Tropical American Kuehneola rust of Rubus - Kuehneola loeseneriana

Species of blackberry or Rubus are attacked by a number of species of rust fungi many of which occur only in Central and South America or Asia. Most of these fungi do not appear to cause much damage and are apparently restricted to native host species. Kuehneola loeseneriana produces distinctive teliospores that are elongated, multiseptate and hyaline, and thus should not be confused with the dark-brown teliospores of the common rust species on Rubus in the genus Phragmidium that occur in North America.

Kuehneola loeseneriana H.S. Jacks. & Holw. 1931

Anamorph: Uredo loeseneriana Henn. 1898

Spermogonia on stems and leaves, brownish to orange-brown, flat to somewhat concave fruiting bodies.

Aecia on stems and leaves, producing galls, 5 cm diam or more, yellowish-orange, powdery, subepidermal, ruptured epidermis evident, scattered, pulverulent, covering entire surface of galls, soon exposed, surrounded by ruptured epidermis; on stems subcortical, linear or narrowly oblong, 1 cm long, 1-1.5 mm wide, opening by a longitudinal, median rupture; on leaves in bright golden-yellow spots 0.1-2 mm diam; aeciospores pedicellate, pale-yellow, ellipsoid, globoid, or oblong-ellipsoid, 25-40 × 16-25 µm, walls nearly hyaline, 1-3 µm thick, 4-7 µm, at apex, verrucose, verrucae arranged in curved lines from both ends, forming spiral striations, germ pores 2, obscure.

Uredinia on lower surface of leaves, pale yellow, round or irregular round, 0.1-0.5 mm, subepidermal; urediniospores ellipsoid to globoid, 25-33 × 18-24 µm, hyaline to yellowish, with spiral striations, walls 1-3 µm thick, becoming 4-7 µm thick at apex.

Telia on lower surface of leaves, white to pale yellow, subepidermal in origin, rounded or irregular rounded, 1-4 mm diam, erumpent, scattered, aggregated, aparaphysate; teliospores pedicellate, in clavate or long-cuneate chains of 2-4 cells, 67-110 µm long, oblong or ellipsoid, upper part ending in digital or crown like projections or attenuate or flat, each cell 24-60 × 17-24 µm, wall 1.5-2 µm thick on sides, 5-8 µm thick at apex, hyaline to pale yellow, germ pores obscure but germinating without dormancy, germ tube emerging from apical corners; pericel thick, as long as a probasidial cell.

Hosts: On numerous species of Rubus including R. amplior Rydb., R. bogotensis Kunth, R. boliviensis Focke, R. brasiliensis Mart., R. erythroclados Mart. ex Hook.f., R. floribundus Kunth, R. guyanensis Focke, R. humistratus Steud., R. imperialis Cham. & Schltdl., R. nubigenus Kunth, R. schiedeanus Steud., R. sellowii Cham. & Schltdl., R. urticifolius Poir., R. trichomallus Schltdl.

Geographic distribution: Widespread in Central American (Costa Rica, Guatemala, Mexico) and South America (Boliva, Brazil, Colombia, Ecuador, Peru, and Venezuela.

Notes: Spermogonia and aecial symptoms are similar to Gerwasia imperialis, another rust of Rubus in South America, however, the surface of the urediniospores is different. The surface structure of urediniospores of Kuehneola loaseneriana is spirally striate while that of G. imperialis is sparsely echinulate (Hernandez & Hennen, 2003) while the surface structure of urediniospores of K. uredinis are uniformly verrucose.

References:

Dennis R.W.G. 1970. Fungus flora of Venezuela and adjacent countries. Kew Bull., Addit. Ser. 3: 1-531.

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

Hennen, J.F., Figueiredo, M.B., de Carvalho, A.A., Jr., and Hennen, P.G. 2005. Catalogue of the species of plant rust fungi (Uredinales) of Brazil. Unknown journal or publisher, 490 pages.

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.

Thurston Jr., H.W. 1940. The rusts of Minas Geraes, Brazil. Based on collections by A. S. Muller. Mycologia 32: 290-309.

Nomenclature

Specimens in BPI

Additional distribution data

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