Selection for Partial Resistance in Rice to Rice Blast

Summary

A detailed study of the components of partial resistance (PR) latency period, lesion number, and size of the sporulating area in lesions, indicated that lesion number was the most important component. No genetic variation was found for latency period. Analysis showed that lesion number is determined by several minor genes. Only young leaf tissue is susceptible to the blast fungus. Older leaves have increased levels of resistance. Resistance was expressed as a more rapid reduction of the number of lesions. The higher the level of PR of a genotype the faster the leaf tissue became resistant. Genotypes with a higher level of PR showed less lesions which usually had smaller sporulating areas compared to the susceptible check. Fewer lesions per plant and fewer leaves with lesions appeared well associated with resistance in the field. Breeders could select entries with fewer affected leaves.