Genes in wheat relatives help stave off stem rust

Wild and obscure species provide resistance to deadly fungus

A scrappy, ancient species of wheat may help today’s widely cultivated bread wheat fight the devastating fungus known as stem rust (shown growing on wheat stems).

The fungal infection called stem rust (shown growing on wheat plants) devastates wheat crops. A new study has identified genes that may help the plants defend against the infection. Courtesy of Evans Lagudah and Zakkie Pretorius

A gene isolated from one of the earliest cultivated wheat species, Einkorn wheat (Triticum monococcum), confers resistance to a deadly version of stem rust, scientists report June 27 in Science. A second gene found in the wild grass Aegilops tauschii, a botanical parent of today’s bread wheat (T. aestivum), also helps bread wheat fight the fungus, another research team reports. 

Both genes are thought to help wheat recognize an invader and kick-start the plant’s defenses. After mapping the whereabouts of the resistance genes in the bread-wheat relatives’ genomes, the research teams inserted copies of the genes, called Sr35 and Sr33, into bread wheat. Exposing the plants to stem rust revealed new resistance, even to the deadly Ug99 strain of the fungus.

Stem rust, which spreads via wind-borne spores, can quickly turn a healthy crop into a decrepit mess of broken stems and shriveled grains. Scientists hope to breed several resistance genes into cultivated varieties, minimizing the odds that the fungus can mutate and overcome the wheat’s resistance.

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