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Bioscience Issues

Something is killing my wheat

Sharon Schmickle award-winning MinnPost writer

Njoro, Kenya,

When it comes to suspenseful global adventure, Hollywood’s Indiana Jones had nothing over crop scientists who are fighting a wheat-killing fungus in Africa.

While Indy combed the planet for archeological treasures, the scientists have searched worldwide for genes that could empower wheat plants to resist the fungus. The search has taken them from ancient stands of wild barley in Israel to farms on the slopes of the Swiss Alps to a rural research station in Kenya’s Rift Valley.

The quest started in southwest Uganda where William Wagoire, a crop scientist, watched helplessly while the dreaded fungus called stem rust killed his test plot of wheat.

How could this be possible? The planet had not seen a major stem rust epidemic since the middle of the 20th Century. Then, crop scientists bred new resistance into wheat, adding genes that have stood up to rust for decades and thus helped filled breadbaskets around the world.

Wagoire shot off an email to a world-class expert, Ravi Singh, a wheat pathologist who directs rust resistance research at the International Maize Wheat Improvement Center (CIMMYT) in Mexico.

Singh could not believe what he saw: Plants that were bred to resist stem rust had succumbed to the fungal parasite.

“It was shocking,” Singh said. “We had never seen such susceptibility. . . . The first thing you think is that it probably is not true.”

New twist in a biological churn

It was true, unfortunately.

Further tests at cereal disease laboratories in South Africa showed why the resistance had failed. In the biological churn that constantly endows old pests with new genetic combinations, stem rust had acquired a frightening ability to punch through the resistance that had guarded wheat for decades.

The name given to this new menace was UG99 for its discovery in Uganda in 1999. In retrospect, scientists say it probably started earlier in Kenya where wheat is a more important crop.

Since then, the virulent new version of an ancient scourge has ravished wheat, across Kenya and jumped to other countries to threaten the stability of the world’s second largest crop.

Coming on the heels of tight grain supplies and food riots, the budding rust epidemic was a startling reminder of the fragility of food-supply systems in many countries. It pointed to a future when an ever larger global population is increasingly vulnerable to the pathogens that inevitably surface somewhere on Earth.

More crucial on a local level, it threatened to push hundreds of millions of families over the hunger line.

Biblical times and earlier

CIMMYT hastened to publish a warning of “a pending disaster in global agriculture.”

The alarmist language was in keeping with the dark history of the disease. Stem rust has robbed farmers of their harvests since the Bronze Age.

The ancient Greeks implored a special Apollo to guard their fields from it long before the Romans sacrificed red-blooded animals in spring-time rituals to win similar protection from Robigus.

“This is the disease that caused the great plagues of biblical times,” said Ronnie Coffman, an international professor of plant breeding at Cornell University in the United States.

Jumping forward to 1916, a stem rust epidemic in the American Midwest set off worries that there would not be enough grain to feed Allied troops fighting World War I.

Most recently, an outbreak in the 1950s slashed yields throughout North America’s Great Plains.

Menace rides the wind

The global nature of CIMMYT’s alarm was warranted because stem rust spores are notorious for their ability to hitch rides – on the wind, clothing and other transport – and travel for hundreds, even thousands, of miles.

They “could provoke epidemics such as farmers have not encountered in many decades,” CIMMYT warned.

In the case of the UG99 that emerged in Kenya and Uganda, the spores took to the wind and hit Ethiopia. In 2006, they jumped the Red Sea to Yemen. They were confirmed in Iran in 2007, South Africa in 2010 and Tanzania in 2011.

Scientists estimate that 80 percent of Asian and African wheat varieties are susceptible. So is barley.

The Food and Agriculture Organization of the United Nations warned Afghanistan, India, Pakistan, Turkmenistan, Uzbekistan and Kazakhstan to be on high alert for the disease. In India alone, more than 50 million farmers were at risk because they rely on wheat for their food and income.

Worldwide, wheat is a major source of calories and nutrition. In developing countries it is second only to rice as a food staple.

“It can take everything.”

This outbreak should not be confused with other, more common rust infestations. In its various forms, rust reduces yields somewhere on Earth every year. Stem rust stands out from the others because it can topple a whole field in a hurry.

“It can take everything,” said Robert McIntosh, former director of Australia’s rust control program.

“It is the most damaging of the rusts,” McIntosh said. “I call it the father of all rusts.”

Farmers with sufficient resources can spray fungicides to salvage at least some of their crops. That’s what Geoff and Luke Nightingale – a father-son team farming in Kenya – did when UG99 hit their 1,350 acres of wheat.

“It went down fast . . . it hit every single variety,” Luke said. “We sprayed twice in three weeks, once by tractor and once by plane.”

Still, Geoff called the yields “terrible, awful.” High wheat prices filled some of the void, but they estimate they lost 2 percent of their profit.

Another worry is for small-scale farmers like Joseph Otrono.

Their success is fragile in the best of years. The route to Otrono’s farm shows why. You bump along a washboard of a road until it fades into a rutted trail where puddles from the October rains swell into wheel-grabbing mud pits. You walk the last quarter of a mile.

Because they lack adequate roads and vehicles to carry crops to market, Otrono and his neighbours must sell to grain brokers who buy in the field. There is no chance to bargain for a better price.

A lack of access to operating capital is another obstacle.

Otrono had spent a good share of his 35 years working for others and saving for the day when he could break into farming on his own. He saw his chance in 2008 when wheat prices skyrocketed because supplies were tight. Wheat typically thrives in Kenya’s fertile Rift Valley where contours of green hills mark the horizon until it fades into a distant haze.

So Otrono rented two acres of land, bought seed and planted his family’s dreams along with the crop.

The seeds worked their magic, and the field was a classic display in the dazzling green of young grass.

“When I looked at it, I felt so good,” Otrono said.

Three of his four sons would be going to school in the fall, and there would be money for clothes and shoes as well as for expanding the planting next year.

What Otrono couldn’t see at that happy time was the parasitic fungus that was latching onto the stems of his plants. It hijacked the nutrients that should have fed the growth of grain in each plant’s spike. And it coated the stems and leaves in powdery, rust-colored blisters and bands.

Otrono couldn’t afford enough fungicide to knock out the rust, so it ran unrestrained through his field, leaving a pathetic tangle of broken stems topped by empty hulls where grain should have formed.

Otrono had no choice but to chop down the barren stalks in hopes of selling them for forage and using the cash to plant beans and potatoes his family could eat in a few months.

In all, Otrono estimates he lost 25,000 Kenyan Shillings (about $337 U.S.) plus his labor for six months.

“Now I have nothing,” he said.

His only reserve was a few scrawny chickens pecking at the dirt outside his family’s mud-and-stick house. He was selling hens one by one to keep beans in the pot his wife, Sally Rono, stewed over a wood fire.

“I keep asking myself what I will do when the hens are gone,” Otrono said. “Where will I get the income to feed my family?”

The story was the same that year all along the ridge where Otrono farms.

Ground Zero in Kenya

Like firefighters responding to a major alarm, wheat experts from around the world have mobilized to fight the rust. Ground Zero for their battle is the Kenya Agricultural Research Institute’s station near Njoro.

The late Norman Borlaug, a Nobel Laureate, was among the big-name crop scientists who came to examine the evidence first-hand. Borlaug was credited with breeding the so-called Green Revolution wheat which resisted stem rust and helped save millions from hunger.

Kenyan crop scientists took Borlaug to nearby Mount Narok where farmers from the Maasai tribe were losing a good share of their yields to stem rust.

“He got very scared by what he saw,” said Peter Njau, a wheat breeder who is deputy director of the Njoro research station.

Only a few living scientists have had first-hand experience with a major stem rust epidemic. For that matter, only a few farmers recognized the first signs of the rust and understood its devastating potential. It was their grandfathers’ scourge, something they had heard about but never witnessed.

Borlaug needed no history lesson. He threw his considerable clout into recruiting top-notch scientists from the world’s major wheat producing countries and raising funds to underwrite their work.

Major foundations in the United States and Japan pitched in to help Njau and his team in Kenya, as did governments in Canada, India and the United States. The Bill and Melinda Gates Foundation awarded $26.8 million to a consortium of universities led by Cornell.

A key step in their strategy was to comb through wheat varieties grown around the world. Any that proved resistant could provide the genetic ammunition to beat back the rust.

“People started sending plant material from all over the world,” Njau said.

And scientists from around the world gathered in Njoro at harvest time each autumn to assess the results in research plots that represented a veritable United Nations of wheat and barley. Njau and his research crew had planted seeds the scientists had sent from dozens of countries and then deliberately exposed the plants to UG99.

High stakes showdown

It was the set up for a high-stakes showdown between UG99 and the world’s toughest varieties of grain.

During the first few years, UG99 gave the grain a beating.

Brian Steffenson, a plant pathologist from the University of Minnesota in the United States, found some promising resistance in barley he had obtained from a high alpine area in Switzerland. But that was only one step toward delivering resistant wheat to farmers who are threatened by UG99.

“Starting to identify resistance in plants we test here is the very, very beginning of a process that can take 10 to 12 years,” Steffenson said.

Wheat is amazingly complex. Its genome is five times the size of the human genome and 40 times that of rice. Further, farmers have localized it over the centuries selecting and cultivating plants that thrive in their particular fields.

Seeds that Steffenson gathered from a gene bank in Geneva, Switzerland, would almost surely be misfits here at the equator. So the solution to the UG99 problem was not as simple as identifying a resistant variety, growing masses of the seeds and sending them to farmers.

Farmers also need optimum yields and resistance to other pests as well as tolerance for drought in dry areas and moisture where it’s wet. Some farmers specialize in wheat that will make the crustiest of French breads. Others serve cravings around the world for tender pastas, crunchy cereals or sprinkles of bulgur on salads.

Plant breeders must shuffle more than 40 characteristics when they introduce something new in wheat, Steffenson said. The process involves cross breeding plants through several generations.

Recently, farmers and scientists have developed tricks for speeding up that breeding process. For example, they now have DNA signposts to mark genes they want to breed into a plant. Rather than wait a full growing season to see if a certain characteristic was carried into the next generation, they can look for the signposts and determine in a hurry whether cross breeding was successful.

Pyramids of resistance

In the case of UG99, wheat breeders couldn’t stop with the resistance they found in a single plant. There was too much risk this potent pest would break it down. Instead, they hoped to build a pyramid of resistance drawn from the genes of several different plants.

Working painstakingly, the scientists identified a few promising plants, so that by 2011, resistant varieties were released or registered for release in Kenya, Ethiopia and six other countries.

Once resistant wheat has proven itself in the field, the seeds must be multiplied to a scale where they can be ready for wide-scale distribution to farmers. It’s a process that could take at least until 2016.


Additional information:

The Borlaug Global Rust Initiative provides up-to-date and in-depth reports

The International Maize and Wheat Improvement Center has developed a Rust Mapper to help trace the spread of UG99

The Food and Agricultural Organization of the United Nations monitors wheat rust country by country