Wheat stripe rust is one of the most important wheat diseases and is caused by the plant-pathogenic fungi Puccinia striiformis f. sp. tritici (Pst). Though Pst is known to be highly host-specific, it is interestingly able to infect two unrelated host plants, wheat and barberry, at different spore stages. Pst infects wheat through its urediniospores and infects barberry with its basidiospores.