Remarkable is a word seldom used of the potato, but an exception might have to be made for a newly discovered purple variety. Its colour is not the issue, however: what has intrigued researchers is its remarkable resistance to deadly potato blight.
Scientists involved in an EU-funded study called Blight-Mop have tried to kill off the so-far unnamed variety using no less than seven killer strains of the fungus that causes blight. While ordinary potato varieties, used as controls, rapidly wilted and died, the purple potato has prevailed, with only minor spots of wilt on its otherwise healthy leaves.
"The tiny lesions on the leaves are particularly encouraging, because they show that the blight is present but not progressing," says Carlo Leifert, professor of ecological agriculture at the University of Newcastle-upon-Tyne.
"This suggests that the plants have a high level of durable resistance, which is preventing the blight from reaching the potatoes underground."
The variety was discovered in Hungary and is nameless because it is little grown, according to the research team, which includes scientists from Newcastle and partners in Denmark, Germany, Switzerland, France, the Netherlands, Norway and Scotland.
It was brought to a test plot in England, near the village of Heddon-on-the-Wall, in Northumberland, by coincidence the origin of Britain's foot-and-mouth epidemic.
Blight is a devastating disease that has changed the course of history. The Great Famine of 1845 to 1847 killed a million people here and drove another million to new lives overseas. Epidemics destroyed potato crops across Europe during the 1840s, leading to famines in other countries.
A fungus-like organism, Phytophthora infestans, causes blight, a specialised disease of potato and, to a lesser extent, tomato, according to the research team. It is easily spread in mild, damp conditions, when its spores are carried over distances on the wind.
Regular spraying with copper-based fungicides such as Bordeaux mixture, which includes copper sulphate and calcium oxide, can prevent it. These are potentially toxic, however, and are banned if the grower hopes to produce organic vegetables.
The new variety's potential in organic farming is particularly noteworthy, according to Prof Leifert. "A potato which can be grown commercially without using chemicals would be an important breakthrough for the organic movement worldwide," he says.
"In England and all other countries, the supply of organically grown potatoes does not meet demand from consumers, because blight is so prevalent."
Blight wipes out organic crops worth millions of pounds each year and deters many farmers from growing them, he says. "That is why supermarkets have a very limited supply of organically grown potatoes. There is little choice of variety and stocks frequently run out."
It is too early to say whether the purple spud will deliver on their promise. It still has to be taste-tested to confirm that it will also work on the plate and palate. Its powerful disease resistance will be pursued, however.
The resistance characteristic potentially could be inserted into other varieties by crossbreeding. Genetic engineering might bring the relevant genes into table varieties, although this would be anathema to organic growers.
