Yield QTL affected by heading date in Mediterranean grown barley

Knowledge regarding quantitative trait loci (QTL) has led to remarkable advances in breeding for a variety of traits, some of which have an effect on yield under particular environmental conditions. However, the same yield QTL are not usually found, even in the same population tested in different environments, as a result of large genotype-by-environment interactions. In this study, we aimed at identifying yield QTL in a series of experiments carried out in Spain. We used a barley doubled haploid population derived from a spring by winter cross. The relationship between heading date and yield, and between the principal heading date QTL and yield, changed depending on the environment. Allelic combinations causing early or late heading dates usually did not favour high yield, whereas intermediate heading dates were associated with not only higher variability but also higher yield potential. To identify QTL for grain yield independent of heading date, the population was divided into three classes: Early, Intermediate and Late. We found three new QTL affecting yield only at specific maturity groups. The implications of these findings in relation to barley breeding are discussed.