September 2001

From University of Newcastle upon Tyne

Purple potato boost for organic food industry

A purple potato from Eastern Europe may be the key to solving the biggest economic obstacle facing the organic farming industry. The variety, so obscure that it has no name, appears to be almost totally resistant to potato blight, making treatment with fungicide unnecessary.

The discovery by scientists at the University of Newcastle upon Tyne, England, has attracted experts from across Europe to admire a humble potato patch at a remote agricultural research station near Hadrian's Wall in Northumberland where the variety is being grown.

While plots of most common potato varieties are wilting and disfigured from the effects of being impregnated with seven deadly strains of the fungus which causes blight, the purple newcomer from Hungary is flourishing, with only a few tiny lesions on its healthy green leaves. The plot has been nicknamed ‘the purple patch’ ‘This is extremely promising for organic farmers and consumers,’ said Carlo Leifert (pictured), professor of ecological agriculture at the University. ‘A potato which can be grown commercially without using chemicals would be an important breakthrough for the organic movement worldwide.

‘The tiny lesions on the leaves are particularly encouraging because they show that the blight is present but not progressing. This suggests that the plants have a high level of durable resistance which is preventing the blight from reaching the potatoes underground.

‘In England and all other countries, the supply of organically-grown potatoes does not meet demand from consumers because blight is so prevalent. It destroys crops worth millions of pounds each year and deters many farmers from growing potatoes because the risks are so high. ‘That is why supermarkets have a very limited supply of organically-grown potatoes. There is little choice of variety and stocks frequently run out,’ said Professor Leifert, adding that it was too early to say whether prices might come down.

The potato trials at Close House research station, near the village of Heddon-on-the-Wall (by coincidence the origin of Britain’s foot-and-mouth epidemic), are England's contribution to a £3.5m European Union research programme called Blight-Mop, in which many new varieties of potato and agronomic control strategies being tested for blight control by Newcastle University and partner research centres in Denmark, Germany, Switzerland, France, Netherlands, Norway and Scotland (full list of contacts is below). Representatives of all nine research centres recently visited Close House to see for themselves the progress of the promising purple potato. Edith Lammerts a senior scientist from the Louis Bolk Institute in the Netherlands, said: ‘Blight is the biggest threat to organic farmers throughout Europe. In the Netherlands and in Northern Germany, blight has wiped out entire potato crops this year. The cost to farmers has been huge.’

While the visitors were intrigued by the purple potato, other promising candidates may yet emerge as the research programme continues. Professor Leifert points out that the variety still has to pass the taste-test and admits there may be marketing issues to address before supermarkets would include purple potatoes in their displays of organically-grown produce.

Facts about potato blight:
* Potato blight is one of the most devastating plant diseases and has changed the course of history. The epidemics that destroyed potato crops in Europe in the 1840s led to mass starvation. For example, in the Great Irish Famine of 1845 to 1847 up to one million people died and a similar number of people emigrated to the rest of Europe and the USA.
* The disease is caused by a fungus-like organism, Phytophthora infestans, which is a specialised disease of potato and, to a lesser extent, tomato. The fungus is dispersed by wind-borne spores, which emerge from the stomata (breathing holes) of infected leaves in humid conditions. When the spores land on a new leaf surface they enter the leaf stomata and germinate. * The first symptoms of potato blight are small lesions on the leaves, which rapidly spread and cause the leafy top of the plant to turn brown, wither and die. As the infection advances, the blight attacks the growing tubers, causing them to disfigure, become inedible and finally rot away.
* Control of potato blight traditionally relies on copper-based fungicides such as Bordeaux mixture (consisting of two chemicals, copper sulphate and calcium oxide). However, copper is potentially toxic and is banned from food produce labelled as organically grown.

Web link: (Tesco Centre for Organic Agriculture at the University of Newcastle upon Tyne)


NOTES FOR EDITORS: 1. The Tesco Centre for Organic Agriculture at Newcastle University was established in January 2001 following a £425m investment from the supermarket chain, Tesco. However, the Blight-Mop project is independent of Tesco, being wholly funded by the European Union.
2. Professor Carlo Leifert would be happy to comment on organic farming production and marketing matters in the future. Please add his details to your contacts files. For broadcasters, the University has a fully-equipped radio studio with ISDN line and is ten minutes from BBC and independent TV studios.

A professional-standard photograph of Professor Carlo Leifert with the purple potato variety at Close House research station is available free of charge (there may be a small charge for transmission by ISDN) from North News and Pictures, phone 0191-233-0223 (44-191-233-0223). The photographer is Stuart Outterside. In the event of difficulty, please contact the Press Office of the University of Newcastle upon Tyne for assistance.


For more information, contact Professor Carlo Leifert on 0191 222 6908 or 5589 or 6573 (international 44-191-222-6908 or 5589 or 6573), e-mail, or his research assistant Helen Newton on 0191-222-7402 (44-191-222-7402). This press release is issued by the University Press Office on (0191) 222 7850. E-mail

This article comes from Science Blog. Copyright © 2004

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