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Seedlings of Eucalyptus diversicolor P. Muell. I noculated with the ectomycorrhizal fungi Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) CokerCouch and Laccaria laccata (Scop, ex Fr.) Berk.Br. were raised under glasshouse conditions in a yellow sand at a gradient of four soil moisture levels ranging from above field capacity to near waterlogged. All fungi enhanced growth of seedlings above that of uninoculated seedlings, but in soils near saturation there was no response to inoculation. Reduced mycorrhizal formation in relation to increasing soil moisture occurred to various degrees for all fungi. This was particularly marked with Pisolithus tinctorius. In contrast, Laccaria laccata maintained a relatively high number of mycorrhizal roots at all moisture levels applied, except at the wettest soil treatment. An isolate of D. maculata from a swamp environment did not produce a greater number of mycorrhizal roots at high soil moisture than an isolate of this species from a forest environment.

Eucalyptus diversicolor thinning stumps were simultaneously inoculated with the pathogen Armillaria luteobubalina and one of Coriolus versicolor, Stereum hirsutum and Xylaria hypoxylon to determine if these saprotrophic wood decay fungi could prevent or limit colonization of stumps by A. luteobubalina . The extent of fungal colonization 2 yr after inoculation was assessed at three positions in the stumps (10 cm above ground level, at ground level and 15 cm below ground level). The three fungi equally significantly reduced colonization of stumps by A. luteobubalina , at each of the positions. C. versicolor decayed the upper portions of stumps most and X. hypoxylon least. Fruit-body production by the test fungi was significantly correlated to the relative wood density of the above ground portions of stumps. Some stumps were also colonized below ground by a naturally occurring cord-forming Hypholoma sp., resulting in complete or partial exclusion of A. luteobubalina and the test fungi from lower portions of those stumps. This fungus may prove more useful than the test fungi for control of A. luteobubalina .

Summary Seedlings of Eucalyptus diversicolor P. Muell. I noculated with the ectomycorrhizal fungi Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) Coker & Couch and Laccaria laccata (Scop, ex Fr.) Berk. & Br. were raised under glasshouse conditions in a yellow sand at a gradient of four soil moisture levels ranging from above field capacity to near waterlogged. All fungi enhanced growth of seedlings above that of uninoculated seedlings, but in soils near saturation there was no response to inoculation. Reduced mycorrhizal formation in relation to increasing soil moisture occurred to various degrees for all fungi. This was particularly marked with Pisolithus tinctorius. In contrast, Laccaria laccata maintained a relatively high number of mycorrhizal roots at all moisture levels applied, except at the wettest soil treatment. An isolate of D. maculata from a swamp environment did not produce a greater number of mycorrhizal roots at high soil moisture than an isolate of this species from a forest environment.

Eucalypt plantations in China have largely been established on soils that are low in phosphorus (P) and have few eucalypt-compatible ectomycorrhizal fungi. Application of superphosphate at establishment, in the presence of a basal fertiliser, increased survival and growth of Eucalyptus urophylla. As little as 20 kg P ha−1 increased stand biomass by 450%. Superphosphate increased the proportion of stem-wood biomass to total biomass. Nursery inoculation of eucalypt seedlings with ectomycorrhizal fungi significantly affected stand volume in the first 3 years, but the effect (positive or negative) was isolate-dependent. After 4.5 years, the positive effect of inoculation on tree growth had diminished. Factors affecting the decline in effectiveness of the inoculant fungi are being investigated.

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The genus Mesophellia, type of the family Mesophelliaceae, has been restudied in light of extensive recent collections. Most past species identifications in the genus have been erroneous, because past workers did not comprehensively study holotypes or fresh material. In this paper, the genus is divided into two subgenera: Mesophellia and Loculatae. Subgenus Mesophellia comprises 12 species, of which 8 are newly described here: M. angustispora, M. brevispora, M. clelandii, M. oleifera, M. pallidospora, M. pawa, M. rava and M. trabalis. Subgenus Loculatae comprises two species, both of which are newly described here: M. labyrinthina and M. westresii.

Nodule production and rates of acetylene reduction by the understorey legume Bossiaea laidlawiana were estimated in Eucalyptus diversicolor (karri) forest stands in south-western Australia in relation to plant age, time of day and season, and phosphorus supply. Highest numbers and masses of nodules, and highest rates of acetylene reduction were observed in the spring and early summer months when soil temperature was rising and soil moisture was adequate for functioning of fine roots (...)

This paper describes two new genera of gastroid (truffle-like) Basidiomycotina. Royoungia boletoides is described from Cooloola, Queensland, and is tentatively assigned to the Boletales on the basis of sporocarp and spore morphology. Mycoamaranthus auriorbis is described from a number of collections from northern Queensland and is not placed in any currently described family.* Part II, Aust. Syst. Bot., 1992, 5, 597–611.

Re-examination of species ascribed to the genus Labyrinthomyces plus our collections of related undescribed taxa revealed three distinct morphological groups which we segregate at the generic level. All have globose to ellipsoid spores ornamented with amorphous, hyaline warts or ridges. Labyrinthomyces is retained as a monotypic genus characterised by a brown-tomentose peridium and paraphyses half as long as the asci. Dingleya contains six species (two newly described here) with tessellate-cracked to verrucose peridia. Reddellomyces has four species (one newly described) with white to pale brown, smooth peridia. The last two genera are known only from Australasia.*Part I, Aust. Syst. Bot., 1990, 3, 653–70.

The effect of Rhizobium isolates on sporulation, hyphal lysis and zoospore survival of P. cinnamomi was examined in extracts of suppressive and conducive soils. Varying degrees of inhibition of P. cinnamomi growth by fifteen Rhizobium isolates were observed on agar media. Inhibition of mycelial growth was enhanced when the rhizobia were inoculated into the agar as compared to the surface streak method. An isolate from nodules of Acacia pulchella was found to be the most antagonistic to mycelial growth. Sporulation and hyphal lysis were stimulated by three of the rhizobia tested, with both suppressive and conducive soils. There was no significant difference between the effects of type of soil on sporangial formation or hyphal lysis. Rhizobia isolated from root nodules of A. pulchella significantly reduced zoospore survival in both the non-sterile suppressive and conducive soil extracts. There was a slightly greater zoospore survival in the conducive yellow podsolic extract than in the suppressive red earth extract, possibly attributable to microbial components of the extracts. These results indicate that Rhizobium , in concert with other soil micro-organisms, actively suppresses the pathogen P. cinnamomi in vitro .

The mycelium of Phytophthora cinnamomi grew along glass fibres in both sterile and nonsterile soil. Addition of glucose and yeast extract to soil significantly increased the longitudinal growth of mycelium. With water potential more negative than — 2080 kPa in the sterile soil and — 1050 kPa in the non-sterile soil there was a significant reduction in growth rate, and complete growth inhibition was recorded at approximately — 4000 kPa in both sterile and non-sterile soil. Hyphal lysis was common in all non-sterile soil treatments, this being attributed to the presence of other soil microorganisms. Sporangia were formed only in the non-sterile water controls. It is suggested that sporangia are important as inoculum in conditions of high water potential, whilst mycelial inocula are important when there are low water potentials in situations of high exogenous nutrients such as in the rhizosphere.

Two new species in the Phallales, Gelopellis purpurascens and Protubera canescens collected from under eucalypts in the Eucalyptus marginata (jarrah) forest of southwestern Australia are described and illustrated.

A hypogeous Cortinarius species, C. globuliformis sp.nov. is described, and its taxonomic affinities with other related hypogeous species are discussed. Ectomycorrhizal roots of Eucalyptus marginata associated with basidiomes of C. globuliformis are also illustrated.

SUMMARY In soil leachates the fungicide, metalaxyl, eliminated sporangia production by Phytophthora cinnamomi as well as enhancing hyphal lysis. There was a marked interaction between lytic soil microorganisms, fungicide application and hyphal lysis.

Investigation of the behaviour of Phytophthora cinnamomi zoospores on non-mycorrhizal and ectomycorrhizal roots of Eucalyptus marginata seedlings showed that zoospores encysted and germinated on both root types, but subsequent infection of root tissues was influenced by the type of ectomycorrhizal symbiont and the mycorrhizosphere population associated with the roots. In general, there was little evidence of colonization of P. cinnamomi zoospore cysts or germ tubes by the bacterial and/or actinomycete flora in the rhizoplane of non-mycorrhizal roots of seedlings growing in podsolic soil. On the other hand, there was extensive colonization of the fungus propagules on non-mycorrhizal roots in litter by bacteria and/or actinomycetes. Recovery of the pathogen was also markedly less from these roots than from similar root types growing in soil. Ectomycorrhizas formed by the ascomycete Cenococcum geophilum and the basidiomycete Hysterangium inflation failed to limit root infection in soil and the pathogen was recovered from both root types after 55 d incubation. There was no recovery of the pathogen from ‘white type’ basidiomycete ectomycorrhizas even after 24 h incubation. Micrographs showed zoospores either germinating but failing to penetrate the mantle or being enveloped and parasitized by a range of morphologically distinctive bacteria and a fungus within hours of inoculation of roots with zoospores. The data indicate a specific role for micro-organisms associated with root surfaces in antagonizing and limiting infection of roots by P. cinnamomi zoospores.

The effect of selected Western Australian soils on sporulation, hyphal lysis and zoospore survival of P. cinnamomi was studied. The soils chosen represented extremes of disease incidence in the forest. They included a red earth, suppressive to P. cinnamomi; a yellow podsol and a red podsol, both conducive soils to disease development initiated by P. cinnamomi. The red earth soil extracts stimulated sporangial production and microbially induced hyphal lysis more than the other soils tested. A positive correlation between sporangial production and hyphal lysis was observed. This relationship could be explained if sporangial production is regarded as a survival response to hyphal lysis. Seven percent of encysted zoospores survived 43 days in all soil extracts. This survival was not influenced by soil sterility, temperature or soil type, suggesting that cysts are more resistant survival structures than hyphae. Motile zoospore survival is reduced by soil microbial factors; this effect is more pronounced in the red earth than in the two podsolic soils. Increased soil extract temperatures also reduced motile zoospore survival. These results show that survival of P. cinnamomi hyphae and zoospores is reduced in the suppressive red earth relative to conducive podsolic soils.

A new species, Labyrinthomyces westraliensis , and a new variety, L. westraliensis var. parvulosporus , are described and illustrated, and a key to Labyrinthomyces is provided.

The amount of calcium in Eucalyptus diversicolor (karri) ecosystems is high in comparison with other eucalypt forest ecosystems in Australia. A large proportion of this calcium is present as crystalline Ca oxalate. Whewellite (CaC2O4·H2O) accumulates in leaf tissue of the over- and understorey species. Up to 70% of the calcium in the leaves of karri is stored as whewellite, the highest concentrations occurring in the oldest leaves. Synthesis of Ca oxalate by karri may be related in part to the high levels of exchangeable soil calcium. Oxalate of plant origin is rapidly metabolized on the forest floor during decomposition of leaf litter. About 70% of the whewellite in fresh karri leaf litter is degraded during the first wet season following leaf fall. However, additional oxalate is formed in the soil and litter layer from microbial production of oxalic acid. These crystals are of the dihydrate calcium salt, weddelite (CaC2CO4· 2H2O). Microbial production of oxalate, particularly by ectomycorrhizal fungi, may be an important mechanism for mobilizing of phosphate from the strongly phosphateadsorbing soils on which these forests grow.

Phytophthora cinnamomi Rands, a soilborne pathogen, is the cause of the disease jarrah dieback, which is destroying the indigenous jarrah forests in Western Australia (Podger 1968, 1972, Newhook & Podger 1972, Batini & Hopkins 1972) and is the major fungal pathogen causing eucalypt dieback in eastern Australia (Marks et al. 1972, Weste & Taylor 1971, Pratt & Heather 1972, Pratt & Heather 1973b, Bird et al. 1975, Podger 1975, 1981, Weste & Marks 1987). The disease affects not only Eucalyptus species but a number of major understorey and ground flora species as well. Lists of susceptible species have been published by Titze & Palzer (1969), Pratt & Heather (1972) and Weste & Taylor (1971) and these include over four hundred species belonging to forty different families. The most susceptible species belong to the families Proteaceae, Leguminoseae, Epacridaceae, Myrtaceae and Xanthorrhoeaceae.

Larger fungi of the jarrah forest represent a relatively poorly understood component of the ecosystem, yet in other forest biomes it has been accepted that they have a vital role to play in the functioning of forests. Key processes include recycling of nutrient elements by decomposition of litter and wood and the enhanced transfer of nutrient elements to trees by symbiotic mycorrhizal fungi. The paucity of information on the functional role of the larger fungi in the jarrah forest is partly a reflection of inadequate taxonomical treatises for those species involved with the above functions. In the last decade there have been a number of isolated observations documenting the larger fungi of the jarrah forest. Recently Hilton (1982) produced a check list of some of the fungi in the form of a census of those species identifiable to specific taxa. A number of popular books are now available collating existing taxonomic knowledge of these fungi (e.g. Young 1982, Griffiths 1985). More recent collections by northern hemisphere taxonomists (R. Watling pers. comm. and E. Horak pers. comm.) have further identified new species and have indicated the richness and uniqueness of these species in the jarrah forest, probably indicating their evolution with the tree species and adaption to the unusual environmental conditions.

ALTHOUGH some workers1 have examined environmental factors affecting the formation of dense clusters of rootlets (‘proteoid roots’) in many taxa of the Proteaceae, the causal agents have not been elucidated. The basic phenomenon is an intense, localised production of short lateral roots occurring particularly in nutritionally poor conditions. Purnell2 and Lamont3 were unable to detect bacteria, actinomycetes or fungi in newly formed proteoid roots although microorganisms were sometimes found in older roots. Here we demonstrate that proteoid roots are caused by non-infecting rhizosphere microorganisms.

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.

Root exudates from seedling eucalypts were collected aseptically, analysed for sugars, amino acids and organic acids and an examination made of their effect on zoospore chemotaxis, mycelium growth and chlamydospore germination of Phytophthora cinnamomi. Seedlings of root-rot susceptible Eucalyptus marginata produced greater concentrations of sugar and amino acid exudates than the root-rot resistant Eucalyptus calophylla at all sampling times. There was, however, little qualitative difference between the eucalypt root exudates. Both eucalypts attracted zoospores to roots in culture tubes. Infection of the roots followed encystment and germination of the zoospores. Germination of chlamydospores and mycelium growth of P.cinnamomi was significantly increased by the presence of root exudates and no differences were observed between exudates of the two species. Only amino acids and organic acids stimulated germination of chlamydospores. It was concluded that differences in root-rot susceptibility of eucalypts to P.cinnamomi are not attributable to differences in root exudate from eucalypt seedlings.

Mycorrhizal root development was more frequent in Eucalyptus calophylla than in Eucalyptus marginata in field and pot samples of soil conductive to Phytophthora cinnamomi. Morphologically different types of mycorrhizas were also observed in the two species, which suggested preferential stimulation of mycorrhizal fungi, and this was supported by cross-inoculation experiments with fungal symbionts isolated from mycorrhizal roots and from basidiomycete sporophores. Isolation of bacteria from mycorrhizal roots, and low power electron microscope study of these roots, indicated a significant mycorrhizosphere effect. Populations of bacteria varied quantitatively and qualitatively for different mycorrhizal roots. In suppressive soil few mycorrhizal roots were formed in either species. It is suggested that the different types of mycorrhizal roots and their associated bacterial microflora may contribute to differential susceptibility of the two species to infection by P. cinnamomi in conducive soil.

Application of calcium carbonate to an acid sand (pH 4.5 in 1/5 0 . 01 M calcium chloride), which increased the soil pH to 6.7, increased the fresh weight of tops of jarrah seedlings and decreased the fresh weight of roots. Calcium carbonate markedly increased the proportion of fine roots and almost suppressed infection of jarrah roots by P. cinnamomi.

An investigation was made of the microflora associated with unsuberized roots of Eucalyptus marginata and Eucalyptus calophylla raised in different soils. The studies were made for 'conducive' lateritic soil (in which E. marginata is susceptible to infection by Phytophthora cinnamomi but E. Calophylla is resistant); and in 'suppressive' loam soil in which both eucalypt species are unaffected by the pathogen. Lateritic soil in some cases contained natural infection of P. cinnamomi. Rhizospheres of both species contained larger microflora populations (expressed as numbers per g of root) than in the soils. In general, the population of rhizosphere microflora was greater for E. Marginata than E. calophylla seedlings in the uninfected lateritic soil. Qualitative differences were also recorded in populations of bacteria, actinomycetes and fungi, and in particular, fluorescent pseudomonads were more numerous in the rhizosphere of E. marginata seedlings. Eucalypt seedlings raised in loam soil harboured greater microbial populations than in lateritic soil. This could in part be attributed to the higher nutrient and organic matter status of the loam. E. marginata had a greater total rhizosphere population, but actinomycetes were more numerous in the rhizosphere of E. calophylla. Qualitative differences in populations of bacteria, actinomycetes and fungi were also noted. In naturally infected lateritic soil the microflora populations were invariably lower than for the other soils. When the counts of bacteria and actinomycetes were expressed as numbers per mm2 of root surface, E. calophylla had a significantly higher number of propagules per unit area than E. marginata. The loam soil was an exception; there E. marginata had three times as many bacteria per unit area of the root surface as E. calophylla. It is suggested that the microflora population differences recorded for the two eucalypts in lateritic soil may contribute to the differential susceptibility of species to infection by P. cinnamomi; and that the higher populations of microflora in the loam soil contribute to the suppression of P. Cinnamomi in that soil.

(1) Rates of acetylene reduction were determined for nodules attached to the roots of seedlings of the native legumes Acacia pulchella, Kennedia prostrate and K. coccinea grown in glasshouse experiments and in the field. (2) In the glasshouse, application of phosphorus to nitrogen-free yellow sand and to surface soil from three forest sites significantly increased yields, the weight of nodules per plant and the rate of acetylene reduction per plant for these native legumes. The legumes did not respond to application of molybdenum or cobalt to the forest soils. (3) In nitrogen-free yellow sand the maximum rates of acetylene reduction for A. pulchella and K. coccinea were approximately 260 nmol and 190 nmol C2H2 reduced per gram fresh weight of nodules per minute respectively. (4) Plants sampled from forest sites in the first season following fire gave mean rates of acetylene reduction of 173, 164 and 159 nmol C2H2 per gram fresh weight of nodules per minute for A. pulchella, K. prostrate and K. coccinea respectively. Acetylene reducing activity occurred from early winter to late spring and the variability between forest sites was small. Molybdenum concentrations in the nodules varied from 1 to 42 Pg Mo g-' dry weight of nodule and did not appear to be related to the rate of acetylene reduction. Application of phosphorus to legumes in the field increased yield and rates of acetylene reduction. However, the legumes did not respond to molybdenum applications. (5) These experiments show that a considerable proportion of the nitrogen in young legumes regenerating after fires may be from biological fixation of N2 and that rates of N2 fixation and growth can be enhanced by phosphorus application. (6) Further studies of N2 fixation by mature legumes and of the distribution of legumes throughout jarrah forests are required to allow quantitative estimates of nitrogen inputs to the ecosystem.

In soils under forest conditions and on seedlings grown under glasshouse conditions jarrah mycorrhizae exhibited strong habitat preferences. Litter on the forest floor was the main site for the formation of the white and brown ectomycorrhizae, and removal of the litter layer by prescribed burning reduced by 90% the numbers of these two ectomycorrhizae. Black ectornycorrhizae were dominant in the mineral horizons of soil and were unaffected by the type of surface litter. In glasshouse experiments litter from different plant species significantly influenced formation of ectomycorrhizae by jarrah seedlings. Litter from Acacia pulchella R. Br. was favourable for formation of ectomycorrhizae but ectornycorrhizae were absent from Banksia grandis Willd. litter. Black ectomycorrhizae, Hysterangium- initiated ectomycorrhizae and vesicular arbuscular mycorrhizae formed on jarrah seedlings in the soils used in glasshouse studies. Addition of nitrogen and phosphorus to these soils influenced the relative abundance of mycorrhizae. It is postulated that inoculum levels, nutrient status of litter and soil and the presence of compounds inhibitory to fungal growth are critical in determining the abundance of mycorrhizae. Factors affecting formation of mycorrhizae by jarrah and the ecological implications of these results are discussed.

Three major morphological types of ectomycorrhizae have been distinguished on roots of Eucalyptus marginara (jarrah). These were broadly classified as white, brown and black types. The variation in type of ectornycorrhizae and number of infected tips with season and depth in the soil were monitored at three forest sites. The sites had been burnt 1 , 6 and 45 years before sampling. Formation of ectomycorrhizae occurred in winter and spring. The black type was found predominantly in the soil whilst the white and brown types were associated with litter. The mean number of ectomycorrhizal root tips was highest in the 45 year unburnt and least in the 1 year unburnt site, suggesting that burning history influences their abundance.

Native forest at Durras in south-eastern New South Wales and Jarrahdale in south-western Western Australia was examined for the presence of Phytophthora cinnamomi by two sampling and isolation techniques. With the lupin seeding baiting technique, randomly selected samples of soil and fine roots collected from the New South Wales site yielded P. cinnamomi when baited, while similar baiting of comparable samples from Western Australia failed. Direct plating of samples of upper roots and root collars of recently dead Banksia grandis from Western Australian sites yielded P. cinnamomi, while this organism was not isolated from comparable samples of chlorotic Macrozamia communis collected at the New South Wales site. The results suggest that the form of occurrence of P. cinnamomi and its association with disease in Australia vary in different situations. Viewing each situation independently might ensure the adoption of control/prevention strategies appropriate to all.