Mutating and migrating stem rust pathogen could soon spread across the world. Two new forms of a devastating wheat fungus, known as Ug99 stem rust, have shown up in South Africa, a study has found.
Close-up of stem rust fungus Ug99 on wheat.
The two South African forms are able to overcome the effects of two resistance genes in wheat that normally prevent stem rust from taking hold. The genes cause plant cells around the infection site to die, stopping the fungus from further infecting the plant. The discovery of the new forms marks the first time that the stem rust fungus with virulence against key genetic resistance has moved south of its origins in Uganda, east Africa, the research says.
The presence of new forms of Ug99 in South Africa makes wheat crops in areas including the Middle East and south Asia vulnerable as the fungus can now migrate using different wind trajectories, says Zacharias Pretorius, a wheat pathologist at the University of the Free State in Bloemfontein, South Africa, and one of the authors of the study.
“It’s mutating and migrating,” says Pretorius. “The concern is that other wheat-growing countries will become vulnerable to infection.”
“Eventually it will reach North America and Europe,” says Ronnie Coffman, a plant-breeding scientist at Cornell University in Ithaca, New York. He warns that in the next few years, farmers across the world will need to replace up to 90% of the current wheat varieties with new, resistant varieties to ensure crops are protected against the fungus.
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Published online 26 May 2010 | Nature | doi:10.1038/news.2010.265
Natasha Gilbert
Photo credit: Cereal Disease Lab / USDA
Questions:
What has been the role of shifting climate patterns in the evolution and emergence of this plant pathogen?
What will be the role of sifting climate patterns, especially in regards to upper level winds, in the potential global spread of this wheat rust a plant disease in such an important global food crop?
