Effect of pseudo-hormones growth regulators on growth and yield of two new Kabuli cultivars of chickpea (Cicer arietinum L.) in rainfed conditions

 Terminal drought stress is one of the important factors reducing the yield of chickpea in rainfed crops in cold and temperate regions. Chickpea (Cicer arietinum L.) as an important grain legumes due to its special properties such as nitrogen fixation ability, deep rooting and effective use of rainfall, play an important role in the stability of crop production in sustainable agriculture (Amiri et al., 2011). In Iran, chickpea cultivation under cold regions is mainly in spring using stored moisture in the soil and spring rainfall. One of the factors affecting the yield of dryland chickpeas is water deficiency or teminal drought stress at the end of the season, which severely reduces the growth and grain yield. The possibility of using some biochemical compounds such as salicylic acid, calcium chloride and ascorbic acid increases the tolerance of drought stress at the end of the growth season and reduces the amount of damage and increases grain yield in such conditions. It has been previously reported that salicylic acid plays an important protective role in the development of tolerance to environmental stresses (Raskin, 1992). Under drought stress conditions, salicylic acid prevents the reduction of auxin and cytokinin hormones, increases cell division and improves plant growth by regulating photosynthetic and chlorophyll processes (Sakhabutdinova et al., 2003: Patel et al., 2012). Also, ascorbic acid protects and integrates chloroplast membranes, accumulates soluble carbohydrates, and enhances the normal function of the photosynthetic apparatus by neutralizing superoxide and oxygen free radicals from stresses. (Shao et al., 2008). It has been reported that the use of ascorbic acid improves morphological and physiological parameters and increases plant resistance to stress, and by increasing plant antioxidant capacity, increases photosynthesis and plant growth (Smirnoff, 2011). On the other hand it has been reported that calcium chloride plays an important role in cell adaptation to abiotic stresses and increases its antioxidant activity and photosynthesis through its effect on water uptake, root growth and maintenance of turgor pressure in plant cells (Rab & Haq, 2012).
 
The experiment was carried out in Sararod rainfed agricultural research station, located in the east of Kermanshah city, at an altitude of 1351 meters above sea level, with a mild cold climate and an average annual rainfall of 454 mm in 2018-19 growing season. The experimental cultivars were new and improved cultivars of Kabuli chickpea, named Mansour (V1) and Adel (V2). The experiment was performed as a factorial experiment in a randomized complete block design with three replications. Foliar application included salicylic acid (S1), ascorbic acid (S2), calcium chloride (S3), salicylic acid + ascorbic acid (S4), salicylic acid + calcium chloride (S5), ascorbic acid + calcium chloride (S6) and spraying with water (S7=control). Foliar application of salicylic acid at a concentration of 1.5 mM, ascorbic acid at a concentration of 10 mM and calcium chloride at a concentration of 5 mM. Triton X-100 non-ionic surfactant with a concentration of 0.01% was used to reduce surface tension. Foliar application was done in two stages: 50% flowering and 50% podding of plants.
 
Results showed that the effect of foliar application on the number of sub-stems, number of seeds per pod, 100-seed weight, biological yield, grain yield and grain protein yield was significant. The effect of the compounds used individually was less than their combined use. Grain yield in Mansour cultivar with an average of 61.87 g.m-2 was better than Adel cultivar with an average of 51.16 g.m-2. Among foliar treatments, the most effect on grain yield belonged to salicylic acid + calcium chloride solution with an average of 67.99 and the least effect was the control treatment with an average of 45.80 g m-2. In general, the highest grain yield was obtained for Mansour cultivar with salicylic acid + calcium chloride solution equal to 71.55 g.m-2. The highest percentage of grain protein was also observed in Mansour cultivar with 23.12% and the lowest percentage of grain protein was observed in Adel cultivar with 20.05%.
 
According to the results of this experiment, although individual foliar application of salicylic acid, ascorbic acid or calcium chloride compared to the control (foliar application with water) was effective in increasing the yield of cultivars, but in Mansour cultivar application of salicylic acid with calcium chloride or ascorbic acid and in Adel cultivar application of salicylic acid with calcium chloride had the greatest effect on reducing the adverse effects of drought stress at the end of the growing season, and preventing reduced yield and economic losses of cultivars.