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Genetic variation in ectomycorrhizal fungi and its exploitation in ecological investigations of eucalypt forests

Glen, Morag (2001) Genetic variation in ectomycorrhizal fungi and its exploitation in ecological investigations of eucalypt forests. PhD thesis, Murdoch University.

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Australian eucalypt forests have extremely high species richness and taxonomic diversity of ectomycorrhizal fungi which are root symbionts. Molecular techniques have the potential to distinguish the species present as root associations. PCR-RFLP (polymerase chain reaction - restriction fragment length polymorphism) has been useful in northern hemisphere ecosystems, but further development was needed for Australian taxa. Primers and conditions were optimised for the specific amplification of basidiomycete DNA. RFLP analysis of the amplified fragments distinguished 96 of 109 species of ectomycorrhizal fungi from a study site in the jarrah (Eucalyptus marginata) forest, though some difficulties arose in the Cortinariaceae. In addition, intraspecific variation occurred in a large proportion of the species for which multiple collections were tested. The PCR-RFLP profiles from identified sporocarps were stored in a database to facilitate identification of fungal species colonising ectomycorrhiza.

The basidiomycete ectomycorrhizal fungal communities of two adjacent forest blocks with different management histories were characterised by PCR-RFLP analysis. Both blocks had a high degree of biodiversity in the ectomycorrhizal fungal communities. Fourteen taxa, including the most abundant species on each of the blocks, were identified by reference to the database of PCR-RFLP profiles from sporocarps. Another 135 PCR-RFLP profiles from root-tips were not matched to profiles from sporocarps. These profiles were probably caused by species which had not been sampled as basidiomes, implying that species richness is even greater than has been estimated from sporocarp surveys.

There was a considerable difference between the blocks in the predominant fungal species. The most common and abundant ectomycorrhizal fungus on block A, which has remained unburnt for the last 66 years, was Russula clelandii. This species was not detected on root tips from block P, which has been burnt every 5-6 years during the last 66 years. Conversely, the most commonly found species on block P, Amanita xanthocephala, was found in very low abundance in only two soil cores from block A. The second most abundant fungus on block A was not matched to the database of PCR-RFLP profiles from sporocarps, and the ITS sequence did not retrieve a close match from searches of Genbank. EMBL or private DNA databases.

As the species delimitation of R. clelandii is not clearly defined and collections show a wide range of morphological characters, DNA sequences of collections from across Australia of R. clelandii and two other red-capped Russula species were analysed. In comparison to the level of intraspecific variation seen in other species, a surprising degree of sequence variation among the R. clelandii collections was found, but with no sub-specific grouping which would permit separation of taxa. This is congruent with morphological characters which also show a high degree of variation without unambiguous groups. R. clelandii appears to be a species complex with a very high level of genetic variation.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Division of Science and Engineering
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): O'Brien, Philip and Tommerup, Inez
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