A population of the stripe rust pathogen, even in a single field, may consist of more than one race (pathotype) which can be determined by reactions on a set of selected host varieties (differentials) with different resistance genes. Different races can infect different varieties with race-specific resistance. Information about races and their distribution and frequencies is important for select resistant varieties to grow and for developing new varieties with effective resistance. For information about differentials for identifying races of the wheat stripe rust pathogen, the barley stripe rust pathogen, and race data click on the categories on the left.