Introduction to Fungi, Third Edition

TREMELLALES
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Fig 21.12 Life cycle of Tremellamesenterica.The monokaryotic part of the cycle is shown only for one of the two mating types
(white nuclei).Basidiospores failing to leave the fruitbody maygain a second chance byrepetitious germination to form a
ballistoconidium.On other substrates, basidiospores germinate by way ofblastoconidia which give rise toyeastcells.Conjugation
of two compatibleyeastcells givesrise to the dikaryotic mycelial stagewhich forms fruitbodiesproducing dikaryotic conidia, haploid
yeastcells by de-dikaryotization (not shown), andhaploidbasidiosporesby meiosis.Key eventsin thelife cycle areplasmogamy (P),
karyogamy (K) andmeiosis (M).Haploid nuclei are drawn as empty or filled circles; the diploid nucleus is drawn larger andhalf-filled.
state (Fig. 21.11b) with an uncertain role in the life
cycle. Additionally, de-dikaryotization to give
yeast cells has been observed in the fruit bodies
of T. mesenterica.
Another common species is T. foliacea (sometimes
synonymized with T. frondosa) with its fleshcoloured
to pale brown, lobed or contorted fruit
bodies on oak and beech stumps. In this species,
basidiospores germinate on suitable substrates
by giving rise directly to budding yeast cells
(Fig. 21.13). This has also been observed in
T. encephala (Ingold, 1985). There are no dikaryotic
conidia in these two species. Most Tremella spp. are
heterothallic with a modified tetrapolar mating
system, but in T. fuciformis both homothallic
and heterothallic strains have been observed
(Fox & Wong, 1990).
Cultivation of Tremella
The ‘silver ear’ fungus, T. fuciformis, has been
cultivated in China on wood and sawdust for
about 200 years (Chang & Miles, 2004). Although
almost always associated with Hypoxylon spp.
in nature (Chen, 1998), mycoparasitism does
not seem to be obligate because cultivation is
possible in monoculture. However, yields are
greatly stimulated in the presence of a ‘friend of
the mycelium’, i.e. the substrate is co-inoculated
with T. fuciformis and Hypoxylon archeri or another
suitable host species (Chang & Miles, 2004).