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  3. One of industrial agriculture’s biggest GMO crops may have just backfired (产生事与愿违的后果). Scientists have confirmed that corn-destr

One of industrial agriculture’s biggest GMO crops may have just backfired (产生事与愿违的后果). Scientists have confirmed that corn-destr

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问题     One of industrial agriculture’s biggest GMO crops may have just backfired (产生事与愿违的后果). Scientists have confirmed that corn-destroying rootworms have evolved to be resistant to the Bt corn engineered to kill them.
    Bt stands for Bacillus thuringiensis (苏云金芽孢杆菌), the name of the genetically modified corn’s "donor" organism. Bacillus thuringiensis is a naturally occurring soil bacterium that produces protein crystals that bind to certain receptors in the rootworm’s intestine (肠), killing it. For years, farmers have planted Bt corn as an alternative to spraying insecticides. Bt corn accounted for three-quarters of all corn planting in 2013. That may have to change.
    After finding a cornfield in Iowa in 2011 that was decimated (大幅度下降) by rootworm despite being planted with the Bt corn, Iowa State University entomologist Aaron Gassmann and his team began to study the pests’ interactions with the genetically modified organism (or GMO) corn in a lab. Their study, published Monday in the Proceedings of the National Academy of Sciences, describes the western corn rootworm’s rapid evolution after feeding on the engineered crop.
    But Bt corn is still capable of warding off other pests, so farmers will likely keep planting it. Except now they’ll need to use pesticides to protect their crop from rootworms. As entomologists warned the Environmental Protection Agency in 2012, rootworm resistance means that the environmental advantage of Bt corn — that it could be raised pesticide-free — may disappear.
    "Unless management practices change, it’s only going to get worse," Gassmann told Wired. "There needs to be a fundamental change in how the technology is used."
    Scientists have predicted for years that this could happen, but warnings were repeatedly ignored by regulators and farmers. It takes millions of dollars to develop seeds like Bt, so engineering an alternative is not an attractive option. Instead, the authors of another study on rootworm Bt resistance, which focuses on Nebraska, take a biodiversity approach.
    "Crop rotation is the best tool," University of Nebraska-Lincoln entomologist Lance Meinke told Farm & Ranch Guide. "Generally, one year of soybeans in a field with resistant western corn rootworms wipes out that population. The beetles will lay eggs that hatch, but when larvae (幼虫) try to feed on soybean plants, they don’t find the nutrients they need and they die."
    Crop rotation can suppress rootworm populations over time, reducing the threat posed by their new Bt resistance.
    But as entomologist Elson Shields of Cornell University told Wired, rootworm is just one symptom of a system wide problem that will likely come back to bite the GMO seed industry’s focus on short-term profit. The next engineered seed trait "will fall under the same pressure," said Shields, "and the insect will win."
What can we know about Bacillus thuringiensis?
选项 A、It is a genetically modified organism.
B、It is an alternative to spraying insecticides.
C、It is a natural bacterium that kills rootworm.
D、It protects rootworm from being killed by bacterium.
答案C
解析 第2段第2句提到，苏云金芽孢杆菌是一种自然生长的土壤细菌，这种细菌会产生蛋白质晶体，从而依附在根虫肠道的某个受体上，进而杀灭根虫。由此可见，苏云金芽孢杆菌是一种能够杀灭根虫的自然细菌，故C)符合题意。第二段首句可知，Bt玉米是转基因的，而苏云金芽孢杆菌是自然生长的，故排除A)。由第三句farmers have planted Bt corn as alternative to spraying insecticides可排除B)。苏云金芽孢杆菌能够杀灭根虫，而不是保护根虫，故D曲原文不符，予以排除。
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