December 16, 2007

Out of Africa: Newly Evolved Fungus Strain Threatens World Wheat Crop

The dark side of fungal evolution rears its rusty head. A new variant of wheat stem rust fungus (Puccinia graminis) has been reported in Kenya. The variant is of the Ug99 strain, a line first reported from Uganda in 1999 that has already managed to cross the Red Sea and is threatening wheat supplies. While the "normal" Ug99 strain already had the potential to infect 80% of the world's wheat, the Kenyan variant has reportedly evolved resistance to genes that are being used to protect those crops. It thus has the potential to destroy even more than its most recent ancestor, already one of the most devastating grain diseases on the planet.

Scientists grapple with fungus that is destroying wheat

...The fungal disease also threatens barley and has crossed the Red Sea towards Yemen. If not checked, it will be soon afflicting wheat fields in Egypt, the Middle East and Asia.

Under GRI, governments and other research institutions in Kenya, Australia, Canada, Egypt, Ethiopia, Iran, South Africa, Uganda , Sudan, Turkey and Yemen are joining in the efforts to address the current crisis...

Prof Jin confirmed that a new variant of Ug99 that has been found in Kenya has shown more resistance to existing genetic treatment, putting more wheat fields in danger.

“It could broaden the disease’s reach to beyond the 80 per cent of the world’s wheat that is at risk,” said lead researcher RickWard of the International Wheat and Maize Improvement Centre (CIMMYT)

Previous field studies in Kenya and Ethiopia showed that ug99 has overcome most of the known stem rust resistance genes deployed in wheat cultivars over the years...
Mutation plus natural selection can be a real bitch. We're used to hearing about antibiotic-resistance bacteria evolving rapidly, but eukaryotes can achieve the same sort of result, especially mass-reproducers like fungi.

More info on the fungal phytopathogen is available from the USDA Agricultural Research Service Cereal Disease Laboratory. The info there is mainly on non-Ug99 strains already known in the US. Ug99 hasn't made it here yet.

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