Direct and indirect sublethal effects of Galanthus nivalis agglutinin (GNA) on the development of a potato-aphid parasitoid, Aphelinus abdominalis (Hymenoptera : Aphelinidae)

Snowdrop lectin (Galanthus nivalis agglutinin, GNA), has been shown to conf er partial resistance to two potato aphids Myzus persicae and Aulacorthum s olani, when incorporated in artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess th e potential effect of GNA on the aphid parasitoid Aphelinus abdominalis. GN A (0.1% w/v) was successfully delivered to Macrosiphum euphorbiae via artif icial diet and induced a reduced growth rate and increased mortality compar ed to aphids fed a control diet. As aphid parasitoid larvae are endophagous , they may be exposed to GNA during their larval development and potential "chronic toxicity" on A. abdominalis was investigated. The amounts of GNA p resent in aphid and parasitoid tissues were estimated by western blotting. Results suggest that parasitoids excrete most of the GNA ingested. Subletha l effects of GNA on several parasitoid fitness parameters (parasitism succe ss, parasitoid development and size, emergence success, progeny survival an d sex ratio) were studied. No direct detrimental effect of GNA on A. abdomi nalis was observed. However, GNA had an indirect host-size-mediated effect on the sex ratio and the size of parasitoids developing in GNA-fed aphids. This work highlights the need to determine the exact "causes and effects" w hen assessing the ecological impact of transgenic plants on non-target bene ficial insects. Such bioassays form the basis of a tiered risk assessment m oving from laboratory studies assessing individuals towards field-scale exp eriments assessing populations. (C) 2001 Elsevier Science Ltd. All rights r eserved.