Archive for the ‘herbicide resistance’ Category

University of Adelaide

Failed antibiotic now a game changing weed killer for farmers

23-May-2023 10:05 PM EDT, by University of Adelaide


Newswise: Failed antibiotic now a game changing weed killer for farmers

(From left) Emily Mackie, Dr Andrew Barrow and Dr Tatiana Soares da Costa.

Newswise — Weed killers of the future could soon be based on failed antibiotics.

A molecule which was initially developed to treat tuberculosis but failed to progress out of the lab as an antibiotic is now showing promise as a powerful foe for weeds that invade our gardens and cost farmers billions of dollars each year.

While the failed antibiotic wasn’t fit for its original purpose, scientists at the University of Adelaide discovered that by tweaking its structure, the molecule became effective at killing two of the most problematic weeds in Australia, annual ryegrass and wild radish, without harming bacterial and human cells.

“This discovery is a potential game changer for the agricultural industry. Many weeds are now resistant to the existing herbicides on the market, costing farmers billions of dollars each year,” said lead researcher Dr Tatiana Soares da Costa from the University of Adelaide’s Waite Research Institute.

“Using failed antibiotics as herbicides provides a short-cut for faster development of new, more effective weed killers that target damaging and invasive weeds that farmers find hard to control.”

Researchers at the University’s Herbicide and Antibiotic Innovation Lab discovered there were similarities between bacterial superbugs and weeds at a molecular level.

They exploited these similarities and, by chemically modifying the structure of a failed antibiotic, they were able to block the production of amino acid lysine, which is essential for weed growth.

“There are no commercially available herbicides on the market that work in this way. In fact, in the past 40 years, there have been hardly any new herbicides with new mechanisms of action that have entered the market,” said Dr Andrew Barrow, a postdoctoral researcher in Dr Soares da Costa’s team at the University of Adelaide’s Waite Research Institute.

It’s estimated that weeds cost the Australian agriculture industry more than $5 billion each year.

Annual ryegrass in particular is one of the most serious and costly weeds in southern Australia.

“The short-cut strategy saves valuable time and resources, and therefore could expedite the commercialisation of much needed new herbicides,” said Dr Soares da Costa.

“It’s also important to note that using failed antibiotics won’t drive antibiotic resistance because the herbicidal molecules we discovered don’t kill bacteria. They specifically target weeds, with no effects on human cells,” she said.

It’s not just farmers who could reap the benefits of this discovery. Researchers say it could also lead to the development of new weed killers to target pesky weeds growing in our backyards and driveways.

“Our re-purposing approach has the potential to discover herbicides with broad applications that can kill a variety of weeds,” said Dr Barrow.

This research has been published in the journal of Communications Biology.

Dr Tatiana Soares da Costa and her team are now looking at discovering more herbicidal molecules by re-purposing other failed antibiotics and partnering up with industry to introduce new and safe herbicides to the market.

Funding for this research was provided by the Australian Research Council through a DECRA Fellowship and a Discovery Project awarded to Dr Tatiana Soares da Costa.

The first author on the paper is Emily Mackie, a PhD student in Dr Soares da Costa’s team, who is supported by scholarships from the Grains and Research Development Corporation and Research Training Program. Co-authors include Dr Andrew Barrow, Dr Marie-Claire Giel, Dr Anthony Gendall and Dr Santosh Panjikar.

The Waite Research Institute stimulates and supports research and innovation across the University of Adelaide and its partners that builds capacity for Australia’s agriculture, food, and wine sectors.


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Herbicide-tolerant rice developed at NRRI

Friday, 03 February 2023 | PNS | CUTTACK

  • Weed infestation causes 18–48% yield loss in rice. The weeds are managed by keeping stagnant water in the field or through manual or mechanical weeding. Thus, availability of any cost-effective weed control method will make rice cultivation economically viable and sustainable.

Besides, broad leaf and grassy weeds, weedy rice is an emerging problem under direct seeded conditions. Its competitive ability is very high and traditional herbicides can’t control such weeds. Herbicides which kill the weedy rice also kill the rice crop. Thus, there is a need for developing rice varieties which can control weedy rice as well as other weeds.

In India, scientists could successfully develop a mutant line ‘Robin’ in upland variety N22 which tolerates the herbicide Imazethapyr due to a mutation in Acetohydroxy Acid Synthase (AHAS) gene.

At the ICAR-National Rice Research Institute here, this herbicide-tolerant gene has been introgressed in four popular rice varieties, (Sahbhagidhan, Naveen, SwarnaSub1 and Pooja) and are currently under national testing.

Imazethapyr herbicide, when sprayed 21 days after sowing, effectively controls the weeds of rice as well as weedy rice without affecting the yield potential of the tolerant variety. Release and large-scale adoption of the herbicide tolerant rice can significantly reduce the cost of cultivation and enhance the acreage under direct seeded rice in India.

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India approves first genetically-modified crops in 20 years: Herbicide-tolerant cotton and mustard

Harvir Singh | Rural Voice | October 24, 2022

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The commercial cultivation of genetically modified (GM) crops may get approval in the country after 20 years. These crops are herbicide-tolerant (HT) Bt cotton, called HTBt cotton, and GM mustard. According to highly placed sources, the road to approval of commercial cultivation of these two crops has almost been cleared.

The mere formality of approval from the Genetic Engineering Appraisal Committee (GEAC) remains. As per the information obtained by Rural Voice, the sub-committee appointed by GEAC has submitted its report to the latter. Positive recommendations have been made in this report for the commercial cultivation of HTBt cotton and GM mustard.

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One of the members of the committee says that the cultivation of HTBt cotton has already been going on illegally in the country in about 30 per cent of the area. Seeds are being supplied for the same illegally. Given this, it would be better if it is given approval so that farmers may get seeds of the right quality and seed sellers may be held accountable in case of any defect.

The other crop likely to get GEAC approval is GM mustard. Mustard plays a key role in the supply of edible oils in the country. But we have constantly failed on the front of increasing mustard productivity. Scientists argue for this that the solution lies in giving approval to the cultivation of GM mustard.

This is an excerpt. Read the original post here

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Weedy rice has become herbicide resistant through rapid evolution

Aggressive, herbicide-resistant weed is a threat in nation’s largest rice production region

Date:September 8, 2022Source: Washington University in St. Louis

Summary: Weedy rice is a closely related cousin of crop rice. It aggressively competes with cultivated rice in the field, leading to loss of yield and reductions in harvest quality that compromise market value. Biologists used whole-genome sequences of 48 contemporary weedy rice plants to show how herbicide resistance evolved by gene flow from crop rice. Almost all other cases of herbicide resistance in agricultural weeds result from selection of tolerant genotypes in the weed species.Share:


In a paper published Sept. 8 in the journal Communications Biology, scientists from Washington University in St. Louis and the University of Arkansas report that a crop pest called weedy rice has become widely herbicide resistant in regions where herbicide-resistant rice is planted. The study highlights challenges facing U.S. rice farmers when they battle a weedy enemy that is closely related to a desirable crop plant.

The genetic investigation was conducted with samples gathered in rice fields in Arkansas, where almost 50% of the nation’s rice is grown.

Weedy rice is a closely related cousin of crop rice. It aggressively competes with cultivated rice in the field, leading to loss of yield and reductions in harvest quality that compromise market value. Weedy rice infestations cause an estimated $45 million in economic losses in the United States each year and hundreds of millions of dollars worldwide.

Biologists used whole-genome sequences of 48 contemporary weedy rice plants to show how herbicide resistance evolved by gene flow from crop rice. Almost all other cases of herbicide resistance in agricultural weeds result from selection of tolerant genotypes in the weed species. Just 20 years after herbicide-resistant rice was first adopted in the southern United States, the majority of fields with a history of herbicide-resistant rice cultivation have weedy rice plants that are also herbicide resistant.

“Throughout its nearly 200-year history in the United States, weedy rice had a very low rate of outcrossing with cultivated rice,” said Marshall Wedger, a postdoctoral research associate in biology in Arts & Sciences at Washington University and first author of the study. “We found that U.S. weedy rice has persisted through herbicide pressure with the survival of those few plants that outcross, consequently acquiring the herbicide- resistance trait.”

“Technological changes in U.S. rice farming since the 2000s have led to a complete genetic revolution in the makeup of the weedy rice that infests U.S. fields,” said Kenneth Olsen, professor of biology at Washington University and senior author on the study.

“In the last 20 years, weedy rice has gone from being very genetically distinct from U.S. crop varieties to nowadays mostly being derived from crop-weed hybridization,” Olsen said. “The weeds are grabbing certain traits from the crop that are beneficial to them, including herbicide resistance.”

Weeds seize their moment

Weedy rice is a scourge of cultivated rice production around the world. But up until the early 2000s, weedy rice in U.S. fields rarely interbred with the kinds of rice that were commonly grown in this country.

Crop rice and weedy rice are the same species, so they are able to interbreed, or hybridize. Their rate of hybridization rate is usually low — generally less than 1% — because rice is self-pollinated.

But something happened that changed the centuries-old dynamic between these two closely related plants. Starting in the early 2000s, two new kinds of crop rice were adopted in U.S. fields. One was a new hybrid rice that offered substantially enhanced yield, compared with traditional inbred (self-pollinating) rice cultivars. The other was a new kind that had been tweaked to be tolerant to a certain kind of herbicide. These so-called Clearfield™ cultivars allowed farmers to plant rice and then apply chemicals to their fields to kill weedy rice and other agricultural weeds without harming the crop.

As early as 2004, just two years after the new rice was adopted locally, Arkansas farmers already were reporting some cases of herbicide resistance in weedy rice. Such resistant plants were likely outcrosses with herbicide-resistant rice.

“The situation is somewhat analogous to human health and the emergence of antibiotic-resistant bacterial pathogens. Widespread use of antibiotics ends up strongly selecting for the rapid evolution of the drug-resistant strains,” Olsen said. “With weedy rice, herbicide-resistant weeds were being detected just a couple of years after herbicide-resistant rice was first commercialized.”

How did it happen? For gene flow from a crop into a weedy relative to occur, the two have to be growing in close enough physical proximity for pollen transfer.

“The herbicide-resistant weedy rice plants are the products of outcrossing with herbicide-tolerant crop,” said Nilda Roma Burgos, professor of weed physiology at University of Arkansas and a co-author of the study. “Outcrossing occurs when weedy rice is not controlled 100% by the herbicide and the remaining weedy rice plants flower at the same time as the herbicide-tolerant rice crop.”

Rice and weedy rice certainly grow in the same fields. However, it was the hybrid rice’s pesky habit of producing volunteers — that is, successfully developing and dropping seeds that overwinter and then emerge as new plants in subsequent years — that opened a door for weedy rice.

The crop volunteers grew up exhibiting variable traits, including changes to flowering timing that made it much more likely that they would swap pollen with weedy rice.

“As a de-domesticated weedy relative, weedy rice has always been able to outcross with cultivated rice. Based on our results, this ability to interbreed is what led to most of the herbicide resistance that we see today,” Wedger said.

A uniquely challenging year for growers

The findings from this new study are being reported during a uniquely challenging year for Arkansas rice farmers. Problems with the global supply chain, as well as increases in the costs of key crop inputs such as fertilizer, have made growing rice more difficult and expensive.

At the same time, global climate change is having local effects on the timing of when rice can be planted. This year, farmers had to cram in planting that usually takes place over a period of four weeks into a much-shortened window. Also this year, nighttime temperatures in northeastern Arkansas were stubbornly high during the months of July and August, with possible negative effects on rice yields. Only time will tell what the 2022 harvest, beginning this month, will bring.

One thing is certain, though: The rapid adaptation of weedy rice to herbicide application serves as yet another example of the dangers of relying on single methods of control for agricultural pests, study authors said.

“How quickly a resistant weedy rice population builds up to a point where the herbicide is no longer useful depends on how the producer manages the herbicide-tolerant rice technology,” Roma Burgos said. “There are best management practices guidelines that help growers avoid resistance evolution for a long time, if implemented.”

“Just like in the case of antibiotic resistance, the rise of resistance to this particular herbicide will be met with a new technology that relies on a new herbicide,” Wedger said. “New herbicide-resistant cultivars are already in development, so I expect this process to repeat.”

Story Source:

Materials provided by Washington University in St. Louis. Original written by Talia Ogliore. Note: Content may be edited for style and length.

Journal Reference:

  1. Marshall J. Wedger, Nilda Roma-Burgos, Kenneth M. Olsen. Genomic revolution of US weedy rice in response to 21st century agricultural technologiesCommunications Biology, 2022; 5 (1) DOI: 10.1038/s42003-022-03803-0

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