Mycorrhizal colonization and calcium spraying modulate physiological and antioxidant responses to improve pepper growth and yield under salinity stress

Abiotic stresses, such as salt and drought, limit plant growth, reduce crop production, and pose the greatest challenge to the sustainability of agricultural development in arid and semi-arid countries. Arbuscular mycorrhizal fungi (AMF) and calcium can play an important role in alleviating the adverse effects of abiotic stresses on plants. Therefore, this study was conducted to evaluate the effect of two levels of mycorrhizal inoculation (inoculated seedlings and non-inoculated seedlings) and three levels of foliar spraying with calcium (0, 0.5%, and 1%), separately or in combination, on growth, physiology, and yield of salt-stressed pepper (Capsicum annuum L.). The experiment was conducted in an open field with saline soil and irrigation water, in a randomized complete block design with split plot arrangement. Mycorrhizal inoculation and calcium spray have been shown to facilitate nutrient uptake, modulate physiological responses, and activate the antioxidant system, enhancing salt stress tolerance and improving the growth and yield of salt-stressed pepper. Combined treatment plants grown from inoculated seedlings and sprayed with 1% Ca recorded the best results, alleviating salt stress-induced oxidative damage by activating the antioxidant system including antioxidant enzymes [Superoxide dismutase (SOD) and catalase (CAT)], and non-enzymatic antioxidants (ascorbic acid and phenols), reducing H2O2 and malondialdehyde (MDA) accumulation, enhancing physiological activities (relative water content (RWC %) and chlorophyll content), and improving nutrient balance (increasing N, P, K and reducing Na content), leading to increased pepper growth and yield parameters. Our results indicated that mycorrhizal inoculation and calcium spray can be recommended as a practical alternative and environmentally friendly approach to enhance plant tolerance to salt stress by improving nutritional status, physiological processes, and antioxidant activities, thus increasing the morphological and yield traits of stressed plants.