Compiled by Ian Thompson, Purdue University
Phakopsora pachyrhizi may infect several
legume hosts in the Midwest and its host range overlaps with other
rust species. The overlapping host range raises the possibility
of misidentification. This table resents information and
images that can be used to differentiate P. pachyrhizi from
other rust species that occur on leguminous hosts in the region.
Unless otherwise noted below, all pictures are courtesy of Ian
Thompson, Purdue University.
Click on image to enlarge
|
Uromyces sp.1,2 |
|
Hosts |
Uromyces spp.
and P. pachyrhizi share many of the same hosts including Phaseolus spp.
(beans), Pisum sp. (Pea), Trifolium spp.
(clover), Vicia spp (Vetch)., Desmodium spp.
(tick trefoil), Lespedeza spp. (lespedeza) |
Sori |
Cinnamon or rust
colored, darker brown or black late in season. Spores
erumpent and emerging through the epidermis. May be
present on both surfaces of leaves (amphigenous sori)
|
Brown. Spores
emerging through a small pore or covered by epidermis. Present
only on underside of leaves.
Image by R. Balardin |
Paraphyses |
Most Uromyces spp.
lack paraphyses. When paraphyses are present they will
lack distinctly thickened apex. |
Paraphyses present
at the margin of sori. Paraphyses are 5-13 mm wide
and distinctly thickened at the apex .
Image by USDA-SBML |
Urediniospores |
Generally obovoid
or ellipsoid, pigmented, golden to cinnamon brown. Walls
generally thicker (1.5 – 2.5 µm) than P. pachyrhizi.
|
More pear-shaped,
lightly pigmented or lacking pigment. Walls generally
thinner (1-1.5 µm) than Uromyces.
Image by USDA-SBML |
Teliospores |
Generally present,
especially later in season. Emerging through epidermis. Obovoid,
ellipsoid, or globose. Pigmented, golden to chestnut
brown. Pedicles often present. Apical germpore
often covered by distinct umbo.
|
Not produced during
growing season. |
1 Uromyces spp. can generally
differentiated from Phakopsorapachyrhizi by the presence
of thick walled, darker pigmented urediniospores. Some Phakopsorapachyrhizi urediniospores
may be distinctly pear-shaped, whereas Uromyces spp do
not produce pear-shaped urediniospores. Phakopsorapachyrhizi may
not produce telia during our growing season, but Uromyces spp.
often do (though they may not always be present).
2 Morphological descriptions generalized
from Cummins, G.B. 1978. Rust Fungi on Legumes and Composites in
North America. University of Arizona Press, Tucson AZ.
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