Introduction to Fungi, Third Edition

430 HYMENOASCOMYCETES: HELOTIALES (INOPERCULATE DISCOMYCETES)
Table 15.1. The families currently placed in or near the Helotiales. Data from Gernandt et al. (2001), Kirk et al.
(2001) and Pfister and Kimbrough (2001). Three families printed in bold are considered in more detail in
this chapter.
Family No. of species Examples
Ascocorticiaceae 3
Bulgariaceae 1 Bulgaria inquinans
Cudoniaceae 10
Cyttariaceae 11 Cyttaria
Dermateaceae (p. 439) 385 Mollisia, Pyrenopeziza, Rhynchosporium,Tapesia
Geoglossaceae 48 Geoglossum,Trichoglossum
Helotiaceae 623 Ascocoryne, Hymenoscyphus, Neobulgaria
Hemiphacidiaceae 12
Hyaloscyphaceae 541 Hyaloscypha, Lachnum (¼ Dasyscyphus)
Leotiaceae 13 Leotia
Loramycetaceae 2
Phacidiaceae 3 Phacidium
Rhytismataceae (p. 440) 219 Rhytisma
Rutstroemiaceae 100 Rutstroemia
Sclerotiniaceae (p. 429) 124 Sclerotinia
Thelebolaceae 15 Thelebolus
Vibrisseaceae 14
DNA-based phylogenetic analyses (Holst-Jensen
et al., 1997). Members of both families produce
stalked apothecia which grow from stromata
located within the colonized host plant tissue.
The apothecia usually develop in spring from
overwintered stromata. The stroma is a food
storage organ and is usually differentiated into
two parts, a rind (cortex) of dark, thick-walled
cells and a medulla of hyaline cells. Two generalized
types of stroma have been distinguished.
To quote from Whetzel (1945),
The sclerotial stroma (commonly called the
sclerotium) has a more or less characteristic form
and a strictly hyphal structure under the natural
conditions of its development. While elements of the
substrate may be embedded in its medulla, they
occur there only incidentally and do not constitute
part of the reserve food supply. The substratal
stroma is of a diffuse or indefinite form, its medulla
being composed of a loose hyphal weft or network
permeating and preserving as a food supply a
portion of the suscept or other substrate (e.g. culture
media).
It is now clear that the sclerotial stroma is typical
of the Sclerotiniaceae where it is often
conspicuous (Plates 7a,b). Fungi belonging to
the Rutstroemiaceae (Plate 7c) produce the less
obvious substratal stroma. The Rutstroemiaceae
grow mainly as saprotrophs, but the Sclerotiniaceae
include some important plant-pathogenic
species. We shall only consider the latter family
further because much more is known about it.
Various types of macroconidia with or without
accompanying microconidia are formed within
the genus Sclerotinia in its widest sense, and species
with different types of conidia are regarded
by many mycologists as belonging to distinct
genera. Since these are very closely related,
Sclerotinia is a good example to illustrate the flexibility
of asexual reproduction in fungi (Weber &
Webster, 2003). For instance, Sclerotinia fuckeliana
has Botrytis cinerea with polyblastic conidia as its
asexual state (Figs. 15.5a,b) and is thus currently
called Botryotinia fuckeliana. It also produces microconidia
from clustered phialides (Fig. 15.5c).
Sclerotinia (Monilinia) fructigena produces Moniliatype
blastoconidia in chains (Fig. 15.3b) and lacks
a microconidial state, whereas S. (Myriosclerotinia)
curreyana produces only Myrioconium-like microconidia
(Figs. 15.1d f) but has no macroconidial