Effect of Supplementary Irrigation on the Accumulation of Compatible Osmolytes and Physiological Parameters in Dryland Wheat Cultivars

In order to investigate the effect of supplementary irrigation on dryland wheat cultivars, an experiment was conducted as a factorial in randomized complete block design with three replications during cropping seasons 2016-2017 and 2017-2018. The factors were drought stress levels (dryland and supplemental irrigation) and wheat cultivars (Homa, Sardari, Rijaw, Ouhadi and Azar2). Supplemental irrigation significantly increased grain yield. In both cropping seasons, drought stress increased free amino acids and glycine betaine and decreased relative water content (RWC) and rate of water loss (RWL). Negative and significant correlation of RWL with free amino acids of leaf and glycine betaine and also positive and significant correlation of RWC with glycine betaine level indicated that the higher the concentration of osmotic compounds in leaves, the lower the rate of leaf water loss and the higher the leaf water content. The results of this study confirmed that adequate water supply by using supplementary irrigation in the most sensitive stages of wheat growth is a viable strategy to improve the physiological traits of the plant and hence obtain an acceptable grain yield under dryland conditions.