Kenyans help world fight wheat pest

The Ug99, also referred to as black or brown rust, affects leaves and stems. It attacks wheat, barley, goat grass, oats and rye. It is characterised by small brown pustules that develop on leaf blades in a random distribution.

Infectious spores are transmitted via the soil.

Before the emergence of Ug99, chemical control by triazole fungicides was sufficient. The new strain is resistant to triazole.

Wheat scientists from East Africa visited Kenya to see first-hand the pathogen’s effects.

Dr Njau said research had found that Kingbird, a new variety of wheat, “can perform well in tests elsewhere where the disease has spread.”

Nakuru district in Kenya “is a hot-spot for the disease,” Njau said, adding: “Disease incidence was so intense this year that 85 per cent of the lines were susceptible, and many resistant lines showed 20 per cent greater infection than usual.”

New variants of the pathogen are appearing that overcome some of the most effective resistance genes in wheat,” he said in a newsletter.

But there is hope, too. “The experimental wheat variety Kingbird looked good under this year’s conditions and has performed well in tests elsewhere.”

Derived from International Centre for Maize and Wheat (CIMMYT) germplasm, Kingbird was being used by the centre to develop new varieties whose seed could be multiplied and distributed quickly to farmers in Ug99’s probable path of migration.

Dr Njau also identified an experimental wheat variety from CIMMYT’s international stem rust resistance screening nursery that out-yielded the best reference variety by 27 per cent and the average yield of varieties in the trial by 80 per cent.

In a new study released at the event, researchers from regional institutes described as a breakthrough their efforts to develop new varieties that are resistant to Ug99 and produce more grain than today’s most popular varieties.

Breeding materials in test fields in Ciudad Obregón and Toluca — and in Aleppo, Syria — are sent to Kenya and Ethiopia for exposure to Ug99 in real world conditions. They are then sent back to Mexico or Syria for further refinement and then back to Kenya and Ethiopia for more exposure.

Through this approach, scientists have produced new high-yield wheat varieties that contain “multiple minor genes” resistant to Ug99.

Although this strategy may not provide the same level of protection as that provided by one or two major genes, it is effective.

Researchers believe that by forcing the fungus to overcome a larger array of genetic barriers, the new wheat varieties could provide long-term protection against stem rust mutations.