Roles of methyl jasmonate in improving growth and yield of two varieties of bread wheat (Triticum aestivum) under different irrigation regimes

Drought stress due to its stage of occurrence is one of the factors affecting wheat yield, and jasmonates are plant growth regulators that play an important role in increasing the resistance of plants to environmental stresses such as drought stress. Therefore, in order to study the effect of spraying different concentrations of methyl jasmonate on water productivity, yield and its components of two wheat cultivars under different irrigation regimes, a split factorial experiment was conducted based on a randomized complete block design with three replications in two crop years (2015-2017). In this experiment, different irrigation regimes, including normal irrigation (control), irrigation cut off from the booting and milk stage as the main factor, and two wheat cultivars and various concentrations of methyl jasmonate in four levels of 0, 50, 100, and 150 mu M were investigated as factorial in subfactor. The results showed that use of 100 mu M methyl jasmonate increase growth period and a number of days until plant physiological maturity. Under drought stress conditions, the number of grains per spike, weight of one thousand seed, grain yield, and harvest index are decreased in every two years of experiment. Also, using 100 mu M methyl jasmonate lead to increase these traits by 22.2, 14.4, 8.5, and 11.4%, respectively in Pishtaz cultivar, and 10.3, 10.7, 8.5, and 11.2%, respectively in the Sirvan cultivar compared to the control group. The highest water productivity at each of the three levels of irrigation was related to the concentration of 100 mu M methyl jasmonate. According to the results, although drought stress reduced yield and its components, methyl jasmonate was able to compensate somewhat (10%) for the reduced yield due to drought stress. The irrigation cut off at the grain milking stage can be beneficial with increasing water productivity in managing this valuable resource. Also, the use of 100 mu M jasmonate in these conditions is recommended as a practical way to increase tolerance to drought stress conditions and improve the growth and yield of wheat.