Weed management is an uphill battle for farmers across the globe—an issue made more difficult in recent years as stubborn “superweeds” become evermore resistant to popular herbicides on the market. This a problem that scientists and agricultural agencies have not been quite as quick to address. However, a recent breakthrough by a team of researchers from the University of Adelaide and La Trobe University in Australia shows promising results that may stop these superweeds “dead in their tracks.”
“We have identified herbicidal compounds that work by blocking the production of the amino acid lysine, which is essential for weed growth,” says lead researcher, Dr Tatiana Soares da Costa, a Future Making Fellow at the University of Adelaide’s Waite Research Institute.“This has the potential to be a game-changer for the agriculture sector, given the lack of new herbicides that have entered the market in the past 30 years.”
Herb-resistant “superweeds” have become a major hurdle for farmers in Australia, where herbicide-resistant weeds like annual ryegrass have reportedly crept into 40 percent of cropping land and cost farmers there $5 billion annually.
The same issue with herbicide-resistant weeds is also taking root across the United States, specifically in the Upper Midwestern region where farmers—particularly soybean and corn growers—are fighting the Palmer amaranth, another herbicide-resistant weed that can reroot itself and grow up to three inches per day. Unchecked Palmer amaranth can suppress soybean yields by nearly 80 percent and corn yields by about 90 percent, according to a recent report in The New York Times.
The team of Australian researchers is on track to crack the case against herbicidal resistance, which they say is “one of the biggest threats to our natural environment and agricultural sector,” by adopting a ‘failed’ antibiotic aimed at treating tuberculosis into a “new and target-specific herbicidal compound.”
“Specifically, we identified an inhibitor of bacterial dihydrodipicolinate reductase (DHDPR), an enzyme involved in lysine biosynthesis in plants and bacteria, that exhibited no antibacterial activity but severely attenuated germination of the plant Arabidopsis thaliana (Thale cress),” explains Dr. Tatiana Soares da Costa, a Future Making Fellow at the University of Adelaide’s Waite Research Institute in the thesis of their study. “We confirmed that the inhibitor targets plant DHDPR orthologues in vitro, and exhibits no toxic effects against human cell lines. A series of analogs were then synthesized with improved efficacy in germination assays and against soil-grown A. thaliana. We also showed that our lead compound is the first lysine biosynthesis inhibitor with activity against both monocotyledonous and dicotyledonous weed species, by demonstrating its effectiveness at reducing the germination and growth of Lolium rigidum (rigid ryegrass) and Raphanus raphanistrum (wild radish).”
Dr. Soares da Costa said the compounds target two steps in lysine production in weeds, which could lead to the development of multi-target herbicides for the first time.
“A multi-target herbicide could make it more difficult for weeds to evolve resistance, helping to prolong the efficacy of existing herbicides and improving crop quality and yield,” she said. “The development of new herbicides, especially multi-target herbicides, is a high priority to combat weeds that are resistant to herbicides.”
While the substances used in the research were initially created for human consumption, the next step for this new, two-target herbicide will be large-scale field trials and toxicology screenings to ensure their safety and effectiveness. This is an important step in light of tightened regulations on dicamba use, an effective but dangerous herbicide linked to multiple types of cancer, deemed harmful to wildlife, and known to cause damage as it drifts over crops that are not dicamba-resistant.
“This work will directly impact farmers by giving them the tools they need to overcome weeds and improve the quality and yields of crops,” Dr. Soares da Costa said.
Sources:
Brown, H. Claire. “Attack of the Superweeds.” The New York Times, 18 Aug. 2021, www.nytimes.com/2021/08/18/magazine/superweeds-monsanto.html.
The University of Adelaide. “Failed antibiotic now a game-changing weed killer for farmers.” ScienceDaily. ScienceDaily, 24 May 2023. <adelaide.edu.au/newsroom/news/list/2022/07/04/new-herbicidal-compounds-may-provide-major-boost-for-aussie-farmers><www.sciencedaily.com/releases/2023/05/230524182017.htm>.
