Are Sebacinaceae common and widespread ectomycorrhizal associates of Eucalyptus species in Australian forests?

A molecular survey of basidiomycete ectomycorrhizal fungi colonising root tips at a site in Eucalyptus marginata (jarrah) forest revealed the presence of many fungal species which could not be identified from a database of ITS-PCR-RFLP profiles from morphologically identified species. Three of these unidentified taxa were among the six most frequently encountered profiles. Phylogenetic analyses of ITS and nuclear LSU sequences revealed a close relationship among the three fungi and that they belong to the family Sebacinaceae (sensu Weiss and Oberwinkler 2001). The possibility that DNA of non-ectomycorrhizal rhizosphere or endophytic fungi had been amplified selectively by the basidiomycete-specific primers was tested by amplification with fungal-specific primers. A single PCR fragment was amplified in all but two of the 24 samples tested and digestion with two restriction enzymes produced RFLP profiles which matched those from the Sebacinoid sequence. We conclude, therefore, that at least three species of Sebacinaceae are common ectomycorrhizal associates of E. marginata.

Multiple origins of sequestrate fungi related to Cortinarius (Cortinariaceae).

The aim of the present study was to investigate the phylogeny and evolution of sequestrate fungi (with gastroid or partially exposed basidiomes) in relation to their gilled relatives from the Cortinariaceae (Basidiomycetes). Phylogenetic analyses of 151 ITS sequences from 77 gilled species and 37 sequestrate taxa were performed using maximum parsimony and maximum likelihood methods. Results show that sequestrate basidiome forms occur in all three major ectomycorrhizal lineages of Cortinariaceae: the clades Cortinarius, Hebeloma/Hymenogaster/Naucoria, and Descolea. However, these forms do not appear within the saprobic outgroup Gymnopilus, indicating multiple origins of sequestrate forms from ectomycorrhizal ancestors. Additionally, within the Cortinarius clade sequestrate forms have multiple origins: emergent Cortinarius spp., Thaxterogaster, Quadrispora, Protoglossum, and two Hymenogaster spp. (H. remyi, H. sublilacinus) share common ancestors with Cortinarius spp., but these sequestrate genera are not closely related to each other (with exception of Thaxterogaster and Quadrispora). Hymenogaster sensu stricto, Setchelliogaster, and Descomyces were placed in the two other major clades. Thus, sequestrate taxa evolved independently many times within brown-spored Agaricales. Furthermore, emergent, secotioid, and gastroid forms have evolved independently from each other, and so are not necessarily intermediate forms. After their establishment, these apparently morphologically stable taxa show a tendency to radiate.

Nature's ground force.

Some of the world's oldest and richest commercial biotechnologies are based on fungi, for example the production of bread, wine, beer and medicines. But they have a far greater, yet largely unrecognised, influence on human existence--they are crucial to some of the processes which ensure that major ecosystems world-wide keep ticking over.

Growth and phosphorus acquisition of karri (Eucalyptus diversicolor F. Muell.) seedlings inoculated with ectomycorrhizal fungi in relation to phosphorus supply.

Growth and phosphorus acquisition of pot-grown seedlings of karri (Eucalyptus diversicolor F. Muell.) were examined following inoculation with four ectomycorrhizal fungi -Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) Coker & Couch, and Laccaria laccata (Scop, ex Fr.) Berk. & Br. Seedlings were raised in steam-sterilized sand to which 13 rates of phosphorus (0.100 mg P kg-1 soil) were applied. All fungi except P. tinctorius produced a plant growth response. L. laccata produced the largest growth response. Responses were greatest at low rates of application of P to soil. There was no effect of the fungi on growth at levels of P application above 28 mg P kg-1 soil. A threshold effect (no increase in growth with increasing additions of P) characteristic of non-mycorrhizal seedlings was eliminated by mycorrhizal infection. Mycorrhizal inoculation increased P content of plant tissues at sub-optimal levels of P supply. The effect of mycorrhizas on seedling P status diminished with increasing soil P. One isolate of D. maculata often had greater rates of P accumulation and produced higher concentrations of P in plant tissues than L. laccata, but did not produce greater plant biomass. Frequency of infection for all fungi was low in soils with no additional P, and greatest with the addition of 2 mg P kg-1 soil (L. laccata and D. maculata isolate A), or 4 mg P kg-1 soil (D. maculata isolate B). Infection was reduced with increasing soil P, and not evident at 36 mg P kg-1 soil or higher levels of soil P. L. laccata had higher infection frequency and mycorrhizal root length at all levels of soil P than the D. maculata isolates. Two fungi produced basidiomes. This occurred at levels of soil P application ranging from 4 to 28 mg P kg-1 soil for D. maculata (isolate B), and at 4 to 28 mg P kg-1 soil for L. laccata.

ECTOMYCORRHIZA FORMATION IN EUCALYPTUS: III. SUPERFICIAL ECTOMYCORRHIZAS INITIATED BY HYSTERANGIUM AND CORTINARIUS SPECIES.

Cortinarius and Hysterangium species are a dominant component of the macrofungi in eucalypt forests of Western Australia, and their hyphae occupy 10 % of the soil surface area. Anatomical studies of jarrah (Eucalyptus marginata Donn ex Sm.) and karri (E. diversicolor F. Muell) roots collected in association with hyphae of Cortinarius globuliformis Boug., C. ochraceus Clel. and Hysterangium inflatum Rodway showed mycorrhizal structures with mantles one to five cells thick and Hartig nets penetrating to the hypodermis. These superficial ectomycorrhizas were similar in size to those of non-colonized feeder roots and lacked the expanded cortex and broad mantle of pyramidal ectomycorrhizas formed by Laccaria laccata (Scop, ex Fr.) Berk. & Br. Colonized host roots responded with polyphenol accumulation in the epidermis/hypodermis and lignification of the outer cortex for both the superficial and pyramidal types.