Few-loculed Asian Rubus rust - Phragmidium pauciloculare

Most hosts of this rust are species of Rubus native to Asia, thus this pathogen is not considered a threat to North American agriculture.

Phragmidium pauciloculare (Dietel) Syd. & P. Syd. 1912

Aecia hypophyllous, mostly on veins or on petioles peduncles and buds, rounded or irregular in shape, confluent, soon nakes, pulverulent, ruptured epidermis inconspicuous, orange yellow.

Uredinia hypophyllous, scattered or loose groups, minute, round, orange yellow, pulverulent 0.2-0.3 mm; paraphyses clavate, erect or incurved, wall thin, hyaline; urediniospores globose, subglobose, obovate, broadly ellipsoid or obovoid, 12-25 × 13-20 µm; walls 1-1.5 µm thick, densely and coarsely echinulate, hyaline, contents orange yellow or pale yellow.

Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.2-0.4 mm diam., pulverulent, black; teliospores cylindrical, 3-7 celled, 35-111 × 18-27 µm, rounded at the apex, not constricted at the septum, chocolate brown, smooth, apical papilla none, not or slightly thickened at the apex 2-3 germ pores in each cell; pedicels hyaline, persistent, about 144 µm long.

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

Host range: Rubus subgenus Idaeobatus, specifically R. flosculosus, R. idaeopsis, R. idaeus, R. illecebrosus, R. lasiostylus, R. minusculus, R. parvifolius, R. phoeicolasius, R. pungens, R. rosaefolius, R. subornatus, R. yabei, R. yoshinoi

Geographic distribution: Asia (China, Japan, Korea, Taiwan)

This fungus is similar to Phragmidium griseum in having smooth-walled teliospores. These species can be distinguished based on the surface ornamentation of the urediniospores that is uniformly echinulate in P. pauciloculare and echinulate at the apex but smooth at the base in P. griseum (Wei, 1988).

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. Few-loculed Asian Rubus rust - Phragmidium pauciloculare . Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .