Research on soil acidity could lead to new wheat varieties

Researchers from the University of Queensland and the CLS have been working to solve the problem of aluminum toxicity in acidic soil.

By Murray Lyons

Wheat seedlings grown in soils containing increasing levels of soluble aluminum. Roots at high aluminum are stunted with few branches. Image courtesy of Steve Carr, Aglime Australia.

Most experts agree food production will need to double by the time Earth’s population grows to nine billion people by 2050. This is a challenge that motivates scientists the world over and Australian crop scientist and plant nutritionist Peter Kopittke is no exception.

The young scientist spent a few days this past summer in the heart of Canada’s wheat belt working on the problem of aluminum toxicity in acidic soil. It’s a problem that affects wheat growers in many parts of the world although not in Saskatchewan, home to the CLS, where Kopittke spent an intense 36 hours earlier this year.

Globally, it is estimated that acid soils result in more than US$129 billion in lost production annually. In Western Australia, farmers lose A$1.5 billion annually because the aluminum in the soil destroys the root system, killing the plant.

Kopittke, associate professor in soil and environmental sciences at The University of Queensland, explains that few Saskatchewan wheat farmers will have ever heard of the aluminum toxicity problem as arable land in Saskatchewan is mostly alkaline, a pH condition that does result in any uptake of the element in plant roots. But Kopittke points out that 30 to 40 per cent of all the arable land in the world is acidic and aluminum is the third most common element in the world.

It’s not a new problem. Kopittke points out soil scientists discovered that aluminum is toxic to wheat plant root systems in 1904.

“Aluminum is extremely toxic and you need very little of it to completely inhibit root growth. It will severely stop the roots growing and you end up with very stunted root systems that can’t take up nutrients and water,” says Kopittke.

“When the aluminum moves into the root, what does it bind to? Even for those fundamental basic questions, we don’t know the answer to it.”

If soils are acidic as they are throughout Western Australia, as few as two parts-per-million aluminum around the root system will kill the plant. Kopittke says farmers see the wheat emerge after planting and it looks fine for a short time before the root system dies and the plant withers on the stalk.

A farmer can inject lime into the soil to bring up the pH to neutral to solve the problem, but Kopittke says this is not an economic way of dealing with the problem long-term, and farming practices will render soil acidic again over time.

Kopittke’s original research was published in a peer-reviewed paper Aluminum Complexation with Malate within the Root Apoplast Differs between Aluminum Resistant and Sensitive Wheat Lines in the August edition of Frontiers in Plant Science. The paper notes that this was the first time that aluminum’s interaction with root system was studied using the tools of X-ray absorption near edge structure analysis, the unique beamlines at the CLS that brought the Australian to Saskatoon.

Kopittke’s travel to the CLS was funded by the International Synchrotron Access Program as the Australian Synchrotron in suburban Melbourne does not have the specific beam line possessed by the CLS and essential for the Australian scientist’s work.

The University of Queensland researcher says he hopes his paper is one of the first steps to coming up with a breakthrough in finding wheat varieties with a root system that resists the uptake of aluminum.  He says the stakes are enormous:  “Ninety nine per cent of all food comes from soil. The soil really underpins life across the whole world.”

Kopittke, Peter M., Brigid A. McKenna, Chithra Karunakaran, James J. Dynes, Zachary Arthur, Alessandra Gianoncelli, George Kourousias et al. "Aluminum Complexation with Malate within the Root Apoplast Differs between Aluminum Resistant and Sensitive Wheat Lines." Frontiers in plant science 8 (2017): 1377. DOI: 10.3389/fpls.2017.01377


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