Scientists have identified four new strains of a wheat-killing fungus that could endanger the global food supply, according to research presented before a conference in Russia.

The mutant strains of the fungus, called Ug99, originated in Africa but are likely to spread into Asia and beyond, said the Borlaug Global Rust Initiative, a US-based advocacy group focusing on wheat contagions.

"The new mutations - identified last year in South Africa - will make wheat crops more vulnerable as pathogens now will find new wind trajectories for migration," BGRI said in a statement announcing the new research.

The study identifying the mutations was done at the University of the Free State, South Africa, and is to be presented at the Eighth International Wheat Conference being held in the Russian city of St Petersburg this week.

Ug99, a variant of the deadly wheat affliction commonly known as stem rust, is a reddish-brown, wind-borne fungus that causes plants to fall over and can wipe out an entire harvest.

It emerged in East Africa a decade ago and has since spread as far as Yemen and Iran, leading scientists to scramble to develop new, Ug99-resistant breeds of wheat, BGRI said.

The new strains of the fungus are a "grave challenge", David Hodson, a wheat expert at the Food and Agriculture Organisation of the United Nations, was quoted as saying in the statement.

Scientists cited by BGRI said the fungus posed a serious risk to the densely populated and impoverished countries of South Asia, and in the longer term could reach Australia and North America.

Ug99 "threatens to spread into other wheat-producing regions of Africa and Asia, and potentially, the entire world," said Arun Kumar Joshi, a scientist with the Mexico-based International Maize and Wheat Improvement Centre.