Does exogenously-applied trehalose alter oxidative defense system in the edible part of radish (Raphanus sativus L.) under water-deficit conditions?

• Effects of trehalose on alteration in the chemical composition of edible roots of radish.
• Role of trehalose on fresh weight of edible root of radish under water stress.
• Whether or not exogenously applied trehalose modulates oxidative defensive system of radish roots under varying water regimes?

It is known that trehalose has the ability to mitigate the adverse effects of abiotic stresses on plants. Thus, the role of exogenously-applied trehalose was examined on water stress-induced changes in the enzymatic and non-enzymatic antioxidative defense system within roots (edible part) of Raphanus sativus L. (radish) plants. Two radish cvs. (Manu and 40-day) were grown under normal and water-deficit conditions. Trehalose was applied through two different modes, i.e., presowing seed treatment and foliar spray using its two levels, 25 and 50 mmol/l. It was observed that water deficiency significantly reduced the root fresh weight, while increased the accumulation of carotenoids, ascorbic acid (AsA), malondialdehyde (MDA), glycinebetaine (GB), and total soluble proteins (TSP) contents coupled with an increase in the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) enzymes in the roots of radish. Both modes of exogenous application of trehalose were effective in reducing MDA contents, while improving root fresh weight, and contents of AsA, total phenolics, GB, total tocopherols and TSP as well as the activities of SOD, CAT and POD. It was observed that cv. Manu was better in MDA, total phenolics, GB, TSP contents and activities of CAT and POD, while cv. 40-day was better in root fresh weight, carotenoids, AsA and total phenolics. Overall, of both modes of exogenous application of trehalose, foliar application was most effective in improving the enzymatic and non-enzymatic antioxidant defense system in edible part of radish.