ASCOMYCETES CONT PYRENOMYCETES I IB 371 General Mycology

ASCOMYCETES (CONT. ) PYRENOMYCETES I IB 371 General Mycology Lecture 22 Tuesday November 11, 2003

ASCOMYCETES (CONT. ) PYRENOMYCETES • Ascomata perithecial or sometimes cleistothecial • Ovoid to cylindrical unitunicate asci, usually formed from ascogenous hyphae and croziers in a hymenium or becoming scattered throughout the ascomata • Hamathecial tissue present or absent at maturity

PYRENOMYCETES • Asci persistent or evanescent • Ascospores usually forcibly discharged from persistent asci • Ascospores comprising a wide range of morphologies • Asexual reproduction by conidia

PYRENOMYCETES • Include numerous and important plant pathogens • Parasites and symbionts of arthropods • Saprophytes capable of degrading lignocellulose • Endophytes of a variety of plants • Mycotoxin producers • Etc.

In-class Activity

XYLARIALES - ASCOMATA • Dark, leathery or carbonaceous • Usually a perithecium but sometimes a cleistothecium • Sometimes embedded in a stroma

Stromata

XYLAIALES ASCI • Formed in a peripheral or basal hymenial layer • Usually cylindrical, sometimes club shaped or subglobose • Usually with an apical ring surrounding a pore through which ascospores are discharged • Apical ring may be amyloid and stain blue in iodine

XYLARIALES HAMATHECIUM • Paraphyses present - attached at base, growing upward and inward, and interspersed among the asci • Periphyses present in the beak of the perithecium

XYLARIALES ASCOSPORES • Usually pigmented • One celled or sometimes transversely septate • With germ pores or slits • Sometimes with a gelatinous sheath

XYLARIALES ANAMORPHS • Mostly holoblastic development with conidiogenous cells proliferating sympodially or percurrently

Hypoxylon multiforme

Hypoxylon ascospores

Xylaria stroma

Xylaria asci

XYLARIALES • Remember Xylaria polymorpha – dead man’s fingers

SORDARIALES • Primarily saproprobic on plant or animal remains, dung • Ascomata rarely in a stroma • Ascomata perithecial or cleistothecial • Peridium thin or thick, transparent to darkly pigmented

SORDARIALES • Asci cylindric to club-shaped with apical pores and often some type of apical apparatus • Paraphyses may or may not be present at maturity • Ascospores various in pigmentation and septation

Sordaria fimicola • Used extensively for genetic studies • Found on dung (fimicolous) • Color mutations in ascospores used as markers in genetic studies • Beaks are positively phototrophic and direct forcibly shot ascospores away from the substrate

Sordaria

Podospora on dung

Podospora

Cercophora alleghensis

CHAETOMIUM • Ubiquitous • Cellulose decomposers • Mesophilic, thermotolerant, thermophilic species • Tooth paste fungus

CHAETOMIUM • Perithecia ostiolate, covered with hairs • Asci thin-walled, evanescent • Ascospores lemon-shaped w. apical or sub-apical germ pores • Conidia, when produced, chlamydospores or phialospores

CHAETOMIUM - PERITHECIA

CHAETOMIUM

Neurospora crassa • Gets its name from the nerve-like striations on the ascospores • Used extensively in genetic studies (1 gene for 1 enzyme theory - Beadle & Tatum) • Field of haploid genetics - all genotypes expressed • Lab pest - very fast growth and conidiation rate, conidia hydrophobic & easily dispersed

Halosphaeriales • Occur primarily in seawater with some species in freshwater habitats • Ascomata membranous or carbonaceous • Hamathecium absent or as catenophyses • Asci thin-walled, usually without apical structures, deliquescing to release ascospores • Ascospores modified for dispersal & attachment in aquatic habitats

Ascospore appendages

HALOSPHAERIALES

Corollospora lacera

HALOSPHAERIALES

Nais glitra ascus

Nais glitra ascospores