Rust on South American Rubus - Gerwasia imperialis

Gerwasia imperialis (Speg.) J.C. Lindq., 1962

Species of blackberry or Rubus are attacked by a number of species of rust fungi many of which occur only in South America or Asia and thus are potentially invasive on North American species of Rubus. Gerwasia imperialis is a macrocyclic rust that produces spermogonia, aecia, uredinia and telia, although the uredinia and telia are rare. The abnormal growth of the infected leaves distinguishes G. imperialis from G. rubi, although the latter is known primarily from Asia.

Spermogonia epiphyllous (on upper surface of leaves), in lenticular cavities, subcuticular in origin, visible on hypertrophied epidermal cells, 115 × 70 µm.

Aecia epiphyllous, intraepidermal, usually in circles surrounding spermogonia, yellowish-orange, without paraphyses or peridia; aeciospores ellipsoidal or obovate, 23-30 × 17-21 µm, walls hyaline, thin, 1-2 µm thick, prominently and sparsely echinulate, most numerous on upper part of spore, pores not seen.

Uredinia hypophyllous (on lower side of leaves), suprastomatal, without papraphyses, yellowish; urediniospores similar to aeciospores but smaller.

Telia hypophyllous, suprastomatal, scattered or aggregated, yellowish, compact; teliospores clavate, 50-65 × 15-17 µm, wall thin, hyaline, 1-1.5 µm thick, unthickened above, pedicel short; germination without dormancy.

See Hernandez & Hennen (2003) and Salazar et al. (2007) for a more detailed description.

Hosts On living leaves of Rubus spp. (Rosaceae) including Rubus boliviensis Focke, R. floribundus Kunth (mora), R. imperialis Cham. & Schltdl., and R. urticifolius Poir.

Geographic distribution: Known from South America, specifically Argentina (Gjaerum, 1995), Bolivia (Hernandez & Hennen, 2003), Peru (Hernandez & Hennen, 2003), and Venezuela (Gjaerum, 1995).

References:

Buritica, P. 1994. Cambios taxonomicos y nuevos registros de uredinales de la flora Andina. Revista del I.C.N.E. 5: 173-190.

Gjaerum, H.B. 1995. Rust fungi from various countries. Lidia 3: 145-170.

Hernandez, J.R., and Hennen, J.F. 2002. Rust fungi (Uredinales) of Northwest Argentina. Sida 20: 313-338.

Hernandez, J.R., and Hennen, J.F. 2003. Rust fungi causing galls, witches' brooms, and other abnormal plant growths in northwestern Argentina. Mycologia 95: 728-755.

Lindquist, J.C. 1982. Royas de la Republica Argentina y Zonas Limitrofes. Inst. Nacional de Tecnologia Agropecuaria., 574 pages.

Salazar-Yepes, M., Pardo Cardona, V.M., and Buritica, P. 2007. Species from Colombia, Ecuador and Peru belonging to the genus Gerwasia Raciborski from the order Uredinales. Caldasia 29: 105-120.

Spegazzini, C. 1898. Fungi Argentini, novi v. critici. Anales Mus. Nac. Buenos Aires 6: 81-365.

Nomenclature

Specimens in BPI

Additional distribution data

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