Heritability estimates in contrasting environments as influenced by the adaptation level of barley germ plasm

Low heritability estimates in marginal or stress environments have often been used as one of the main justification for conducting selection work in environments with optimum or near-optimum conditions for plant growth and grain yield. In this study, we have examined the relationships between grain yield and broad-sense heritability in four groups of recombinant inbred lines (RILs) obtained from four barley crosses derived from parents differing in adaptation to stress. The RILs and the parents were grown in 13 combinations of years and locations (environments) in Syria and Jordan. Grain yields ranged from about 30 kg ha(-1) to nearly 4000 kg ha(-1) and genotype x environment interactions explained about half of the total variance for environmentally standardised data. Broad-sense heritability in the individual year-location combinations varied from 0 to 0.68 and both the simple correlation and the rank correlation coefficients between grain yield and heritability were not significant. Genotype x years within individual locations, which measures the repeatability of a location in discriminating between genotypes, was also independent from the yield level, confirming that low-yielding locations can be reliable selection environments. Also, there was no relationship between the type of cross and the magnitude of heritability in the various environments, but, as expected, the magnitude of heritability was significantly associated with the genetic distance between the parents. it is concluded that, holding all other factors affecting response to selection constant, concerns about the magnitude of heritability at low-yielding locations are not justified and should not prevent them from being used as selection sites.