Differential antioxidative responses to water stress among five mulberry (Morus alba L.) cultivars

Ascorbate, antioxidant enzyme activities and foliar contents of proline, glycine betaine and abscisic acid (ABA) along with lipid peroxidation rates and electrolytic leakage were determined in five mulberry (Morus alba L.) cultivars (BC2-59, K-2, MR-2, S-13 and TR-10) subjected to water stress by withholding water until the leaf water potential (psi) reached -2.50 MPa. The activities of antioxidant enzymes which include superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), peroxidase (POD, EC 1.11.1.7), glutathione reductase (GR, EC 1.6.4.2) and monodehydroascorbate reductase (MDAR, EC 1.6.5.4) were significantly high in the water-stressed leaves. The contents of ascorbate and monodehydroascorbate in the leaf extracts of five cultivars of mulberry also showed variations in response to water deficit. Higher antioxidant enzyme activities were observed in the leaf extracts of S-13 while the lowest activities were recorded with cv. TR-10. Lower rates of membrane lipid peroxidation and electrolytic leakage were noticed in the leaves of BC2-59 and S-13 under water deficit. Quantitative differences were also noticed in foliar proline, glycine betaine and abscisic acid contents among five cultivars in response to drought. The leaves of BC2-59 and S-13 accumulated more proline, glycine betaine and abscisic acid under water stress compared to K-2, TR- 10 and MR-2. Our data demonstrate that among five mulberry cultivars, cvs. S-13 and BC2-59 have efficient antioxidative characteristics which could provide better protection against oxidative stress in leaves under water limited conditions. (C) 2004 Elsevier B.V. All rights reserved.