Induced mutation of two-rowed barley resistant to powdery mildew, Erysiphe graminis f. sp. hordei. I.Comparison of effects of gamma-rays and ethylene imine in induction of resistant mutation

Abstract

Seven mutant lines resistant to powdery mildew, Erysiphe graminis f. sp. hordei race IX have been screened from 1, 240, OOO plants of M1 spike progenies raised from gamma-ray irradiation and ethylene imine (EI) treatments of seeds of three two-rowed barley varieties, Azuma Golden, Nitta Nijou N0.1 and Fuji Nijou. ML-3A from Azuma Golden had high resistance but a few colonies developed in severe infection. The reaction type was similar to O/(4) as described by Nover (1972). The mutant was also resistant to race XIV in which all virulence genes L0und in Japan were accumulated by crossing. Three mutants, ML-4F, ML-9F and ML-13F from Fiji Nijou were similar in reaction to ML-3A. The results of crossing between four mutants, and with the respecitve original variety showed that the resistance genes of the mutants were recessive to the original allele and allelic or identical to each other. A11 these four mu-tants showed light necrotic spots on leaves after heading. ML-7N and ML-10N from Nitta Nijou No.1 were moderately resistant, while ML-7N showed large necrosis on leaves at high temperature regardless of existence of pathogen. Resistance genes of these two mutants were not allelic to one in ML-3A. ML-12N from the same variety proved highly resistant showing no sign of colony. Although almost equal number of M1 spike progenies were tested for mildew resistance between gamma-rays and EI treatment, mutants were obtained only from EI treatment. The efficiency for inducing mildew resistant mutation differed among the varieties; the ratio of resistant mutants to chlorophyll mutants in Azuma Golden was ab, Dut one fiftieth, of that of the other two varieties. The efficlency for screenlng mlldew reslstant mutants of "M spike progeny method" were discussed in comparison with "one-spike-one-grain method"