Abstract: The contents of total phenolics, carbohydrates and the acidity in threewheat cultivars with different levels of resistance to the grain aphid, Rhopalosiphum padi (Linnaeus), were determined. The data indicated that a higher degree of wheat resistance to aphid was associated with a higher amount of phenolics, and some correlationwere found for carbohydrate content and acidity. In addition, aphids were analysed for their amylase and carboxylesterase activities, and it was found that aphids feeding on resistant wheat had higher activity of amylase and carboxylesterase, comparing with thosefeeding on susceptible variety.

Key words: Phopalosiphu padi (L.), wheat, resistance