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Fungus Gene Map Offers Hope Against Cereal Disease

Scientists may be able to find new ways to tackle plant diseases after discovering how a fungus attacks barley, a staple around the world and a main ingredient in brewing and malting.

In a study in the journalScience on Dec. 9, researchers from Imperial College London said they had decoded the gene map of Blumeria, a fungus that causes powdery mildew on barley.

They found that “parasitic DNA” within the genetic makeup of the fungus – pieces of genetic code that are capable of growing and reproducing inside the host’s own genes – helps it to adapt and overcome the plant’s defences.

“With this knowledge of the genome, we can now rapidly identify which genes have mutated, and then can select plant varieties that are more resistant,” said Pietro Spanu of Imperial’s life sciences department, who led the study.

Powdery mildew affects a wide range of fruit, vegetable and cereal crops in northern Europe. Infected plants become covered in powdery white spots that spread all over the leaves and stems and dramatically reduce yields.

The genetic code will also help in monitoring the spread and evolution of fungicide resistance in an emerging epidemic, and in the development of new agricultural techniques for protecting cereal crops from infection.

Farmers use fungicides, genetically resistant crop varieties and crop rotation to try to prevent mildew epidemics, but the fungus often evolves too rapidly for these techniques to be effective, Spanu’s team explained in their study.

Parasitic DNA appeared to be the key to this rapid mutation – the researchers found that Blumeria has unusually large numbers of these pieces of DNA, known as transposons.

“It was a big surprise, as a genome normally tries to keep its transposons under control. But in these genomes, one of the controls has been lifted,” Spanu said in a statement.

“We think it might be an adaptive advantage for them to have these genomic parasites, as it allows the pathogens to respond more rapidly to the plant’s evolution and defeat the immune system.”

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