Academic literature on the topic 'Ectomycorrhizas – Western Australia'

Descolea maculata sp. nov. is described, illustrated and compared with other species of the genus. A Gondwanaland/Nothofagus origin proposed for the genus is discussed in the light of the Western Australian record. Ectomycorrhizae initiated by D. maculata on roots of Eucalyptus diversicolor and E. marginata, under both aseptic and non-sterile conditions, provide confirmation of the ectomycorrhizal status of the genus Descolea. Cystidia associated with the fungal mantle are similar to those reported for other mycorrhizal fungi of eucalypts.

Seven species of the putatively obligately ectomycorrhizal fungal genus Rozites are described from Australian Nothofagus and myrtaceaeous forests. Rozites metallica, R. armeniacovelata, R. foetens, and R. occulta are new species associated with Nothofagus in south eastern Australia. Rozites fusipes, previously known only from New Zealand, is reported from Tasmanian Nothofagus forests. Rozites roseolilacina and R. symea are new species associated with Eucalyptus in south eastern and south western Australia respectively. The significance of these Rozites species to mycorrhizal and biogeographical theories, such as the origin of ectomycorrhizal fungi associated with myrtaceous plants in Australia are discussed. The diversity of Rozites species in Australia, which equals or exceeds that of other southern regions, furthers the notion that many species of the genus co-evolved with Nothofagus in the Southern Hemisphere. Rozites symea in Western Australia occurs well outside the current geographic range of Nothofagus. It is considered to be a relict species that has survived the shift in dominant ectomycorrhizal forest tree type from Nothofagus to Myrtaceae (local extinction of Nothofagus 4–5 million years ago), and is most likely now confined to the high rainfall zone in the south west. Data on Rozites in Australia support the concept that at least some of the present set of ectomycorrhizal fungi associated with Myrtaceae in Australia are those which successfully completed a host change from Nothofagus, and adapted to changing climate, vegetation and soil conditions during and since the Tertiary. We suggest that the ancient stock of Rozites arose somewhere within the geographical range of a Cretaceous fagalean complex of plant taxa. By the end of the Cretaceous, Rozites and the fagalean complex may have spanned the Asian–Australian region including perhaps many Southern Hemisphere regions. A northern portion of the ancestral Rozites stock gave rise to extant Northern Hemisphere Rozites species and a southern portion speciated as Nothofagus itself speciated.

Currently in Western Australia, phosphite is being used to contain the root and collar rot pathogen, Phytophthora cinnamomi, in native plant communities. There have been reports of negative effects of phosphite on arbuscular mycorrhiza (AM), so there are concerns that it may have a deleterious effect on other mycorrhizal fungi. Two glasshouse experiments were undertaken to determine the impact of phosphite on eucalypt-associated ectomycorrhizal fungi. In the first experiment, non-mycorrhizal seedlings of Eucalyptus marginata, Eucalyptus globulus and Agonis flexuosa were sprayed to runoff with several concentrations of phosphite, and then planted into soil naturally infested with early colonising mycorrhizal species. Assessments were made of percentage of roots infected with mycorrhizal fungi. There was no significant effect on ectomycorrhizal formation but there was a four-fold increase in AM colonisation of A. flexuosa roots with phosphite application. In the second experiment, E. globulus seedlings mycorrhizal with Pisolithus, Scleroderma and Descolea were treated with different levels of phosphite and infection of new roots by ectomycorrhizal fungi was assessed. There was no significant effect on ectomycorrhizal formation when phosphite was applied at the recommended rate (5 g L–1), while at 10 g L–1 phosphite significantly decreased infection by Descolea.

The secotioid form of fruit bodies of mushroom-forming fungi may be an intermediate evolutionary modification of epigeous agaricoid or pileate–stipitate forms (i.e., with pileus, spore-bearing tissues, and stipe) and typically hypogeous, gasteroid- or truffle-forming species, in which the fruit bodies have been reduced to enclosed structures containing modified spore-producing tissues. To date, only a single secotioid species (Auritella geoaustralis Matheny & Bougher ex Matheny & Bougher) has been described in the ectomycorrhizal family Inocybaceae, a hyperdiverse clade of ca. 500–700 species with a cosmopolitan distribution. Fieldwork in Australia and western North America, however, has revealed two novel secotioid forms of Inocybe (Fr.) Fr., the first to be formally described in the genus. In this investigation, we analyze their phylogenetic relationships using molecular sequence data from multiple unlinked loci to test whether these are environmental variants of agaricoid forms or represent independent lineages. Results of phylogenetic analyses suggest these fungi have converged to the secotioid form independently. However, the California secotioid taxon (Inocybe multifolia f. cryptophylla f. nov.) is a phenotypic variant of the newly described agaricoid taxon (Inocybe multifolia sp. nov.). Similarly, the Australian secotioid form (Inocybe bicornis f. secotioides f. nov.) is nested within a clade of otherwise agaricoid forms of a second novel species (Inocybe bicornis sp. nov.) described from southwest Western Australia. Overall, four species with sequestrate forms within Inocybaceae can now be recognized, three of which are distributed in Australia and one in western North America, in the genera Auritella and Inocybe.

The woylie (Bettongia penicillata) was once common and abundant over the southern third of the Australian continent. Since European settlement the range of this rat-kangaroo has become reduced by more than 97%, and until the early 1990s, only 3 small natural populations remained, all in south-western Australia. These medium-sized (c. 1 kg) marsupials create a large number of diggings as they forage for the hypogeous fruiting bodies of ectomycorrhizal fungi upon which they feed. The effect of such foraging activity on the availability of plant nutrients in the vicinity of such diggings was evaluated in simulated digging experiments. Available nitrate, ammonium, and sulfur decreased significantly 3 years after diggings were constructed and had filled in, whereas phosphorus, potassium, iron, and organic carbon remained unchanged. The results suggest that preferential water infiltration via woylie diggings leads to a decrease in those soil nutrients that are susceptible to leaching and indicates that digging vertebrates may influence the distribution of surface soil nutrients.

Two new species of sequestrate (truffle-like fungi) Basidiomycetes of the putatively ectomycorrhizal genus Torrendia Bres. with contrasting basidiome morphology are described from remnant patches of eucalypt woodland in the wheatbelt of Western Australia: Torrendia grandis Bougher and Torrendia inculta Bougher.Like other species of Torrendia, they have basidiomes which develop and mature mostly underground but may break through to the soil surface at a late stage of maturity. The gleba of Torrendia species does not become powdery. A comparison of the main diagnostic features of all known taxa of Torrendiais provided. T. grandishas stocky basidiomes with an agaric-like pileus. T. inculta has a gleba which fragments during stipe elongation. The basidiome development of T. incultaisdescribed and illustrated, and some possible mechanisms of spore dispersal are discussed.

Many orchids require mycorrhizal symbioses with fungi for their development and survival. Rhizanthella gardneri the Western Australian underground orchid is associated with the companion plant Melaleuca uncinata and its ectomycorrhizal fungus symbiont. Much less is known about the habitat requirements of its sister species, R. slateri, which occurs in Eastern Australia. The absence of chlorophyll from Rhizanthella gardneri and R. slateri results in total dependency on associations with fungal symbionts. Many ecological and biological aspects of these fascinating orchids remained poorly known, including the identity of the fungal associates and the nature of their tripartite associations with Rhizanthella and Melaleuca. Extremely high specificity of these mycorrhizal relationships is likely to be the most important factor explaining the highly specific habitat requirements of underground orchids. The purpose of this study was to conduct further investigations of the role of the mycorrhizal associations of Australian underground orchids by identifying the fungi involved in these associations, optimising their growth in sterile culture and devising efficient means for synthesising their tripartite associations with R. gardneri and M. uncinata. In total, 16 isolates of fungi were successfully obtained from the two underground orchids and used in a series of experiments to understand both the nature of the fungi and their relationship with orchids. The identity of these fungi was established by using conventional morphological and molecular methods. Cultural and morphological studies revealed that all isolates from R. gardneri and R. slateri were binucleate rhizoctonias with affinities to members of the genus Ceratobasidium. However, the teleomorph state that was observed from the R. slateri symbiont during this study more closely resembled a Thanatephorus species. Further identification using ITS sequence comparisons confirmed that mycorrhizal fungi of Rhizanthella belonged to the Rhizoctonia alliance with relatives that include Thanatephorus, Ceratobasidium, or Rhizoctonia from other continents with over 90% similarity. Most of these related fungi are known as plant pathogens, but some were orchid mycorrhizal fungi. However, the isolates from the two underground orchids were most closely related to each other and formed a discrete group relative to other known members of the Rhizoctonia alliance. Sterile culture experiments determined culture media preferences for mycorrhizal fungi from Rhizanthella and other orchids. A fully defined sterile culture medium designed to more closely resemble Australian soil conditions was formulated. This new medium was compared to undefined media containing oats or yeast extract and recommendations for growth of these fungi are provided. The undefined media based on oats provided the best growth of most fungi, but the new Australian soil media was also effective at growing most orchid mycorrhizal fungi and this fully defined media was less prone to contamination and should provide more reproducible results. A comparison of three methods for inoculating M. uncinata with the underground orchid fungi resulted in the production and characterisation of ectomycorrhizal roots and hyphae formed by fungi isolated from R. gardneri and R. slateri. These underground orchid fungi could easily be distinguished from other mycorrhizal fungi (caused by airborne contamination) by the characteristic appearance of these roots and hyphae. A new system for growing and observing tripartite mycorrhizal associations was devised using pots with side viewing windows and the use of transparent seed packets to contain Rhizanthella seeds. This method allowed all the stages of seed germination to be observed in the glasshouse, culminating in the production of underground orchid rhizomes. Seed germination was only successful when seed was placed directly over active M. uncinata ectomycorrhizas confirmed to belong to the correct fungus by microscopic observations through the side of window pots. The importance of these new scientific discoveries concerning the biology and ecology of the underground orchids and their associated fungi for the recovery of these critically endangered orchids are discussed.

Thesis (Ph.D.)--University of Western Sydney, 2000.
"Thesis submitted in accordance with the requirements for the degree of Doctor of Philosophy, School of Science, University of Western Sydney (Nepean)." "October 2000." Bibliography : leaves 143-179.

The black truffle (Tuber melanosporum Vitt.) industry in Australia is relatively new and has enormous potential but some truffières (truffle farms) fail to meet anticipated harvest projections. Inappropriate soil conditions and climate, and the management of such factors are suggested as the primary reasons for inadequate yield. In addition, requirements for ascocarp initiation and development and the role of the host plant in such processes are unknown. This study examines interactions between European hazel (Corylus avellana L.) and the ectomycorrhizal (ECM) black truffle symbiont in a commercial truffière (Hazel Hill) in south-western Australia. Specific studies were initiated to examine the interactions of host physiology, mycorrhizal infection and the interaction with abiotic factors. The study related specific physiological processes of the host plant to the known life cycle of the black truffle to determine the role of the host plant in ascocarp production, if any. The work also examined the effect of silvicultural treatments intended to increase truffle production. A review of existing literature was undertaken to determine the key soil and climatic factors required for successful truffle production. Climatic conditions appeared more important than soil chemistry and structure in Western Australia, with significant seasonal variation in air and soil temperatures required plus irrigation to supplement summer rainfall. This information was used to define areas with potential for truffle production in the south-west of Western Australia: the cooler, high rainfall regions (>1000 mm annual rainfall) where there is sufficient seasonal variation in soil temperature and availability of adequate quantities of quality water for irrigation. Subsurface soil acidification and salinity, as well as groundwater salinity, are constraining factors. Lime amendment is necessary to create sufficiently high pH and CaCO3 levels required by the truffle fungus. A field trial was established to monitor the seasonal C dynamics of European hazel in the context of the life cycle of the black truffle. Maximum translocation of sucrose in the phloem sap coincided with the period of anticipated rapid growth of the truffle ascocarp implicating the use of current photosynthate in C nutrition of the ascocarp. Sampling of non-structural carbohydrates (NC) of above and belowground plant material indicated maximum storage of C in the host coincides with maturation of the ascocarp. These observations provide evidence of a synchronous growth habit of the plant host and the ascocarp. The C allocation patterns of European hazel in response to liming a loamy soil, taken from near the Hazel Hill truffière, and inoculation with ECM fungi (T. melanosporum, Hebeloma sp. and Scleroderma sp.) were examined in a glasshouse pot trial. Liming increased biomass allocation to the shoot and induced deficiencies of phosphorus and manganese. Colonisation by ECM fungi significantly increased net photosynthesis, indicating the sink strength of these fungi, but there was no relationship between the level of mycorrhizal infection and fine root NC. The maximum rate (40 g lime kg-1 soil) reduced infection by Hebeloma and Scleroderma and had no impact on T. melanosporum. Further, infection rates of T. melanosporum did not increase in response to lime suggesting lime is not necessary for ECM development in this soil type. Fertiliser is widely used in commercial truffières in Australia but the consequences for truffle production are unknown. In a field trial, the growth and physiological response of European hazel to forms of phosphorus (34 and 68 kg ha-1 apatite-P and 68 kg ha-1 triple super phosphate -P) and nitrogen (50 kg ha-1 of NO3- and NH4-N) were examined as well as the mycorrhizal response to fertiliser. Apatite-P increased phloem sap sucrose concentrations which was attributed to increased root biomass and associated sink capacity. Fertiliser application did not change fine root NC concentrations suggesting no increase in allocation of C to ECM structures. The highest rate of apatite-P decreased mycorrhizal infection rates of T. melanosporum and, most likely, was the result of increased infection rates of Hebeloma. In contrast to the literature relating to indigenous Australian ECM fungi, the highest rate of soluble-P did not decrease ECM infection rates in T. melanosporum. Nitrogen treatments increased foliar N content and improved gas exchange efficiency of plants, and had no adverse impact on the level of ECM infection. Fertilisation with N significantly increased soil respiration rates suggesting N limits mineralisation at this site. Some truffières manage the canopies of the host tree to ensure maximum exposure of the soil surface in order to increase soil temperatures. As there are no published data on the effect of pruning on black truffle production, a field trial was established to document the impact of canopy pruning on host physiology and soil temperature. The removal of 65% of canopy leaf area reduced phloem sap sucrose concentrations, soil respiration rate and the soluble: insoluble NC ratio of fine roots in the short term (1-3 weeks). There was no compensatory response of leaf gas exchange parameters as a result of pruning. Generally, there was no long term impact on plant physiological parameters as a result of pruning. Long term effects on soil temperature were observed as a result of pruning. Mean annual temperature and amplitude increased significantly beneath pruned trees and spring, summer and autumn soil temperatures increased as did diurnal variation as a result of pruning. Pruning did not increase winter soil temperatures and therefore would probably not impact on ascocarp maturation during this period. This research has provided insight into the C physiology of hazel associated with the black truffle and the consequences for truffle production. The results provide anecdotal evidence of direct C transfer between the host and the developing truffle, contrary to the existing paradigm that the ascocarp is saprotrophic for the majority of its growth and development. There is a need to validate this finding as there are consequences for management of commercial truffières. Liming of loam duplex soils can reduce the abundance of the most common competitor ECM fungi and should be encouraged in commercial truffières. Applying phosphorus and nitrogen to commercial truffières will improve growth rates of planted trees without adversely impacting on ECM infection by black truffle fungi, although the impact on truffle production remains unknown. It is anticipated truffle production will improve in the longer term as a result of pruning and prudent canopy management. Management options should include tree removal to reduce planting density and increase soil exposure in truffières. There is a need for longer term trials to be established to determine the C nutrition of the truffle ascocarp and to clearly define the key stages of the black truffle life cycle in Western Australia.