Nambu Rubus rust-Phragmidium nambuanum

This rust attacks species of Rubus native to Asia and does not appear to pose a threat to economically important species of Rubus in North America.

Phragmidium nambuanum Dietel 1908

Uredinia hypophyllous (on undersurface of leaves), scattered or in small groups, minute, round, orange-yellow, pulverulent 0.1-0.6 mm; paraphyses clavate, erect or incurved, wall uniformly thin, 1 µm, hyaline; urediniospores globose to subglobose, obovate, broadly ellipsoid or obovoid, 18-26 × 16-23 µm, walls 0.8-1.5 µm thick, densely and coarsely echinulate, hyaline, contents orange-yellow or pale yellow, germ pores obscure, about 4-5, scattered.

Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.2-0.6 mm diam, pulverulent, black; teliospores cylindrical, 4-10 (mostly 7-8) celled, 63-147 × 24-43 µm, rounded at apex, not constricted at septum, walls 4-6 µm, chocolate brown, minutely and closely verrucose, with 3 germ pores in each cell, apical papilla lacking, pedicels hyaline, persistent, 53-119 µm long.

See Hiratsuka et al. (1992) and Wei (1988) for a more detailed description.

Host range: Rubus subgenus Idaeobatus, specifically R. crataegifolius, R. innominatus, R. kinashii, R. lasiostylus, R. mesogaeus, R. phoenicolasius, R. pirifolius, R. simplex, Rubus subgenus Cylatis, specifically R. xanthocarpus, and Rubus sp. This hosts are native species in Asia.

Geographic distribution: Asia (China, Japan, Taiwan)

This fungus is similar to Phragmidium arisanense; however, P. nambuanum can be distinguished by the 7-8-septate teliospores that are 28-43 µm wide (Hiratsuka et al., 1992; Wei, 1988).

Wei (1988) reported that the pedicel is 53-119 µm long, while Hiratsuka et al. (1992) reported the length as 54-150 µm. In our observations, the pedicel length is 68-89 µm long, shorter than other reports.

References:

Wei, S.X. 1988. A taxonomic study of the genus Phragmidium of China. Mycosystema 1: 179-210.

Nomenclature

Specimens in BPI

Additional distribution data

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