ABSTRACT
Chemical interactions between cereals and the grain aphid, focusing on the role of the cereal allelochemicals have been studied. Cereal allelochemicals showed allelopathic action towards the grain aphid at the surface, within peripheral tissues (epidermis and mesophyll), and within the phloem sap. The grain aphid accepted cereal cultivars heavily covered with surface waxes considerably less. GLC-MS analysis of dichloromethane extracts from flag leaves and ears showed that such cultivars contained high level of ß-diketones and lauric acid derivatives. High content of the cereal allelochemicals: phenolic compounds, hydroxamic acids and indole alkaloids within peripheral tissues as well as low concentration of nutrients and feeding stimulators in phloem sap strongly reduced the abundance and development of the grain aphid population on the studied cultivars. The relationship between the cereal allelochemicals and acceptance of the cereals during host-plant selection by the grain aphid is discussed.
