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）细菌产生多种对毛虫、甲虫和其他害虫有活性的杀虫蛋白。与化学杀虫剂相反，Bt生物杀虫剂对靶标昆虫具有特异性，对人类和其他脊椎动物无害，并且对环境和生物多样性友好。Bt毒素是肠道毒素。在地上植物上生活和取食的昆虫害虫可以通过将现有的Bt商业制剂喷洒在可触及的植物部位来消灭。然而，攻击植物根部或钻入、取食和在植物其他部分内挖隧道的害虫无法通过喷雾到达。通过转基因植物提供了对该问题的有效解决方案，在转基因植物中插入Bt基因，使得毒素在植物中表达（Bt作物），使它们对昆虫害虫具有抗性。转基因作物已在29个国家广泛采用，其中加拿大排名第五，2011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，昆虫害虫可能会对这种策略产生抗药性。因此，必须设计和实施谨慎的昆虫抗性管理计划。对植物、害虫及其环境的生物学以及Bt毒力机制的深入科学了解，对于成功预防或延迟害虫对Bt产生抗药性至关重要。

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.