Interspecific and intraspecific variation in the performance of three pestaphid species on five grain legume hosts

The suitability of five grain legume species (narrow-leafed lupin, chickpea , faba bean, field pea, lentil) as hosts for three aphid species (green pea ch aphid, cowpea aphid, bluegreen aphid) was evaluated by measuring the mea n relative growth rate (MRGR) and survivorship of nymphs over a 5 day perio d. For each aphid species, intraspecific (interclonal) variation was also d etermined by independently measuring the performance of 30 clones collected from a variety of hosts and from different parts of the Western Australia (WA) wheatbelt. The suitability of the grain legumes varied among aphid spe cies. Chickpea was not a suitable host for any of the aphids tested. Averag ed over all clones, lentil and faba bean were the most suitable hosts for c owpea aphid, and narrow-leafed lupin was the most suitable host for green p each aphid. Field pea was a suitable host for all three species, but only a t a suboptimal level. Cowpea aphid showed the greatest amount of intraspeci fic variation, with significant variation in MRGR among clones on all hosts except chickpea and significant variation in survivorship on chickpea and lupin. For green peach aphid, there was significant variation in MRGR among clones on field pea and lupin, but in survivorship on lupin only. Bluegree n aphid clones showed significant variation only for MRGR on faba bean and lupin. There were positive correlations in performance of green peach aphid clones on faba bean and lentil, and of cowpea aphid clones on faba bean an d lentil. Bluegreen aphid clones showed a negative correlation in performan ce on field pea and faba bean. These results show the importance of screeni ng cultivars against a wide variety of aphid clones when assessing aphid su sceptibility in breeding programmes. The implications of these results on t he adaptability of parthenogenetic aphids are discussed.