Wild grass gene gives wheat the power to intercept fertilizer pollution

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Scientists have developed wheat plants that can quell nitrogen pollution from chemical fertilizers, potentially preventing tons of greenhouse gases from entering the atmosphere each year.

Wheat plants, which incorporate a genetic trait from a type of wild grass, ooze compounds from their roots into the soil, disrupting the enzyme activity of soil microbes. This slows down the ability of these microorganisms to break down fertilizer ingredients and release the resulting pollution into surrounding ecosystems.

This harmful process is called nitrification, and it is one of the main reasons that fertilizers have such an impact on our planet. Farmers apply fertilizers because they contain ammonia, which helps plants grow. But soil microbes intercept this process, oxidizing ammonia to form nitrate, an ingredient that can end up draining from the soil into waterways, causing dead spots in the ocean, and even polluting it. drinking water for humans. This process also reduces the availability of readily usable ammonia to plants, which sometimes leads to over-application of fertilizer on farms to make up for the loss.

In addition, during the oxidation process, microbes release nitrous oxide, a powerful greenhouse gas – 300 times more powerful than CO2 – as a by-product. This greatly adds to the footprint of agriculture.

Yet modern agriculture needs fertilizers to produce food, and so does wheat in particular, which gobbles up up to one-fifth of the world’s chemical fertilizers each year. As wheat is a staple food for millions of people around the world, its polluting impact is an obstacle we must get out of. Now, the team of international researchers from the new study believe they have found a solution.

They based their research on a body of work that had explored the ability of certain plants to secrete compounds from their roots and to control aspects of soil microbe behavior – a characteristic called ‘inhibition of biological nitrification’ ( BNI). Many grasses, such as wild rye, have this characteristic, and it is linked to a particular chromosome segment in their genes. The researchers therefore extracted the relevant genetic sequence from wild rye plants and then selected it from a common wheat cultivar.

Then, in laboratory experiments, they discovered that these modified wheat plants were able to reduce the presence of polluting nitrates in the soil by 30%. The abundance of soil microbes around plants also decreased by 20-36% in soil samples. Importantly, emissions associated with fertilizers have also been significantly reduced: emissions of nitrous oxide in incubated growth pods have decreased by 25%.

Interestingly, the wheat plants with the BNI trait had also improved the absorption of nutrients from the fertilizer, possibly because the reduced microbes left more of the nutrients in the fertilizer intact for them to absorb. . This finding suggests that wheat plants could increase fertilizer efficiency and reduce the amount farmers have to apply, as much less is lost to microbial degradation and pollution. In addition, the increased uptake measured by researchers also resulted in increased biomass and productivity of wheat.

The study showed that the greatest drops in nitrates occurred in slightly acidic soils, suggesting that these wheat growing environments would be the best candidates for their discovery. But the researchers also think we could expand the search for BNI traits in grasses that grow in alkaline soils, which may then be suitable for transfer to wheat crops that also grow under these conditions.

Because wheat is grown so widely, researchers believe that if farmers adopted these pollution-control varieties of wheat, the cultivation could help significantly reduce agriculture’s greenhouse gas footprint and could be factored into. national climate plans to meet reduction targets.

Soon, the researchers will embark on the next phase of their work: a trial to grow wheat plants equipped with BNIs in India, where they will test how well they can tackle fertilizer pollution in the real world. “This paves the way for farmers to feed future wheat consumers by using lower doses of fertilizer and reducing nitrous oxide emissions,” the researchers say.

Subbarao, and. Al. “Enrolling Wild Herb Genes to Combat Nitrification in Wheat Cultivation: A Nature-Based Solution”. PNAS. 2021.

Image: Matt Lavin via Flickr


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