Genetic studies of two QTLs for rice [Oryza sativa] stripe resistance identified in Japanese upland rice line, Kanto 72

Quantitative trait locus (QTL) analysis was performed to identify the chromosomal region controlling rice stripe virus (RSV) resistance in Japanese upland rice, Kanto 72. As a result, two QTLs were detected on chromosomes 2 and 11. Using near-isogenic lines possessing a single QTL (QTL-NILs) on chromosomes 2 and 11, the effects of two QTLs were evaluated. The target QTL regions were introduced in the genetic background of Koshihikari with marker-assisted selection. A combined QTL-NIL, possessing two QTLs, was developed from the cross between two QTL-NILs. Investigation of RSV resistance using three QTL-NILs revealed that the effects of the two QTLs clearly differed in the reaction to RSV. The QTL on chromosome 11 provided a major effect on reducing the infection rate of RSV. The QTL on chromosome 2 did not affect the infection rate, but made symptoms of diseased plants milder. The combined QTL-NIL showed high and stable resistance to RSV equivalent to upland rice, Kanto 72. From these results, RSV resistance in upland rice, Kanto 72, was controlled by the complementary effect of two QTLs. Major agricultural traits of the three QTL-NILs were not significantly different to those of Koshihikari, therefore, these QTL-NILs were thought to be useful in RSV-resistant rice breeding.