Assessment of partial resistance to Pyricularia oryzae in six rice cultivars

The partial resistance to blast of six rice cultivars was assessed in greenhouse experiments and in an upland nursery experiment. IR36. Milyang30 and Milyang42, which have shown relatively little disease in farmers' fields for several years, had lower relative disease efficiency and smaller lesions with lower sporulation capacity than did IR50. Milyang 57 and Suweon 264. Latent period was the least important component of partial resistance. Using the area under disease progress curves as a measure of relative disease progress in the nursery, disease development on IR36 and Milyang 42 was slight and on Milyang 30 intermediate. By comparison, the three susceptible cultivars showed rapid increases in disease. Partial resistance may be associated with more durable blast resistance in certain cultivars.