Effects of seed priming and foliar application of salicylic acid on some of physiological characteristic and yield on mung bean (Vigna radiata L.) under drought stress condition

Mung bean is a warm seasonal annual legume, grown mostly as a rotational crop with cereals like wheat. The crop’s main advantages are that, as a legume and that it has a short growth cycle (75-90 days), requires little water and fits easily into crop rotations with cereals. It grows well under most adverse arid and semiarid conditions. Plants in nature are continuously exposed to several biotic and abiotic stresses. Among these stresses, drought stress is one of the most adverse factors of plant growth and productivity and considered a severe threat for sustainable crop production in the conditions on changing climate. Drought stress disrupts photosynthetic pigments and reduces the gas exchange leading to a reduction in plant growth and productivity. Salicylic acid (SA) is a naturally occurring plant hormone, influences various physiological and biochemical functions in plants. It can act as an important signaling molecule and has diverse effects on tolerance to biotic and abiotic stresses. Salicylic acid plays a key role in providing tolerance to the plants, exposed to water stress. The exogenous SA application also enhanced the growth and photosynthetic rate in crops under water stress. The aim of this study was to investigate the effect of salicylic acid (include two method of seed priming and foliar application) on two cultivars of mung bean, under drought stress. In order to study the effect of exogenous application of salicylic acid on yield an physiological characteristic of two mung bean cultivars under drought stress an experiment was conducted as a split- split plots based on randomized complete block design with three replications in agricultural research farm of karezan of Ilam province in 2017. Treatments were 2 levels of irrigations (irrigation after 60 and 110mm evaporation from the evaporation pan) as main plots and 2 mung bean cultivars (Gohar and Mehr) as first sub plots and 3 levels of salicylic application (control, seed priming and foliar application) as second sub plots. Salicylic acid was sprayed in two steps: 1- Two weeks after emergence and five days before applying the stress, 2- Early flowering stage. Physiological characteristic were measured at flowering stage. Yield and yield components measured for each treatment separately in the physiological maturity time. Analyze of variance showed that the effect of interaction of cultivar, drought stress and salicylic application on the grain yield, biological yield, number of pod in plant and number of seed in plant were significant. The highest value of grain yield (1894 kg.ha-1) and biological yield (4997 kg.ha-1) were obtained in Gohar cultivar under without stress and foliar application of salisylic acid. Also, the application of salicylic acid, especially in drought stress conditions, increased the content of chlorophyll a, chlorophyll b and carotenoid. The highest (96%) and lowest (71%) relative water content were observed in non-stress treatment with salicylic acid application and stress treatment without salicylic acid, respectively. Exogenous application of salicylic acid improved the drought tolerance of mung bean by enhancing photosynthetic pigments, carotenoid and relative water content which ultimately increased the yield of mung bean. Under drought stress and non-stress conditions, the yield of Gouhar cultivar was higher than that of Mehr cultivar. But the difference between control treatment and application of salicylic acid treatment was higher, under drought stress condition. Application of salicylic acid was raised 70 percent of Mehr cultivar yield under drought stress condition