''Melampsora medusae'' is a

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

, causing a disease of

woody plant A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to herbaceous plants that die back to the ground until sp ...

s. The infected trees' leaves turn yellowish-orange. The disease affects mostly conifers, e.g. the

Douglas-fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...

western larch The western larch (''Larix occidentalis'') is a species of larch native to the mountains of western North America (Pacific Northwest, Inland Northwest); in Canada in southeastern British Columbia and southwestern Alberta, and in the United States ...

tamarack ''Larix laricina'', commonly known as the tamarack, hackmatack, eastern larch, black larch, red larch, or American larch, is a species of larch native to Canada, from eastern Yukon and Inuvik, Northwest Territories east to Newfoundland, and als ...

, ponderosa, and

lodgepole pine ''Pinus contorta'', with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalpine, ...

trees, but also some broadleaves, e.g. trembling aspen and poplars. Coniferous hosts are affected in late spring through early August, and trembling aspens and poplars from early summer to late fall. It is one of only two foliage rusts that occur naturally in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

."Melampsora Foliage Rusts." 30 January 2007. Melampsora medusæ.
Canadian Forest Service. Retrieved on 9 September 2007.

Life cycle

Symptoms usually are contained to a single year on conifers, shedding the affected needles in fall. To survive the winter ''Melampsora medusae'' remain as

teliospore Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi ( rusts and smuts), from which the basidium arises. Development They develop in '' telia'' (sing. ''telium'' or ''teliosorus''). The telial host is the p ...

s on the dead leaves of the host, coming back in the spring to be spread by the wind as

basidiospore A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are pro ...

s, and infecting new conifers. After about two weeks,

aeciospore Aeciospores are one of several different types of spores formed by Rusts. They each have two nuclei and are typically seen in chain-like formations in the aecium. References Fungal morphology and anatomy {{mycology-stub ...

s are produced on the coniferous needles. Those spores serve as

inoculum In biology, inoculum refers to the source material used for inoculation. ''Inoculum'' may refer to: * In medicine, material that is the source of the inoculation in a vaccine * In microbiology, propagules: cells, tissue, or viruses that are used t ...

for an infection in live trembling aspen and other poplar trees in another two weeks.

Urediniospore Urediniospores (or uredospores) are thin-walled spores produced by the uredium, a stage in the life-cycle of rusts. Development ''Urediniospores'' develop in the uredium, generally on a leaf's under surface. Morphology *Urediniospores usually hav ...

s are produced on the poplar leaves, where the infection spreads. Winter then comes, and the cycle begins again.

References

Bibliography

* Brown, J.S. (1984) ''Recent invasions of Australia and New Zealand by pathogenic fungi and counter measures''. Bulletin OEPP/EPPO Bulletin 14, 417-428. * CMI (1991) Distribution Maps of Plant Diseases No. 547 (edition 2). CAB International, Wallingford, UK. * Hepting, G.H. (1971) ''Diseases of forest and shade trees of the United States''. Agricultural handbook No. 386, pp. 209, 212, 299, 382, 387. Forest Service, US Department of Agriculture, USA. * Kraayenoord, C.W.S. van; Laudon, G.F.; Spies, A.G. (1974) ''Poplar rusts invade New Zealand''. Plant Disease Reporter 58, 423-427. * McBride, R.P. (1965) ''A microbiological control of Melampsora medusae''. Canadian Journal of Botany 47, 711-715. * McMillan, R. (1972) ''Poplar leaf rust hazard''. New Zealand Journal of Agriculture 125, 47. * Nagarajan, S.; Singh, D.V. (1990) ''Long-distance dispersion of rust pathogens''. Annual Review of Plant Pathology 28, 139-153. * OEPP/EPPO (1982) ''Data sheets on quarantine organisms No. 33, Melampsora medusae''. Bulletin OEPP/EPPO Bulletin 12 (1). * OEPP/EPPO (1990) ''Specific quarantine requirements''. EPPO Technical Documents No. 1008. * Pinon, J. (1986) ''Situation de Melampsora medusae en Europe.'' Bulletin OEPP/EPPO Bulletin 16, 547-551. * Prakash, C.S.; Heather, W.A. (1985) ''Adaption of Melampsora medusae to increasing temperature and light intensities on a clone of Populus deltoides''. Canadian Journal of Botany 64, 834-841. * Prakash, C.S.; Heather, W.A. (1989) ''Inheritance of partial resistance to two races of leaf rust Melampsora medusae in eastern cottonwood'', Populus deltoides. Silvae Genetica 38, 90-94. * Prakash, C.S.; Thielges, B.A. (1987) ''Pathogenic variation in Melampsora medusae leaf rust of poplars''. Euphytica 36, 563-570. * Prakash, C.S.; Thielges, B.A. (1989) Interaction of geographic isolates of Melampsora medusae and Populus: effect of temperature. Canadian Journal of Botany 67, 486-490. * Schipper, A.L., Jr.; Dawson, D.H. (1974) ''Poplar leaf rust - a problem in maximum wood production''. Plant Disease Reporter 58, 721-723. * Shain, L. (1988) ''Evidence for formae speciales in poplar leaf rust fungus Melampsora medusae''. Mycologia 80, 729-732. * Sharma, J.K.; Heather, W.A. (1977) ''Infection of Populus alba var. hickeliana by Melampsora medusae Thüm''. European Journal of Forest Pathology 7, 119-124. * Siwecky, R. (1974) ''The mechanism of poplar leaf resistance to fungal infection''. Polish Academy of Sciences, Annual Report, 1973, 32 pp. * Spiers, A.G.; Hopcroft, D.H. (1985) ''Ultrastructural studies of pathogenesis and uredinial development of Melampsora larici-populina and M. medusae on poplar and M. coleosporioides and M. epitea on willow''. New Zealand Journal of Botany 23, 117-133. * Spiers, A.G.; Hopcroft, D.H. (1988) ''Penetration and infection of poplar leaves by urediniospores of Melampsora larici-populina and Melampsora medusae''. New Zealand Journal of Botany 26, 101-111. * Trench, T.N.; Baxter, A.P.; Churchill, H. (1987) ''Report of Melampsora medusae on Populus deltoides in Southern Africa''. Plant Disease 71, 761. * Walker, J. (1975) ''Melampsora medusae''. CMI Descriptions of Pathogenic Fungi and Bacteria No. 480. CAB International, Wallingford, UK. * Walker, J.; Hartigan, D. (1972) ''Poplar rust in Australia''. Australian Plant Pathology Society Newsletter 1, 3. * Ziller, W.G. (1955) ''Studies of western tree rusts. II. Melampsora occidentalis and M. albertensis, two needle rusts of Douglas-fir''. Canadian Journal of Botany 33, 177-188. * Ziller, W.G. (1965) ''Studies of western tree rusts. VI. The aecial host ranges of Melampsora albertensis, M. medusae and M. occidentalis''. Canadian Journal of Botany 43, 217-230. * Ziller, W.G. (1974) ''The tree rusts of western Canada''. Forest Service, British Columbia, Canada, Publications No. 1329, pp. 144–147. Forest Service, British Columbia, Canada.

External links

Index Fungorum

USDA ARS Fungal Database
{{Taxonbar, from=Q3018634 Pucciniales Fungal tree pathogens and diseases Fungi described in 1878 Taxa named by Felix von Thümen