Lipid peroxidation is an early event in necrosis of wheat hybrid

We previously reported enhanced superoxide anion generation in an F1 necrotic hybrid produced from normal parents (Khanna-Chopra et al., Biochem. Biophys. Res. Commun. (1998) 248, 712-715). Further investigation of the mechanism of necrosis shows the possibility of lipid peroxidation as an early event in the death of necrotic leaves. Lipid peroxidation resulting from the inability of free radical scavenging is often associated with cell death. In this study the accumulation of malondialdehyde, an end product of lipid peroxidation, was measured in hybrid leaves and those of the parents. Lipid peroxidation was higher in the hybrid leaves through out the leaf ontogeny. This was accompanied by increased membrane permeability. Cell viability measured by a TTC reduction test showed a significant correlation with conductivity. There was no apparent effect on photosynthetic pigments and maximum efficiency of PSII (Fv/Fm) until the appearance of necrotic lesions on the hybrid leaf. There seems to be a close relationship among lipid peroxidation, membrane permeability, and cell viability in the leaves undergoing necrosis. This suggests the possibility of a genetic mechanism whereby the scavenging of free radical is impaired, leading to enhanced lipid peroxidation and membrane permeability, resulting in necrosis and death of the hybrid leaves in wheat.