Exoteliospora osmundae
Exoteliospora osmundae (Peck) R. Bauer, Oberw. & Vánky 1999, in Bauer et al., Mycologia, 669-675 (1999).
Diagnosis: Sori (Figure 1) external on both sides of deformed and hypertrophied leaves of the host plant, yellowish-, cinnamon- to reddish-brown depending on age. Coralloid haustoria present in epidermal cells (Figure 2). Teliospores produced in basipetal chains (Figure 2), globose, subglobose, rarely ellipsoidal, variable in size and ornamentation, 9-18(-23) X 10-19(-23) µm, light to orange-brown; wall 1-1.5 µm thick, smooth to prominently verrucose (Fugues 5-8). Septal pores with non-swollen lips and membrane caps (Figures 13- 16). Teliospore germination unknown. On Osmundaceae, 0. regalis L. and 0. cinnamomea L. Known from several collections in North America
Index Fungorum Number: IF460677
Figure 1. Infected pinnules of Osmunda regalis. Scale bar 1 cm.
Figure 2. Coralloid haustoria in epidermal cells from a freehand section and the mode of teliosporogenesis of Ustilago osmundae = Exoteliospora osmundae. Scale bar = 10 µm.
Figure 3. Hyphae and teliospores of Ustilago osmundae = Exoteliospora osmundae, seen by TEM (3, 4), LM (5) and SEM (6-8). 3. Section showing a thin-walled hypha (arrow) and thick-walled hyphae (arrowheads) adjacent to the cuticle of the epidermis (c). Scale bar = 1 µm. 4. Section through a hypha showing the fibrillate wall. Scale bar = 0.2 µm. 5. Teliospores. Scale bar = 10 µm. 6. Hyphae and teliospores on the host surface. Note the ring-like structure (r) on the surface of some teliospores. Scale bar = 20 µm. 7. Pair of teliospore initials partly covered by the original wall of the sporogenous hypha. Scale bar = 5 µm. 8. Teliospores with variable ornamentation. Scale bar = 5 µm.
Figure 9-12. Teliosporogenesis of Ustilago osmundae = Exoteliospora osmundae, seen by TEM. 9. Teliospore and sporoge- nous hypha (arrowhead) separated by a septum. Note the plugged septal pore (arrowhead). Scale bar = 1 µm. 10. Section showing two connected teliospore initials. The plugged septal pore is visible at the arrowhead. Dark lines in the initials are artifacts. Scale bar = 5 µm. 11. Detail from 10 showing the ruptured wall of the sporogenous hypha (arrows). Note that the warts are continuous with the original wall of the sporogenous hypha. Note also the septal pore between the two initials (arrowhead). Scale bar = 0.5 µm. 12. Section through the wall of a teliospore initial showing the teliospore wall (w) and the original wall of the sporogenous hypha (arrow). Note that te wart is continuous with the original wall of the sporogenous hypha. Scale bar = 0.5 µm.
Figures 13-16. Septal pore apparatus with two caps (arrows in 13) of Ustilago osmundae = Exoteliospora osmundae. Scale bars = 0.1 µm. 13. Section illustrating a septal pore in a sporogenous hypha. 14. Section showing a septal pore in a thick- walled hypha. 15. Detail from 10, 11 showing a septal pore between two teliospore initials. The septal pore is overgrown at both sides by teliospore wall layers. 16. Septal pore between a teliospore initial and a sporogenous hypha. The septal pore is overgrown at one side by spore wall layers. Detail from 9.
Figures 17-20. Haustoria of Ustilago osmundae = Exoteliospora osmundae, seen by TEM. 17, 18. Sections through two haustoria showing the penetration points through the epidermal walls. Note that the haustorium illustrated in 17 is continuous with its external hypha. Haustoria are surrounded by an electron-opaque matrix (arrows) and encased partly (18) or completely (17) by appositional material (arrowheads). The host nucleus is visible in 18 at N. Scale bars = 2 µm. 19. Section through the branches of a haustorium showing the coralloid appearance. The matrix surrounding the haustorial branches is visible at arrows. Scale bar = 0.5 µm. 20. Interface between a haustorium (h) of Exoteliospora osmundae and a host cell of Osmunda regalis (W) with fungal cell wall (fw), matrix (m), matrix vesicles (V), lacunae (L) and appositional material (M). Scale bar = 0.2 µm.
Reference:
Bauer, R., Oberwinkler, F., & Vánky, K. (1999). Ustilaginomycetes on Osmunda. Mycologia, 669-675.
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