May 2, 2007

Wheat rust Ug99 unlikely to threaten India, China

 

Wheat growers in Asia and Africa are susceptible to the threat of wheat rust Ug99, a crop-damaging fungus, as most of the wheat varieties grown in these continents are not resistant to this pathogen, experts told Dow Jones Newswires.

But there is no immediate danger of major growers such as India or China facing the problem, as climate conditions in these countries are vastly different from those in regions where the fungus has spread so far, according to officials.

Earlier last month, the UN Food and Agriculture Organization, or FAO, said a new virulent fungus, called Ug99, has spread from East Africa to the Arabian peninsula.

The wheat stem rust, or Puccinia graminis, was recently detected in Yemen, the group said. Also known as black rust, the fungus is capable of causing severe yield loss and can destroy entire wheat fields.

The spores of wheat rust are usually carried by wind over long distances and across continents.

"The problem with this strain (Ug99) is that it is virulent to most of the resistance genes that are used in modern wheat varieties globally," said Wafa Khoury, a pathologist who works in the FAO team of international scientists dealing with Ug99.

"It is estimated that around 80 percent of all varieties planted in the developing world are susceptible to Ug99," added Khoury in an e-mail interview.

According to Richard Ward, a scientist working with the International Food Policy Research Institute, or IFPRI, it is likely Ug99 and its derivative pathogens will eventually migrate to most wheat growing areas of the world.

"Rust spores can be transported by air currents several thousand kilometres in a single event. More certain is a wavelike progression from one adjacent or nearby wheat crop to another," added Ward in an e-mail interview.

He said that while the arrival of Ug99 in an area does not indicate there will be an immediate epidemic, "it does enhance dramatically the chance that an epidemic or pandemic will occur. Losses from stem rust can be extraordinary within a given field or region."

FAO's Khoury said a panel of scientists observed in March 2007 that the risk of this pathogen spreading to two of Asia's largest wheat growing nations, India and China, are not very high at the moment, while the chances of the rust reaching Australia is also remote.

Ug99 first emerged in Uganda in 1999 and is therefore referred to as Ug99. It subsequently spread to Kenya and Ethiopia.

A recent FAO mission confirmed for the first time that Ug99 had infected wheat fields in Yemen. It appears the strain found in Yemen is already more virulent than the one found in East Africa, the group said.

Samples of the pathogen were sent to the US and Canada for further analysis. There is a high risk that the disease could also spread to Sudan, according to the FAO.

Government officials in India and China have discounted the possibility of an immediate spread of the virus, though officials in both countries say they are vigilant.

Scientists in India said that stem rust Ug99 does not pose any immediate danger to domestic farmlands especially because, for it to spread, it requires high temperatures at levels that do not prevail in India's wheat growing provinces during winter when the crop is grown.

"Ug99 may not reach India at all and even if it does, it will take seven to eight years. The temperature here will not suit its attack on the wheat crop," said S.S. Singh, Principal Scientist at the state-run Indian Agriculture Research Institute.

He added that in the new types of wheat that are being developed, India is already incorporating genes such as SR-24, which are resistant to Ug99.

Xue Liang, a spokesman of China's Ministry of Agriculture said, "Crop epidemics are restricted by regions and diseases that happen in other regions may not necessarily happen in China."

Xue said experts on the pathogen will pay attention to the issue, and China will inform the public if any such infestation occurs in the country.