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Lethal power of rice fungus discovered

Ian Sample

Hopes of ways to tackle it rise

London: The lethal weaponry of a fungus which has brought devastation to rice fields around the world has been discovered by scientists in a breakthrough that will help researchers to develop ways to tackle it.

Rice is the world's most important crop, with nearly half of the world's population relying on successful harvests and the fungus destroys enough rice to feed 60 million people a year.

Effective fungicides

By understanding how the fungus attacks, scientists believe they will be able to formulate more effective fungicides and create genetically modified crops that can resist the pathogen.

``This is hugely important,'' said Martin Gilbert, a plant biologist at Exeter University, England. ``Rice is especially important in the developing world and any handle we can get on better ways of tackling the fungus will help reduce the devastation it causes.''

The rice blast fungus, Magnaporthe grisea, destroys the plants by puncturing holes in the leaves and slowly injecting proteins that break down the plant tissues.

The fungus infiltrates and devours the plant.

The fungus is believed to be present in at least 85 countries and can infect domestic grasses; even burning rice crops to try to contain it is not always effective. In many parts of the world, it is resistant to fungicides and to genetic modifications created by plant breeders.

Researchers at Exeter University discovered a gene which is necessary for the fungus to secrete the plant-destroying enzymes. Some rice plants are able to detect the fungus's attack in time and can launch a defence by either beefing up cell walls or killing off leaves. But the specific signals the rice plant uses to detect the attack have remained a mystery.

In tests, the researchers knocked out a gene in the fungus, known as MgAPT2, and found that this in effect disarmed it.

The change also triggered no defence mechanism in rice plants.

The study was published in the journal Nature on Thursday. Further work will focus on the variety of molecules the fungus pumps into rice plants; researchers know that only some trigger the self-defence system, and if those can be identified they could be incorporated into fungicides.

Last year, an international team of scientists decoded the entire genome of the fungus, hoping this would reveal other weaknesses that could be exploited to kill it or make rice more resistant. —

© Guardian Newspapers Limited 2004

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