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 two 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.