Foliar rust fungi cause a major disease of poplar species
worldwide. In northwestern North America, Melampsora
medusae, M. occidentalis, and their hybrid
M. x columbiana occur naturally on
Populus spp. in sections Aigeiros and
Tacamahaca. The hybrid M. x columbiana
has a broader host range than either parent, and as a result poses
a threat to poplar production.
Like all rust pathogens, M. x columbiana is an
obligate biotroph with a complex life history. The pathogen is
heteroecious, with five spore states. Populus spp. are the
telial hosts; Pseudotsuga menziesii, or Douglas-fir, is
the principal, aecial host (other, alternate hosts may also
exist).
Reference:
Newcombe G, Stirling B, McDonald S and HD Bradshaw. 2000.
Melampsora x columbiana, a natural hybrid of
M. medusae and M. occidentalis. Mycological
Research 104(3): 261-274.
