CBGG

Rice blast caused by Pyricularia oryzae (syn. Magnaporthe oryzae) is a destructive disease of rice worldwide that poses a serious threat to rice production. Strengthening blast resistance is an important objective in rice breeding programs. Race-specific resistance genes (R-genes) confer complete resistance to blast, but new races of blast pathogen can overcome it. After the first report of breakdown of resistance conferred by the R-gene Pik in 1963, this type of resistance has frequently been broken 1–7 years after the release of resistant varieties to farmers in Japan and other countries. To overcome this genetic vulnerability, Japanese rice breeders have focused on the use of race-nonspecific resistance in Japanese upland rice varieties whose resistance has been maintained for a long time. However, linkage drag between genes controlling this type of blast resistance and undesired traits has hindered its use. Therefore, researchers genetically dissected race-nonspecific resistance to rice blast. Among detected QTLs, a single recessive resistance gene, pi21, was identified by map-based cloning. The use of pi21 has improved durable resistance in rice breeding programs.

race-nonspecific resistance; quantitative resistance; durable resistance; multiline variety; gene pyramiding; marker-assisted selection; rice; blast disease