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Tremendous diversity of willows
(Salix species) occurs in North America. From the northern
limit of bare soils in the high Canadian Arctic to the humid tropics
of Mexico (and even far into South America). These willows are infected
by biotrophic rust fungi in the genus Melampsora. Despite
significant differences in hosts, geography and life cycles, current
taxonomy combines all willow rusts in North America into one species,
Melampsora epitea.
Our lab is currently using molecular and morphological
traits to compare Arctic and temperate collections of Melampsora
rust from willows. Arctic willow is an extremely important species
in the Arctic ecosystem and currently there is very limited information
about this serious rust disease.
On two field events to the high Canadian Arctic
(Cornwallis Island, Ellesmere Island and Beechey Island, Nunavut,
Canada) our team has made observations and collections of Salix
arctica infected with Melampsora rust. During these
trips we discovered several unique characteristics of Arctic willow
rust such as infection of floral tissue (catkins) and systemic infection
of stems and both leaf surfaces. Samples
collected in the Arctic are being compared to collections of rust
on willow in Minnesota and other temperate areas using molecular
and morphological methods. Molecular (ITS rDNA sequences) and morphological
characteristics of spores from Arctic and temperate samples suggests
that significant speciation and diversity has occurred among willow
rusts in North America.
For more information on willow rust in the Arctic
see our recent publication: Mycologia
96 1330-1338.
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Arctic willow among other plants of Baffin
Island tundra showing fall color |
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