Oxidative stress tolerance potential of milk thistle ecotypes after supplementation of different plant growth-promoting agents under salinity.

Abstract The aim of the present work was to evaluate the effect of different plant growth promoters (PGPs) such as ascorbic acid (500 μM), thiourea (250 μM) and moringa leaf extract (3%) to mitigate salinity stress (120 mM NaCl) in four different milk thistle [Silybum marianum (L.) Gaertn.] ecotypes from Faisalabad (FSD), Gujranwala (GUJ), Kallar Kahar (KK), and Quetta (QTA) under field conditions for two years (2017–2018). In the present study, oxidative stress indicators such as malondialdehyde (MDA) and hydrogen peroxide (H2O2) and activities of different antioxidant enzymes and levels of non-enzymatic antioxidants were significantly differed among ecotypes, salinity, and PGPs. Supplementation with ascorbic acid and moringa leaf extract improved antioxidant defense machinery during the acclimation process against salinity, and milk thistle ecotypes represent their background of ecological zones and inherent tendency to face and confronting stress with improving antioxidant levels to a significant extent in varying ways. Ecotypic variations showed that QTA ecotype Followed by FSD, GUJ, and KK had more antioxidant capacity, with minimum reactive oxygen species production. Interestingly, the correlation data revealed that MDA and H2O2 had a positive correlation with each other and showed a negative correlation with all the enzymatic and non-enzymatic antioxidants.