Introduction to Fungi, Third Edition

HYPOCREALES
341
Fig12.16 Conidiophores of
Hypocrea spp. (a) Gliocladium-type
conidiophores of H. gelatinosa.
(b) Details of phialides of
H. gelatinosa.(c)Trichoderma viride
conidial state of H. rufa. (d) Detail
of phialides of H. rufa. (a,c) to same
scale; (b,d) to same scale.
The mating behaviour of Hypocrea spp. is
poorly understood because perithecial development
in culture occurs only rarely, except for the
tropical species H. jecorina. This species shows
bipolar heterothallism, half of its ascospores
being of one and half of the opposite mating
type (Lieckfeldt et al., 2000). Another tropical
species, H. poronioidea, also forms perithecia in
culture but the genetic basis of sexual reproduction
is not clear. Cultures from eight partascospores
in each of several asci were self-fertile
(i.e. homothallic), whilst the other eight partascospores
produced only conidia and were selfsterile.
Another unusual feature of this fungus
is that, in addition to having a Trichoderma
anamorph, it has an Acremonium-like synanamorph.
The Acremonium-like conidia can germinate,
i.e. they have an asexual function, but it is
possible that they also have a spermatial role
(Samuels & Lodge, 1996).
12.4.2 Nectria (Nectriaceae)
The concept of the genus Nectria has changed in
recent years. Previously considered to include
about 200 species, the genus has now been
narrowed to about 30, centred around
N. cinnabarina (Rossman, 1983; Rossman et al.,
1999). Perithecia of Nectria are common on twigs
and branches of woody hosts. Many are saprotrophic
or weakly parasitic but some cause
economically important diseases, e.g. N. coccinea
causes bark disease of beech (Fagus sylvatica),
whereas N. galligena infects apple and pear trees.
Although there are some reports that N. galligena
may have a prolonged latent (endophytic) phase,
the fungus acts as a wound pathogen in most