Scientists led by a group at Imperial College London have sequenced the genome of the major European crop pest Blumeria, commonly known as powdery mildew, which they say points the way to new approaches to tackling the fungal disease.
The research suggests that parasites within the genome of the fungus help the disease to adapt and overcome the plant’s natural defences. The research was led by Pietro Spanu from the Department of Life Sciences at Imperial College.
Powdery mildew affects a wide range of fruit, vegetable and cereal crops in northern Europe, with infected plants becoming covered in powdery white spots that spread over the leaves and stems, preventing them from producing crops, and having a devastating impact on the overall agricultural yield.
Farmers use fungicides, resistant varieties and crop rotation to prevent mildew epidemics, but the fungi often evolve too rapidly for the techniques to be effective. The mildew is able to evolve so quickly because multiple parasites within the genome, known as transposons, help it to disguise itself and go unrecognised by the plant’s defences. The researchers have discovered that Blumeria has unusually large numbers of transposons Spanu said this is a surprise finding. “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 to have these genomic parasites, as it allows the pathogens to respond more rapidly to the plant's evolution and defeat the immune system.”
The research will make a significant contribution to the design of new fungicides and resistance in food crops. “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,” Spanu said. The sequence will also help scientists monitor the spread and evolution of fungicide resistance in an emerging epidemic. “We'll be able to develop more efficient ways to monitor and understand the emergence of resistance, and ultimately to design more effective and durable control measures.” said Spanu.
The study was supported by the UK Biotechnology and Biological Sciences Research Council, the Max Planck Society and the Institut Nationale de la Recherche Agronomique.Genome expansion and gene loss in powdery mildew fungi reveal functional tradeoffs in extreme parasitism
Spanu, P.D. et al.
Science, 10 December 2010