Rust never sleeps

– Recognizing patterns in the vast river of data that passes us by each day is one way to see the future.  But, unfortunately, our attention span is generally too short and we’ve not trained ourselves to be observant in this way,

– You may have seen a story like this a year or two ago and noted it and forgotten it.  It’s easily done.

– When I searched this, my own, site for “wheat rust“, I was surprised how many stories I’d already reported on this subject.

– It’s a bit scary how much passes us unseen in the river.  But I believe most of our futures are there if we just look….

– – – – – – – – – – – – – – – – – – – – – – –

A new flare-up in an age-old battle between wheat and a fungal killer

Scientists everywhere have taken up arms against the rust. Tens of thousands of wheat varieties and wild relatives have been screened for anti-rust genes that can be incorporated into future arsenals. This spring, more than 500 researchers from 77 wheat-growing nations gathered for two major wheat conferences in St. Petersburg, Russia, to share strategies and discuss progress on various fronts. And in August, a team of British scientists released a very rough sketch of wheat’s genetic blueprint, which in a more complete form could simplify and speed up the breeding of rust-resistant varieties.

“There is a lot happening,” says wheat geneticist Jorge Dubcovsky of the University of California, Davis. “We are trying to develop better technologies, better breeding approaches.… I think at some point we will defeat the bastard.”

But scientists also lament a lack of funding, coordinated action and basic knowledge about wheat and its pathogens. A great deal more effort is needed to turn the first crack at wheat’s genome into information that’s meaningful for fighting the rust.

Worldwide, only a handful of labs do hard-core rust-related research, and many will accept samples of the fungus only during the winter months, when it’s too cold for potential escapees to survive. The rust is so feared that some trigger-happy researchers frantically deploy plants bred with single resistance genes — even though most scientists agree that a well-constructed genetic cocktail offers the best hope for staving rust off.

Rust’s reemergence

Wheat rust’s current rampage began more than a decade ago. In October of 1998, a plant breeder noticed a stem rust infection on wheat growing in his nursery at Kalengyere Research Station in Uganda. The discovery was perplexing because the wheat contained a gene called Sr31, which, along with a handful of others, had provided protection against the rust for more than a quarter century. A rust virulent enough to defeat Sr31 triggered alarm in the wheat community.

“Should the Sr31-virulent pathotype migrate out of Uganda, it poses a major threat to wheat production in countries where the leading cultivars have resistance based on this gene,” scientists from Africa and CIMMYT, the International Maize and Wheat Improvement Center in Mexico, wrote in Plant Disease in 2000.


SPREAD OF A KILLERStem rust strains that can overcome key resistance genes have recently spread across Africa and beyond. Some scientists worry that prevailing winds may soon carry spores to major wheat-growing areas of the Middle East and Asia.Redmal/iStockphoto, adapted by E. Feliciano

Those fears have since been realized. This extremely aggressive strain of the fungus, called Ug99 (for the place of discovery and the year that the samples were analyzed), spread to most of the wheat-growing areas of Kenya and Ethiopia by 2003. The fungus’ spores, easily windborne, reached Sudan in 2006. Ug99 then crossed the Red Sea into Yemen, the doorway to major wheat-growing areas in the Middle East and southwest Asia. Ug99 has now been sighted in Iran. And not only is the rust still on the move, but it is also mutating: Within the Ug99 lineage, scientists have identified seven variants that can overcome additional important resistance genes in wheat. One Ug99 variant that overpowers Sr31 and the gene Sr24 caused epidemics in Kenya’s crops in 2007. Another Ug99 relative has turned up in Ethiopia and South Africa, and Kenya reported in June rust infestations in 80 percent of inspected fields.

Ug99 has yet to rear its ugly spores in the Americas. But that doesn’t mean U.S. wheat farmers are rust- or worry-free. In North America, Australia and Europe, as well as in Asia and Africa, a sibling of stem rust — the stripe or yellow rust — is taking a toll. In 2003, yellow rust wiped out a quarter of California’s wheat crop. Last year, it devastated crops in China. This year, farmers in the United States, the Middle East and northern Africa have already reported serious yellow rust infestations.

“The presence of two virulent and highly aggressive yellow rust strains … at high frequencies at epidemic sites on five continents (including Europe) may represent the most rapid and expansive spread ever of an important crop pathogen,” researchers from Aarhus University in Denmark wrote in an editorial in the July 23Science.

– More…

Comments are closed.