Physiological Responses of Bread Wheat (Triticum aestivum) Cultivars to Drought Stress and Exogenous Methyl Jasmonate

Drought is believed to be one of the most important abiotic stresses, which drastically affects wheat production worldwide. Jasmonates, as plant growth regulators, could modify the effects of environmental stresses. Therefore, we conducted the present study to investigate the physiological responses of wheat cultivars to exogenous methyl jasmonate (MeJA) under drought stress during two crop years of 2015-2017. The results revealed that the irrigation cut-off regime at the booting decreased Fv/Fm, RWC, peroxidase activity, and grain yield; whereas it increased proline, malondialdehyde content, protein, and electrolyte leakage. The drought-tolerant cultivar, Sirvan had 13.7% higher grain yield than Pishtaz cultivar in drought stress owing to higher Fv/Fm, proline, RWC, peroxidase activity, and lower electrolyte leakage and MDA. Spraying 50 mu M of MeJA increased chlorophyll and carotenoids (8.7% and 6.93%), proline (26.8%), and peroxidase activity (31.4%); whereas 100 mu M of MeJA increased the RWC (2.5%), Fv/Fm (9.3%) and decreased membrane electrolyte leakage (6.7%) compared to hormone-free conditions. According to the results drought stress decreased certain physiological traits, the foliar application with 100 mu M of MeJA could increase the grain yield (9.2% in irrigation cut-off at booting and 6.8% at the milk stage) and then partially compensate for the reduction caused by drought stress. Therefore, for minimizing the effect of drought stress, we could recommend the use of MeJA and drought-tolerant cultivar.