Scientists at Britain's Imperial College London have sequenced the genome of a major fungal disease that affects barley and other cereal crops. The research, published in December in Science, suggests that parasites within the genome of the fungus help the fungus to adapt and overcome plant defences. The findings could advance our understanding of how plant diseases evolve and improve food security.

The research, led by Dr Pietro Spanu, decodes the genome of Blumeria, which causes powdery mildew in barley. Plants become covered in powdery white spots that prevent them from cropping, which has a devastating impact on agricultural yield.

Blumeria often evolves too rapidly for current prevention methods, such as fungicides and crop rotation, to be effective. The new research suggests that this rapid evolution occurs because the fungus genome contains multiple parasites, known as transposons, which help the fungus disguise itself and go unrecognised by the plant's defences. It is as though the transposons confuse the host plant by changing the target molecules that the plant uses to detect the onset of disease.

The researchers discovered that Blumeria had unusually large numbers of transposons within it. "It was a big surprise," said Dr Spanu, "as a genome normally tries to keep its transposons under control. But in these genomes, one of the controls has been lifted. 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."

(Source: Genome of barley disease reveals surprises [Imperial College London])