AECIOSPORES OF CRONARTIUM-FLACCIDUM, CRONARTIUM-RIBICOLA AND ENDOCRONARTIUM-PINI SHOW NO DIFFERENCES IN MORPHOLOGY

The morphology of the aeciospores of the pine stem rust fungi Cronarti um flaccidum, Cronartium ribicola and Endocronartium pini, collected f rom nine locations in Finland, Sweden and Italy, was compared. Surface structures of 900 aeciospores were visually classified using a scanni ng electron microscope, and dimensions of 1100 aeciospores were measur ed from micrographs. The data grouping was tested with discriminant an alysis. The spores had well-defined smooth areas and annulate warts on their surface. E. pini, C. flaccidum and C. ribicola could not be dis tinguished by the surface structures of the spores. The grouping of sp ores by dimensions into sample locations was statistically significant by one discriminant function, while the grouping into species was not . The observed similarities corroborated the current views on the clos e relationship of C. flaccidum and E. pini.