Rice resistant to blast disease

© Science/AAAS

Scientists in Japan have found a way to create high-yielding rice with long-lasting resistance to the devastating rice blast fungus.

Sufficient rice to feed 60 million people is destroyed by the blast fungus, Magnaporthe grisea — also known as Magnaporthe oryzae — every year.

Some rice is naturally resistant but is often also of lower yield. Now a team led by Shuichi Fukuoka from the National Institute of Agrobiological Sciences in Japan has engineered good quality rice that is both resistant to blast disease and high-yielding.

Their research was published in Science last week (21 August).

By comparing japonica rice that is resistant to blast disease with rice that succumbs to infection, Fukuoka found that a change in a key gene called Pi21 can mean the difference between devastating infection and mild disease.

Fukuoka says even plants with the resistant form of the gene become infected, but "The damage they suffer is not so serious, making it possible to reduce the amount of fungicide used by 50 per cent."

He says his team's findings will be particularly useful in mountainous areas where blast disease is a serious threat.

There have been many previous attempts to engineer resistant rice strains by making specific adjustments to plant immunity to allow the plants to recognise and resist the fungus.

But according to Nick Talbot, professor of molecular genetics at Exeter University in the UK, many of these modifications have a field life of just 2–3 years, as the fungus is quick to find ways to circumvent them and avoid being recognised.

Having the resistant form of Pi21, however, means a plant increases its defences against infection in general, making it much harder for the blast fungus to find a way to take hold, says Talbot.

He says the Japanese researchers have made a big discovery with universal applicability. When this is combined with other methods of engineering rice, scientists may be in a position to "exclude blast infections in a durable manner".

Fukuoka has also managed to isolate the resistant form of Pi21, meaning it can be separated from other genes associated with poor yield. Previously this has been difficult because when scientists have tried to transfer the resistant Pi21 gene into new strains of rice, the genes affecting quality have also hitched a ride.

Fukuoka says the fact that his research has shown the exact location of the Pi21 gene means scientists can ensure it is not replaced by a more vulnerable form when breeding new rice strains.

Link to full article in Science