Phylum Ascomycota Orders Erysiphales & Laboulbeniales

1. Phylum AscomycotaOrders Erysiphales & Laboulbeniales General Mycology Pl P 421/521 Lecture 7

2. Pyrenomycetes Plectomycetes (Eurotiales) Chaetothyriales Loculoascomycetes 1 Loculoascomycetes 2 Filamentous ascomycetes Inoperculate discomycetes Lecanoralean discomycetes Operculate discomycetes Erysiphales (powdery mildews) Laboulbeniales Saccharomycetales Archiascomycetes Basidiomycota

3. Blackwell et al. 2006. Mycologia 98: 834

4. Blackwell et al. 2006. Mycologia 98: 834

5. Erysiphales • Common name = Powdery Mildews • Biotrophs of vascular plants • Biotroph: an obligate parasite growing on another living organism • 21 genera, 437 species infecting > 40,000 species of plants (mostly dicots) • Most species are host specific, a few are omnivorous, infecting hundreds of host species

6. Powdery Mildew Symptoms Photo by Claudia Nitschwitz

7. Characteristics • Mycelium is mostly superficial • Anchored to host epidermis by appressoria • Nutrients obtained via haustoria • Haustoria are intracellular structures • Overwinter as mycelium in infected buds or as ascomata • Asexual reproduction via conidia • Sexual reproduction via ascospores formed in cleistothecia

8. From APSnet.org

9. appressorium Plasma membrane Penetration peg haustorium Host cytoplasm Plasma membrane Plant cell wall fungus

10. Asexual reproduction • Erect, hyaline conidiophores are usually formed on superficial mycelium; • One-celled, hyaline thin-walled conidia are produced holoblastically in basipetal chains • One colony can produce > 30,000 conidia

11. Conidia • Wind-dispersed • Germination can occur at low relative humidity • Germination involves germ tube, appressorium and penetration peg formation • Apex of penetration peg enlarges to form haustorium

12. Ovulariopsis Oidium type anamorph Oidiopsis Streptopodium Fibrosin bodies From Braun, 1987

13. Microsphaera alni anamorph on Vaccinium

14. Sexual reproduction • Cleistothecia formed on superficial mycelium in late summer/early fall • Asci • Formed in basal layer • Globose to pyriform • Discharge by rupture of ascus tip

15. Asci/Ascospores • One to numerous asci/cleistothecium • Ascospores hyaline, one-celled, ovoid • 1-8 ascospores/ascus • Number of asci/cleistothecium is important character in identification

16. From APSnet.org

17. Identification • Anamorph type • Number of asci/ascocarp • Cleistothecial appendages • Mycelioid • Rigid • Spear-like with inflated base • With curled tips • With dichotomously branched tips

18. Microsphaera alni cleistothecia

19. Sawadaea bicornis cleistothecia

20. Sawadaea bicornis cleistothecial appendages

21. Blumeria • B. graminis--only powdery mildew on grasses • Mycelial setae • Digitate haustoria • Several asci/ascocarp • Inflated base on conidiophore

22. Mycelioid Appendages • Several asci/ascocarp: • Eryisiphe (100 spp) • Oidium anamorph • Leveillula (8 spp.) • Internal mycelium • Oidiopsis anamorph (emerges through stomate) • One ascus/ascocarp: • Sphaerotheca (50 spp.) • Appendages with curled tips • Oidium anamorph with fibrosin bodies

23. Dichotomously branched appendage tips • One ascus/ascocarp: • Podosphaera (12 spp.) • Oidium anamorph with fibrosin bodies • Several asci/ascocarp: • Microsphaera (125 spp.) • Oidium anamorph • Sawadaea (6 spp.) • Curved tips on appendages • Oidium anamorph with fibrosin bodies

24. Spear-like appendages--Phyllactinia • 24 species • Appendages lift ascocarp off leaf surface • Brush cells on top of ascocarp • Ovulariopsis and Streptopodium anamorphs

25. Appendages with curled tips • Uncinula (81 spp) • Oidium anamorph • Several asci/ascocarp • Uncinuliella • Differs by bristle-like appendages on top of ascocarp

26. Molecular data vs. morphology • Phylogeny analyses of powdery mildews based on rDNA sequence data shows lineages corresponding to anamorph type rather than teleomorph morphology (Saenz & Taylor 1999, Can. J. Botany 77:150-168; Mori et al 2000, Mycologia 92:74-93)

27. Saenz & Taylor 1999

28. Class Laboulbeniomycetes • Orders Laboulbeniales and Pyxidiophorales • 5 families, 140 genera, > 1800 species • Members of 4/5 families lack hyphae, reduced to thallus attached to host • Parasitize arthropods

29. Laboulbeniomycetes • Most species are highly host specific, found on only one arthropod species • Roland Thaxter (1858-1932) at Farlow Herbarium, Harvard was one of the leading experts on this group • Published a series of monographs on Laboulbeniales (1896-1931)

30. Roland Thaxter’s "Contributions towards a monograph of the Laboulbeniaceae"

32. Laboul images by Alex Weir

33. Hosts of Laboulbeniales (From Meredith Blackwell) Most species of. Laboulbeniales have been reported from beetles and flies in temperate regions, but recent studies in the tropics indicate that diversity in these regions may be much greater than in temperate areas, primarily because diversity of hosts, especially beetles, is much higher.

34. Pyxidiophorales • 2 genera, 16 species • Specialized for dispersal by arthropods (bark & dung beetles, phoretic mites) • Perithecia with ascospores that undergo extreme morphological changes during maturation

35. Blackwell et al. 1986. Hyperphoretic dispersal of a Pyxidiophora anamorph. Science 232: 993-995

36. Pyxidiophora perithecia Development of anamorph Photos by M. Blackwell

37. Presumptive anamorph (above) From Kirschner (2003). Mycological Progress 2: 209-218.