Battling bugs

Potatoes with blight are black and rotten inside. Image: USDA

The microbe that causes potato late blight – responsible for the 19th-century Irish potato famine that killed around a million people – destroys 20% of the worldwide potato crop every year.

Potato farmers have to spray their crops with pesticides, sometimes as often as 15 times a year, to rid them of the disease. This is very expensive and time-consuming for the farmer.

A number of pesticides were recently banned in Europe, so the need to find a blight-resistant potato is even more urgent.

The chips are down

Modifying potato plants at the Sainsbury Laboratory. Image: Sainsbury Laboratory

Researchers at the Sainsbury Laboratory in Norwich are at the front line of the fight against late blight. They are using GM to help our favourite spud varieties fend off the disease.

They haven't solved the problem yet, but they think that within the next 3–5 years we could have blight-resistant potatoes on our plates.

So how do scientists make a blight-resistant potato?

Beating the blight

South American potatoes come in all shapes and sizes – some are resistant to blight. Image: Centro Internacional de la Papa

Jonathan Jones, a crop expert at the Sainsbury Laboratory, reveals that beating blight isn't about making potatoes toxic.

'Like us, all plants have an immune system. When fighting off a disease, first the plant needs to recognise an invading microbe. Next, a series of reactions kills the microbe off,' he says.

'We have found blight resistance genes in wild South American potatoes that allow them to recognise and resist the disease. We have transferred these genes into some familiar potato varieties in the lab.'

Uber tuber

Jonathan Jones believes that GM is the best way to beat the blight. Image: Sainsbury Laboratory

Potatoes might look simple. But genetically they are very complicated. They have four copies of every gene, whereas humans only have two. This makes it difficult to predict what will happen when you breed two potatoes together.

'People like the familiar varieties of Desiree, Maris Piper, Jersey Royals, and so on, but it is impossible to breed blight resistance into these potatoes without losing the combination of qualities that people like,' says Jones. 'Only genetic modification allows us to do this.'

Top banana

Bananas are an important staple food for many people in Africa.

Bananas and plantains, their savoury cousins, are also tricky to breed conventionally. Most common varieties are sterile, making it difficult to introduce new characteristics.

'Genetic modification of bananas makes sense,' says Howard Atkinson, plant expert at Leeds University. Atkinson is making bananas that are resistant to nematodes. These microscopic worms destroy 20% of bananas globally every year. But Atkinson has found a way to stop the nibbling nematodes.

Home-grown technology

Many Ugandan scientists are working on the project. Image: University of Leeds

'We have transferred a gene into the bananas from rice, which produces a protein that kills the worm,' says Atkinson.

Nematodes pose a particular problem in sub-Saharan Africa, where bananas are an important part of the diet. In Uganda, each person eats 250 kg of bananas every year.

The Ugandan government is enthusiastic about using GM technology to help solve the problem, and is leading the project. 'Scientists in Leeds are providing knowledge and technology, but most of the work is happening in Uganda,' explains Atkinson.