Abstract

Epicuticular waxes from two cultivars of red raspberry (Rubus idaeus) were collected from the newly emerging crown leaves, and also from the group of 4 more mature leaves immediately below the crown. Cultivars of raspberry susceptible (Malling Jewel, MJ) and resistant (Autumn Bliss, AB) to Amphorophora idaei were used. Biological activity was primarily associated with the more mature leaves. Epicuticular wax esters consisted predominantly of long-chain aliphatic compounds in which even-carbon-number acids were esterified to even-carbon-number alcohols. Lesser amounts of odd-carbon-number esters were also present. Terpenyl esters were also present. Compositional differences between the more mature leaves (which may relate to resistance to A. idaei) were higher levels of cycloartenyl esters and α-amyryl esters in wax from AB. There were also differences between the cultivars in the distribution of individual alkyl esters and their component acids and alcohols. Esters with longer acid:shorter alcohol combinations were more abundant in MJ than AB. Alkyl esters were more abundant and cycloartenyl esters were not detected in wax from the immature leaves. Small amounts of an unusual class of triacylglycerol were found only on leaves of the MJ, which had been subject to bioassay with raspberry aphid, which were thought to be aphid derived. It is suggested that the abundance of aphid triacylglycerols on the leaf surface may provide a measure of susceptibility to aphids.