Exogenous applications of moringa leaf extract effect on retrotransposon, ultrastructural and biochemical contents of common bean plants under environmental stresses

•Spraying bean plant in MLE alleviated the adverse effects of environmental stresses.•MLE supported the antioxidant system in bean plants to tolerate different stresses.•Many retrotransposons were showed to be activated by environmental stresses.

Moringa oleifera leaf extract (MLE) is rich in amino acids, ascorbate, zeatin, minerals, and many other compounds known for their growth-promoting potential. Therefore, a pot experiment was aimed to study the effect of foliar spray with aqueous extracts of Moringa oleifera leaves on some physiological, biochemical, and molecular markers of common bean plants (Phaseolus vulgaris) grown under salt stress (200 mM), high temperature (45 °C), and gamma rays (200 Gy). The results showed that the shoot and root length, fresh and dry weights of shoots and roots, photosynthetic pigments, and phytohormone contents were decreased significantly in stressed plants as compared with untreated plants under all environmental stresses. On the other hand, total soluble sugars content, glutathione, malondialdehyde, O2•−, and H2O2 contents were significantly increased in stressed plants as compared to untreated plants. The exposure to different environmental stresses caused damage in leaf ultrastructure, which led to both vesiculation and swelling in the chloroplast stroma. In addition, many retrotransposons were showed to be activated in response to environmental stresses. Retrotransponson detecting the differences between control and stress samples in terms of different fragment length which reflects the effect of MLE and both stresses. The foliar application of moringa leaf extract caused significantly increased in all the above parameters. Results of this study suggested that MLE as antioxidant could activate the antioxidants in plants to enable them to alleviate the oxidative damage leading to improvements in physiological and molecular attributes in plants grown under the adverse conditions of environmental stresses.