The food and environmental safety of Bt crops

Abstract

Bacillus thuringiensis (Bt) microbial pesticides have a 50-year history of safety in agriculture. Cry proteins are among the active insecticidal ingredients in these pesticides, and genes coding for Cry proteins have been introduced into agricultural crops using modern biotechnology. The Cry gene sequences are often modified to enable effective expression in planta and several Cry proteins have been modified to increase biological activity against the target pest(s). Additionally, the domains of different but structurally conserved Cry proteins can be combined to produce chimeric proteins with enhanced insecticidal properties. Environmental studies are performed and include invertebrates, mammals, and avian species. Mammalian studies used to support the food and feed safety assessment are also used to support the wild mammal assessment. In addition to the NTO assessment, the environmental assessment includes a comparative assessment between the Bt crop and the appropriate conventional control that is genetically similar but lacks the introduced trait to address unintended effects. Specific phenotypic, agronomic, and ecological characteristics are measured in the Bt crop and the conventional control to evaluate whether the introduction of the insect resistance has resulted in any changes that might cause ecological harm in terms of altered weed characteristics, susceptibility to pests, or adverse environmental impact. Additionally, environmental interaction data are collected in field experiments for Bt crop to evaluate potential adverse effects. Further to the agronomic and phenotypic evaluation, potential movement of transgenes from a genetically modified crop plants into wild relatives is assessed for a new pest resistance gene in a new crop. This review summarizes the evidence for safety of crops containing Cry proteins for humans, livestock, and other non-target organisms.

Specificity determinants for Cry insecticidal proteins: Insights from their mode of action

“…Apart from their efficacy in controlling targeted pest species, Bt crops are also recognized for their environmental safety as a result of their high specificity (Koch et al, 2015). As with other proteins, specificity of Cry toxins is determined by the different steps involved in their mode of action, which are in part reflected in the three dimensional (3D) structure of the protein.…”

Interaction between toxin crystals and vegetative insecticidal proteins of Bacillus thuringiensis in lepidopteran larvae

“…Probably there was a significant damage (Sena et al 2009;Qian et al 2015). Development of insect-resistant transgenic plants expressing the B. thuringiensis toxin-encoding genes provided effective control against important pests and cost reduction associated with spraying (Koch et al 2015). However, constant pressure of one-toxin plants on insects causes resistance occurrence.…”

“…The use of B. thuringiensis (Bt) crops provides benefits in insect control, reduction of technical difficulties and costs associated with spraying the plants and reducing the amount of mycotoxins (e.g. fumonisin) in maize grain (Koch et al 2015). However, continuous exposure of insects to toxins produced by genetically engineered plants contribute in decreasing susceptibility of pests population.…”

Genetically engineered (modified) crops (Bacillus thuringiensis crops) and the world controversy on their safety

“…In 2013, four insect-resistant Bt brinjal (eggplant) varieties were approved for seed production and initial commercialization in Bangladesh (Koch et al 2015). Recently, Bt soybean varieties expressing Cry1Ac+ Cry1Ab were approved for commercial use in Latin America to control lepidopteran insects (Koch et al 2015). Bt crops, containing Bt toxins, were planted in almost 100 million ha (Brookes and Barfoot 2017).…”

“…Currently, the most common Bt crops are corn and cotton (Vaek et al 1987). In 2013, four insect-resistant Bt brinjal (eggplant) varieties were approved for seed production and initial commercialization in Bangladesh (Koch et al 2015). Recently, Bt soybean varieties expressing Cry1Ac+ Cry1Ab were approved for commercial use in Latin America to control lepidopteran insects (Koch et al 2015).…”