Interspecific and intraspecific variation of ectomycorrhizal fungi associated with Eucalyptus ecosystems as revealed by ribosomal DNA PCR-RFLP

Abstract

Gondwanan vegetation, and the Australian region in particular, is species rich for ectomycorrhizal fungi in epigeous and hypogeous forms with over 100 species recorded in small (1 ha) patches of forests. Distinguishing co-occurring ectomycorrhizal fungi as root associations in native (natural or wildlands) vegetation or plantations and discriminating them from other larger basidiomycetes, e.g. wood and leaf litter decomposer fungi, places large demands on molecular identification, especially if interspecific similarities and intraspecific variation occur in target sequences. One hundred and nine species of larger basidiomycetes from a single forest location were characterised by PCR-RFLP profiles of two genomic regions (nuclear rDNA ITS and mtLSU). Over one-third of the species for which multiple isolates were tested showed intraspecific variation in either one or both genomic regions. This remarkably high variation questions previous assumptions about intraspecific ITS sequence variation and highlights the value of integrated molecular and morphological databases including voucher specimens. It also emphasises the value of molecular investigations that use more than one genomic region. Interspecific similarities were common among the Cortinariaceae, especially in the ITS region. Discrimination of most Cortinariaceae species was achieved using variation in the mtLSU region in conjunction with the ITS. This new information raises the possibilities that the ITS sequence is more conserved and the mtLSU more variable than among species of the other 23 families. In the other families, interspecific ITS variation was greater and the mtLSU profiles grouped species within families. The high variation in the two genomic regions indicated possible differences in the fungal population structure between two adjacent, differently managed blocks of Eucalyptus marginata forest. The significance of this variation to ecology, biodiversity assessment and ecosystem management are discussed.

Fungi on stems and twigs in initial and advanced stages of dieback of European ash (Fraxinus excelsior) in Poland

“…Each sequence was identified to the lowest taxonomic rank possible. Sequences with 97-100 % similarity were identified to species and with 91-97 % similarity to genus (Glen et al 2001); however, the morphological analyses have been also taken into account. Sequences of representative isolates were deposited in GenBank (Table 2).…”

The new genus Auritella from Africa and Australia (Inocybaceae, Agaricales): molecular systematics, taxonomy and historical biogeography

“…In Australia, Auritella is probably mycorrhizal with species of Eucalyptus and Corymbia (Myrtaceae). Numerous studies have demonstated that Eucalyptus sensu lato forms ectomycorrhizas and that natural and plantation eucalypt ecosystems are ectotrophic (Bougher et al 1990;Brundrett et al 1996;Castellano and Bougher 1994;Glen et al 2001). However, other plant associates of the Casuarinaceae (Allocasuarina) and Fabaceae (Acacia, Dillwynia and Gastrolobium) remain possible symbionts as well (Warcup 1980;Tommerup and Bougher 1999).…”

Polymorphism in the internal transcribed spacer (ITS) of the ribosomal DNA of 26 isolates of ectomycorrhizal fungi

“…The PCR-RFLP technique, coupling two known procedures to detect polymorphisms in DNA regions which have been amplified by specific oligonucleotide primers and restricted with different endonucleases, has been successfully used to analyze regions of ribosomal DNA of ectomycorrhizal fungi (Gardes et al, 1991;Erland et al, 1994;Henrion et al, 1994;Farmer and Sylvia, 1998;Gomes et al, 1999;Glen et al, 2001a). The internal transcribed spacer (ITS) region separating genes 17S and 25S, can be amplified by specific primers anchored in these two units.…”