Diatrype disciformis (Hoffm.) Fr.

Summary from Lecture 11: Prototunicate Ascomycetes 

•Prototunicate Ascomycetes have spherical asci that lack dehiscence 

mechanisms (no pore, no operculum, no jack-in-the box). 

•Prototunicate asci are associated with cleistothecia (closed ascomata 

- ascoma = fruitbody of ascomycete). Spores escape from 

cleistothecia passively, e.g. by sifting out through weft of hyphae 

that comprises cleistothecial wall. 

•Many dermatophytes are prototunicate ascomycetes in the 

Onygenales. Many have synanamorphs, some have only asexual 

reproduction, some transmit from host to host without spores (how?). 

•The Eurotiales are notable for the production of secondary 

metabolites such as aflatoxins. Also as gene expression systems. 

Lecture 12 : Ascomycetes with hymenia & unitunicate asci 

Reading: TEXT, Chapter 4 and Study Guide 12. You should 

read through: http://tolweb.org/Pezizomycotina/29296 AND 

http://www.forestpathology.org/dis_chestnut.html 

Objectives: Know the what a unitunicate asci is and be able to recognize 

the characteristic features of these fungi in the field, in the, Sphaeriales, 

Clavicipitales, Hypocreales, Pezizales and Leotiales (We will see All!). 

Think about Chestnut Blight as another introduced tree disease (compare 

with DED). Understand why Neurospora crassa is a model system.

Tree of Life http://tolweb.org/Pezizomycotina/29296 is up-to-date and DNA sequence-based. 

We are still in the Pezizomycotina, but in new classes today. Your Text, The Fifth 

Kingdom presents a taxonomy based on ascus and ascoma (unitunicate inoperculate asci 

in perithecia, called Pyrenomycetes; or unitunicate asci, in apothecia, called 

Discomycetes in many texts). Unitunicate, operculate asci are only in the order Pezizales. 

Green arrow = lichenized 

Series Unitunicatae-Operculatae 

Order Pezizales: 150 genera, 900 species. The 'operculate discomycetes' 

-- Your TEXT looks at 7 of the 13 families currently recognized. 

Familiy Pezizaceae is the core of the Order: Their asci have a diagnostic pop-open 

lid or operculum, and the tips of the asci are amyloid (sometimes expressed as I+ -this 

means giving a blue, starch-like reaction in an iodine solution known as 

Melzer's reagent). Below right: evolution of hypogeous forms (the true Truffles):

Photo from Algonquin Park, BIO 335 trip, 2010: Operculate ascus –no “toilet” lid yet 

- Note tip of ascus is blue in Melzer’s reagent. See that ascus tip is thin. 

- Note 8 ascospores with reticulate walls, each contain 2 oil vacuoles. 

Order Pezizales (Pezizales is placed in order Pezizomycetes in 

Tree of Life), Family Morchellaceae 

Morel 

Choice Edible 

Verpa (left 2 photos) 

May be Poisonous 

Gyromitra infula 

Poisonous. 

Morel (right 2 photos) 

Choice Edible 

TEXT

Order Pezizales 

Family Tuberaceae - the truffles. 

The inoperculate ascus has a 

thick tip that is perforated by a 

pore (there is a hole through the 

tip). The pore wall may turn 

blue in Melzer’s reagent. 

Ascus (showing an apical perforation 

pore with the wall turning blue in 

iodine solution), paraphyses and 

ascospores of Mollisia ventosa. © 

Hans-Otto Baral 

http://tolweb.org/Leotiomycetes 

The ascomata are closed, hypogeous and 

solid (no air spaces any more -- as you can 

see in this bisected specimen of Tuber 

aestivum, which a truffle dog brought to me 

at Scheggino in Italy) 

The asci, produced in a highly convoluted 

hymenium, are rounded and thin-walled 

(those of Tuber albidum are shown at left) 

with no trace of an operculum or other 

shooting mechanism, and usually contain 

only 1-3 spores. TEXT.

Order Leotiales: 13 families, 400 genera, 2000 species. The 'inoperculate 

discomycetes.' The apothecial ascomata are superficially similar to those of the 

Pezizales, but the asci are inoperculate, and usually have amyloid apical ring. 

Family Sclerotiniaceae (images from Prof. Kohn and TEXT). 

As the name implies, these fungi often form sclerotia, which may be solid 

masses of fungal tissue, or may be of mixed origin -- fungal hyphae riddling a 

mummified host such as a peach, plum or cherry, or a catkin (right). Having 

overwintered in this guise, they germinate in spring and use the stored energy 

to produce stalked apothecial ascomata (right). Ascospores are shot when the 

host is in flower, and gain entrance through the stigma.

Order Leotiales: Sclerotiniaceae. 

http://www.agf.gov.bc.ca/cropprot/tfipm/brownrot.htmt 

http://www.apsnet.org/education/LessonsPlantPath/BrownRo 

t/text/CYCLE.HTM Also TEXT 

Order Leotiales: Family Leotiaceae contains some more normal-looking 

'discomycetes' such as Bisporella, which produces those small yellow 

discoid apothecia so common on fallen, decorticated tree-trunks... 

Family Geoglossaceae - literally "earth-tongues" 

TEXT

http://www.naturefg.com/pages/fu-ascomycota.htm Nature Photography by Dragiša Savić 

Holwaya mucida is a Leotiales fungus with black, gelatinous, turbinate apothecia (sexual 

fruitbodies also called ascomata, singular is ascoma). The asexual stage is large also – 

note the white head is mucilaginous and contains numerous asexual conidia (mitospores). 

Amit Patel collected the anamorph (mitosporic, asexual state) at Algonquin Park. 






Green arrow = lichenized

Order Sphaeriales: 225 genera, 1300 species. 

Dark, crusty, globose to pear-shaped individual perithecial 

ascomata with prominent ostioles. 

OR many perithecial cavities immersed in a single stroma to 

form a compound fructification, as in Xylaria below 

The asci often have an apical ring or sphincter, which is 

usually, though not always, amyloid (stains blue in iodine). 

Thread-like, sterile elements called paraphyses are present 

between the asci in the hymenium of some members, absent 

from others 

Ascospores can be light or dark, simple or septate, with or 

without germ pore or slit, sometimes with gelatinous sheaths or 

appendages. 

Diatrype disciformis (Hoffm.) Fr. 

http://www.bioimages.org.uk/html/P158449.HTM

Nature 422, 859 - 868 (24 April 2003); doi:10.1038/nature01554 

The genome sequence of the filamentous fungus 

Neurospora crassa 

Neurospora crassa is a central organism in the history of twentiethcentury 

genetics, biochemistry and molecular biology. Here, we 

report a high-quality draft sequence of the N. crassa genome. The 

approximately 40-megabase genome encodes about 10,000 proteincoding 

genes—more than twice as many as in the fission yeast 

Schizosaccharomyces pombe and only about 25% fewer than in the 

fruitfly Drosophila melanogaster. Analysis of the gene set yields 

insights into unexpected aspects of Neurospora biology including 

the identification of genes potentially associated with red light 

photobiology, genes implicated in secondary metabolism, and 

important differences in Ca2+ signalling as compared with plants 

and animals. Neurospora possesses the widest array of genome 

defence mechanisms known for any eukaryotic organism, including 

a process unique to fungi called repeat-induced point mutation 

(RIP). Genome analysis suggests that RIP has had a profound 

impact on genome evolution, greatly slowing the creation of new 

genes through genomic duplication and resulting in a genome with 

an unusually low proportion of closely related genes. 

Order Hypocreales: 80 genera, 550 species. 

This order is recognized by its brightly coloured, simple or compound, 

perithecial ascomata -- usually yellow, orange or red -- which are fleshy or 

waxy in texture, and usually borne on supporting layers of mycelium (subicula) 

or in stromata. Four genera are especially well-known. 

Nectria (27 spp) has bright red, superficial perithecia 

(right) containing 2-celled (didymosporous) ascospores. 

Some species cause cankers and die-backs of trees. 

Below: commonly encountered anamorph, 

Tubercularia, causes “coral spot”.Nectria species 

can cause cankers and die-backs of trees.

Order Hypocreales continued: 

The most economically important of the 

nectriaceous anamorphs are certain Fusarium 

specie), many of which cause destructive wilt 

diseases of higher plants, or produce mycotoxins. 

Gibberella also has Fusarium anamorphs, which 

are producing the reddish pigment seen in the 

picture 

The lower picture shows Gibberella (dark) and its 

Fusarium anamorph (reddish-orange) growing 

together on a corn cob. 

One species of Gibberella causes a disease of rice 

called 'foolish seedling' in which seedlings grow 

too rapidly and consequently fall over. The active 

principle, a plant growth hormone called 

gibberellic acid, has been extracted and is now 

widely used to stimulate plant growth. 


TEXT 

Hypomyces lactifluorum, an orange fungus which, 

like other species of the genus, parasitizes 

basidiiomycetes, in this case the agaric genera 

Lactarius and Russula... 

Left: The ostiole is the opening of the perithecium.


Hypocrea forms fleshy stromata on wood 

(LEFT). The dark spots are the ostioles of the 

embedded perithecial cavities. 

The teleomorph of Hypocrea is recorded far less 

often than its green-spored, phialidic 

anamorph, Trichoderma (lower right) which, 

because it is a broad-spectrum mycoparasite, 

and produces cellulases and antibiotics, is one of 

the most important moulds in forest soils. Used 

in biological control of pathogenic fungi and 

for production of enzymes which can convert 

cellulose to glucose. 

Order Clavicipitales: 27 genera, 

270 species. 

Sophisticated, obligate parasites: 

(a) frequently stalked, all-fungal 

stromata (below, A,B,D,E), (b) 

long asci without apical rings, but 

with thickened tips (below, right, 

F), and (c) long, thread-like 

ascospores that in some taxa 

fragment at or following release 

(below, right, F). TEXT. 

Trichoderma viride 

(anamorphic fungus) 

TEXT and:fungus) 

http://www.bioimages.org.uk/HTML/ 

P164979.HTM

Chestnut Blight Disease 

Contributed by 

Sandra L. Anagnostakis 

Connecticut Agricultural Experiment Station 

Box 1106 

New Haven, CT 06504 

Phone 203-974-8498 

Sandra.Anagnostakis@po.state.ct.us 

Figure 1. An American chestnut stem with a chestnut blight canker. (Click image for larger view and more information). 

Chestnut blight, or chestnut bark disease, is caused by an introduced fungus, Cryphonectria parasitica 

(Murrill) Barr, (formerly Endothia parasitica [Murrill] Anderson & Anderson). The fungus enters wounds, 

grows in and under the bark (Fig. 1), and eventually kills the cambium all the way around the twig, 

branch, or trunk (33). Sprouts develop from a burl-like tissue at the base of the tree called the ‘root 

collar,’ which contains dormant embryos (39). Sprouts grow, become wounded and infected, and die, and 

the process starts all over again. 

Cankers were first reported in the United States in 1904 on American chestnut trees (Castanea dentata 

[Marshall] Borkhausen) (Fig. 2) in New York City (32). None of the control attempts (chemical treatments, 

clearing and burning chestnut trees around infection sites) were successful (47). By 1926 the fungus was 

reported throughout the native range of American chestnut (Fig. 3), and a major forest tree had been 

reduced to a multiple-stemmed shrub (17). In 1912 the Plant Quarantine Act was passed to reduce the 

chances of such a catastrophe happening again (49). 

Fig. 1 

Fig 3 

Fig. 1. An American chestnut stem with a chestnut blight canker (Castanea dentata with a 

Cryphonectria parasitica canker). The fungus enters through wounds such as the broken branch 

stub on the left, and grows in and under the bark, killing the cambium. Fungal stromata break 

through the lenticels and pycnidia producing conidia and perithecia producing ascospores are 

formed. Photo by R. A. Jaynes. 

Fig. 2. An American chestnut tree (Castanea dentata [Marshall] Borkhausen) growing in Scotland, 

Connecticut in 1905. The tree was 83 feet tall, 27 inches in diameter, and 103 years old. 

Figure 3. The natural range of American chestnut as presented by Saucier in 1973 

http://www.apsnet.org/online/feature/chestnut/top.html 

Fig. 2






Green arrow = lichenized 

Ascoma 

(teleomorph) 

Ophiostoma ulmi causes 

Dutch Elm Disease. 

Hair-like hyphae at the top 

Of ascoma. 

Graphium anamorph Synnemata. 

Sporothrix anamorph 

Order Ophiostomatales (Sordariomycetes in Tree of Life): 15 genera, 130 species. 

Ascomata have long, tubular necks, with the ostiole at the tip. The asci are not 

arranged in a hymenium, and autolyse early. The spores ooze out of the ostiole and 

form a slimy droplet that is supported by a ring of specialized, hair-like hyphae at 

the top of the neck.These fungi often fruit in bark beetle tunnels - elevated spore 

drop ensurse beetle carries spores with it when it flies off in search of another tree. 

Ophiostoma ulmi, my example of the Ophiostomatales, has a Graphium anamorph 

that produces many conidiomata each bearing a slimy droplet of conidia at its tip - 

anamorph is completely analogous to the teleomorph; both ensure that beetles 

don't leave home without them. Another anamorph, Sporothrix, produces conidia 

and yeast cells in tree xylem, releasing wilt toxin, cerato-ulmin. FROM TEXT.

Plant Disease Lessons: http://www.apsnet.org/Education/LessonsPlantPath/DutchElm/top.htm 

As early as June, the leaves on a DED-infected elm 

will wilt, turn yellow, then curl and turn brown. 

Symptoms usually first appear in the crown on the 

tree, and can be seen until fall colours appear. 

Dutch elm disease is spread by the native elm bark 

beetle which can fly up to 2 km as it searches for 

healthy elms to feed on. The DED fungus has sticky 

spores that become attached to the beetle during 

its breeding period. The beetle then spreads the 

fungus when it feeds on and over-winters in healthy 

elms. 

Do not prune your elms between April 13th and July 

31st. The Elm Bark Beetle that spreads the DED 

fungus is attracted to freshly cut elm and is most 

active during this period. 

http://www.sdeda.ca/what_is.html 

http://www.fs.fed.us/na/morgantown/fhp/palerts/ded/elm.htm

DED early symptoms: 

Yellowing of leaves in 

crown. 

http://www.sdeda.ca/what_is.html 

DED symptoms: brown discoloration of xylem.

Diatrype disciformis (Hoffm.) Fr.

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