of fungicides, which leads to high environmental and production costs, the introduction of resistant cultivars represents a safe strategy to reduce the negative aspects of the disease effects. The sources of horizontal resistance to Late Blight in the Argentinean Potato Breeding Program have been varied. One of the interesting species to evaluate is Solanum tarijense since its adaptation to long days is promissory, producing tubers of good size and aspect. Many studies have demonstrated that the expression of pathogenesis related proteins (PR) differ with the level of disease resistance in potato cultivars. These results suggest that the constitutive or inducible expression of PR proteins may contribute to the resistance to P. infestans. In this study, the enzymatic activity of different PR proteins in the specie S. tarijense was measured. Two potato clones with different levels of resistance were used. These clones were more resistant to Late Blight than Bintje and Pampeana INTA cultivars, used as control. The activity of glucanases, chitinases, peroxidases and poliphenoloxidases were 8, 1.5, 2.5, and 3 times higher respectively, in S. tarijense than in Bintje and Pampeana INTA. These results together with future studies on the interaction S. tarijense-P. infestans, will allow the introgression of S. tarijense genes in breeding programs and the use of some PR proteins as biochemical markers to assist selection towards the identification of horizontal resistant cultivars.Fil: Wolski, Erika Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Korgan, Samanta. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Capezio, Silvia Beatriz. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Huarte, Marcelo Atilio. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Andreu, Adriana Balbina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; Argentin
