Detection of bsd1, a gene responsible for breaking seed dormancy by machine threshing in barley (Hordeum vulgare L.)

Seed dormancy is essential to avoid pre-harvest sprouting (PHS), and germination is vital for agricultural production planning and malting. The malting barley genetic resource Chikukei 9713 is PHS tolerant but quickly breaks seed dormancy after harvest. We found that Chikukei 9713 and the barley cultivar Seijo 17 were PHS tolerant because exon-9 of the seed dormancy gene sd1 was of the dormant type. However, the rapidity of breaking seed dormancy depended on the threshing method. Both varieties germinated slowly after hand threshing, whereas Chikukei 9713, but not Seijo 17, germinated quickly after machine threshing. Using the 94 F₂ individuals and 94 F₃ lines populations derived from a cross between Chikukei 9713 and Seijo 17, we found a genetic region that controlled the effect of the threshing method on breaking seed dormancy (named bsd1) located on the short arm of chromosome 2H (23.4-24.9 Mbp) with GRAS-Di (Genotyping by Random Amplicon Sequencing-Direct) and CAPS markers. Further analysis revealed that bsd1 had a maximum LOD score of 21.4 and explained 65% of the variance. Our findings regarding this novel gene are an important genetic resource for stable malting barley production and sowing planning. Utilizing bsd1 and other seed dormancy genes will enable breeding of PHS-resistant barley cultivars that germinate quickly after machine harvesting.