Osmotic adjustment in wheat in relation to grain yield under water deficit environments

Six greenhouse and three field experiments were conducted at the International Center for Improvement of Maize and Wheat (CIM-MYT), Mexico, on bread wheat (Triticum aestivum L.) genotypes to ascertain the role of osmotic adjustment (OA) in sustaining grain yield and its stability under water deficit conditions. Under simulated water deficit conditions of the greenhouse and field, the genotypes differed considerably regarding OA, ranging from 0.31 to 0.86 MPa and from 0.60 to 0.99 MPa, respectively. When the mean values of OA across the six greenhouse experiments were regressed against those of grain yield obtained at different moisture levels of the line source, the correlation coefficient value increased with the increase in moisture stress, turning positively significant (P < 0.001) at the highest water deficit level. Similarly, osmotic potential at full turgor (OP100) and turgor potential (TP), measured in the greenhouse, were positively correlated (P < 0.05) with grain yield at the highest line source water deficit level. Osmotic adjustment and grain yield, both measured in the simulated water deficit condition in the field, were also positively correlated (P < 0.05). Besides, OA maintained yield stability through maintenance of turgor under water deficit during reproductive period of crop growth. The heritability of OA, OP100, and TP, computed by pooled analysis of variance across the six greenhouse experiments, was 0.74, 0.73, and 0.79, respectively. The results indicated that OA, as well as OP100 and TP, could be used as screening tools for drought-resistant bread wheat genotypes in the greenhouse. This study also demonstrated the appropriate greenhouse screening methodology in this regard.