Peroxidative Responses of Leaves in Two Soybean Genotypes Injured by Twospotted Spider Mites (Acari: Tetranychidae)

Abstract

Levels of resistance in soybean genotypes to the twospotted spider mite, Te-tranychus urticae Koch, and cumulative lipid peroxidation of the tissues were strongly related. Both were also correlated with loss of carotenoids and chlorophyll. Activity of the prooxidant enzyme Iipoxygenase (LOX) and of peroxidase increased in parallel with T. urticae population levels and lipid peroxidation. Antioxidant enzymes catalase and super-oxide dismutase did not change with increasing T. urticae population levels and lipid peroxidation. The mite-resistant soybean cultivar showed greater loss of carotenoids and chlorophyll and greater lipid peroxidation with initial T. urticae infestation than the mite-susceptible soybean cultivar. Increased resistance could be induced in remote tissues of the mite-resistant soybean cultivar by brief exposure to T. urticae feeding. Possible direct and indirect roles of lipid oxidation and LOX in pest resistance are discussed.