Assistance of phenotype-genotype selections for developing blast disease resistance of Thai jasmine rice, RD15

Thai jasmine rice, RD 15 variety is well known for its fragrance, cooking and eating qualities. However, it is susceptible to blast disease, a major rice disease caused by the fungus Pyricularia oryzae. The aim of this research was to transfer blast disease resistant QTLs from KD4-14 line into RD15 variety by using phenotype and genotype selections by the aid of markers. In this study, the two resistant QTLs were transferred from KD4-14 rice line into a RD15. Our analysis led to the breeding of elite lines with two resistant QTLs for blast disease by phenotype and foreground selections. The background genome recovery of the lines expressed more than 92.4% by using genome wide SSR markers analysis. The pathogenicity assays of the five resistant-QTL-derived lines were validated under greenhouse conditions with 17 blast isolates, prevalent in Thailand. These lines exhibited resistant reaction to all isolates with agronomic and grain quality traits similar to those of the RD15. The strategy of simultaneous phenotype and genotype selections to introduce multiple resistant QTLs is very useful for reducing the cost and time required for the isolation of desirable recombinants with target resistant genes in rice. The resistant-QTL-derived lines have practical breeding value in providing broad spectrum resistance, without a yield penalty, against most of the existing races of blast in Thailand. These lines could have a great impact on the yield stability and sustainability of rice productivity.