Changes in compatible osmolite contents in four wheat cultivars under water stress

This study aimed to investigate the alteration of compatible osmolite contents (including the content of reducing sugars and proline), as well as polysaccharides 4 wheat cultivars under water deficit conditions, this study was conducted in the field condition. Treatments were water stress and wheat genotypes that studied in a split plot experiment in RCBD design with three replications. Water stress treatments were done as cutting irrigation from anthesis period and optimum irrigation. Studied cultivars were Marvdasht (sensitive), Pishtaz and Bahar (semi-resistant), WS-82-9 (resistant). The results showed that the lowest decrease in grain yield was observed in WS-82-9 due to water stress in the grain filling period, the data did not reveal a significant difference among other cultivars (30% vs. 35-43% in the other cultivars). Biochemical studies showed that water stress caused accumulation of proline content in flag leaf, (21-20 μg/g FW in the control plants versus 57μg/g FW in WS-82-9 or 83 μg/g FW in Bahar cultivar, on the 6th days after drought stress). Over time, the difference between leaf proline content of the varieties were decreased in terms of water availability and water stress. Changes in the percentage of soluble sugars and proline contents showed the same trend. According to our results water stress caused to increased levels of soluble sugars in the stems especially in Marvdasht and Bahar cultivars and WS-82-9 line. Increased levels of soluble sugars occurred at the middle stage of grain filling in the flag leaf of Bahar and Pishtaz cultivars and WS-82-9 line, also this was occurred in Marvdasht at the late stage of grain filling. Polysaccharide content of the leaves and stems decreased in all cultivars by Water deficit, especially in susceptible varieties (highest decrease was observed about 0.52% and 0.67% respectively in leaves and stems of Marvdasht and Pishtaz and the lowest was found about 0.31% and 0.37% respectively in leaves and stems of Bahar and WS-82-9. It seems that compatible osmolites and proline accumulation (osmoregulation) is a common response of all wheat genotypes to drought stress but the rate of increase in these compounds was higher in resistant cultivars during stress