Global perspectives on field-evolved resistance to transgenic Bt crops: a special collection

Abstract

Crops genetically engineered to produce insect-killing proteins from Bacillus thuringiensis (Bt) have revolutionized management of some major pests, but their efficacy is reduced when pests evolve resistance. Practical resistance, which is field-evolved resistance that reduces the efficacy of Bt crops and has practical implications for pest management, has been reported in 26 cases in seven countries involving 11 pest species. This special collection includes six original papers that present a global perspective on field-evolved resistance to Bt crops. One is a synthetic review providing a comprehensive global summary of the status of the resistance or susceptibility to Bt crops of 24 pest species in 12 countries. Another evaluates the inheritance and fitness costs of resistance of Diabrotica virgifera virgifera to Gpp34/Tpp35Ab (formerly called Cry34/35Ab). Two papers describe and demonstrate advances in techniques for monitoring field-evolved resistance. One uses a modified F2 screen for resistance to Cry1Ac and Cry2Ab in Helicoverpa zea in the United States. The other uses genomics to analyze nonrecessive resistance to Cry1Ac in Helicoverpa armigera in China. Two papers provide multi-year monitoring data for resistance to Bt corn in Spain and Canada, respectively. The monitoring data from Spain evaluate responses to Cry1Ab of the corn borers Sesamia nonagrioides and Ostrinia nubilalis, whereas the data from Canada track responses of O. nubilalis to Cry1Ab, Cry1Fa, Cry1A.105, and Cry2Ab. We hope the new methods, results, and conclusions reported here will spur additional research and help to enhance the sustainability of current and future transgenic insecticidal crops.

Critical Facets of European Corn Borer Adult Movement Ecology Relevant to Mitigating Field Resistance to Bt-Corn

“…IRM based on the HDR strategy for European corn borer in Bt-corn has been quite successful, with no reports of practical field resistance during the first two decades after its commercialization [ 57 , 66 , 71 , 76 ]. Bt-crops targeting other pests have not always fared so well, with steadily growing reports of confirmed practical field resistance [ 67 , 71 ].…”

“…“Early warning of resistance” is a classification that denotes a significant decrease in susceptibility to a Bt toxin but not at a level affecting crop efficacy against the insect in the field. “Practical resistance” is attained when >50% of the individuals in a population are resistant and efficacy of the crop has been reduced; both types of resistance are genetically-based and field-evolved in response to selection [ 67 , 71 , 75 , 76 , 77 ].…”

Genetically Modified Plants Based on Bacillus Genes and Commercial Bacillus-Based Biopesticides for Sustainable Agriculture

“…In this sense, the main concern about the potential risks of recombinant Bt strains and GM-Bt crops is the impact on non-target beneficial species [70], the effects of introducing genes to the relevant microorganisms and unpredicted effects among others, especially food safety (Figure 4). To avoid the problem of their impact on non-target beneficial species, the main aim is to increase host specificity and persistence to achieve better efficacy and lower insect resistance [74][75][76][77]. Laboratory and field studies have been conducted on the effects of GM crops on the environment and human health, resulting in little risk for human health [76][77][78].…”

“…To avoid the problem of their impact on non-target beneficial species, the main aim is to increase host specificity and persistence to achieve better efficacy and lower insect resistance [74][75][76][77]. Laboratory and field studies have been conducted on the effects of GM crops on the environment and human health, resulting in little risk for human health [76][77][78]. Risks are assessed by performing laboratory tests, followed by small-and large-scale field trials to ascertain environmental safety before the release a commercial transgenic crop.…”

“…There have been several studies regarding human health and how Bt food can influence health in humans, demonstrating that Bt toxins are easily degraded in the presence of digestive fluids of the human gut within 0-7 min. Therefore, the risk of Bt foods for human health is small [42,[71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90]. A recent review gives evidence that Bt maize is highly selective against pests with relatively few negative consequences, especially when compared with chemical insecticides [78,80].…”