Munich

Aggressive strains of potato blight could trigger a potentially catastrophic potato famine in Russia, scientists have warned.

The researchers want an international effort to provide Russian potato-growers with fungicides and seed varieties that are resistant to virulent late blight pathogens, which last year destroyed more than 15% of the country's total crop.

“The situation is worrying, and it could quickly worsen,” warns Kandukuri Raman, a plant scientist at Cornell University in Ithaca, New York, and head of the Cornell–Eastern Europe–Mexico (CEEM) project on control of potato late blight.

Potato late blight, which is caused by the fungus Phytopthora infestans and originated in Mexico, is one of the world's most devastating crop diseases, with annual losses and fungicide costs estimated at US$3 billion.

Potatoes are a vital subsistence crop grown by poor Russians who cannot afford to buy vegetables or meat. Russia is the world's second-largest potato producer, after China.

Raman fears that the state of its economy means that Russia will not be able to control the disease without outside support. He points out that Russia has no strong potato-breeding programme aimed at developing varieties resistant to late blight.

Spores of P. infestans constantly reproduce and take on characteristics that enable them to survive and spread. The new, aggressive strains proliferate freely and can survive in the soil over winter, attacking potatoes in summer and destroying the harvest.

At risk: Russia's potatoes are vulnerable because their growers lack access to fungicides. Credit: CORBIS

Late blight caused the Irish potato famine in the 1840s, leading to the death of a million people and a huge wave of migration. But fungicides have been available since the late nineteenth century, and have fought off even the more virulent strains across Europe. However, late blight remains a major threat to small farmers and householders in Russia, who lack access to suitable fungicides.

“Pesticide-resistant and virulent strains of P. infestans have appeared in the major potato-growing regions in Russia,” says Patrick Russo, a plant geneticist at the University of Helsinki in Finland and a technical adviser on control of late blight in Russia. Even types of potato that showed some resistance to late blight “are no longer resistant to the newer strains”, he adds.

The CEEM project aims to help distribute seeds of resistant potato varieties to Russian smallholders, but has limited resources. It is also collaborating with Polish and Russian scientists to test wild potato species, and to study the molecular biology of the interaction between P. infestans and the potato.

Much of the work is being done at the N. I. Vavilov All-Russian Scientific Research Institute of Plant Industry in St Petersburg, which holds one the world's oldest and largest potato collections.

The US Department of Agriculture and the CEEM project are sponsoring a June workshop in Warsaw on potato late blight. Experts from ten countries will discuss the use of plant genetics and traditional breeding methods to develop broad-based resistance, and explore the possibility of a programme to forecast the arrival of different strains of the pathogen.

→ http://www.cals.cornell.edu/dept/plantbreed/CEEM