RESISTANCE OF POTATO TO POWDERY SCAB (SPONGOSPORA-SUBTERRANEA) UNDER ANDEAN FIELD CONDITIONS

Six field trials were carried out in naturally infested soil to identify resistance to powdery scab. Trials were conducted at Anta, Cusco, in southern Peru (3300 m altitude) during six seasons. A scale of 1 (0%) to 9 (>95%) of tuber surface showing infection was used to evaluate resistance. Ratings 1-3 were considered resistant (R), 4 moderately resistant (R) and 5 or more, susceptible (S).Among 467 tested potato accessions (cultivars and advanced clones) of the potato germplasm collection held at the International Potato Center (CIP), 17 were R and 33 MR during mio or more seasons. Another 55 were R and 70 MR during only one season. In addition, 251 were S and 41 did not grow for different reasons. Resistant were G-6, LT-6, DGV-103 A, Santiaguina, Alka Pinu, G84270.4, Serrana INTA, Esperanza, Gabriela, Albina, Primicia INTA, Pentland Crown, Ultimus, Katahdin, DTO-28, AL-624, and G81422.6. Cultivars Gabriela and Albina and clone G81422.6 can now be used by Cusco farmers because of their high yield, adaptability, and good resistance to powdery scab.