Surface morphology of aeciospores, urediniospores, and teliospores of Uromyces trifolii-repentis

The surface markings of the spores from the aecial, uredinial, and telial stages of Uromyces trifolii-repentis Liro on leaves and petioles of small white clover (Trifolium repens L.) were examined using scanning and transmission electron microscopes. The short, cylindrical aecium was borne within a peridium which was one cell layer thick. The peridial cells were rhomboidal with irregular club-shaped ornaments. The yellowish aeciospores were densely ornamented with smooth, knoblike verrucae. Thin areas of the spore wall were differentiated into germ pores. Two or three germ pores were equatorially arranged on the golden-brown urediniospores, which except for a circular hilar region were evenly covered with minute conical spines. The spines were situated singly in very shallow depressions surrounded by circular ridges. The dark-brown teliospores had smooth walls with a few linearly arranged fine warts, and the walls were thicker at the apex than on the side. A pale papilla covered the germ pore at the apex of the teliospore, which was borne singly on the fragile pedicel.