Gray Rubus rust - Phragmidium griseum

Most hosts of this rust are species of Rubus native to Asia, thus this pathogen is not considered a threat to the North American berry industry. However, R. spectabilis (salmonberry) is an important part of the vegetation in the Pacific Northwest.

Phragmidium griseum Dietel 1902

Uredinia hypophyllous, scattered or irregularly grouped, subglobose to globose, 0.3-0.8 mm diam, early exposed, pulvinate, finally pulverulent, orange yellow, pale yellow; paraphyses clavate, 34-70 × 7-16 µm, erect or incurved, wall smooth, colourless, uniformly thin, 1 µm; urediniospores subglobose, obovate, pyriform, ellipsoid or irregularly ellipsoid, 18-30 × 13-21 µm; walls 1.5 µm thick, densely, coarsely echinulate, inconspicuous or smooth at the base; contents orange yellow or pale yellow.

Telia hypophyllous, scattered or gregarious, round or ellipsoid, 0.2-0.7 mm diam, subpulvinate, early exposed, reddish brown; teliospores cylindrical, 2-6 (mostly 3-4) celled, 38-106 × 18-28 µm, rounded at apex, rounded or somewhat attenuate at base, not or slightly constricted at septum, 2 or 3 germ pores in each cell, walls 2-3 µm, pale yellow brown, with 3 to 5 rows of warts; pedicels subhyaline, persistent, 20-114 µm long, 10-16 µm wide, 1 septate, not hygroscopic.

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

Host range: Rubus subgenus Idaeobatus, specifically R. aculaetiflorus, R. croceacanthus, R. crataegifolius, R. illecebrosus, R. micophyllus, R. mingetsensis, R. minusculus, R. palmatus, R. rosifolius, R. rosifolius subsp. maximowiczii, R. spectabilis- salmonberry, R. trianthus, R. wrightii

Geographic distribution: Asia (China, Japan, Korea, Taiwan) This fungus resembles Phragmidium okianum and P. rubi-thunbergii. However it varies in the number of the teliospore septa of P. okianum (Hiratsuka et al., 1992).

References:

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

Zhuang, W.-Y., Ed. 2005. Fungi of northwestern China. Mycotaxon, Ltd., Ithaca, NY, 430 pages.

Nomenclature

Specimens in BPI

Additional distribution data

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