Morphological variation of Peridermium pini and Cronartium flaccidum aeciospores

Morphological variation of germ tubes originating from aeciospores of Perid ermium pini and Cronartium flaccidum populations on Pinus sylvestris was in vestigated in rust populations from Finland, the United Kingdom and Italy. The observed morphological variation was generally higher among than betwee n these rust populations. The variation in germ tube length of the rust sam ples was high over the incubation period. Peridermium pini could not be dis tinguished from C. flaccidum based on its germ tube morphology.