Quantitative Trait Loci and Candidate Loci for Heading Date in a Large Population of a Wide Barley Cross

Spanish barley (Hordeum vulgare L.) landraces exhibit good adaptation to Mediterranean conditions. This study aims at revealing the genetic control of heading date on a large population of 464 doubled haploid lines from the cross between the Spanish line SBCC145 (a 6-row barley with low vernalization requirement and good agronomics) and the German cultivar Beatrix (a 2-row, spring-type, short stature, high yield, malting quality barley). The population was evaluated using augmented designs in two field trials with contrasting sowing dates. The study was done in a two-step process to optimize cost effectiveness of genotyping. First, a sample of 184 lines was genotyped with 1536 single nucleotide polymorphisms, which allowed building a map with 408 markers. Then the entire population was further genotyped with markers from flowering time genes VrnH1, VrnH2, VrnH3, and PpdH1 and a simple sequence repeat linked to Eam6. Quantitative trait loci were detected for growth habit, heading date, plant height, and individual grain weight on chromosome 3H in a region that possibly contains the denso gene. The effect of VrnH3 on heading date confirmed previous results from association mapping, and showed an interaction with PpdH1, to which it is linked in the photoperiod pathway. PpdH1 had an opposite effect on heading date at the two trials. Besides revealing interesting effects for particular alleles of the genes studied, this population demonstrates that it is possible to combine short stature with early heading date and good grain size in six-row barley and shows good prospects for its use in breeding.