Jennifer A. Saleeba

Utilisation of carbon substrates by orchid and ericoid mycorrhizal fungi from Australian dry sclerophyll forests

The utilisation of a range of cell-wall-related and aromatic carbon substrates by multiple genotypes of three ericoid mycorrhizal fungal taxa was compared with two orchid mycorrhizal fungal taxa. Both groups of fungi catabolised most common substrates, though significant inter- and intraspecific variability was observed in the use of a few carbon substrates. Orchid mycorrhizal fungi had limited access to tannic acid as a carbon source and did not use phenylalanine, while the ericoid mycorrhizal fungi used both. Utilisation of tryptophan was limited to single genotypes of each of the orchid mycorrhizal fungi, and to only two of the three ericoid mycorrhizal fungi examined. Although broadly similar, some significant differences apparently exist in carbon catabolism of ericoid and orchid mycorrhizal fungi from the same habitat. Functional and ecological implications of these observations are discussed.

Molecular identification of fungi isolated from stem tissue of Upland cotton (Gossypium hirsutum)

Molecular techniques such as restriction fragment length polymorphism (RFLP) analysis, random amplification of polymorphic DNA (RAPD) fingerprinting, and DNA sequencing and database comparison, were employed to identify fungi isolated from field-grown cotton plants (Gossypium hirsutum L.). DNA fragments of between 510 and 590 bp, representing the two rDNA (rDNA) internal transcribed spacers (ITS1 and ITS2) and the intervening 5.8S rRNA gene, were amplified from the fungi with eukaryotic consensus primers. Subsequent digestion with the restriction endonucleases AluI, CfoI, HaeIII, HinfI and HpaII enabled the allotment of all 57 isolates to 13 different groups. Restriction analysis was supported by RAPD–PCR analysis of multiple isolates and rDNA sequencing of representative fungi from each group. Sequence alignment and comparison with rDNA sequences of other fungi available in GenBank allowed for putative identification of three different taxa of Fusarium, two taxa each of Cladosporium, Diaporthe and Nectria, and one taxon each of Alternaria, Ampelomyces, Bartalinia, Phaeosphaeria and Rhizoctonia. Many of the stem-colonising fungi identified in this study are either pathogenic on cotton or have elsewhere been found to act as biocontrol agents.

TreeGeneBrowser: phylogenetic data mining of gene sequences from public databases

MOTIVATION Sequence databases represent an enormous resource of phylogenetic information, but there is a lack of tools for accessing that information in order to assess the amount of evolutionary information in these databases that may be suitable for phylogenetic reconstruction and for identifying areas of the taxonomy that are under-represented for specific gene sequences. RESULTS We have developed TreeGeneBrowser which allows inspection and evaluation of gene sequence data for phylogenetic reconstruction. This program improves the efficiency of identification of genes that may be useful for particular phylogenetic studies and identifies taxa and taxonomic branches that are under-represented in sequence databases.