Genetics of osmotic adjustment in breeding maize for drought tolerance

Osmotic adjustment in higher plants refers to the maintenance of turgor by lowering of osmotic potential arising from the net accumulation of solutes in response to water deficits. Genetic variation for osmotic adjustment has been reported in several crops, but little is known about its inheritance and potential use as selection criteria in tropical maize ( Zea mays L.). Two tropical lowland maize populations were used in this study to quantify the magnitude of genetic variability in osmotic adjustment; to estimate components of its genetic variance and heritability; and to determine the importance of this trait in breeding tropical maize for improved drought tolerance. Full-sibs within half-sib groups were developed using the Design I mating scheme and evaluated at two locations in Mexico for two seasons using water stress and non-stress environments. Results showed that in both populations, dominance genetic effects were more important than additive effects in controlling the expression of the trait. However, very little genetic variability was present in either population for the trait, although more genetic variation was detected with data collected at flowering stage, when water stress was more severe than at the vegetative stage. Non-significant phenotypic and genotypic correlations were found between osmotic adjustment and yield. Not much genetic gain could be expected from selection for osmotic adjustment in these populations.