Plant Growth Regulators Improve Yield and Yield Components of Wheat under Deficit Irrigation Treatments With Considering the Productive Capacity

Plant Growth Regulators Improve Yield and Yield Components of Wheat under Deficit Irrigation Treatments With Considering the Productive Capacity Mohammad Hashem Azizi 1 , Ali Soleymani 1,2* , and Hamid Reza Javanmard 11- Department of Agronomy and Plant Breeding, Isfahan (Khorasgan) Branch, Islamic Azad University,Isfahan, Iran 2- Plant Improvement and Seed Production Research Center, Isfahan (Khorasgan) Branch,Islamic Azad University, Isfahan, Iran  *Corresponding email address: a.soleymani444@gmail.com   Received:  15 November October 2022                                Accepted: 28  January  2023   Abstract Wheat (Triticum aestivum L.) is one of the major crop plants, which is an important source of various compounds such as carbohydrates, lipids, proteins, and nutrients. Several methods have been used so far to improve wheat growth, seed yield and yield competition under drought stress, and one of the most important one is application of different plant growth regulators (PGRs). In order to determine the effects of different PGRs on the grain yield and yield components of wheat under water shortage treatments, an experiment was designed as a split plot on the basis of a complete randomized block design with three replications in two different experimental locations, namely Abarkuh and Faragheh in 2018-2019. Main plots were the evaporation from the pan class A, namely control treatment (80 mm), 100 mm, and 120 mm evaporation from pan class A, and subplots were control treat (water), foliar application of PGRs of gibberellic acid (GA3 at 100 mgL-1), salicylic acid (SA at 1.5 mM), benzyl adenine (BA at 60 mgL-1), GA3+SA, as well as superoxide dismutase (SOD at 5 gL-1). In this experiment the effects of irrigation treatments and foliar application of PGRs were significant on all experimental characteristics, such as plant height, spike length, the number of tillers per plant, and peduncle length. The highest values of plant height (68.06 cm), spike length (8.81 cm), the number of tillers per plant (3.37), and peduncle length (9.55 cm) was related to 80 mm evaporation from pan class A, and combined application of gibberellic acid and salicylic acid also had obtained the maximum plant height (69.47 cm), spike length (9.23 cm), the number of tillers per plant (3.93), and peduncle length (10.40 cm). The maximum value of plant height (71.27 cm), spike length (10.53 cm), the number of tillers per plant (5.47), and peduncle length (11.69 cm) was related to interaction between 80 mm evaporation from pan class A, and combined application of gibberellic acid and salicylic acid. Other experimental characteristics such as leaf area index (LAI), the number of grains per spike, one thousand grain weight, grain yield, biological yield and harvest index (HI) were significantly affected by irrigation treatments and different PGRs. The highest values of LAI at anthesis stage (187.71), the number of grains per spike (28.53), one thousand grain weight (32.35 g), grain yield (555.18 ton/ha), biological yield (1178.92 ton/ha), and harvest index (47.11 %) were obtained for interaction between 80 mm evaporation from pan class A and combined application of gibberellic acid and salicylic acid. According to the findings, the combined application of gibberellic acid and salicylic acid was the most effective treatments followed by usage of superoxide and benzyl adenine which reveal the importance of application of plant hormones for wheat growth under drought conditions. To sum up, it is important to use tested PGRs to increase wheat yield and yield components particularly under drought stress condition.