Evaluation of advanced potato (Solanum spp.) clones for late blight (Phytophthora infestans) resistance and yield

The stability of late blight resistance and the yield potential of a set of cultivars were evaluated during wet and dry seasons at five locations in Benguet Province on the island of Luzon in the Philippines. Higher yields were obtained during the dry season due to greater solar radiation and canopy cover and lower late blight infection, with the highest yield registered at Natubleng. Cultivars CIP 380083.4, Dalisay, I-1039, Montanosa, Cruza-148 and Granola were the top six in terms of relative yield in all experiments. Late blight infection significantly influenced canopy cover at 45, 60, and 75 days after planting in all locations during both wet and dry seasons. There was no significant relationship between late blight and yield across all locations during the dry season, and in the locations La Trinidad and Caliking during the dry season. A significant negative correlation was observed between late blight infection and tuber yields at Natubleng, Sayangan and Abatan during the dry season. Based on the lack of a correlation during the wet season it was concluded that long days and reduced solar radiation were the overriding constraints to yield. Based on the rate of foliar late blight infection, three groups of cultivars were distinguished. The first group, which was the most susceptible, included cultivars MS-82.60, Ica Sirena, Granola, Cosima, Greta, and Conchita all of which exhibited signs of major gene resistance. The second group comprised cultivars Dalisay, Montanosa, ASN-69.1, BL-29, I-931 and I-1062. The third group, which was the most resistant, were cultivars P-3, P-7, 380083.4, I-1039 and Cruza-148. The second and third group showed both minor and major gene resistance. New cultivars must be adapted to low solar radiation, long day conditions of the wet season and exhibit polygenic resistance to Phytophthora infestans across numerous locations for several seasons.