Academic literature on the topic 'Mycorrhizal fungi – Western Australia – Morphology'

Species of Cyperaceae and Restionaceae were examined for presence of vesicular-arbuscular (VA) mycorrhizal fungi in natural habitat in south-west Western Australia. VA mycorrhizal fungi were detected in roots of two species of Cyperaceae (Lepidosperma gracile and Tetraria capillaris), and two species of Restionaceae (Alexgeorgea nitens and Lyginia barbata), all representing the first records for these genera. Results indicated a very short seasonal period of infection, with VA mycorrhizal fungi representing the genera Acaulospora, Glomus, Scutellospora and Gigaspora identified in roots. VA mycorrhizal fungi were prominent from late autumn to early winter (April-June) and in up to 30% of the young, new season's roots as they penetrated the upper 10 cm region of the soil profile. Mycorrhizal infection was not evident during the dry summer months. This study suggests that mycorrhizas may be important for nutrition of these hosts in these environments but their activity is restricted to a brief period of the growing season.

Orchids require mycorrhizal fungi for germination of seed and growth of seedlings. The colonisation of bauxite-mine rehabilitation areas by orchids is therefore dependent on the availability of both seed and mycorrhizal fungi. Orchid mycorrhizal fungi baiting trials were carried out in rehabilitation areas that were 1, 10 and 26 years old (established in 2001, 1992 and 1976) and adjacent unmined jarrah forest areas at Jarrahdale, Western Australia. Fungal baits consisted of buried six-chambered nylon-mesh packets containing seed of six jarrah forest orchid taxa, Caladenia flava subsp. flava R.Br., Disa bracteata Sw., Microtis media subsp. media R.Br., Pterostylis recurva Benth., Pyrorchis nigricans (R.Br.) D.L.Jones & M.A.Clem. and Thelymitra crinita Lindl. Detection of orchid mycorrhizal fungi was infrequent, especially at the youngest rehabilitation sites where only mycorrhizal fungi associated with P. recurva were detected. Mycorrhizal fungi of the other orchid taxa were widespread but sparsely distributed in older rehabilitation and forest areas. Detection of mycorrhizal fungi varied between taxa and baiting sites for the two survey years (2002 and 2004). Caladenia flava subsp. flava and T. crinita mycorrhizal fungi were the most frequently detected. The presence of C. flava mycorrhizal fungi was correlated with leafy litter cover and maximum depth, and soil moisture at the vegetation type scale (50 × 5 m belt transects), as well as tree and litter cover at the microhabitat scale (1-m2 quadrats). The presence of T. crinita mycorrhizal fungi was positively correlated with soil moisture in rehabilitation areas and low shrub cover in forest. The frequency of detection of orchid mycorrhizal fungi both at rehabilitated sites (15–25% of baits) and in unmined forest (15–50% of baits) tended to increase with rehabilitation age as vegetation recovered. The failure of some orchid taxa to reinvade rehabilitation areas is unlikely to be entirely due to absence of the appropriate mycorrhizal fungi. However, since the infrequent detection of fungi suggests that they occur in isolated patches of soil, the majority of dispersed orchid seeds are likely to perish, especially in recently disturbed habitats.

This survey included 109 plants native to the jarrah forest (a mediterranean eucalypt woodland in south-western Australia dominated by Eucalyptus marginata and E. calophylla). Mycorrhizal formation by seedlings of these plants was examined after inoculation with isolates of vesicular-arbuscular mycorrhizal (VAM) fungi, or after growth in intact cores of natural habitat soil containing VAM and ectomycorrhizal (ECM) fungi. These methods were supplemented by examining roots from mature forest-grown plants, so that different methods and criteria for designating mycorrhizal association types could be considered. Most plants had one of the following types of mycorrhizal association: VAM only (56% of species); both ECM and VAM (16% of species); or non-mycorrhizal roots (25% of species, which also had long root hairs and/or cluster roots). Plants with dual ECM/VAM associations often formed ECM more readily than VAM. With the exception of the large and diverse families, Papilionaceae, Myrtaceae and Anthericaceae, plants within a family had consistent mycorrhizal relations, as did the members of most genera.

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.

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.

The influence of biochar (biomass-derived black carbon) on crop growth and nutrient uptake varies based on the rate of biochar applied with fertilisers. We investigated the effect of deep-banded oil mallee biochar at different rates (0, 1.5, 3.0, and 6 t/ha) with 2 types of fertiliser (non-inoculated MultiMAPS® at 30 or 55 kg/ha; inoculated Western Mineral Fertiliser at 100 kg/ha) on wheat growth at a farmer’s field in a low rainfall area of Western Australia. Wheat yield increased significantly when biochar was applied with inoculated fertiliser and 30 kg/ha non-inoculated fertiliser. Mycorrhizal colonisation in wheat roots increased significantly with biochar application with inoculated mineral fertiliser. Mycorrhizal hyphae may have improved water supply to reduce drought stress in these treatments by extending crop exploration of water from the wide inter-rows. Grain yield increases were due to better grain survival and grain fill with reduced drought stress. Early stage phosphorus uptake was not improved by mycorrhizal colonisation—phosphorus supply from the soil and applied fertiliser was already adequate. The residual effect of biochar and mineral fertilisers was assessed using a mycorrhizal bioassay for soil collected from the field trial 2 years after application of biochar. Biochar and both fertilisers increased mycorrhizal colonisation in clover bioassay plants. Deep-banded biochar provided suitable conditions for mycorrhizal fungi to colonise plant roots.

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.

Rhizanthella gardneri (Rogers) is a critically endangered orchid restricted to two isolated regions of south-western Australia. Rhizanthella gardneri is an entirely subterranean mycoheterotrophic species that purportedly forms a tripartite relationship with a mycorrhizal fungus (Ceratobasidiales) that links with an autotrophic shrub of the Melaleuca uncinata complex to acquire nutrients. Whether the rarity of R. gardneri is intrinsic is overshadowed by the recent effect of extrinsic factors that means R. gardneri requires some form of conservation and may also be a viable candidate for restoration. To create an integrated conservation strategy for R. gardneri, reasons for its decline and knowledge of its biological and ecological functioning must be elucidated. This thesis focuses on three key questions; 1) what are the habitat requirements and limitations to R. gardneri survival; 2) what is the identity and specificity of the fungus R. gardneri forms mycorrhizas with; and 3) does R. gardneri form a nutrient-sharing tripartite relationship with a mycorrhizal fungus and autotrophic shrub. Key climate, soil and vegetation characteristics of known R. gardneri habitats were quantified to provide baseline data for monitoring known R. gardneri populations, to better understand how R. gardneri interacts with its habitat, and to identify possible new sites for R. gardneri introduction. Habitats of the two known R. gardneri populations differed considerably in soil chemistry, Melaleuca structure and Melaleuca productivity. Individual sites within populations were relatively similar in all attributes measured while overall Northern and Southern habitats were distinct from each other. These results suggest that R. gardneri can tolerate a range of conditions and may be more widespread than previously thought, given that there are extensive areas of Melaleuca thickets with similar habitat characteristics across south-western Australia. The fungus forming mycorrhizas with R. gardneri was identified, using nuclear ribosomal DNA sequences, as a Rhizoctonia-type fungus within the Ceratobasidiales. All fungi isolated from R. gardneri individuals representative of its currently known distribution were genetically similar, suggesting R. gardneri is highly dependent on this specific fungal species. Given that R. gardneri appears to exclusively associate with a specific fungal species, species-specific molecular primers were designed and used to analyse the fungi’s presence in known and potential R. gardneri habitats. These results 6 suggest that the fungus exists beyond the known R. gardneri habitats and gives hope to finding new populations.

[Truncated abstract] Currently, Alcoa World Alumina Australia (Alcoa) mines and undertakes procedures to rehabilitate approximately 550 ha of jarrah forest each year at two open-cut bauxite mines in South-West Western Australia. Alcoa aims to establish a self-sustaining jarrah forest ecosystem that maintains the functions of the landscape prior to mining, including biodiversity, on areas that have been mined for bauxite. Indigenous terrestrial orchids form a significant proportion of the indigenous geophytic plant species that either fail to colonise rehabilitated areas or do so very slowly. Terrestrial orchids are considered to be particularly sensitive to competition from weeds and disturbance, which combined with the obligate nature of the orchid-mycorrhizal fungus association suggests that orchids would colonise rehabilitation areas only when both microhabitat sites and soil microflora have established. Occurrence of certain orchids may therefore be expected to be useful as indicators of ecosystem health, the success of vegetation establishment and the recovery of edaphic conditions suitable for orchid mycorrhizal fungi. Vegetation surveys were undertaken to compare orchid species richness and population size of a chrono-sequence of rehabilitation areas with adjacent unmined forest. ... Orchid taxa present in each vegetation assemblage were generally not exclusive to these assemblages, with the following broad exclusions: D. bracteata was found only in species assemblages associated with rehabilitation areas; and Eriochilus sp. and T. crinita were found only in species assemblages associated with unmined forest. No single orchid species appears to be an indicator of ecosystem recovery. However, the presence of populations of C. flava, P. sp. crinkled leaf (G.J.Keighery 13426) or P. recurva in combination with the absence of the disturbance opportunist orchid taxa D. bracteata and M. media appears to be a measure of the maturity of the rehabilitation vegetation. Orchid species richness and clonal orchid population size were correlated with changes in vegetation structure, but apart from the absence of orchids in 1 year old rehabilitation areas, these orchid population characteristics did not show any direct relationship with rehabilitation age or vegetation maturity. Only two orchid taxa appeared to have potential as indicators of vegetation characteristics: T. crinita as an indicator of undisturbed jarrah forest; and D. bracteata as an indicator of disturbed ecosystems. The results of this study suggest that most jarrah forest orchid taxa will readily colonise the post bauxite mining landscape, but that the unassisted colonisation by recalcitrant orchid taxa may be a prolonged process. It is recommended that field-based transplantation and/or seeding trials be undertaken with these recalcitrant taxa to determine if these procedures will enhance recruitment. The results of this work have applications not only in the management of post-mining landscapes but also in vegetation monitoring and conservation work in Western Australia and elsewhere.