Estimates of Genetic Parameters of Quantitative Resistance to Bacterial Leaf Blight of Rice Variety IR26 and Their Implications in Selection

Abstract

Inheritance of quantitative resistance of IR26 was studied through the analysis of 5 populations, P1, P2, F₁, F₂ and F₃, derived from the cross Kinmaze/IR26, and an effective means of selection for the resistance was presented. Experimental results showed that IR 26 exhibited a non-specific resistance to all the five bacterial groups existing in Japan. According to the analysis of variance, the resistances of the F₃ lines originating from IR26 differed non-specifically, and the strains from the bacterial groups I to V differed in aggressiveness but not in virulence. Selection experiments for the resistance in the F₂ generation indicated that individual selection was effective and the selection by using a single bacterial group resulted in significant improvements not only in the resistance to the relevant bacterial group but also in the resistances to all the others. The selection of plants non-specifically resistant to all the bacterial groups could be obtained without the inoculation of all the bacterial groups. This was attributable to the fact that the quantitative resistances to the bacterial groups I to v originating from IR26 had a high heritability each and were highly correlated with each other both genotypically and phenotypically. Experimental results also showed that a strain with a relatively strong aggressiveness was best for the selection, and the degree of aggressiveness of a strain to a hybrid population could be estimated by that to the resistant parent.