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）细菌产生多种杀虫蛋白，对毛虫、甲虫和其他害虫有活性。与化学杀虫剂不同，Bt生物杀虫剂对昆虫具有特异性，对人类和其他脊椎动物无害，并且对环境和生物多样性无害。Bt毒素是肠道毒素。以地上植物为食的害虫可以通过将Bt商业制剂喷洒在可接近的植物部位来消灭。然而，那些侵袭植物根部或钻入、觅食和在植物其他部位钻洞的害虫是无法通过喷洒来消灭的。解决这一问题的一个有效方法是转基因植物，在转基因植物中插入Bt基因，使毒素在植物（Bt作物）中表达，使它们对害虫具有抵抗力。bt作物已在29个国家广泛采用，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做法，害虫可能会对这一策略产生抗药性。因此，必须精心设计和实施抗虫管理方案。深入了解植物、害虫及其环境生物学以及Bt毒性机制是成功预防或延缓害虫对Bt产生抗性的关键。

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.