Combined effects chitosan and genotype on agronomic, physiologic, and biochemical characteristics of soybean under drought stress conditions

Abstract

The current study investigated the responses of physiological, biochemical, and agronomic of four soybean genotypes to foliar application of chitosan under optimal water supply and drought stress conditions. A factorial split-plot experiment was set up in a randomized complete block design with three replications for two years (2022 and 2023). The enzymes activity of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) as well as chlorophyll content (a, b, and total), ß-carotene content, seed yield, protein yield, and oil yield were measured. Drought stress enhanced the ß-carotene content and the activity of SOD, POD, APX, and CAT compared with the full irrigation regime. By contrast, the chlorophyll content (a, b, and total) was reduced when soybean plants were grown under water-limited condition as compared with the water-limited condition. The drought stress regime led to decreases of 60 %, 12.5 %, and 23.3 % (on average across years, genotype, and chitosan treatments) in soybean seed yield, oil content, and protein content, respectively. The soybean genotypes differently responded to the foliar application of chitosan under both irrigation regimes in terms of the activity of SOD, POD, APX, and CAT enzymes. The chlorophyll a, b, and total contents roughly enhanced when the soybean plants were treated with chitosan compared with the control treatment. A slight reduction was observed for the ß-carotene content when the chitosan was applied under optimal water supply condition while the ß-carotene content was depleted for all studied genotypes under drought stress condition. On average across genotypes and chitosan treatments, applying chitosan boosted the soybean seed yield, oil content, and protein content by 6.9 %, 8.1 %, and 6.7 %, respectively. Overall, foliar application of chitosan and Williams genotype would be recommended under both irrigation regimes (drought and well-watered) to achieve the highest soybean seed yield, oil content, and protein content.