Resistance of cereals to aphids: Interaction between hydroxamic acids and the aphid Sitobion avenae (Homoptera: Aphididae)

The hydroxamic acids in the seedlings of four varieties of winter wheat were extracted initially in boiling methanol in order to avoid enzymatic hydrolysis. The increase in numbers of aphids on these varieties of wheat were recorded. HPLC analysis of hydroxamic acids in the extracts showed the presence of DIMBOA-glucoside, DIMBOA-aglucone and its benzoxazolinone (MBOA). There was a highly significant negative correlation between the concentration of DIMBOA-aglucone in the seedlings and aphid performance. However, the association between aphid performance and DIMBOA-aglucone in the tips of the seedlings was weaker. In general aphid infestation of wheat seedlings slightly increased the concentration of all the hydroxamic acid derivatives. Moreover, aphids ingested hydroxamic acids and were able to detoxify some of the DIMBOA-aglucone they ingested.