www.checkbiotech.org ; www.raupp.info ; www.czu.cz

British scientists have made a breakthrough in the fight against a major
agricultural pest which each year destroys enough food to feed 60 million
people, March 2006 by Steve Connor.

The researchers believe they have identified the Achilles heel of
apernicious fungus that spoils the annual crop of millions of rice farmers
around the world. Rice blast fungus is probably the most serious pest of the
most important staple crop in the world and there is little that farmers can
do to defend their crops against it.

But a study published in the journal Nature holds out the promise of
developing environmentally friendly fungicides that can target the precise
mechanism which allows the pest to infect a crop of rice.

Scientists led by Nicholas Talbot, of the University of Exeter, have
identified a key gene of the rice blast fungus which plays an essential role
in the infection process. The researchers believe the discovery may also
lead to better selective breeding, or even the genetic engineering of new
rice varieties that are resistant to rice blast fungus. "This is a very
important disease of rice and we've been able to show how it delivers its
'weapons' into a rice plant to cause disease," Dr Talbot said. "We believe
this is something of a break-through because it's the first time that we've
been able to learn something about the process of how the disease happens."

Rice blast is so widespread because its spores are present all-year round in
the high humidity of the rice-growing areas of the world. The fungus can
also infect the rice crop at any stage in its development. Fungal spores are
easily spread from plant to plant and they can also lie dormant for many
months in the ground as a result of fallen rice grains or stubble.

When a spore comes into contact with the leaf of a rice plant, it forms a
tiny cell-like bubble which has an internal pressure of about 40 times the
pressure of a car tyre.

This is used to burst open the tough waxy surface of the leaf. Once the
leaf's outer barrier has been breached, the fungus releases small packets,
or vesicles, of enzymes that help to break down the plant's cell walls to
enable the fungus to invade. The Exeter team identified a key gene of the
fungus that is responsible for a protein which appears to play a critical
role in controlling the formation of these vesicies.

"We have identified a secretion system that we think is responsible for
delivering the fungal weaponry that causes rice blast disease," Dr Talbot
said.

"We were able to generate a strain of the rice blast fungus which lacks this
secretion system and lt was completely unable to cause disease.

"The discovery is significant because it will allow us to identify the
fungal proteins which bring about this devastating disease and cause rice
plants to die."

Dr Talbot said that lt could take another five or 10 years to develop
practical solutions to the problem of rice blast based on the findings of
the latest study.

"lt's estimated that half the world's population relies on rice to survive
and in one year alone this disease kills enough rice to feed 60 million
people, so we hope this discovery will help to develop chemicals to inhibit
this disease," he said.

Staple facts about rice

There may be as many as 140,000 varieties of rice grown on every continent
except Antarctica.

The Mandarin Chinese word for rice is the same as the word for food' in
Japan, the word for "meal" is the same as that for "cooked rice".

Rice was cultivated in China as far back as 7,000 years ago, but it may have
been indigenous to India much earlier.

In 2003, the world produced 589 million tons of rice. About 534 million tons
of that was grown in Asla.

Rice is the first food that an Indian bride offers to her husband and the
first food offered to a baby.

Ninety per cent of the calories in rice come from complex carbohydrates or
starch. When all developing countries are put together, rice provides 27 per
cent of people's energy intake and 20 per cent of their protein.

Rice and its by products are used for making straw and rope, paper, wine,
crackers, beer, cosmetics, packing material, and even toothpaste.

[www.independent.co.uk]

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