Orange rust of sugarcane - Puccinia kuehnii

The two major rust fungi on sugarcane are brown rust caused by Puccinia melanocephala and orange rust caused by P. kuehnii. While brown rust is relatively common, the range of orange rust has expanded recently and now infects the sugarcane-growing regions in the southeastern United States, Central and South America, and the Caribbean Basin (Comstock et al. 2008, personal communication).

Puccinia kuehnii Butler 1914

Spermogonia and aecia unknown.

Uredinia primarily hypophyllous (on lower surface of leaves), orange to reddish-brown, linear up to 4 mm, urediniospores obovoid or pyriform or broadly ellipsoidal, 33-53 × 21-31 µm, orange to cinnamon-brown, echinulate, germ pores 4-5, equatorial, wall 1-2.3 µm; paraphyses inconspicuous, sometimes absent, hyaline to pale brown, pyriform to clavate, 24-60 µm long, 6-14 µm head, wall thin, >1 µm.

Telia hypophyllous, translucent, teliospores 2-celled, hyaline, 31-55 × 10-17 µm, smooth, fusiform to clavate, walls uniform, 0.5-1.2 µm, sessile or pedicels thin-walled, hyaline, up to 12 µm long; telial paraphyses absent.

Host range: Primarily on species of Saccharum in the Poaceae, specifically Saccharum arundinaceum Retz., S. barberi Jeswiet, S. edule Hassk., S. narenga (Nees ex Steud.) Wall. ex Hack., S. officinarum L., S. rufipilum Steud., S. ravennae (L.) L., S. sinense Roxb., S. spontaneum L., Sclerostachya fusca (Roxb.) A. Camus.

Geographic distribution: Widespread in Asia, Australia, and South Africa, recently discovered in the Western Hemisphere and now known from the sugarcane-growing regions in the southeastern United States, Central and South America, and the Caribbean Basin (Comstock et al. 2008, personal communication).

See Mordue (1985) and Virtudazo et al. (2001) for a more detailed description.

Though highly variable in size, orange rust urediniospores are typically larger than brown rust, although the size ranges overlap. Orange rust is distinct from brown rust in producing uredinia with inconspicuous paraphyses. When paraphyses are present, they are extremely thin walled and hyaline. Urediniospores are orange to reddish-brown with apical wall thickenings.Teliospores are hyaline with uniformly thin walls, and may or may not be sessile. Telial paraphyses are absent. Like brown rust, spermogonia and aecia are unknown.

Here is a link to a chart comparing Puccinia kuehnii and Puccinia melanocephala.

References:

Comstock, J.C., Sood, S.G., Glynn, N.C., Shine Jr., J.M., McKemy, J.M., and Castlebury, L.A. 2008. First Report of Puccinia kuehnii , Causal Agent of Orange Rust of Sugarcane, in the United States and Western Hemisphere. Pl. Dis. 92: 175.

Mordue, J.E.M. 1985. Urediniospore ornamentation in the sugarcane pathogens Puccinia kuehnii and P. melanocephala. Trans. Brit. Mycol. Soc. 84: 758-760.

Virtudazo, E.V., Nojima, H., and Kakishima, M. 2001. Taxonomy of Puccinia species causing rust diseases on sugarcane. Mycoscience 42: 167-175.

Nomenclature

Specimens in BPI

Additional distribution data

Suggested citation: Dixon, L. . Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Orange rust of sugarcane - Puccinia kuehnii. Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .