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01-08-2024

Corn found to have genetic vulnerability to common tolpyralate herbicide

Recent scientific investigations have unveiled a critical discovery in the world of agriculture — a newfound genetic vulnerability in corn to the tolpyralate herbicide.

This revelation is very significant in the agricultural realm as it sheds light on a potential risk to a staple crop of the global food system.

Collaborative research efforts

The collaborative effort, led by Marty Williams, an ecologist at the ARS Global Change and Photosynthesis Research Unit, along with partners from the University of Wisconsin-Madison and Illinois Foundation Seed Inc., has identified this sensitivity in 49 varieties of corn.

This includes six types of field corn and 43 types of sweet corn. Such a finding is pivotal as it equips farmers with crucial information to avert possible crop losses.

They can now make informed decisions, such as selecting tolpyralate-tolerant varieties or opting for alternative herbicides.

Understanding tolpyralate herbicide

Tolpyralate, an herbicide registered in 2017, is known for its use in fallow fields and various types of corn, including field, pop, and sweet corn. It falls under the category of HPPD (4-Hydroxyphenylpyruvate dioxygenase) inhibitors.

When used post-emergence, tolpyralate sets off a biochemical reaction in weeds leading to their demise, beginning with leaf bleaching and culminating in plant death.

Normally, corn plants are able to metabolize HPPD inhibitor herbicides quickly, thus averting damage. This ability is contingent on the presence or absence of specific alleles (alternate gene copies) in a region of their genome known as NSF1.

However, Williams’ research indicates that this is not the case with tolpyralate.

What the research team learned

The team’s investigation began in late summer 2021 following reports of severe damage to a sweet corn inbred line, XSEN187, after tolpyralate application.

Surprisingly, the damage was traced to a unique cluster of genes on chromosome 5, different from the expected alleles.

This was confirmed through genetic mapping techniques and observations in offspring plants derived from crosses between the sweet corn inbred and two tolerant corn lines.

Another intriguing aspect is the relationship between tolpyralate sensitivity and oil-based adjuvants – additives mixed with herbicides for better absorption in weeds.

While these adjuvants are essential for effective weed control, they also play a role in the herbicide’s impact on sensitive corn varieties.

Key implications and further tolpyralate research

The case of the inbred line IL677a, known for introducing the popular sugary enhancer gene in sweet corn, further complicates matters.

This line exhibited severe sensitivity to tolpyralate, suggesting that the same vulnerability might have been widely introduced into sweet corn varieties.

Understanding the exact physiological mechanism behind this sensitivity remains a challenge. Williams emphasizes the need for deeper insight into this mechanism to aid manufacturers and seed companies in mitigating crop injury risks.

This research could also extend beyond tolpyralate, considering several new HPPD-inhibiting herbicides are in development.

In summary, this disturbing study highlights the genetic vulnerability of certain corn varieties to tolpyralate herbicide, while also opening doors for further research and precautionary measures in crop management.

For farmers, this means adapting their practices to ensure crop safety and productivity in the face of emerging agricultural challenges.

The full study was published in the journal Pest Management Science.

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