QTLs for agronomic traits from a Mediterranean barley progeny grown in several environments

In order to identify quantitative trait loci (QTLs) controlling agronomic trait variation and their consistency under Mediterranean conditions in barley, a progeny of 167 recombinant inbred lines (RILs) and the parents Tadmor and Er/Apm, originating from the Mediterranean basin, were grown under Mediterranean conditions in 1995, 1996, 1997 and 1999. For the 2 first years (M95 and G96), one replicate was grown, but for the latter (M97 and M99) two rainfed (rain) and two irrigated (ir) replicates were produced. M95, G96, M97rain, M97ir, M99rain and M99ir were considered as six different environments and were compared in terms of their meteorological conditions and water supply. Grain yield and yield components were assessed, as well as heading date and plant height. Highly significant differences were noted between environments. QTLs were obtained from each environment separately and from a multiple environment analysis (simple interval mapping and simplified composite interval mapping). Despite heterogeneity between environments, numerous QTLs were common to several environments. This was particularly true for traits like plant height and thousand-grain weight. The most reliable QTLs which explained the largest part of the phenotypic variation were obtained for plant height on chromosomes 3 (3H) and 6 (6H). The multiple-environment analysis provided an opportunity to identify consistent QTLs for agronomic traits over six Mediterranean environments. A total of 24 consistent QTLs were detected. Out of these, 11 presented main effects, seven presented QTL×E interaction, and six presented both effects. In addition, 18 of the consistent QTLs were common to other published work and six seemed specific to this study. These latter QTLs could be involved in Mediterranean adaptive specificities or could be specific to the studied genetic background. Finally, when the rainfed and the irrigated environments of M97 were considered separately, a total of 16 QTLs presenting main effects over the two water conditions were identified, whereas five QTLs seemed dependent on the water conditions.