Delaying resistance of corn insect pests to Bacillus thuringiensis biocontrol: mode of action of new Bt products

苏云金芽孢杆菌(Bt)细菌产生大量的杀虫蛋白，对毛虫、甲虫和其他害虫具有活性。与化学杀虫剂相反，Bt生物杀虫剂针对目标昆虫，对人类和其他脊椎动物无害，对环境和生物多样性友好。Bt毒素是一种肠道毒素。通过在可接触到的植物部位喷洒可用的Bt商业制剂，可以消灭以地上植物为食的害虫。然而，攻击植物根部或钻入、取食和进入植物其他部分的害虫不能通过喷洒达到。转基因植物是解决这一问题的有效方法，在转基因植物中插入Bt基因，使毒素在植物(Bt作物)中表达，使它们对虫害具有抗性。转基因作物已在29个国家得到广泛采用，其中包括排名第五的加拿大，2011年种植了超过1000万公顷的转基因油菜、玉米、大豆和甜菜作物。然而，随着时间的推移和特定的农业实践，害虫可能会对这一策略产生抵抗力。因此，必须设计和实施仔细的抗虫性管理计划。深入了解植物、害虫及其环境的生物学和Bt毒力机制的科学知识，对于成功预防或延缓害虫对Bt的抗药性至关重要。 这项合作研究和开发赠款提案解决了Bt控制玉米根虫的问题，以及开发玉米根虫对Bt的抗性。该害虫对玉米作物造成重大经济损失(北美每年损失100多万美元)。该项目的目的是与Dow AgroSciences Canada Inc.合作，阐明该公司的一组Bt毒素摧毁这种害虫的机制。预计这一研究伙伴关系将有助于向加拿大提供新的以Bt为基础的抗虫植物。它们将更有针对性，更不容易引起目标昆虫对Bt的抗性，Bt是综合害虫管理工具箱中最成功的生物防治工具。

Bacillus thuringiensis (Bt) bacteria produce a large variety of insecticidal proteins that are active against caterpillars, beetles and other pest insects. Contrary to chemical insecticides, Bt bio-insecticides are specific to target insects, are harmless to humans and other vertebrates, and are environment- and biodiversity friendly. Bt toxins are intestinal poisons. Insect pests that live and feed on above-the-ground plants can be destroyed by available Bt commercial preparations sprayed on accessible plant parts. However, pests that attack the plant roots or bore into, feed, and tunnel within other parts of plants cannot be reached by spraying. An efficient solution to this problem is provided by transgenic plants in which Bt genes are inserted so that the toxins are expressed in the plants (Bt-crops), rendering them resistant to insect pests. Bt-crops have been widely adopted in 29 nations, including Canada, which ranks 5th, with over 10 million hectares of transgenic canola, corn, soybean and sugar beet crops planted in 2011. However, insect pests may become resistant to this strategy with time and particular agricultural practices. Therefore, careful insect resistance management programs have to be designed and implemented. In-depth scientific knowledge on the biology of plants, pests and their environment, and on the mechanisms of Bt toxicity is critical to the success of preventing or delaying the onset of resistance of pests to Bt. This collaborative research and development grant proposal addresses the problems of corn rootworm control by Bt and development of corn rootworm resistance to Bt. This pest causes major economic damages to corn crop (over one million dollars losses annually in North America). The aim of the project is to elucidate, in partnership with Dow AgroSciences Canada Inc., the mechanisms by which a group of the company's Bt toxins destroy this pest. It is expected that this research partnership will help providing Canada with new Bt-based insect-resistant plants. These will be better targeted and less susceptible to elicit resistance of the target insects to Bt, the most successful biological control tool in the integrated pest management tool box.