Teleutospores of Uromyces Species on Geranium in Europe

Abstract

There is one common and widespread species of Uromyces on species of Geranium throughout Europe, viz. U. geranii (DC.) Lev. which, according to Guyot (1951), infects 14 species in at least 20 countries. This is an auteu-form with all five spore forms produced on Geranium and according to most authors it produces smooth-walled teleutospores. In Plate 12/A-B we illustrate scanning electron micrographs of teleutospores of U. geranii on Geranium pratense L. from Seahouses, Northumberland, 2 Sep. 1972, D. A., D. G. & P. M. Reid, from which it will be seen that at least the race of the fungus on that host in Britain has indeed quite smooth-walled teleutospores. A second species on Geranium was published in 1904 as Uromyces truncatulus Trotter on G. striatum L. (syn. G. versicolor L.) in southern Italy. This, too, was said to have smooth-walled teleutospores but they were distinguished from those of U. geranii by having an apical papilla with truncate tip. On 17th July 1972 one of us (R. W. G. D.) collected a Uromyces on G. striatum at the Cipo Garibaldi, high on Aspromonte in Calabria, and was surprised to find that even under the light microscope the teleutospore wall appeared to be distinctly ornamented. Comparison with authentic material of U. truncatulus distributed as D. Saccardo's Mycotheca Italica 1426 indicated that the diagnosis was erroneous in this respect and that teleutospores of U. truncatulus differ from those of U. geranii in surface ornament as well as in shape. The type of ornament is clearly seen in the scanning electron micrograph Plate 12 C-D. The surface appears foveate, bearing a uniform pattern of more or less circular depressions which are irregular in size. Uromyces truncatulus appears to be confined to a single host species and to have a limited distribution in southern Italy, Sicily and Greece (Epirus, Petrak 1956). When it was discovered to have an ornamented teleutospore wall it became desirable to compare it with U. carpathicus in which this character had already been recognized. Guyot (1951) amended the description of the teleutospore of U. geranii to read: 'lisse ou parfois un peu verruculeuse' and from an appended note it is clear he did this to accommodate the description of U. carpathicus Namyslowski (I 911), which he had cited with a query as a synonym of U. geranii. U. carpathicus Namyslowski had been described on G. phaeum L. in southern Poland, a host already known to harbour U. geranii in adjacent countries. We experienced considerable difficulty in obtaining Namyslowski's fungus, for it seems not to have been reported again, but were able eventually to borrow from the Naturhistoriska Riksmuseum, Stockholm, a leaf supplied