LAUSR

Stability of combining ability and the nature and extent of genetic and genotype×environment interaction is poorly understood in orchardgrass especially under climate change conditions. In the present study, first-generation half-sib families of orchardgrass derived from the polycross of 25 parental genotypes were evaluated in the field during five years under two irrigation regimes of normal and water deficit. Considerable genotypic variation was observed among half-sib families for all of the evaluated traits, demonstrating high potential for improving these traits through half-sib mating. The effects of water deficit on dry forage yield increased from the first to fifth year and consequently declined the persistence of half-sib families. Results showed that both genetic and non-genetic gene actions played a role in the control of dry forage yield; indicating that selection based on an index would be more useful to attain genetic progress. Moreover, the estimates of narrow-sense heritability for most of the traits were higher under deficit irrigation, which is advantageous for successful selection. The stability of general combining ability, plant productivity, and drought tolerance clearly identified G4, G5, G6, and G14 as the superior and stable parental genotypes able to transmit both stability and forage productivity to their progenies.