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Nitrogen compounds control disease resistance in cereals

Nitrogen compounds play an important role in the plant’s fight against fungal diseases. Researchers are now seeking a better understanding of these mechanisms. This may present plant breeders with some new genetic tools for their work.

Source: CropSite News

Fungal disease attacks in cereals can severely damage the crop and lead to lower yields. Agriculture is therefore using several approaches to protect cereal from fungal diseases. One of the approaches is to use crop varieties that are bred for resistance to such attacks.

In a new research project, scientists are examining the genetic and molecular mechanisms that influence crop resistance to fungal attack. A better understanding of these mechanisms is an important part of the continued preparedness of plant breeders to fight fungal diseases in cereals.

Denmark has developed barley cultivars with resistance to the two major fungal diseases – brown rust and mildew. But since fungi are in a continuous state of change, there is constantly a need to find new ways of maintaining cereal resilience.

“Over 75 per cent of the Danish fields under spring barley use varieties where a single gene protects cereal against mildew. But there are signs of growing problems with mildew in cereals that carry this gene. There is therefore a need to explore alternative mechanisms that can help increase resistance to fungal attacks in barley,” explained assistant professor Kim Hebelstrup from the Department of Molecular Biology and Genetics at Aarhus University.

He leads the new project in close partnership with the Global Rust Centre at AU Flakkebjerg, and other universities in Denmark and abroad.

Nitrogen is important

Researchers will be looking more closely at the interaction between various stress factors and plant resistance to fungal attacks. One of the mechanisms that they will focus on is the connection between fertiliser type, plant nitrogen status and plant resistance to fungal diseases.

Nitrate-N fertiliser affects the resistance of the cereal crop to fungal infection, where the variation in resistance depends on the cereal variety. Nitric oxide (NO) apparently also plays a part in this process, where NO increases the plant’s resistance to disease. The researchers will look closely at the interaction between the turnover of nitrogen in the plant, the plant nitrogen status and the type of nitrogen used as fertiliser.

Previous studies at Aarhus University have shown that plant haemoglobin affects the turnover of NO in plants infected with the disease. By turning on genes that affect the haemoglobin status, the plant’s resistance to the disease is boosted by increasing the signal for NO. The opposite happens when the genes are turned off. The researchers will now use this mechanism to control the barley NO content – and thus its resistance to brown rust and mildew.

“We have demonstrated that haemoglobin is found in plants where its role is to degrade NO, and that a change in the genetic expression of haemoglobin is a powerful tool for altering the formation of NO in plants, which then affects disease susceptibility,” said Kim Hebelstrup.

The four-year project has a total budget of DKK 7 million, of which DKK 6.3 million has been granted by the Danish Council for Independent Research, Technology and Production.

The project is a collaboration between Aarhus University, University of Oxford and Aberystwyth University in United Kingdom, Memorial University in Canada and the German Research Centre for Environmental Health.

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