The UN Food and Agriculture Organization is warning about a ?new and virulent fungus? that can attack many varieties of wheat. It already has spread from East Africa to Yemen.

The wheat stem fungus is known as black rust and it can destroy entire wheat fields. Peter Kenmore, chief of the FAO?s Plant Protection Service, says rust is one of the oldest wheat diseases.

?This particular strain comes from East Africa. If we look at the old records it may have been around in the 1990?s in fact. And it?s called Ug99 because the first official publication of it came from material that was from Uganda. In fact, Uganda and Kenya are the first countries that had it and then Ethiopia. It arrived in Yemen, as far as we can tell, sometime in the last six to nine months,? he says.

Kenmore says the strain of the fungus changes over time, and in this case has gotten worse.

?It evolves a little bit everywhere it goes. So that the very, very precise exact genetic fingerprint of what?s in Yemen is slightly different from what it is in East Africa. But it?s close enough to be called the same overall strain of Ug99,? he says

The FAO estimates that as much as ?80 percent of all wheat varieties planted in Africa and Asia are susceptible to this new strain.?

The FAO is working with two organizations to track the fungus -- ICARDA, the International Center for Agriculture Research in Dry Areas, and CIMMYT, the International Maize and Wheat Improvement Center. Kenmore says if it reaches Egypt, Ug99 could spread quickly.

?It hasn?t gotten to Egypt. People have looked in the field in the last month. There?s no evidence of it at this point in Egypt. But Egypt is a major wheat growing area in the Nile and that would be a real serious thing if it spread there. It would also be a jumping off point both to go into the Near East and up towards Turkey or west across North Africa,? he says

Winds, like those in the Rift Valley, can blow the fungus to new locations.

Kenmore says strategies to combat Ug99 include introducing wheat varieties with genes that are resistant to the disease and restricting times of the year when wheat is grown to cut the cycle of the fungus so it can?t multiply.

The chief of the FAO?s Plant Protection Service says introducing new wheat varieties does not mean using genetically modified crops.

?At this point, what we?re talking about is conventional breeding. Now the identification of where to find those genes may include tracking genetic markers. In other words, using molecular biology to track where the genes are, but the actual cross (breeding) is done by conventional (means). It?s not transgenic. It?s not GMOs. It?s normal wheat breeding as has been done with a fairly high level of sophistication and intensity for the last 60 to 70 years,? he says.

GMOs ?- or genetically modified organisms -- are plants or animals that have had their genetic make-up altered to exhibit characteristics they don?t normally have. Some countries have objected to their use.