Exposure of arthropod predators to Cry1Ab toxin in Bt maize fields

Abstract

Abstract. 1. To assess the risks of an insect‐resistant transgenic plant for non‐target arthropods, it is important to investigate the exposure of non‐target species to the transgene product. Exposure of predators in the field depends on the toxin levels in food sources, their feeding ecology and that of their prey.2. To verify the transmission of Cry1Ab toxin through the food chain, and thus exposure of predators in the field, samples from different plant tissues, herbivores, and predators in Bt maize fields in Spain (Event 176) were collected at different periods over the season and the toxin content was measured using ELISA. Complementary laboratory studies were performed with the omnivorous predator Orius majusculus to assess the toxin uptake and persistence after feeding on variable Bt‐containing food sources.3. Field results revealed that toxin content in some herbivores was negligible (aphids, thrips, leafhoppers) compared with those in spider mites. The latter herbivore only occurred after pollen shed and contained three times greater toxin levels than Bt maize leaves.4. Data confirmed that the Bt toxin can be transferred to predators, that is to say to Orius spp., Chrysoperla spp., and Stethorus sp. This only applied when Bt maize pollen or spider mites were available. The passage of Bt toxin to O. majusculus via these two food sources was also confirmed in the laboratory. Contrastingly, some predators in the field (hemerobiids, Nabis sp., Hippodamia sp., Demetrias sp.) contained no or negligible toxin levels even when pollen or spider mites were present.5. Besides essential information for exposure assessment of numerous arthropod predators, this study provides an insight into the feeding ecology of different arthropods in the maize system.

Spiders from multiple functional guilds are exposed to Bt-endotoxins in transgenic corn fields via prey and pollen consumption

“…Numerous potential prey species for spiders tested positive for Bt-endotoxins from the field, including several beetles (Coleoptera), true bugs (Hemiptera), moth larvae (Lepidoptera: Noctuidae), adult and nymphal crickets (Orthoptera: Gryllidae), harvestmen (Opiliones), millipedes (Diplopoda: Julida), centipedes (Chilopoda: Lithobiomorpha, Geophilomorpha), and earthworms (Haplotaxida: Lumbricidae) (Table S2). Previous studies have also shown clear evidence for the uptake of Cry1Ab Bt-endotoxins from transgenic corn by potential prey items, including corn flea beetle Chaetocnema pulicaria (Coleoptera: Chrysomelidae), Japanese beetle Popillia japonica (Newman) (Coleoptera: Scarabaeidae), pink spotted lady beetle Coleomegilla maculata (DeGeer) (Coleoptera: Coccinellidae), and damsel bug Nabis roseipennis Reuter (Hemiptera: Nabidae) (Harwood et al, 2005(Harwood et al, , 2007Obrist et al, 2006;Wei et al, 2008;Zwahlen & Andow, 2005). These studies, as well as our own, found a large degree of variation in the uptake of Cry proteins by different prey species (see Table S2).…”

“…Techniques using monoclonal and/or polyclonal antibodies, such as enzyme-linked immunosorbent assay (ELISA), have been successfully employed to detect the presence of Bt-endotoxins in field-collected arthropods, such as Coleoptera (Harwood et al 2005(Harwood et al , 2007Peterson et al 2009;Zwahlen & Andow 2005), Acari (Obrist et al 2006;Torres & Ruberson 2008), and Araneae (Harwood et al 2005). Ahmad et al (2005) measured ground-dwelling arthropod abundance (including spiders) and, in parallel, used ELISA to quantify Bt-endotoxin concentration in the soil, but did not test for the uptake of proteins by the arthropods themselves.…”

Environmental Risk Assessment of Genetically Modified Crops: General Principles and Risks to Non-target Organisms

“…For risk assessment, one may wish to know the highest concentration of a substance that elicits no adverse effect on an organism; this is the no observable adverse effect concentration or NOAEC. If no organism were Raybould et al 2007 3 E.g., Head et al 2001;Raps et al 2001;Dutton et al 2002;Howald et al 2003;Obrist et al 2005;Obrist et al 2006a;Obrist et al 2006b;Torres et al 20064 Babendreier et al 2004 5 Westgate et al 2003;Depuis et al 1987 6 E.g., Khan & Afzal 1950;Thies 1953;Sidhu & Singh 1961;Llewelyn & Fitt 19967 Crocker et al 2002 exposed to concentrations of a substance greater than its NOAEC, then that substance would pose minimal risk to non-target organisms. Thus a third hypothesis can be tested to determine the safety of exposure to a transgenic protein, or to any other potential toxin detected in a GM crop:…”

Cry protein in the predatory mite Neoseiulus californicus and spider mite Tetranychus urticae prey fed with transgenic maize

“…The predatory mite Neoseiulus californicus McGregor (Acari: Phytoseiidae) feeds on mites of the family Tetranychidae (McMurtry and Croft, 1997) and can acquire the Cry protein by ingesting T. urticae mites that feed on Bt plants (Dutton et al, 2002;Obrist et al, 2006 (Figure 1a). The results were positive with Bt maize leaf discs samples (30F35 Hx), in which a second test line was developed in the region between the control line and the lower end of the strip.…”