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Fungi could reduce reliance on fertilisers

Introducing fungi to wheat boosted their uptake of key nutrients and could lead to new, ‘climate smart’ varieties of crops, according to a new study.

Researchers at the University of Leeds have demonstrated a partnership between wheat and soil fungi that could be utilised to develop new food crops and farming systems which are less reliant on fertilisers, reducing their contribution to the escalating climate crisis.

Higher levels of carbon dioxide

It is the first time the fungi, which form partnerships with plant roots, have been shown to provide significant amounts of phosphorus and nitrogen to a cereal crop. The fungi continued to provide nutrients under higher levels of carbon dioxide (CO2) predicted for 2100, which has important implications for future food security.

Most plants form partnerships with fungi in their root systems, known as arbuscular mycorrhizas, which enable them to draw nutrients from the soil more efficiently. In exchange, the plants provide carbohydrates to the fungi as a form of payment, known as a symbiosis.

Fungi help plants increase growth

Plants can give 10-20% of the carbon they draw from the air to their fungal partners, in exchange for up to 80% of their required phosphorus intake. These fungi can also help plants increase their growth, nitrogen levels, water uptake, and defend the plant against pests and disease.

But over the last 10,000 years, crop plants have been domesticated through intensive breeding, which has inadvertently stopped some varieties from having such close relationships with beneficial fungi.

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Liquid fertiliser is being sprayed on wheat. Reducing the use of fertilisers can help lower agriculture's overall contribution to climate change. - Photo: Hans Prinsen
Liquid fertiliser is being sprayed on wheat. Reducing the use of fertilisers can help lower agriculture's overall contribution to climate change. - Photo: Hans Prinsen

Wheat yield has reached a plateau

Across the globe, wheat is a staple crop for billions, and wheat farming uses more land than any other food crop (218 million hectares in 2017). Despite increasing the application of nitrogen and phosphorus fertilisers to boost yields, the amount of wheat that can be produced from a given area has reached a plateau in recent years.

Whilst some varieties of the wheat grown by farmers form these partnerships with beneficial fungi, many do not. The Leeds researchers therefore suggest there is potential to develop new varieties of wheat that are less dependent on fertilisers.

How the study was done

Scientists allowed the fungi to colonise the roots of 3 different varieties of wheat in the laboratory and grew them in 1 of 1 chambers – either mimicking current climatic conditions or those projected for 2100, when CO2 concentration in the atmosphere is predicted to be double that of today if emissions are not curbed. They wanted to know what benefits the different varieties could gain from their fungal partners and how the relationships would be affected by increasing atmospheric CO2.
By chemically tagging phosphorus and nitrogen in the soil and CO2 in the air, the researchers were able to demonstrate that the different varieties of wheat absorbed the nutrients through their fungal partners, in both climate scenarios.
As expected, the 3 varieties of wheat underwent different levels of exchange with the fungi, with some varieties gaining much more from the relationship than others for a similar carbohydrate ‘cost’.
In particular, the Skyfall variety of wheat took up far more phosphorus from the fungi compared to the other 2 varieties, acquiring 570 times more than the Avalon variety and 225 times more than Cadenza.
There was no difference in phosphorus or nitrogen exchange from the fungi to the wheat at the higher CO2 level for any of the 3 crop varieties. It therefore appears that the fungi can continue to transfer nutrients to the crop even under future climate conditions.

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