Isolation and Culture of Lichenicolous Fungi
The lichenicolous fungi are characterised by their habit of growing on lichens. Hawksworth (1982) has estimated that as many as 1000 fungal species within 300 genera can be assigned to this group, and it is clear that they form a myriad of associations wi
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PROTOCOL
Isolation and Culture of lichenicolous Fungi JAMES
D.
LAWREY
Introduction The lichenicolous fungi are characterised by their habit of growing on lichens. Hawksworth (1982) has estimated that as many as 1000 fungal species within 300 genera can be assigned to this group, and it is clear that they form a myriad of associations with lichens. Many attack living lichens and are obviously parasitic (mycoparasites) or pathogenic, but with levels of virulence that vary considerably. There are parasites that cause massive destruction oflichen tissues, but many cause little or no damage. Of these, some (called parasymbionts) appear to be lichen-forming fungi that share the photosynthate produced by another lichen's captured photobiont cells. Still others are saprophytic and colonise only dead lichen tissues. Because lichens are now known to harbour many opportunistic fungi that are not restricted to lichens (e.g., Petrini et al. 1990), some investigators (Rambold and Triebel 1992) prefer to exclude saprophytes from the lichenicolous fungi. I will restrict my discussion here to those lichenicolous fungi that are obviously parasitic or pathogenic. Thorough laboratory study oflichen fungal parasites requires that they be isolated and brought into culture. As a general rule, standard mycological techniques can be employed to isolate these fungi. However, there are some special considerations to be taken. It is my objective in this chapter to summarise techniques for the isolation and culture of lichen mycoparasites. To encourage investigators to bring more of these fungi into culture, I will also briefly list some of the research questions that can be addressed using these cultured fungi as experimental organisms.
James D. Lawrey, George Mason University, Department of Biology, Fairfax, Virginia, 22030, USA (phone +01-703-993-1059; fax +01-703-993-1046; e-mail [email protected])
I. C. Kranner et al. (eds .), Protocols in Lichenology © Springer-Verlag Berlin Heidelberg 2002
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JAMES
D.
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Subprotocol 1 Isolation of Lichenicolous Fungi From Living Collections Materials Equipment
Chemicals
Culture media
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Laminar flow bench
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Incubator
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Autoclave
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70% Ethanol
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10% - 20% sodium hypochlorite
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Sabouraud's medium with dextrose (SDA) or maltose (SMA)
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Potato dextrose agar (PDA)
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Cornmeal agar (CMA)
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Malt-yeast extract (MYA)
For more details see also Chapters 1-3 and 18.
Procedure 1. Lichenicolous fungi are usually collected attached to lichens from nor-
mal lichen substrates. It is sometimes not immediately evident that a fungal parasite is included with a lichen collection. What is frequently seen in the field are discoloration of lichen thalli or oddly coloured spots where parasites have developed fruiting structures. When discoloured lesions are observed microscopically in the laboratory, fungal parasites can frequently be seen and identified. Some general comments about collections: • Identification generally requires fruiting material (ascomata, basidiomata, conidia-forming struc
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