New wheat varieties resist deadly fungus, boost yields in Kenya

By Isaiah Esipisu

NJORO, Kenya (Thomson Reuters Foundation) - After counting their losses for over a decade, wheat farmers in East Africa are looking forw
ard to a brighter future now that new varieties developed by scientists have proven to be resistant to a devastating wheat disease, and are boosting yields into the bargain.

Known as Ug99, the fungal stem-rust disease thrives in warmer temperatures, and the spores can travel thousands of miles aided by wind, according to Peter Njau, a research scientist at the Kenya Agricultural Research Institute (KARI).


As the name suggests, Ug99 was discovered in Uganda in the year 1999. It has since spread through Kenya to Ethiopia, Sudan and Egypt, and across the Red Sea to Yemen and Iran, causing havoc for farmers along the way. There are fears the disease could reach India and other major wheat-producing countries in Asia.

Stem rust has been around in different forms since Roman times, and in the early part of the 20^th century, it repeatedly destroyed more than 20 percent of the U.S. wheat harvest.

By the 1970s, it was apparently extinct. But over the decades, the fungus that causes stem rust evolved a way around the single resistant gene that was protecting modern varieties, resulting in Ug99. When tested, up to 80 percent of the world’s wheat was found to be susceptible.

Virginia Gitau, a district agricultural officer in Njoro in western Kenya, told Thomson Reuters Foundation that before the first two stem rust-resistant wheat varieties were released two years ago, many farmers had abandoned the crop.

“This disease is a real threat to food security in Kenya and the entire region,” she said. “Coupled with shifting climatic conditions, such emerging diseases can be real challenges to livelihoods.”

DEMAND RISING
Wheat is an important cereal in Africa, and demand is growing faster than for any other food crop.

According to the International Maize and Wheat Improvement Center (CIMMYT), the continent produces between 20 million and 25 million tonnes of wheat annually. But in 2010 - the latest year for which data is available - African countries imported around 38 million tonnes of wheat to help meet demand.

Antony Kimani is one farmer who suffered losses after his wheat fields were infected by the stem-rust disease.

“When it attacked my field three years ago, I actually thought that the leaves were drying up because the crop was nearing maturity. I almost collapsed during harvest time when I found out that there were no kernels in the heads,” said the 32-year-old farmer from Njoro, in Kenya’s Rift Valley region.

The young farmer lost all the wheat he had planted on a 50-acre leased plot, and harvested an average of just six 90 kilogramme bags per acre from his remaining 100 acres. In normal conditions, the Kwale variety he had planted yields up to 17 bags per acre.

Geoffrey Kurgat, another farmer from the same area, lost almost 90 percent of his crop on a 30-acre piece of land in 2010. Both men have now turned to the new stem rust-resistant wheat varieties, which have also proven to be higher yielding than the existing vulnerable varieties.

KEEPING UP WITH MUTATIONS
Scientists say Ug99 is the most virulent pathogen in the history of stem rust. When it attacks, the fungus absorbs nutrients that would otherwise be used for grain development. The disease also interferes with the plant’s vascular tissue, leading to shrivelled grains, said Sridhar Bhavani, a CIMMYT wheat pathologist and breeder who coordinates nurseries set up to screen stem rust in East Africa.

The disease has the capacity to turn a healthy-looking crop, only weeks from harvest, into nothing. Losses due to the fungus have been recorded at between 70 and 100 percent.

Since 2006, CIMMYT scientists, with technical support from KARI, have been testing and crossbreeding thousands of wheat varieties sourced from all over the world to identify particular varieties that are resistant to Ug99. The research is funded by the Bill and Melinda Gates Foundation, Britain’s Department for International Development (DFID) and USAID.

Bhavani said the CIMMYT-KARI collaboration has led to the development of eight wheat varieties that are resistant to the stem-rust disease and are also very high-yielding.

But he was quick to warn that the disease keeps on mutating. “As the Nobel Peace Laureate (and CIMMYT founder) Dr. Norman Borlaug puts it, the stem rust does not sleep - hence scientists must keep on observing it as they develop new strategies,” Bhavani said.

The re-emergence of stem rust in the late 1990s has not been linked to climate change, but it does favour higher temperatures.

So far, two of the Ug99-resistant wheat varieties - “Robin” and “Eagle10” - have been released and have become popular with the farmers. The remaining six are still undergoing seed multiplication before being made available to farmers.

HIGH DEMAND
Those who have used the two new varieties seem to appreciate the larger harvests more than the disease-resistance aspect for which they were bred.

“I have never seen such a high-yielding variety since I started wheat farming 20 years ago,” said Oliver Nightingale, a large-scale farmer from a family that has been growing wheat and barley in Kenya for the past 107 years under the name Sasumua Agriculture Ltd.

For the first time in his farming life, Nightingale said he was able to harvest up to 33 bags of wheat per acre last season, after planting the new variety dubbed “Kenya Robin”. The preferred variety in the area - which is susceptible to stem rust – yields less, at up to 25 bags per acre.

“Seed demand for the stem rust-resistant varieties is very high at the moment,” said KARI’s Njau.
In response, the government is growing the new varieties for seed multiplication on 53 acres of land belonging to farmers’ groups in Nakuru County, under the East Africa Agricultural Productivity Programme backed by the World Bank.

In addition, KARI expects to harvest 600 metric tonnes of seed to be supplied to farmers come next season.