Role of Exogenous Osmolyte Supplementation in Ameliorating Osmotic and Oxidative Stress and Promoting Growth in Salinity-Stressed Soybean Genotypes

Salt stress has been a serious problem for various agricultural crops including soybean and is regarded as one of the main causes of compromised agricultural productivity all over the world. In the world, 20% of all arable lands and 33% of irrigated areas are already covered with soil salinity. By 2050, the amount of agricultural land is projected to increase by 50% globally. It is therefore inevitable to explore the new avenues that help to mitigate the deteriorative impact of salinity to agricultural productivity for ensuring food security. The goal of the current experiment was to determine how various osmolytes improved the growth of soybean under salt stress. For this research experiment, we conducted a pot experiment to examine the effects of foliar supplementation of different osmoprotectants, i.e., proline and glycine betaine osmolytes on various morphological (shoot length, fresh and dry weight of shoot and root), physiological parameters (Chlorophyll contents, RWC, MSI), antioxidant enzymatic activity (SOD, POD, CAT, APX), endogenous level of osmolytes (proline and GB), ionic (Na + , K + ), and cessation of damaging lipid peroxidation (H 2 O 2 , and MDA) in three soybean genotypes such as Ajmeri, Rawal, and Faisal-Soya under moderate saline stress. Salinity stress reduced the soybean growth by up to 75% and physiological parameters by up to 52%. The salt stress enhanced the indigenous cell contents of proline, glycine betaine, and antioxidant enzymes activity up to two times as compared to control conditions; however, this increase was insufficient to combat the increasing salt stress damages. It also enhanced the process of lipid peroxidation up to three times in all genotypes of soybean. The statistical analysis of our results indicated that supplementation of osmolytes especially 20 mM proline improved the tolerance of soybean plants against salinity stress by enhancing the growth (52%), physiological response (64%), and antioxidant enzymatic activity (24%) and decreasing the degree of lipid peroxidation (29%). The most remarkable results were found in the Ajmeri genotype as compared to other genotypes at 20 mM foliar application of proline. Therefore, it is concluded that the use of exogenous osmolytes especially proline is helpful in enhancing soybean production and alleviating the salt stress effects on soybean. In comparison of genotypes investigated, the Ajmeri genotype showed the most promising outcomes against salinity stress, which supports the preference for using the Ajmeri genotype in salt-stressed conditions.