Assessment of Blast Disease and Yield Loss in Susceptible and Partially Resistant Rice Cultivars in Two Irrigated Lowland Environments

The importance of blast disease, caused by Pyricularia oryzae, varies with environment, and irrigated lowland rice in Korea is more prone to the disease than irrigated lowland rice in the Philippines. Rice cultivars with partial resistance can reduce losses from blast. Fungicide-protected and inoculated field plots were used to assess the effectiveness of locally adapted partially resistant cultivars in reducing leaf blast, neck blast, and yield losses. Over six trials conducted from 1987 to 1989, yield loss was positively correlated with the incidence of severe neck blast (r 2 =0.95). The incidence of neck blast was low and yield losses negligible in partially resistant cultivars IR36 in the Philippines and Seomjin in Korea (.)