Individual locus effects on dormancy during seed development and after ripening in barley

Genetic control of seed dormancy in barley (Hordeum vulgare L.) has been studied recently by means of quantitative trait loci (QTL) mapping. Four QTL, designated SD1 to SD4, were found associated with about 75% of the phenotypic variation for dormancy in 'Steptoe'/ 'Morex' crosses, The objective of this study was to investigate the individual effects of seed dormancy (SD) QTL and the nature of their epistatic interactions on dormancy during seed development and after ripening. Six F-1-derived doubled haploid lines from Steptoe-Morex crosses, selected on the basis of the flanking marker alleles for the four SD QTL, and the two parents were grown under greenhouse conditions. The same lines and four additional doubled haploid lines from the same cross were also grown in a field experiment. Genotypic dependence of onset, maintenance, and release of dormancy was studied, To assess dormancy, germination tests of excised embryos from fresh and artificially dried seed were conducted during seed development. All genotypes showed a similar pattern of germination of excised embryos, Since no differences in the time of dormancy inception were found, this phenomenon does not seem to be controlled by the SD QTL, Rather, the SD QTL were involved in the release of dormancy at the end of the development process and during after ripening, The presence of the Steptoe allele at SD1 on chromosome 7 (5H) kept precocious germination to a minimum until the end of the seed development process, On the basis of the dormancy profiles at after ripening, genotypes could be classified as affecting early, intermediate, and late dormancy release. These groups Here genotypically dependent. A model for allele interactions among the SD QTL was developed.