Genetic analysis of seed dormancy QTL in barley

Seed dormancy in wild barley enables drought escape by preventing germination during the hot summer in and environments. Dormancy in cultivated barley has different effects: it can delay the malting process and/or it can prevent pre-harvest sprouting. Thus, cloning dormancy genes in barley will contribute to understanding the domestication process and it will facilitate optimizing the trait for efficient agronomic and industrial uses. Rates of seed germination were used to evaluate dormancy on physiologically matured grain samples that were dried and stored frozen until use. With this phenotypic scoring procedure, many genetic factors controlling seed dormancy has been reported as quantitative trait loci (QTL). Of these QTL, one at the centrometic region of chromosome 5H (Qsd1) has been most frequently identified and shows the largest effect across mapping populations. We also identified this QTL using the EST map based on Haruna Nijo (H. vulgare ssp. vulgare) crossed with wild barley H602 (H. vulgare ssp. spontaneum). We have derived both doubled haploid and recombinant chromosome substitution lines (RCSLs) from this cross. At least four QTLs are segregating in this germplasm. RCSLs having only the Qsd1 segment of wild barley in a Haruna Nijo genetic background were identified and 910 BC3F2 plants were scored for dormancy. In these lines, segregation for dormancy fit a mono-factorial ratio. These germplasm resources are appropriate for map based cloning of Qsd1. Strategies for cloning Qsd1 with these resources are discussed.