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Worm genome researched to save potatoes

By Jess Halliday , 27-Nov-2007

Researchers in the UK are taking a novel approach to improving the competitiveness of the potato market - decoding the genome of a parasitic worm to find out how it can have such a devastating effect on crops.

Globodera pallida is a potato cyst nematode (PCN) that attacks potato crops in 55 countries around the world, including 18 in the EU and developing counties where the potato is a subsistence crop. Some commercial potato varieties are naturally resistant to other PCNs - for instance the Maris Piper potato is naturally resistant to Globodera rostochiensis, which means it has been possible to breed this resistance into other varieties. Not so G pallida. "There is no strong natural resistance that is commercially useful", Dr Peter Urwin from the University of Leeds Faculty of Biological Sciences told "Either natural resistance doesn't exist or we haven't found it." This means that the worm has had free-reign to feast on whatever potatoes it can get to. In the UK alone, farmers currently spend £50m (€69.5) a year trying to control the parasite, usually though chemicals that can render the soil sterile. But Dr Urwin believes that an environmentally-friendly approach to controlling the problem could improve the competitiveness of the potato industry, which in the UK alone is worth some £3bn (€4.2bn) a year (including processing and retail). "We think that consumers are more likely to support UK production that avoids pesticide residues and environmental harm and that is soundly based on a sustainable approach," he said. "If we can find out exactly how this worm works so efficiently, it should lead to measures that will help the potato plant to withstand attack." Despite measuring just 1mm long and 0.5mm in diameter, even when it is full of 400 eggs, G pallida is highly destructive. It goes to work on the plants by injecting a substance into its roots, which makes the plant create a special cell from which the worm feeds. The effect of this on the plant is that root growth is stunted, the plant is deprived of essential nutrients and the crops end up smaller and of lower quality. What is more, the eggs of the worm can stay in the soil for as long as 20 years. They can hatch any time they sense potato roots in the vicinity - meaning it is very difficult to get rid of the bugs altogether. "The tiny parasite has evolved many clever mechanisms that we hope to be able to understand more fully through this research", said Dr Urwin, who added that the team presently has no idea what the substance is that is injected into the root, or how it cajoles the plant into creating a feeding cell. He said that once the sequencing has been completed - expected to be 2012 - that will open up new opportunities to use breeding or biotechnology to develop a resistant potato, or for industry to develop environmentally nematocides. In the event, he does not expect that the upshot will be a 100 per cent resistant crop, but a solution could be found in the combination of a plant with some resistance and a nematocide that is not 100 per cent efficacious either. Dr Urwin and his team at leads are working on the project with other experts from the Wellcome Trust Sanger Institute, Rothamstead Research and SCRI, the Scottish centre for crop research. The project has received £1.7m (€2.4m) funding from the Biotechnology and Biological Sciences Research Council - a sum Dr Urwin described as "huge" for a single project. But there is a hope that, when the specific genes responsible for the destruction are fished out, they may prove similar to genes in nematodes that affect other crops. Dr Urwin told that this is the first time the team at Leeds has used the approach of genetically decoding a nematode. However it has investigated the biological make-up of nematodes that affect other plants. For instance, one other project has concerned East African highland bananas, a food staple. When these top-heavy plants are attached by nematodes the roots are undermined, causing them to topple over. This affects not only the main plant, but also the offshoot sibling that grows alongside, thus ruining more that one season's crop.

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