11 August 2009

Securing spuds from disease

It may have taken 160 years, but scientists may have their arms around the cause of a blight-causing pathogen in potatoes and are working to accelerate breeding of more durable, disease resistant spud.

Over 160 years ago, the potato blight wreaked havoc in Ireland and other northern European countries, but by using pathogen genomics, researchers identified genes that may fight off those pathogens.

Using pathogen genomics, the most significant potato suspect, Phytopthora infestans, is under investigation into how it causes disease, said Professor Paul Birch from the Division of Plant Sciences, at the University of Dundee (at Scottish Crop Research Institute - SCRI), who worked on a team from Warwick HRI and the University of Aberdeen. They are now in the process of identifying essential pathogen virulence genes that may be durable targets for host resistance proteins.

Costs associated with crop losses and chemical control of blight exceed $5 billion (£3billion) globally each year. “What we have seen is an evolutionary arms race between a pathogen and its host and, so far, the pathogen has been winning,” Birch said.

However, this could soon change due to a greater understanding of the role effector proteins play in the process. These proteins end up secreted by the pathogen and go onto manipulate the plant cell structure, defenses, and metabolism to establish disease.

The discovery of more than 500 genes encoding these effectors, along with recent advances in technology to study protein—protein interactions provides an unparalleled opportunity to investigate how plant defenses end up suppressed by invading microbes.

Within these effector proteins, Birch and his team discovered a genetic motif called RXLR, which is necessary for the P. infestans pathogen proteins to enter the potato cells.

“We are really excited by the discovery of RXLR. This has provided a signature to search for proteins that are delivered inside host cells, where they may be exposed to plant defense surveillance systems,” Birch said.

The scientists hope their understanding of how effectors interact with their targets in the host will lead to strategies to control or prevent crop losses and environmental damage for a wide variety of plant diseases, not just potato blight.

“Potatoes are the third most important food crop in the world, but blight continues to devastate crops worldwide, having huge economic and dietary ramifications,” said Biotechnology and Biological Sciences Research Council Chief Executive Professor Doug Kell. “This exciting research highlights the invaluable role that genomics has to play in preventing crop losses in potatoes and other crops and helping to address the urgent issue of global food security.”

For related information, go to www.isa.org/environment.