Differential response of antioxidant enzymes in leaves of necrotic wheat hybrids and their parents.

The leaves of necrotic hybrid of wheat (Triticum aestivum L.) exhibited high superoxide content associated with increased lipid peroxidation and membrane damage in earlier studies (Khanna-Chopra et al. 1998, Biochem Biophys Res Commun 248: 712-715; Dalal and Khanna-Chopra 1999, Biochem Biophys Res Commun 262: 109-112). In the present study, we investigated the activities of the antioxidant enzymes in the leaves of necrotic wheat hybrids, KalyansonaxC306 (KxC) and WL711xC306 (WLxC) and their parents at different developmental stages. The KxC hybrid exhibited more severe necrosis than WLxC. In KxC, superoxide dismutase (SOD) activity showed no increase over the parents, while WLxC showed an early increase, but it was possibly insufficient to scavenge increased superoxide. Activities of guaiacol peroxidase, ascorbate peroxidase and glutathione reductase were enhanced, while catalase exhibited a decrease in activity, with the appearance of visible necrosis in both the hybrids. The isozyme profile of the antioxidant enzymes was similar in the hybrids and their parents. One existing isoform of guaiacol peroxidase showed an early appearance in the hybrid and increased in intensity with the progression of necrosis. The results reveal a differential response of antioxidant enzymes in necrotic wheat hybrids as compared to their parents. The response differed in magnitude at developmental stages of the leaves, which might be related to the intensity of necrosis expressed by the hybrids.