Wheat disease that gives experts food for thought

Tuesday December 5 2017

Scientists warn that stem rust could hamper food security efforts. FILE PHOTO | NMG

Scientists warn that stem rust could hamper food security efforts. FILE PHOTO | NMG 

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Over the last 10 years the greatest challenge facing wheat production in Kenya and globally has been getting varieties that are resistant to the deadly Ug99 strain of stem rust.

The remedy to this strain of stem rust remains elusive, giving local and international experts sleepless nights.

Scientists at an international training workshop to tackle rust diseases and the threat they pose to production, held at the Njoro Kenya Agricultural Livestock and Research Organisation (Karlo) Food Centre, Nakuru County, recently warned that this disease needs to be tamed to ensure global food security.

Wheat, according to food experts, is one of the top staple foods in the world. It is grown on more than 218,000,000 hectares, larger than for any other crop.

Many farmers in the wheat growing countries in Africa suffer massive losses annually as their crops are devastated by stem rust. This makes Kenya and the region to be net importers of the crop.

According to the researchers and breeders some of the latest varieties of the crop have too succumbed to the Ug99 disease as the ailment keeps mutating as it tries to survive in different environments.

Dr Ruth Wanyera, Karlo principal research scientist and plant pathologist at the Njoro Food Crop Centre,  says Ug99 is a strain of stem rust that attacks a gene in the wheat variety that is grown globally.

She says the emerging strain of Ug99 may pose a big disaster in the wheat producing countries if no global action is taken.

Dr Wanyera notes that in Kenya about five strains of the disease which keeps on mutating were detected in 2013 while 13 African countries are battling to reduce the spread of the affliction.

“The only medicine for stem rust disease is use of resistant varieties,” said Dr Wanyera.

At the same time she said that farmers should be given subsidy to avoid the spread of the disease as they wait for “resistant varieties”.

“One of the biggest challenges facing wheat farmers in Kenya is that they don’t enjoy subsidy like their counterparts in Europe and other developed countries who can afford to skip planting the crop as they wait for resistant varieties,” said Dr Wanyera.

She said while farmers could use fungicides to control the disease, this is not highly recommended as some of the chemicals are not environment-friendly.

“Use of fungicide is a short-term measure because it ends up reducing the spread of the disease but not eliminating it,” she said.

Dr Godwin Macharia, a top breeder at Karlo and wheat researcher, says that 1.5 million tonnes of wheat might be required in Kenya by 2020 due to ballooning population and the ravaging disease.

“We must overcome the key wheat production challenges because the population boom is increasing by the day,” said Dr Macharia.

Besides diseases, he notes that some of the challenges in wheat production in Kenya include pests such as Russian wheat aphids, drought, soil acidity, depleted soils and pre-harvest sprouting.

Professor Robert MacIntosh from the University of Sydney in Australia says the buildup of Ug99 is due to increase of use of susceptible varieties by farmers.

“This has seen the disease spread to other farms across the globe and this has seen the races change and complicate the fight against the rust diseases,” said Prof MacIntosh who is a leading breeder and researcher in the world.

Prof MacIntosh admits that Ug99 is a global threat as it never sleeps and attacks a specific gene that is used in most parts of the world to develop new wheat varieties.