The Hindu Business Line : Wheat plague: South Asia still faces risk

Thiruvananthapuram, March 24 Leading wheat experts have reported significant progress in developing new varieties of wheat capable of resisting a virulent form of an old plant disease that threatens wheat production worldwide.

Every region of the world was represented at an international workshop held recently in Mexico where the findings were made public. The Indian Council of Agricultural Research was among the leading research institutions in attendance.

But research released at the Borlaug Global Rust Initiative 2009 Technical Workshop also confirmed that the dangerous and newly-emerged stem rust race known as Ug99 is now in Kenya, Uganda, Ethiopia, Sudan, Yemen and Iran, and is on the march toward South Asia.

Not ruled out

According to scientists, longer distance movement to other regions cannot be ruled out. They estimate that 90 per cent of the varieties planted in farmers’ fields around the world lack resistance to the pathogen.

Named for its discovery in Uganda 10 years ago, Ug99 is well established already in Kenya, where in some areas the reddish, wind-borne fungus has decimated 80 per cent of the wheat in farmers’ fields.

“We should keep a close eye on any movements into southern Africa as well, because there is historical evidence that high altitude winds and even hurricanes can transport plant pathogens from that region into the Americas and Australia, although these would be rare events,” said Dr David Hodson, a Geographic Information Systems expert.

Meanwhile, researchers from CIMMYT of Spain, the Kenya Agricultural Research Institute and the Ethiopian Institute for Agricultural Research described a breakthrough in their efforts to develop new varieties of wheat that are not only resistant to Ug99, but also produce more grain than today’s most popular varieties.

New varieties

Dr Ravi Singh, a CIMMYT wheat geneticist and pathologist and lead author of the study, said high-yielding, Ug99-resistant spring wheat varieties were rapidly emerging through an intensive international “shuttle breeding programme.”

Breeding materials under development in CIMMYT’s test fields are sent to Kenya and Ethiopia, where they are exposed 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 types of high-yield wheat that contain what plant breeders call “multiple minor genes” that have resistance to Ug99.

Though this strategy may not provide the same level of protection as that provided by one or two major genes, it is high enough to be effective, and the researchers believe that by forcing the fungus to overcome a larger array of genetic barriers, these new wheat varieties could provide long-term protection against future stem rust mutations.

A significant achievement with the varieties produced in the project is that they provide superior yields. This is of major importance, as the battle against Ug99 appears to be shifting from a scientific challenge to a logistical one.

Averting a crisis will require farmers to replace their existing varieties with resistant ones, even though they may not face an immediate threat from Ug99. But convincing the farmers to switch requires offering resistant varieties that also produce higher yields.