Aecial and Telial Host Specificity of var. , a Eurasian Crown Rust Fungus of Two Highly Invasive Wetland Species in North America.

The Eurasian crown rust fungus var. () was recently reported in North America and is widespread across the Midwest and Northeast United States. is a close relative of major pathogens of oats, barley, and turfgrasses. It infects two highly invasive wetland plants, glossy buckthorn () and reed canarygrass (), and could be useful as an augmentative biological control agent. We conducted large greenhouse trials to assess the host specificity of and determine any threat to cultivated cereals, turfgrasses, or native North American species. A total of 1,830 accessions of cereal crop species and 783 accessions of 110 other gramineous species were evaluated. Young plants were first inoculated with a composite uredinial inoculum derived from aecia. Accessions showing sporulation were further tested with pure urediniospore isolates. Sixteen potential aecial hosts in the families Rhamnaceae and Elaeagnaceae were tested for susceptibility through inoculation with germinating teliospores. Thirteen grass species within five genera in the tribe Poeae (, , , , and ) and four species in Rhamnaceae (, , , and ) were found to be susceptible to , with some species native to North America. All assessed crop species and turfgrasses were resistant. Limited sporulation, however, was observed on some resistant species within Poeae and four other tribes: Brachypodieae, Bromeae, Meliceae, and Triticeae. Among these species are oats, barley, and , suggesting the possible use of in studies of nonhost resistance.