Identification and occurrence of rust species (Phragmidium spp.) on roses in Europe

The occurrence of Phragmidium spp. on wild accessions and cultivars in Belgium, France, Germany, Sweden and the Netherlands was studied. Apart from host specificity, determination of the rust species was based on morphologic parameters of teleutospores. Herbarium specimens of the National Botanical Garden of Belgium were used as reference material. Only P. tuberculatum, P. mucronatum and P. rosae-pimpenellifoliae were found in our research. As P. rosae-pimpenellifoliae is only found on R. pimpenellifoliae it was rarely observed. The other two species are of more importance and have more characteristics in common. A grouping of isolates based on the host plant, showed significant differences in the amount of cells in the teliospore, for other characteristics there was no clear difference between P. tuberculatum and P. mucronatum. Due to a large overlap in the amount of cells found, it was not possible to identify individual isolates. Some isolates could also not be determined since both Phragmidium species are hosted on the same rose species. Differences between rose species in infection rates were observed which could be important for breeding.