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Wheat-killing fungus set to sweep the fertile crescent and beyond

Rust fungus threatens to push food prices even higher

A deadly fungus is spreading in the Middle East. Although the fungus is not lethal to man, from a human perspective it attacks the next worst thing: wheat. The fungus, called Ug99, first surfaced in Uganda in 1999, and sparked international apprehension by wiping out entire fields within weeks. Since then, it has spread northward, and evolved to infect wheat varieties that were resistant only a few years ago.

This does not bode well for Asia. On March 27, a UN commission pronounced that, in Asia, “rapidly rising food prices will be the key challenge in the coming year.” Rising food prices are due in part to the biofuel boom and low crop yields. These high prices could skyrocket if the fungus gets out of control – a frightening but conceivable outcome, given that, according to the United Nations Food and Agricultural Organization, “up to 80 per cent of all Asian and African wheat varieties are susceptible to the fungus.” The result would be widespread famine.

But Asia is not the only region under threat. The fungus can’t be quarantined because its spores can be carried by wind and clouds between countries, and between continents. If major exporters of wheat, such as the U.S. and Canada, are affected by the fungus, the price of wheat will rise dramatically.

The danger has mobilized researchers around the world, including Dr. Kushalappa, a McGill professor in the Plant Science Department. The fungus – called a “rust” fungus, after its ochre color – attacks the stalk of the plant, and “inhibits food uptake,” he explains. “The plant starves to death.” Although farmers have grown numerous varieties of rust-resistant wheat, the fungus continues to evolve through hybridizations and mutations. The fungus’ flexibility means that plants in North America are vulnerable. Dr. Kushalappa explains that were the fungus to reach Canada, it would need to travel northwards through Mexico and the U.S., “where it can survive all year round.”

The main strain of wheat grown in Canada is especially susceptible because it only has a single disease resistance gene. Why have only one resistance gene? Because the more energy the plant spends defending itself, the less energy it puts into growth – and the lower the yield during harvest. The downside of trading off resistance for growth is that, when a new pathogen appears, it only has to undergo a few small mutations to be able to infect the plant.

Dr. Kushalappa’s lab is working on finding chemical compounds produced by wheat to resist infection. According to him, his lab is “the first to apply Metabolomics technology,” which tries to “identify and quantify of all metabolites in a biological system.” A metabolite is any small molecule produced or used by a living thing; organisms contain thousands of different metabolites, and use them for many different purposes. Buried in the haystack of wheat’s metabolites are chemical needles that are lethal to rust fungus. Dr. Kushalappa’s lab has already found some compounds in wheat which combat another fungus infection, and his sights are now set on compounds which fight the rust fungus specifically. Once he finds them, the next step will be to breed wheat that uses its natural defenses more effectively. Until then, farmers will have to rely on fungicides – and the global community should hope the fungus doesn’t spread.