Characterization of resistance to multiple aphid species (Hemiptera: Aphididae) inMedicago truncatula

Abstract

AbstractAphids are phloem-feeding insects that damage many important crops throughout the world yet, compared to plant–pathogen interactions, little is known about the mechanisms by which plants become resistant to aphids.Medicago truncatula(barrel medic) is widely considered as the pre-eminent model legume for genetic and biological research and in Australia is an important pasture species. Six cultivars ofM. truncatulawith varying levels of resistance to two pests of pasture and forage legumes, the bluegreen aphidAcyrthosiphon kondoiShinji and the spotted alfalfa aphidTherioaphis trifoliif.maculata. (Buckton) are investigated. Two resistance phenotypes againstT. trifoliif.maculataare described, one of which is particularly effective, killing most aphids within 24 h of infestation. Each resistance phenotype provided a similar but somewhat less effective degree of resistance to the closely-related spotted clover aphidTherioaphis trifolii(Monell). In the case ofA. kondoionly one resistance phenotype was observed, which did not vary among different genetic backgrounds. None of the observed resistance againstA. kondoiorT. trifoliif.maculatasignificantly affected the performance of green peach aphidMyzus persicae(Sulzer) or cowpea aphidAphis craccivoraKoch. The existence of multiple aphid resistance mechanisms in similar genetic backgrounds of this model plant provides a unique opportunity to characterize the fundamental basis of plant defence to these serious agricultural pests.