Non-Bt protein offers option for fighting corn pest

By Stephen Davies

© Copyright Agri-Pulse Communications, Inc.



WASHINGTON, Sept. 22, 2016 - A newly discovered non-Bt protein could be a solution for farmers struggling with corn rootworm resistance to existing Bt corn varieties, DuPont Pioneer scientists report.

In a paper published Thursday in the journal Science, DuPont Pioneer researchers detailed their findings, which Neal Gutterson, the company's vice president for research & development, called a “breakthrough for addressing a major challenge in agriculture.”

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“We have discovered a non-Bt protein that demonstrates insecticidal control of western corn rootworm with a new and different mode of action than Bt proteins currently used in transgenic products,” Gutterson said. “This protein could be a critical component for managing corn rootworm in future corn seed product offerings. The work also suggests that bacteria other than Bt are alternative sources of insecticidal proteins for insect control trait development.”

Relief for farmers cannot come soon enough, but DuPont Pioneer cautioned that the traits are in Phase 2, or early development, of research and development. Under today's global regulatory environment, the estimated length of time to introduce products with biotech traits from this stage is eight to 11 years, the company said. 

Corn growers have struggled for decades with damage from western corn rootworm, one of the most destructive pests of the corn crop in North America. The cost to growers of crop losses and inputs to control rootworm is estimated to meet or exceed $1 billion annually.

But in recent years, the adaptable pest has become resistant to transgenic varieties of Bt corn, prompting efforts to manage the problem through the planting of refuges without the Bt toxin, use of crop rotation, and planting of “pyramided” varieties that contain more than one protein to combat the voracious rootworm larvae.

But the rootworm is not so easily vanquished. Recent research has uncovered evidence of cross-resistance. “Laboratory selection experiments indicate that western corn rootworm has the ability to develop resistance to all currently commercialized Bt toxins following three to seven generations of selection,” according to a paper published earlier this year.

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The latest paper discusses results of field experiments using the insecticidal protein IPD072Aa, which was isolated from Pseudomonas chloroaphis. IPD072a has the ability “to kill WCR larvae resistant to mCry3A or Cry34Ab1/Cry35Ab1,” the paper says.

“Thus, IPD072Aa is effective in killing WCR insects that are resistant to either of the two types of Bt proteins used in current commercial transgenic corn lines,” the paper says.

“Non-Bt proteins and RNA-based products highlight our efforts to identify alternative methods for effective control of insect feeding damage in agriculture,” Gutterson said. “Pioneer is committed to delivering superior germplasm, native and biotech traits, seed treatments and agronomic advice for the most productive products to its customers. 

Nathan Fields, director of biotechnology and crop inputs for the National Corn Growers Association, said farmers would welcome a new mode of action for fighting rootworm. “If it clears all the safety protocols, we'll be looking forward to it getting to market sooner rather than later,” he said. 


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