K. Saeki¹, C. Miyazaki², N. Hirota¹, A. Saito³, K. Ito¹, and T. Konishi⁴

1 Plant Bioengineering Research Laboratories, Sapporo Breweries Ltd., 37-1 Kizaki, Nitta, Gumma 370-0393, Japan. ² Nagasaki Laboratory, Japan Science and Technology Corporation, Ohmura 856-0021, Japan. ³ Kyushu National Agriculture Experiment Station, Nishigoshi, Kumamoto 861-1102, Japan. ⁴ 294 Okada, Mabi-cho, Kibi-gun, Okayama 710-1311, Japan.

Barley yellow mosaic virus (BaYMV) which is transmitted by the soil-borne fungus, Polymyxa graminis Led., causes one of the serious diseases in barley. Among BaYMV resistance genes, ym3 is effective against all strains of BaYMV in Japan (Kashiwazaki et al. 1989), China (Chen et al. 1992) and Europe (Ordon et al. 1989; Gotz and Friedt 1993). The ym3 gene was first detected in a BaYMV resistant mutant, Ea 52, induced from the susceptible cv, Chikurin Ibaraki 1, by gamma-ray irradiation (Ukai and Yamashita 1980), and confirmed to be allelic to the BaYMV resistance gene of Ishuku Shirazu introduced from Haganemugi (Kawada and Tsuru 1987). However, the ym3 gene has not been located on any chromosome, while most of the BaYMV resistance genes have already been mapped on respective chromosomes. Our objectives were to map the ym3 resistance gene on chromosome using RFLP markers, and to identify molecular markers linked to ym3 that can be used for marker assisted selection in barley programs for BaYMV resistance.

For RFLP mapping, a total of 153 F₂ plants derived from the cross between the BaYMV resistant cv Ishuku Shirazu carrying ym3 and the susceptible cv Ko A were cultivated in the BaYMV-free field and harvested individually. And, each 30 F₃ seedlings from F₂ individuals were grown in a hill plot of the BaYMV-infested field, and score the susceptibility of each F₃ progeny to BaYMV.

DNA was extracted from mature leaves of F₂ individuals, and digested with six restriction enzymes, Bam HI, Bgl II, Dra I, Eco RV, Hin dIII and Xba I. Hybridization was performed by using probes presented from NABGMP, Dr. A. Graner and Dr. M. Sorrells, and the RFLP loci were mapped using MAPMAKER version 2.0.

The ym3 gene was found to be linked with nine markers on the short arm of chromosome 7 (5H), and located between ABG705 and CDO749 with 11.7cM and 5.4cM, respectively (Fig. 1). This suggests that these markers may contribute to marker assisted selection of the BaYMV resistant ym3 genotypes at the seedling stage.

Chen, J., M.J. Adams, F. Shi, and C. Chen. 1992. Response of some Asian and European barley cultivars to UK and Chinese isolates of soil-borne barley mosaic viruses. Ann. Appl. Bot. 121:631-639.

Gotz, R. and W. Friedt. 1993. Resistance to the barley yellow mosaic virus complex-differential genotypic reaction and genetics of BaMMV-resistance of barley (Hordeum vulgare L.). Plant Breed. 111:125-131.

Kashiwazaki, S., K. Ogawa, T. Usugi, and T. Tsuchizaki. 1989. Characterization of several strains of barley yellow mosaic virus. Ann. Phytopath. Soc. Japan 55:16-25.

Kawada, N. and M. Tsuru. 1987. Genetics and breeding of resistance to barley yellow mosaic virus. In: Yasuda, S. and T. Konishi (eds.) Barley Genetics V, Proc. 5th Int. Barley Genet. Symp. , Sanyo Press Co., Okayama, Japan. pp. 651-657.

Ordon, F., R. Gotz, and W. Friedt. 1989. Genetic stocks resistant to barley yellow mosaic viruses (BaMMV, BaYMV, BaYMV-2) in Germany. BGN 22:46-49.

Ukai, Y. and A. Yamashita. 1980. Induced mutation for resistance to barley yellow mosaic virus. Japan. J. Breed. 30:125-130.