GENOTYPE-BY-ENVIRONMENT INTERACTIONS OF BARLEY IN THE MEDITERRANEAN REGION

In the Mediterranean region, progress in selection for yield in harsh environments is hampered by large environmental variation between seas ons and locations. This study analyzes the genotype-by-environment (GE ) interaction of 36 two-rowed genotypes of barley (Hordeum vulgare L.) , grown in 14 environments in Syria and North Africa. It assesses the effect of growth type (winter or spring type) and heading date on the GE interaction and determines whether or not high-yielding (HY) enviro nments are representative of low-yielding (LY) ones. Average grain yie ld per environment ranged from 7 to 513 g m-2. Genotypes and environme nts were classified by a cluster analysis and the interaction was anal yzed with an additive main effects and multiplicative interaction mode l. Genotypes were classified into four clusters, related to their grow th type and earliness of heading. Environments were clustered in a HY and LY group; this classification was related to seasonal rainfall and temperature. Medium-early heading winter types had a positive interac tion with LY environments and a negative interaction with HY environme nts, whereas late heading genotypes (spring and winter types) had the opposite interaction pattern. Early beading spring types had above-ave rage mean yields; the highest-yielding among them tended to have a low interaction with environments. High-yielding environments did not dis criminate well between genotypes with high or low yields in LY environ ments, and may thus have limited value for yield selection for LY envi ronments. For a breeding program aimed at improving yield in environme nts where favorable conditions are rare, selection for yield should be done in representative less-favorable environments.