研究人员：较大的避难所需要延迟耐生物技术玉米的害虫

To slow resistance of western corn rootworm beetles to genetically protected crops, much larger “refuge” acreages of conventional crops have to be planted, two experts warn in a paper published in the Journal of Economic Ecology.

自1996年以来，从细菌苏云金菌（BT）产生杀死昆虫的蛋白质的转基因作物降低了对杀虫剂喷雾剂的依赖。这些蛋白质对某些毁灭性的作物有害生物具有致命性，但不会伤害包括大多数其他生物，包括人类在内的大多数其他生物。

In Nebraska, more than 90 percent of the corn and soybeans planted on nearly 15 million acres are biotech crops.

Yet, according to researchers, just as insects become resistant to conventional insecticides, they also can evolve resistance to the Bt proteins in transgenic crops.

为了延迟对BT蛋白的耐药性，美国环境保护署（EPA）要求农民种植不在BT农作物附近产生BT蛋白质的农作物的“避难所”。避难所种植了标准的非BT农作物，无需摄入BT毒素就可以食用。

Planting refuges promotes survival of susceptible pests. If susceptible pests greatly outnumber resistant pests, resistant individuals are unlikely to mate with each other and produce resistant offspring.

But how much refuge acreage is enough?

在2012年6月的《经济昆虫学杂志》上发表的一篇文章中，来自亚利桑那大学的作者布鲁斯·塔巴什尼克（Bruce Tabashnik）和北卡罗来纳州立大学的弗雷德·古尔德（Fred Gould抗昆虫，鼓励综合害虫管理或IPM，并促进更可持续的作物保护。

在西部玉米根虫（Diabrotica virgifera virgifera）中缓慢耐药性，这是美国最重要的农作物害虫之一的甲虫，EPA目前需要将总面积的20％放在一边，作为玉米产生一种BT的储备蛋白质（cry3bb1），玉米的避难所为5％，同时产生两种不同的BT蛋白。

但是，作者指出，这种适应性的害虫在美国玉米带的某些地区迅速发展了对Cry3BB1的抗性。为了使BT玉米对根虫保持有效，他们建议将避孕药的需求增加到50％，以产生一种BT蛋白，而产生两种BT蛋白的玉米为20％。

“玉米根虫每年可能使美国农民接近10亿美元。BT玉米有助于降低这些成本并减少杀虫剂喷雾，但是害虫抵抗的演变可以减少甚至消除这些收益。

“To delay pest resistance and sustain the benefits of Bt corn, we recommend planting more corn that does not produce Bt toxins active against rootworms. This refuge strategy allows the susceptible pests to survive and has worked to slow resistance of other pests to Bt crops.”

“Most of the corn seed currently produced in the U.S. is transgenic and includes genes for insect control,” said Gould. “Enlarging refuges will require more seed without corn rootworm control genes. This shift in production will take time, so this process should begin immediately.”

除了增加避难大小外，作者还写道，推迟抵抗力的最佳方法是使用IPM，其中BT玉米与其他控制策略（例如作物旋转和明智地使用杀虫剂喷雾剂）结合使用。

Tabashnik说：“我们主张更多地使用综合的害虫管理，这是一种基于最佳策略组合的常识方法。”“目标是限制害虫损害，最大化农民利润并保持环境质量。保持BT毒素的有效性可以帮助我们实现这些目标。

“We’re seeing the early signs of rootworm resistance to Bt corn, which fit predictions from evolutionary theory and experiments in the lab and greenhouse,” he added.

该论文表明，在2009年在爱荷华州首次发现了对BT玉米的根虫具有抗性，这是在美国开始销售杀死虫子的BT玉米六年后，此类BT玉米首次种植在超过2500万英亩之后仅一年。

根据Tabashnik Cry3Bb1 enoug是有效h to be economically useful, but not effective enough to meet the so-called high dose standard, the ability to kill at least 99.99 percent of susceptible pests and also nearly all of the hybrid pests that are produced when resistant pests mate with susceptible pests.

“When Bt crops meet the high dose standard, resistant individuals are extremely rare, and smaller refuges work fine, because you might have one resistant insect in a million,” he said. “In this case, a 20 percent refuge provides enough susceptible individuals to dilute that rare resistance.”

但是具有Cry3BB1的植物允许生存1-6％的害虫，预计将迅速选择耐药性。

“A single farm can have millions of these beetles,” Tabashnik explained. “If 1 to 6 percent survive on Bt corn, you have tens of thousands of potentially resistant insects and the refuge needs to be much bigger.”

His research has shown that in Arizona, Bt cotton meets the high dose standard against pink bollworm and the small refuge strategy has prevented resistance for more than a decade.

另一方面，塔巴什尼克（Tabashnik）指出了波多黎各的一个案子，那里没有种植足够的避难所。几年之内，害虫进化出了抗性并吞噬了BT玉米植物。生物技术公司自愿停止在那里出售BT玉米种子，但是五年后，昆虫仍然对毒素具有抵抗力。

Tabashnik说，尽管生物技术公司最近开始出售一些产生BT毒素组合的BT玉米，但对一种毒素的抵抗仍然引起了人们的关注。

“您可以将多BT毒素方法视为金字塔：基础必须稳定。如果您的构建块之一（对Cry3BB1的易感性）正在崩溃，那么您会有问题。”他说。“对任何一种毒素的抗药性都危及整个系统的有效性。

“We’re at a tipping point where decisive action can provide long-term benefits and avoid loss of an environmentally friendly tool for pest control.”

信息不可用。