Salinity-induced modulation of growth and accumulation of phytochemicals composition in in vitro root cultures of Azadirachta indica

Abstract

Salinity is a destructive abiotic factor that negatively impacts the growth and development of stress-intolerant plants. Although the effect of salinity on the growth of Azadirachta indica (neem) under in vitro conditions has been widely studied, little is known about the biochemical properties of in vitro root cultures exposed to salinity stress. Therefore, this study aimed to investigate the effects of varying concentrations of salinity on the biochemical properties of A. indica root cultures, specifically on total pigment and phenolic contents, antioxidant activities, and the presence of phytochemicals and azadirachtin compound, at different incubation periods. The results demonstrated that the root cultures coped with increasing NaCl concentrations by altering their phenotype. The highest antioxidant potential was observed in root cultures grown on MSN media (Murashige and Skoog media containing 3 mg L−1 NAA) supplemented with 0.5% w/v NaCl for 4 weeks. Additionally, this media composition and incubation period also resulted in the highest total phenolic and anthocyanin contents. The accumulation of photosynthetic pigments significantly decreased when exposed to NaCl treatments after 4 and 8 weeks. Interestingly, short-term exposure to NaCl had a positive impact on the azadirachtin (AZA) content, while longer treatment duration significantly decreased it. The highest amount of AZA was quantified from root cultures elicited with 1.5% w/v NaCl for 4 weeks. These findings contribute to a better understanding of the effects of salinity stress on the biochemical properties of in vitro root cultures of A. indica. The findings can aid in the development of strategies to enhance the production of bioactive compounds with potential applications in the food and pharmaceutical industries. Additionally, the study provides insights into the physiological mechanisms and manipulation of secondary metabolite production associated with salt tolerance in A. indica and other related species.