Wheat stem rust, a previously well-controlled disease, has reemerged as a major threat to wheat, with major outbreaks in Africa, Europe, and central Asia. The stem rust resistance gene Sr22 encodes a nucleotide-binding and leucine-rich repeat receptor, which confers resistance to the highly virulent African stem rust isolate, Ug99. Hatta et al. show that the Sr22 gene is conserved among grasses in the Triticeae and Poeae lineages.​