Tri-trophic interactions involving pest aphids, predatory 2-spot ladybirdsand transgenic potatoes expressing snowdrop lectin for aphid resistance

Transgenic crops genetically engineered for enhanced insect resistance shou ld be compatible with other components of IPM for the pest resistance to be durable and effective. An experimental potato line was genetically enginee red to express an anti-aphid plant protein (snowdrop lectin, GNA), and asse ssed for possible interactions of the insect resistance gene with a benefic ial pest predator These extended laboratory studies are the first to demons trate adverse tri-trophic interactions involving a lectin-expressing transg enic crop, a target pest aphid and a beneficial aphidophagous predator. Whe n adult 2-spot ladybirds (Adalia bipunctata [L.]) were fed for 12 days on p each-potato aphids (Myzus persicae Sulzer) colonising transgenic potatoes e xpressing GNA in leaves, ladybird fecundity, egg viability and longevity si gnificantly decreased over the following 2-3 weeks. No acute toxicity due t o the transgenic plants was observed, although female ladybird longevity wa s reduced by up to 51%. Adverse effects on ladybird reproduction, caused by eating peach-potato aphids from transgenic potatoes, were reversed after s witching ladybirds to feeding on pea aphids from non-transgenic bean plants . These results demonstrate that expression of a lectin gene for insect res istance in a transgenic potato line can cause adverse effects to a predator y ladybird via aphids in its food chain. The significance of these potentia l ecological risks under field conditions need to be further evaluated.