European yellow lupine, Lupinus luteus, and narrow-leaf lupine, Lupinus angustifolius, as hosts for the pea aphid, Acyrthosiphon pisum

The pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae), fed, developed, and reproduced on yellow lupine, Lupinus luteus L. (Fabaceae: Genisteae). No clear preferences for any variety within L. luteus were found. Acyrthosiphon pisum showed negative values of relative growth rate and no aphid completed development on any variety of narrow-leaf lupine Lupinus angustifolius L. Aphids did not ingest phloem sap while probing on L. angustifolius and the probes were very short. All varieties of L. angustifolius were rejected by aphids during an early stage of probing in peripheral tissues, that is, epidermis or mesophyll. There were qualitative and quantitative differences in alkaloid and soluble sugar content between the two lupine species. Within species, the relative content of individual compounds differed among the varieties. Lupinus angustifolius contained four quinolizidine alkaloids (13-hydroxylupanine, dehydrolupanine, lupanine, and angustifoline), while L. luteus contained two (lupanine and sparteine). Lupanine occurred in all varieties of both lupine species. The total content of soluble carbohydrates was similar in L. luteus and L. angustifolius . The following cyclitols were found in both lupine species: myo -inositol, D-ononitol, and D-pinitol. Lupinus angustifolius also contained D- chiro -inositol. The study of aphid probing behaviour, development, and reproduction demonstrated that L. luteus is a suitable host plant for A. pisum while L. angustifolius is not. It is likely that the rejection of L. angustifolius by A. pisum was caused by chemical factors detected by aphids at the epidermis and mesophyll level.