Effect of two wheat cultivars differing in hydroxamic acid concentration on detoxification metabolism in the aphid Sitobion avenae

Hydroxamic acids (Hx) are wheat secondary metabolites conferring resistance for cereals against aphids. The activity of five enzymatic systems were ev aluated in the aphid Sitobion avenae reared on the high-Hx wheat cultivar C hagual and the low-Hx wheat cultivar Huayun for 10 generations. Enzyme solu tions were prepared from aphid homogenates and assayed for mixed function o xidases (including cytochrome P-450 monooxygenases and NADPH cytochrome c r eductase), glutathione S-transferases, esterases, and catalase. Specific ac tivities per aphid individual of cytochrome P-450 monooxygenases, NADPH cyt ochrome c reductase, glutathione S-transferases. and esterases were signifi cantly increased in wheat cultivars relative to oat (only marginal increase of esterases in Chagual). Aphids fed on cv. Huayun showed an overall highe r induction of enzymatic systems than those fed on cv. Chagual. Comparison of these results with reported effects of Hx on detoxifying enzymes in othe r insects, including aphids, support the hypothesis that these enzymatic pa thways play an important role in the detoxification of toxic host-plant sec ondary metabolites.