Puccinia hordei is a species of rust fungus. A plant pathogen, it can cause leaf rust of barley, also known as brown rust of barley. It was originally found on the dry leaves of Hordeum vulgare in Germany.
At the time of Johnston et al., 2013's discovery of severe susceptibility in Golden Promise, this was considered to be the most susceptible variety in the world. Soon thereafter however, Yeo et al., 2014 found SusPtrit was slightly worse. These results alter the meaning of such a basic term as "fully susceptible" to brown rust.
In 2007 several resistance genes for this pathogen including receptor-like kinase (RLK), ', s, peroxidases, superoxide dismutase and thaumatin were found in barley.