Prey mediated effects of Bt maize on fitness and digestive physiology of the red spider mite predator Stethorus punctillum Weise (Coleoptera: Coccinellidae)

Abstract

The present study investigated prey-mediated effects of two maize varieties expressing a truncated Cry1Ab, Compa CB (event Bt176) and DKC7565 (event MON810), on the biology of the ladybird Stethorus punctillum. Although immuno-assays demonstrated the presence of Cry1Ab in both prey and predator collected from commercial maize-growing fields, neither transgenic variety had any negative effects on survival of the predator, nor on the developmental time through to adulthood. Furthermore, no subsequent effects on ladybird fecundity were observed. As a prerequisite to studying the interaction of ladybird proteases with Cry1Ab, proteases were characterised using a range of natural and synthetic substrates with diagnostic inhibitors. These results demonstrated that this predator utilises both serine and cysteine proteases for digestion. In vitro studies demonstrated that T. urticae were not able to process or hydrolyze Cry1Ab, suggesting that the toxin passes through the prey to the third trophic level undegraded, thus presumably retaining its insecticidal properties. In contrast, S. punctillum was able to activate the 130 kDa protoxin into the 65 kDa fragment; a fragment of similar size was also obtained with bovine trypsin, which is known to cleave the protoxin to the active form. Thus, despite a potential hazard to the ladybird of Bt-expressing maize (since the predator was both exposed to, and able to proteolytically cleave the toxin, at least in vitro), no deleterious effects were observed.

Expression of a barley cystatin gene in maize enhances resistance against phytophagous mites by altering their cysteine-proteases

“…Because of their short generation time and high population growth rates, mites have developed resistance to the major pesticide groups (Croft and Van de Baan 1988). In addition, no resistant plant cultivars are currently available, and phytophagous mites are not sensitive to toxins encoded by Bt genes (Rovenska et al 2005;Obrist et al 2006;Alvarez-Alfageme et al 2008;Li and Romeis 2010).…”

Environmental Impact of Genetically Modified Crops

“…The passage of Cry1Ab to O. majusculus via these two food sources was confirmed in the laboratory using maize cultivars containing the Event Bt176 that expresses the toxin in pollen (Obrist et al, 2006). Likewise, it has been possible to confirm the transmission of Cry1Ab toxin from MON810 varieties to S. punctillum via T. urticae (Álvarez-Alfageme et al, 2008). Exposure of predators and parasitoids via the environment may also occur when toxins from plant residues persist in the soil.…”

“…15.2). Although the passage of Bt toxin to S. punctillum via its prey has been confirmed (Obrist et al, 2006;Álvarez-Alfageme et al, 2008), no subsequent negative effects on larval development, and adult longevity and fecundity were reported (Álvarez-Alfageme et al, 2008); No differences in abundance of the three main predatory groups recorded in pitfall traps -ground beetles, spiders and earwigs -were found between Bt and non-Bt plots (De la Poza et al, 2005;Farinós et al, 2008). The only group of ground-dwelling predators that showed a significant reduction in abundance in Bt plots were the staphylinids in field trials carried out in Madrid in 2000.…”

“…In principle, genes from microbes, plants or animals could be used in genetically modified (GM) plants to protect them from insect attack (Schuler et al, 1998;Moar, 2003;Ferry et al, 2004Ferry et al, , 2006Cohen, 2005;Gatehouse, 2008;see Chapter 6, this volume). Silencing of insect genes with ribonucleic acid (RNA) interference also has potential for defending GM plants from insects .…”

Establishing a database of bio‐ecological information on non‐target arthropod species to support the environmental risk assessment of genetically modified crops in the EU

“…In addition, C. septempunctata is a standard test organisms for the evaluation of plant protection products (Schmuck et al 2000). In case that risk to ladybirds can not be ruled out and additional tests under more realistic conditions would be required, tri-trophic studies studies could be conducted with S. punctillum, which is exposed to relatively high concentrations of toxin under field conditions, a tri-trophic test protocol exists (Álvarez-Alfageme et al 2008;Li & Romeis 2010), and the species is commercially available (van Lenteren 2012).…”