THE ROLES OF ACTIVE OXYGEN SPECIES AND LIPID PEROXIDATION IN THE RESISTANCE OF COTTON SEEDLINGS TO FUSARIUM WILT

Seeds of cotton ( Gossypium hirsutum ), either resistant or susceptible cultivar to Fusarium wilt, were sown in soil treated with trifluralin at 2 μg a.i./g soil. The 10 day old seedlings were inoculated with Fusarium oxysporum f.sp. vasinfectum (Fov) . Active oxygen species and lipid peroxidation levels in the seedling stems/roots were determined to evaluate their relationship to cotton resistance against the disease. The levels of malondialdehyde (MDA) and the content of unsaturated fatty acid in membrane significantly increased after the inoculation in the seedlings of resistant cultivar, especially in the trifluralin-treated seedlings, showing the enhanced lipid peroxidation. Moreover, the generation rate of superoxide anion (O [SX(B-3]-· 2), the level of hydrogen peroxide (H 2O 2) and the activity of lipoxygenase (LOX) were also increased markedly in the seedlings mentioned above. But no significant increases in the activities of superoxide dismutase (SOD) and catalase (CAT) were observed in those seedlings. In contrast, the MDA level,the production rate of O [SX(B-3]-· 2,the content of H 2O 2,and LOX activity in cotton seedlings of susceptible cultivar increased slightly. The content of unsaturated fatty acid in membrane decreased slightly after infection by Fov ,while the activities of SOD and CAT increased significantly. The trifluralin treatment, showing effect on inducing cotton resistance to Fusarium wilt,increased the LOX activity,the contents of O [SX(B-3]-· 2 and H 2O 2,and MDA level. The results suggested that the accumulation of active oxygen species (O [SX(B-3]-· 2 and H 2O 2) and the increased activity of LOX may play a role in the resistance of cotton seedlings to Fusarium wilt by initiation of lipid peroxidation.