South American Rubus rust-Gerwasia mayorii

The rust fungi on Rubus are numerous and difficult to distinguish. Some species such as G. mayorii have not been collected often and may be synonyms of more commonly known taxa. They do not seem to pose a threat to species of Rubus in North America.

Gerwasia mayorii (H.S. Jacks.) Buritica 1994

Uredinia hypophyllous (on lower side of leaves), round or irregular round, yellowish; urediniospores 16-21 × 21-33 µm (26-30 × 18-20; Jackson, 1931), walls 3-5 µm (1.5-2.5 µm; Jackson, 1931), verrucose echinulate and moderately spaces.

Telia hypophyllous, scattered, round; Teliospores appear all to be germinated as described by Mayor and 18-22 × 50-75 µm, walls very slightly thickened at sides near pore.

Host range: Rubus floribundus, R. guyanensis, and Rubus spp.

Geographic distribution: Colombia and Venezuela

Most species of Gerwasia were originally described in Mainsia, all of which occur on Rubus. Gerwasia mayorii (as Mainsia mayorii) is similar to Gerwasia clara and G. quitensis in having teliospores longer than 50 um. Gerwasia mayorii has both a uredinial and teliospore stage unlike G. quitensis that lacks a uredinial state. Gerwasia mayorii has teliospores that are wider than 18 µm while teliospores of G. clara are less than 18 µm wide. Jackson (1931) provides a key to most species of Gerwasia (as Mainsia).

See Jackson (1931) and for a more detailed description.

References:

Buritica, P., and Pardo Cardona, V.M. 1996. Flora Uredineana Colombiana. Rev. Acad. Colomb. Cienc. 20: 183-236.

Chardon, C.e., and Toro, R.A. 1934. Mycological Explorations of Venezuela. Monogr. Univ. Puerto Rico, B 2: 1-351.

Dennis, R.W.G. 1970. Kew Bulletin Additional Series III. Fungus Flora of Venezuela and Adjacent Countries. Verlag von J. Cramer, 531 pages.

Jackson, H.S. 1931. The rusts of South America based on the Holway collections - IV. Mycologia 23: 332-364.

Jackson, H.S. 1931. The rusts of South America based on the Holway collections - V. Mycologia 23: 463-503.

Jackson, H.S. 1931. The Rusts of South America based on the Holway Collections - III. Mycologia 23: 96-116.

Nomenclature

Specimens in BPI

Additional distribution data

Suggested citation: Yun, H.Y. Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. South American Rubus rust-Gerwasia mayorii. Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .