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Another country hit by wheat fungus Ug99

It is sad but not surprising to learn that yet another country has been invaded by the destructive wheat fungus known as Ug99.

It is sad but not surprising to learn that yet another country has been invaded by the destructive wheat fungus known as Ug99.

The journal Nature reported online this week that mutating and migrating spores of the fungus have been found in South Africa. The fungus causes stem rust which can wipe out a wheat crop within a few days.

As MinnPost reported, this latest version of the virulent wheat disease surfaced in East Africa in 1999, jumped the Red Sea to Yemen in 2006 and turned up in Iran in 2008 where it endangers much of Asia.

About 80 percent of Asian and African wheat varieties are susceptible. So is barley. Those crops are a major source of nutrition worldwide. More than 1 billion people in developing countries count on wheat for their food and incomes.

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University of Minnesota scientists have travelled the globe to help find resistant varieties before the fungus causes widespread crop failure. And a secure lab at the U of M’s St. Paul campus is one of a few research facilities in the world authorized to work with spores of the highly contagious fungus. The Minnesota research is part of a project coordinated by Cornell University in Ithaca, New York.

The latest discovery is that two new versions of Ug99 have punched through resistance built into South African crops. One reason this development is alarming is that spores of the fungus travel by wind. From South Africa, they are positioned to ride new wind trajectories toward the Middle East and south Asia, making those areas even more vulnerable, Nature reported.

Fear about other countries

“It’s mutating and migrating,” Zacharias Pretorius, a wheat pathologist at the University of the Free State in Bloemfontein, South Africa, told Nature. “The concern is that other wheat-growing countries will become vulnerable to infection.”

Pretorius and his colleagues are to present their research this month at a conference in St Petersburg, Russia, organized by the Borlaug Global Rust Initiative. The initiative was founded by Norman Borlaug, the late University of Minnesota graduate whose fight against wheat stem rust led to his winning the 1970 Nobel Peace Prize.

I saw firsthand the devastation Ug99 can cause when I visited Kenya’s Rift Valley in 2008. African farmers led me to barren fields where the parasitic fungus had latched onto the stems of wheat plants and hijacked nutrients that should have fed the growth of grain.

Some Kenyan farmers sprayed fungicides, but lost a good share of their crops anyway. Those who couldn’t afford to spray lost everything. Small-scale farmers are most vulnerable.

Isolate new resistance genes

Over the years, crop scientists like Borlaug have bred into wheat some 50 different genes that help plants resist stem rust. Given the discoveries in South Africa, it now appears the fungus and its variants can overcome at least 32 of those genes Nature reported, quoting Ravi Singh, a plant geneticist and pathologist at the Mexico-based International Maize and Wheat Improvement Centre.

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The Cornell-led project is on track to isolate eight new resistance genes by years’ end, Nature reported.

Finding the genes is just the beginning, though.

Wheat around the world is an intricate mosaic of subtly different plants that farmers have localized over the centuries to meet conditions in their particular fields. Resistance will need to be bred into every local frame on the mosaic.

Further, it will need to be coupled with high yields and other traits farmers need to make their crops marketable and profitable. Plant breeders must shuffle more than 40 traits when they introduce something new in wheat, Brian Steffenson, one of the U of M researchers on the project, told me during an interview in Kenyan research fields.

Not the least of the challenges will be proving that these new genes truly do block Ug99’s amazing ability to knock down resistance by mutating and reinventing itself in persistent new forms.

Meanwhile, Ug99’s appearance in South Africa doesn’t help.