Lecture 13. Ascomycota III

Lecture 13 Ascomycota III - Pezizomycotina: Leotiomycetes Lutzoni et al., 2004, American Journal of Botany Traditional “Discomycetes” Leotiomycet...
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Lecture 13 Ascomycota III - Pezizomycotina: Leotiomycetes

Lutzoni et al., 2004, American Journal of Botany

Traditional “Discomycetes” Leotiomycetes: Inoperculate Discomycetes Pezizomycetes: Operculate Discomycetes (Lecture 12)

Leotiomycetes Include the traditional Inoperculate Discomycetes - asci unitunicate, release their spores through an apical, circular perforation or pore (“sphincter”). - apothecium: cup, disk, tongue-like - Major taxa ---- Rhytismatales: Rhytisma, Lophodermum ---- Leotiales: Leotia, Geoglossum; Sclerotinia, Orbilia ---- Cyttariales; Cyttaria

Phylogenetically, also includes the Erysiphales with cleistothecium-type ascomata and unitunicate, inoperculate asci.

Lutzoni et al., 2005

The traditional Leotiales Traditional Leotiales includes Leoticaeae and Geoglossaceae (“Earth-tongues”) - apothecia on tongue-, club-, or fan-shaped ascocarps; often “pileate” (stalk); - ascospores vary from one- to many-celled, and from hyaline to dark-brown; - saprobic --- in forests, growing on soil, decaying leaves, wood, or other organic matter …. but “Earth-tongues” ascomata are polyphyletic and the different clades are consistent with ascospore and paraphyse morphologies

Leotiomycetes 2 = Geoglossaceae

Leotiomycetes 1

(From Kendrick)

Geoglossum with black or brown club- to tongue-shaped apothecia

Spathularia with tongue/spoon-shaped ascocarps

Leotiomycetes 2 = Geoglossaceae

Ex: Geoglossum glabrum From http://flickr.com/photos/[email protected]/2299285726/

Leotiomycetes 1 : Orbiliaceae Some species of Orbilia have Arthrobotrys anamorphs, which are nematode-trapping fungi

Orbilia xanthostigma


(a) constricting rings and (b) sticky networks of loops. (from Malloch)

Leotiomycetes 1 : Leotiaceae - yellow or green; club-shaped to pileate apothecia



Leotiomycetes 1 : Helotiaceae Chlorociboria - stains wood bright green



http://users.skynet.be/sky37166/champignons/c/ chlorociboria_aeruginascens.htm

A traditional Discomycetes: Cyttaria - Cyttariales and Cyttariaceae include a single genus… Cyttaria; about 10 species - phylogenetic affinities not fully known; DNA sequence analysis indicated a possible relationship with Helotiales (e.g. Chlorociboria) - ascocarps (apothecia) embedded in fleshy, globose white, bright orange, or yellow stromata (golf ball-size) --- edible;regularly sold in markets in southern Chile. - conidia are produced on a stroma and later apothecia develop within the same stroma

- known only from species of Nothofagus, the Southern Hemisphere beech --- distribution: southern South America and Australasia (Australia and New Zealand) --- not found throughout thewhole range of Nothofagus: the fungus is absent from PapuaNew Guinea and New Caledonia. --- possible coevolution of some fungus-host pairs (host specificity, co-speciation).


Nothofagus “Southern beech”; a Gondwana relic? Host of Cyttaria

Nothofagus forest in southern Chile: http://www.madrimasd.org/blogs/universo/

Leotiomycetes 1 : Rhytismataceae - ascocarps = black; sphaerical, discoid, or elongated; --- often of the epithecium=type (=fusion of paraphyses that ‘covers’ the hymenium --- develop immersed in host tissue, often from a stroma, which ultimately ruptures to expose the hymenium. - asci and apical ring usually inamyloid; paraphyses present; - ascospores ovoid to filiform, hyaline to brown, often with a gelatinous (slimy) sheath; often septate; - ecology: saprobes, endophytes, and plant pathogens, (several species cause needle diseases in conifers);

Major genera: Lophodermum, Rhytisma Lophodermum - endophyte (asymptomatic) of pine needles, eventually saprobic when the needle die.

Pics from Kendrick

Leotiomycetes 1 : Rhytismataceae Rhytisma - most species produce numerous apothecia within a stroma; - Rhytisma acerinum forms saucer-shaped ascocarps in fallen, dead maple leaves. The flat, circular, black, tarlike stromata, which bear the apothecia within them, give the disease its name: tar spot of maple. --- the fungus passes the winter in the fallen leaves in the immature ascocarp stage --- in early spring, the asci complete their development; the stroma splits along preformed, radiate lines, and the ascospores are forcibly ejected. Pics from Kendrick

Rhytisma acerinum

Rhytisma punctatum produces a similar syndrome on maple leaves, but the small, individual ascomata do not fuse as in R. acervinum.

Rhytisma acerinum . A. Leaves with young (left) and older blackened (right) stromata in field conditions. B. Habit on leaf. C. Part of stroma with ascomata viewed with a dissecting microscope. D. Part of stroma and ascoma in vertical transverse section. E. Asci, ascospores and paraphyses. F. Part of conidioma in vertical transverse section. G. Detail of conidiomatal upper wall in horizontal section. H. Conidiogenous cells and conidia.


Leotiomycetes 1 : Sclerotiniaceae (from Kendrick)

Sclerotinia - soil-born pathogen - causes plant diseases including vegetables and crops - infection occurs either by direct mycelial germination of sclerotia or through ascospores produced from apothecia that germinate from sclerotia. - sclerotia can survive several years in soils. http://www.ndsu.nodak.edu/plantpath/sclero.htm:

Stem rot in onions and sunflowers;

http://www.hri.ac.uk/site2/research/ http://www.gov.mb.ca/agriculture/crops/ path/sclerpat/scleropa.htm diseases/fac31s00.html

We have calculated that as many as 1 million sclerotia per acre were returned to the soil from dry beans severely infected by Sclerotinia. […] Each apothecium can produce from 2 to 30 million spores over a period of several days. In some grain fields infested with sclerotia from diseased dry beans, we have assayed over 40,000 apothecia per acre. This means the potential spore load would equal a billion to a trillion spores from each acre of infested land. […] Spores can be transported in the wind for miles and a sticky mucilage insures spores stick to any surface they contact. If spores contact weakened plant material, the fungus can grow saprophytically and then proceed into healthy plant material as a parasite.

Leotiomycetes 1 : Sclerotiniaceae

Monilia anamorphs

(From Kendrick)


(From Malloch)

A gourmet note: Botrytis on overripe grapes = 'noble rot' - 'pourriture noble’ in French -- in small quantitie, add and exquisite flavour during fermentation, e.g. Chateau d'Yque and Sauternes wines are most expensive French wines.

Botrytis anamorphs

Leotiomycetes 1 : Erysiphales (= “powdery mildew”) - obligatory parasites on plants (mostly leaves); do not grow in culture - 28 genera, ca. 100 species



Example: Erysiph; common on grass (including cereals and lawns), ornamentals, vegetable crops, etc..

Powdery mildew


Diagram of powdery mildew fungus Erysiphe graminis. The fungus is on the surface of a leaf except for its feeding organs (haustoria), which invade the epidermal cells. www.ipm.uiuc.edu/ diseases/series400/rpd406/

Disease Cycle Powdery mildew fungi live chiefly on the outer surface of the host plant. They obtain food and water by means of small, branched, rootlike organs (haustoria) that penetrate the grass leaf or sheath and enter the surface layer or epidermal cells (Figure 2). The mildew appears powdery because it produces tremendous numbers of microscopic chains of spores (conidia). During cool (55 to 70 F; 13 to 21 C), humid cloudy weather, spores are continuously produced for 7 to 14 days until the host tissue dies. The conidia are easily carried by air currents to other grass plants in the same or neighboring turf areas, where they produce new infections and start the cycle once again. The conidia are capable of germinating and producing infections within 2 hours after landing on a leaf. New conidia are produced within a week after infection occurs. As the fungus matures, the grayish white powdery growth forms dense mycelial mats. Occasionally, speck-sized, black, fungus-fruiting bodies (cleistothecia) develop in the mycelial mats during autumn. These bodies are especially evident on dead grass leaves. Sexual or overwintering spores (ascospores) are sometimes produced in the cleistothecia. Cleistothecia, however, are not common in turfgrasses. The powdery mildew fungus survives the winter as cleistothecia on dead plant tissues and as mycelial mats on living grass plants. The ascospores and/or conidia are released in early spring and produce the initial infections.

Leotiomycetes 1 : Erysiphales - ascomata of Erysiphales = cleistothecium-type;often with appendages - When the asci expand they break the cleistothecium - Unclear (debated) in the literature if asci are of the type “unitunicate” or “bitunicate”; inoperculate with sphincter. Example:Erysiphe deistothecium


Cleistothecia types in the Erysiphales Erysiphe cichoracearum

http://highplainsipm.org/ HpIPMImage/ ImageSearch.exe? criteria=Powdery +Mildew&x=20

Cleistothecia of Uncinula necator in various stages of maturity.