Telium

Abstract: A series of experiments were conducted to promote chrysanthemum breeding for resistance to white rust (Puccinia horiana P. Hennings), For testing the resistance to white rust, three plants of each species and cultivar were incubated in a box kept at 17'C under 100% relative humidity and the inoculation was effected by hanging leaves with telia actively producing sporidia from the ceiling of the box. The inoculum concentration was restricted to ca. 70 sporidia per 1mm2 leaf area. Reliable criteria for grading and rating inLection were established based principally on the extent of telium formation on the fully unfolded top leaves. White rust resistance of chrysanthernum cultivars could be evaluated by this testing method at an early stage of the plants, for their reactions to white rust at the young plant stage and the flowering stage were highly correlated. Variation in resistance depending on the fungal isolates was found in the tests of 40 cultivars inoculated with 6 typical isolates in Japan, suggesting physiological specialization in the pathogen. Among 6 isolates, some showed a wide range of pathogenicity and others medium and narrow ranges. Besids the existence of unstable cultivars showing various reactions to the fungal isolates, cultivars with stable resistance to all the isolates were also found.

Abstract: Teliospore initials of Puccinia podophylli develop from binucleate sporogenous cells lining the base of the telium. The teliospores are formed in basically the same fashion as those of other rusts that have been examined at the ultrastructural level. The long, straight or slightly curved spines present on mature teliospores initially develop as slight bulges or protrusions on the spore surface. The spore wall in such a region then evaginates to form a slender spine that is initially filled with cytoplasm. The cytoplasmic material is then progressively excluded from the tip of the spine as a result of the thickening of the spine wall. Mature teliospores of P. podophylli possess a wall consisting of a thick, outer, electron-dense layer in which stratification is only rarely visible and an inner thinner, less electron-dense layer.

Abstract: Chrysomyxa weirii (Uredinales) is the only autoecious, microcyclic species of Chrysomyxa occur- ring in North America. The telia form on second-year needles of spruce, causing premature needle loss. The morphology of the telia was studied in herbari- um specimens from diverse locations, and the telio- spore germination, nuclear condition, and reproduc- tive biology of fresh collections were studied on mi- croscope slides and on artificially and naturally in- fected host tissue using light and scanning electron microscopy. Basidiospore production was infrequent in mature sori, but teliospores dispersed readily in water and germinated to produce a two-celled basid- ium and two basidiospores. The two cells of the ba- sidium could also separate to form two sporelike cells that could produce germ tubes, or the teliospore pro- duced a long hyphalike promycelium. The type of germination was influenced by temperature. The ready dispersal of teliospores in water and their pres- ence on the surface of current-year needles confirms that they function as diaspores. The distribution pat- tern of this rust and the elongated, smooth, thin- walled spores that are held rigidly together until wet suggest a water-dispersal mechanism. A cytological study showed that the vegetative hyphae are mostly monokaryotic. Dikaryotization and karyogamy occur in the cells at the base of the telium and result in teliospores with one large nucleus. During germina- tion, the teliospore nucleus migrates into the basidi- um, where it divides once before a septum forms. A