Title : Rice blast resistance of Korean rice cultivars associated with the allele type of R-gene linked DNA marker
Rice blast is one of the most serious diseases in the world that cause considerable yield losses. In South Korea, the breakdown of blast resistance frequently occurs due to increase rice cultivars with similar genetic backgrounds or rapid changes in the blast pathogenic races. This disease can be managed by using the recommended dose of nitrogen fertilizer, treatment of chemical fungicides, and resistant varieties. Cultivation of disease-resistant rice cultivars is the most effective and economical way to control rice blast disease. In the present study, the genetic diversity of blast resistance genes using gene functional/linked markers, and rice blast resistance for 3 years were investigated in 300 Korean rice varieties. Blast resistance was determined using the 0–9 scoring system (a scale 0=no lesions to 9=dead leaves) from IRRI in the nursery test of the experimental field at Wanju in Korea. The genetic diversity at 12 blast resistance gene loci was evaluated using 18 functional/linked markers. The blast score of 300 rice varieties showed a significant correlation between years (r > 0.64, p < 0.001). Among the 300 varieties, the blast score average of the 263 Japonica varieties was significantly higher in all test years than that of the 37 Tongil-type varieties. The 88 early maturing varieties showed blast resistance than the 114 mid-late maturing varieties or 98 medium maturing varieties. Analysis of variance showed that the ‘9871.T7E’ marker linked with Pi40 was strongly associated with blast disease with the phenotypic variance of 16% to 29% for 3 years (p < 0.001). Among varieties harboring the Pi40 allele, the early maturing verities accounted for 87%. These results implied that the blast resistance of early maturing varieties in Korea is associated with Pi40 gene. These results will be beneficial for breeding of blast resistance rice in Korea. The research was funded by the Rural Development Administration(RDA) of South Korea, grant number PJ0168302022.