This study was conducted to select a DNA marker linked to the new recessive resistance gene rym7t, which is derived from ‘Tokushima mochihadaka’ and confers resistance to Barley yellow mosaic virus (BaYMV) strains I, II and III. A genetic linkage map neighboring rym7t was constructed using doubled haploid lines derived from a cross between the resistant parent ‘DH21-73,’ which includes rym7t, and susceptible parent ‘Haruna Nijo’. Two SSR markers, Bmac0031 and Bamc0167 were selected, adjacent to each side of the rym7t locus. The genotype of the two SSR markers corresponded well to the phenotype of BaYMV resistance. The field test of Barley yellow mosaic disease (virus strain I) resistance of F₂ individuals derived from a cross between the susceptible parent ‘New Golden’ and resistant parent ‘DH42-84,’ which includes rym7t, showed that the correspondence rates between phenotypes of BaYMV resistance and genotypes with Bmac0031 and Bamc0167 were 98.6% and 98.8%, respectively. In the case of correspondence between the two markers’ genotypes, they corresponded exactly with the phenotype of BaYMV resistance of F₂ individuals. The two SSR markers were co-dominant, so both could clearly identify susceptible plants with heterozygous rym7t. The two SSR markers could be useful for marker-assisted selection of resistant lines including rym7t.

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Discolored grain is one of the most important types of damage in two-rowed hulled barley. We attempted to elucidate the occurrence factors in discolored grain and to establish an evaluation method. To reveal the occurrence factors in discolored grain, three color values (L* value: brightness, a* value: redness and b* value: yellowness) of discolored grain were investigated to see whether they correlated with the amount of precipitation during the maturation period. The hue of grains showed no correlation with the amount of precipitation from 4 to 2 weeks (yellow ripe stage) before the mature stage, whereas the L* value and b* value of grains correlated negatively with the amount of precipitation during from the yellow ripe stage to the mature stage. The differences in the L* value and b* value of grains with high humidity treatment for 4 days and no treatment using detached spikes in the yellow ripe stage in 31 varieties correlated positively with the degree of discoloration of grain under natural conditions. These results showed that discolored grain developed by exposure to rainfall from the yellow ripe stage to mature stage, could be evaluated by high humidity treatment, and varieties tolerant to grain discoloration could be selected using this treatment.

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