Deadly rust threatens world's wheat crop

CROP yields have virtually doubled over the past 40 years, thanks to plant breeders and the development of a wide range of agri-chemicals. However, one of the fathers of the "green revolution," the Nobel laureate Norman Borlaug, warns that a virulent new strain of black rust poses a major threat to global production of wheat.

Borlaug told New Scientist that "this thing has immense potential for social and human destruction".

The disease is Ug99 and was first discovered in Uganda in 1999 and appears to be a mutation of the more common strains of rust to which most varieties of wheat have a considerable degree of resistance.

Ug99 spread slowly across east Africa, but earlier this year spores were discovered in Yemen and the general opinion is that it is only a matter of time before the disease reaches Egypt, the Middle East, India and, very possibly, southern countries of Europe.

However, scientists are now looking at some strains of wheat, which appear to have a degree of resistance to Ug99. But the fact remains that it can take the better part of 20 years to produce new varieties and even then the yields may not match up to current strains.

The threat of a major disease outbreak, very possibly on the same lines as the great potato famine in Ireland in 1845-6 when millions died, has come a time when world stocks of wheat are at their lowest level for more than 30 years.

Prices rose last year by as much as $40 per tonne and, according to the Chicago futures market, there is every possibility of further increases in the coming months as consumption continues to exceed production.

Rust in its various forms is not a new phenomena, but farmers and scientists have learned to cope with the threat of major disasters.

However, it was only just over 50 years ago that up to 40 per cent of the wheat crops on the American prairies were wiped out by black rust.

Borlaug commenced his work on breeding wheat resistant to stem rust in Mexico in 1954 and his success in this field led to being awarded the Nobel peace prize in 1970. The general view is that modern agri-chemicals can be used to treat Ug99 with some success.

However, poor farmers in the developing countries of the world are unlikely to be able to afford these products and also lack the knowledge of how and when to apply them.

A major problem in tackling the disease is that Ug99 appears to be mutating all the time. Initially it was thought that certain genes in several varieties of wheat would give a degree of protection if they could be incorporated in newer types of wheat. However, researchers have now found that Ug99 has become modified to the extent that it can defeat these genes.

There is also a sinister aspect to Ug99 in that the US government fears that it could be used by terrorists to create major problems anywhere in the world. Ultimately, Borlaug believes that scientists will defeat the disease but he laments the fact that research programmes have been severely cut back in many countries over the last 40 years and that agriculture has become far too complacent.