Modification of host–parasite interactions through mutagenesis in quantitative resistance of rice to bacterial leaf blight

Abstract

SummaryA number of mutant lines showing different levels of improved quantitative resistance to bacterial leaf blight (BLB) were obtained through selection of plants or lines derived from seeds of the rice cultivar Harebare exposed to thermal neutrons and gamma-rays. The selections were made on M2–M4 materials under natural BLB-epidemic conditions and/or by artificial inoculation of one of the BLB isolates. Bacterial isolates predominating under the natural conditions were identified as belonging to the differential BLB isolate group I, and the isolates of this group were used in the artificial inoculation for selection of mutants. The selected M4 mutant lines were tested in M5 for BLB resistance by artificial inoculations of four differential bacterium isolates, groups I, II, III and IV. The M6 mutant lines showed quantitatively elevated resistances to the isolate of bacterium group I and also to the other three differential isolates. Analysis of variance of the data demonstrated that the observed elevated quantitative resistances of the mutants to the isolates I, II, III and IV were isolatespecific. Host-parasite interactions in quantitative resistance to BLB and their modification by induced mutations are discussed.