Utilisation of organic nitrogen and phosphorus sources by mycorrhizal endophytes of Woollsia pungens (Cav.) F. Muell. (Epacridaceae)

 The ability of four ericoid mycorrhizal endophytes isolated from roots of Woollsia pungens (Cav.) F. Muell. (Epacridaceae) to utilise organic forms of nitrogen and phosphorus during growth in axenic culture was assessed. All isolates were able to utilise glutamine, arginine and bovine serum albumin (BSA), along with NH₄ ⁺ or NO₃ ^–, in most cases yielding at least as much biomass as the ericoid mycorrhizal endophyte Hymenoscyphus ericae (Read) Korf & Kernan. All isolated endophytes were able to utilise BSA, arginine and glutamine as sole sources of N and C. With the exception of a single isolate (C40), which showed little growth on glutamine, biomass yields on glutamine as the sole N and C source was significantly greater for all isolates than on either of the other two organic N sources. Two isolates from W. pungens (C40 and A43) utilised DNA and sodium inositol hexaphosphate as sole P sources, in each case yielding significantly more biomass than H. ericae. The results suggest that mycorrhizal endophytes from epacrid plant hosts and those from ericaceous hosts have similar abilities to utilise organic forms of N and P. Accepted: 4 September 1998     

First synthesis of ericoid mycorrhizas in the Epacridaceae under axenic conditions

The first axenic synthesis of morphologically typical ericoid mycorrhizas of the Epacridaceae has been achieved in micropropagated Epacris impressa Labill. with eight fungi isolated from roots of two epacrid species, E. impressa and Astroloma pinifolium (R.Br.) Benth. Mycorrhizal synthesis has also been achieved between E. impressa and both Hymenoscyphus ericae (Read) Korf and Kernan and Oidiodendron griseum Robak, recognized endophytes of Ericaceae, suggesting that the endophytes of the Epacridaceae and Ericaceae are capable of cross-infection. Infection rate of epidermal cells on hair roots varied from 3–77% infection and the density of hyphal coils varied widely. This synthesis makes possible studies of the roles of these endophytes in the Epacridaceae and comparison with their roles in the Ericaceae.     

Molecular diversity within and between ericoid endophytes from the Ericaceae and Epacridaceae

This study investigated the relationships between ericoid mycorrhizal endophytes of the Ericaceae (Northern Hemisphere) and the Epacridaceae (Australia). Over 200 fungi were isolated from the roots of two species of Epacridaceae from Victoria, Australia. The isolates were divided into 12 groups by morphology on quarter-strength potato dextrose agar. All were slow-growing and most were dematiaceous, but groups varied from white through pink to dark olive. The ITS1–5.8S–ITS2 ribosomal DNA was amplified and sequenced from eight isolates, forming typical ericoid mycorrhizal morphology in Epacris impressa and one nonmycorrhizal isolate. Sequences were compared, by using similarities and maximum-parsimony analysis, with those of Hymenoscyphus ericae (Leotiales) and Oidiodendron species (Hyphomycetes), the most common endophytes of the Ericaceae. Maximum-parsimony analysis produced four clusters: (1) all Oidiodendron species (at least 90% similarity); (2) all five Victorian dark grey-olive isolates (at least 96% similarity); (3) one Victorian isolate and Cistella grevillei (88% similarity); (4) two light-coloured Victorian isolates and H. ericae (81% similarity). This suggests that these isolates from the Epacridaceae do not belong to the same species as those forming ericoid mycorrhiza in the Ericaceae.     

Phytogeography, Biology and Conservation of Western Australian Epacridaceae

The Epacridaceae of Western Australia comprise 181 named speciesdistributed in 17 genera. One hundred and seventy seven species(98% of the total) and ten genera are endemic to the region.within Western Australia, all members are confined to the south,with a bimodal pattern of species diversity centred on the sandplainsand uplands around the Stirling Ranges and Mount Lesueur.Leucopogon, the largest genus, reflects this pattern, however, speciesdiversity is greatest on the south coastal sandplains. All species are woody shrubs, mostly found on neutral or acidicsandy soils. Plants of at least 120 species are killed by fire;Astrolomacontainsthe only significant number of resprouting species. Althoughsome species are in flower every month every year, autumn/winterflowering is a common feature of many members of the family.All species are biotically pollinated. Bird pollination is foundin 18 species in six genera. The remaining species are insectpollinated. Bees are the major pollinators inLeucopogon, ConostephiumandColeanthera.Moths and butterflies are important pollinators inAndersonia,Leucopogon,LysinemaandStyphelia. Flies are minor pollinators of some speciesofAndersonia, LeucopogonandMonotoca. All species studied areprotandrous and outbreeding, with onlyCosmeliabeing capableof self pollination. Fruits are fleshy inAstroloma, Brachyloma,Croninia, in certain species ofLeucopogonandStypheliaand areanimal dispersed. Other genera have dry, dehiscent fruit withgravity or wind dispersed seeds. Many species have relatively narrow distribution ranges, 90species having ranges of over 300km, 54 species have rangesof 100–300km and 37 have ranges of less than 100km (andthere are many undescribed species in this group). The conservationstatus of many species is still poorly known. Dieback diseaseis a major threat to the family, and could cause the extinctionof several species in the wild. Western Australia; Epacridaceae; phytogeography; biology; pollination; dispersal; conservation; disease     

Pectic Zymograms and Water Stress Tolerance of Endophytic Fungi Isolated from Western Australian Heaths (Epacridaceae)

Forty-nine isolates of root-inhabiting fungi were obtained fromthirteen species of eleven genera of native Epacridaceae andcompared in relation to host taxonomy and habitat of origin.Pectic zymograms of extracts of the cultured endophytes showeda marked degree of homogeneity of banding patterns amongst isolatesfrom a mesic wetland site, whereas those from dryland habitatdisplayed more heterogenous banding. It is speculated that hostspecies can operate with only a limited number of fungal associatesunder mesic conditions but require a higher degree of endophytevariation when combating dry and impoverished environments.Considerable distinction between the geographically diverseendophytes isolated from the common hostLysinema ciliatum suggestedthat selection of endophytes was not driven primarily by hosttaxonomy. Ascribing functional significance to the observed differencesbetween endophytes was studied by examining responses of culturedisolates to polyethylene glycol induced-water stress coveringa range of potentials from -0.16 to -2.96MPa. Three responsetypes were observed: (a) the isolate produced minimal radialgrowth at all water potentials tested, (b) maximum growth ofthe isolate occurred under least water stress, with progressivesuppression of radial extension with decreasing water potentialand (c) maximum growth of the isolate occurred under a degreeof water stress. The broad range of responses to water stressobserved was suggested to reflect the diverse habitat tolerancedisplayed by epacrids and their endophytic partners in southwest Australia. ericoid mycorrhizas; pectic zymogram; water stress; Epacridaceae     

Ericoid mycorrhizal association: ability to adapt to a broad range of habitats

Ericoid mycorrhizal fungi are symbiotically associated with the roots of members of the Ericaceae which include genera such as Calluna, Epacris, Erica, Rhododendron and Vaccinium. These ericoid mycorrhizal associations have adapted to a broad range of habitats, from mor humus soils of the northern hemisphere to sandy soils occurring in the southern hemisphere. They also play an important part in enabling plants like Calluna vulgaris (L.) Hull in the northern hemisphere to colonize mine spoils which are inhospitable environments of toxic waste for growth of most plants. The mechanisms of utilizing complex forms of nitrogen and phosphorus and providing protection against toxic metals are described. These mechanisms carried out by ericoid mycorrhizal associations enable host plants to establish in diverse habitats.     

Diversity of root-associated fungal endophytes in Rhododendron fortunei in subtropical forests of China

To investigate the diversity of root endophytes in Rhododendron fortunei, fungal strains were isolated from the hair roots of plants from four habitats in subtropical forests of China. In total, 220 slow-growing fungal isolates were isolated from the hair roots of R. fortunei. The isolates were initially grouped into 17 types based on the results of internal transcribed spacer-restriction fragment length polymorphism (ITS-RFLP) analysis. ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with known sequences of ericoid mycorrhizal endophytes and selected ascomycetes or basidiomycetes. Based on phylogenetic analysis of the ITS sequences in GenBank, 15 RFLP types were confirmed as ascomycetes, and two as basidiomycetes; nine of these were shown to be ericoid mycorrhizal endophytes in experimental cultures. The only common endophytes of R. fortunei were identified as Oidiodendron maius at four sites, although the isolation frequency (3–65%) differed sharply according to habitat. Phialocephala fortinii strains were isolated most abundantly from two habitats which related to the more acidic soil and pine mixed forests. A number of less common mycorrhizal RFLP types were isolated from R. fortunei at three, two, or one of the sites. Most of these appeared to have strong affinities for some unidentified root endophytes from Ericaceae hosts in Australian forests. We concluded that the endophyte population isolated from R. fortunei is composed mainly of ascomycete, as well as a few basidiomycete strains. In addition, one basidiomycete strain was confirmed as a putative ericoid mycorrhizal fungus.     

Pectic zymogram variation and pathogenicity of <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> AG-4 to bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>) isolates in Isfahn,Iran

Rhizoctonia disease, caused by Rhizoctonia solani is one of the most important fungal diseases in bean fields in Isfahan, Iran. Bean plants showing stem and root cankers were collected and Rhizoctonia-like fungi obtained from the samples were identified by anastomosis. Pure cultures of bean isolates of R. solani were identified as AG-4. There were also AG-4 isolates from tomato, potato, cucumber, alfalfa and sugar beet in the areas sampled. A total of 163 isolates of R. solani AG-4 originating from stem and root cankers of beans were examined using pectic zymogram electrophoresis. Polygalacturonase (PG) and pectin estrase isozymes were observed in all AG-4 isolates tested. One (PG) and one pectic esterase (PE) band was found in common between all isolates examined. The electrophoretic patterns were grouped into seven zymogram groups (ZGs) according to the diagnostic PG and PE bands. One ZG occurred in a high frequency throughout the areas sampled. A pathogenicity test was conducted and representative isolates of each ZG were used to inoculate healthy bean plants. The results showed that each ZG caused different symptoms with varying severity. Isolates belonging to two ZGs were highly pathogenic causing root, stem and hypocotyl cankers whereas isolates of the other ZGs produced weak or no symptoms.     

Utilisation of carbon substrates by multiple genotypes of ericoid mycorrhizal fungal endophytes from eastern Australian Ericaceae

The abilities of six genotypes of two putative Helotiales ascomycete ericoid mycorrhizal fungal taxa from Woollsia pungens and Leucopogon parviflorus (Ericaceae) to utilise glucose, galactose, mannose, cellobiose, carboxymethylcellulose, crystalline cellulose, starch and xylan as sole carbon sources were tested in axenic liquid culture. With the exception of all taxon II isolates on carboxymethylcellulose, all genotypes of both taxa produced measurable biomass on all substrates. Significant intraspecific variation was observed in biomass production on all substrates. While pooled data for all genotypes of each taxon revealed significant interspecific differences in biomass production on carboxymethylcellulose, glucose, cellobiose, and starch, mean biomass production for each taxon on the latter three substrates differed less than threefold, suggesting that the saprotrophic abilities of the two taxa are broadly similar.     

A new species of Conostephium (Epacridaceae) from gypsum dunes in Western Australia

A new species of Conostephium, C. pungens , is described and illustrated. The new species is confined to gypsum dunes found on primary saline sites in southern Western Australia.     

Ericoid mycorrhizal colonization and associated fungal communities along a wetland gradient in the Acadian forest of Eastern Canada

Wetlands provide numerous ecosystem services, and ericaceous plants are important components of these habitats. However, the ecology of fungi associated with ericaceous roots in these habitats is poorly known. To investigate fungi associated with ericaceous roots in wetlands, ericoid mycorrhizal colonization was quantified, and fungal communities were characterized on the roots of Gaultheria hispidula and Kalmia angustifolia along two upland – forested wetland transects in spring and fall. Ericoid mycorrhizal colonization was significantly higher in the wetlands for both plant species. Both upland and wetland habitats supported distinct assemblages of ericaceous root associated fungi including habitat specific members of the genus Serendipita. Habitat was a stronger driver of ericoid mycorrhizal colonization and ericaceous root associated community composition than host or sampling season, with differences related to soil water content, soil nutrient content, or both. Our results indicate that ericaceous plant roots in forested wetlands are heavily colonized by habitat specific symbionts.     

Diversity of ericoid mycorrhizal fungi isolated from hair roots of Rhododendron obtusum var. kaempferi in a Japanese red pine forest

 The diversity of ericoid mycorrhizal fungi of Rhododendron obtusum var. kaempferi was examined in a stand of Pinus densiflora at Tsukuba, Japan. In total, 153 slow-growing fungal isolates were obtained from roots of R. obtusum var. kaempferi, in which 113 isolates formed an ericoid mycorrhizal structure in vitro. Among them, 53 isolates were morphologically identified as Oidiodendron maius, but the others were not identified due to their sterilities. PCR-RFLP analysis in the rDNA-ITS region divided them into four different RFLP types. Phylogenetic analysis from sequence data of the region suggested that the four RFLP types belonging to distinct taxa and one sterile type are considered to be Hymenoscyphus ericae. This study is the first report of ericoid mycorrhizal fungi in a natural habitat in Japan. Received: August 23, 2002 / Accepted: December 11, 2002 Acknowledgments We thank Dr. K. Narisawa, Plant Biotechnology Institute, Ibaraki Agricultural Center, and Dr. R.S. Currah, Department of Biological Science, University of Alberta, for their helpful advice. Contribution no. 176, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan Correspondence to:M. Kakishima     

Dark septate endophytes: a review of facultative biotrophic root-colonizing fungi

Dark septate root endophytes (DSE) are conidial or sterile fungi (Deuteromycotina, Fungi Imperfecti) likely to be ascomycetous and colonizing plant roots. They have been reported for nearly 600 plant species representing about 320 genera and 100 families. DSE fungi occur from the tropics to arctic and alpine habitats and comprise a heterogeneous group that functionally and ecologically overlaps with soil fungi, saprotrophic rhizoplane-inhabiting fungi, obligately and facultatively pathogenic fungi and mycorrhizal fungi. Numerous species of undescribed sterile and anamorphic taxa may also await discovery. Although DSE are abundant in washed root and soil samples from various habitats, and are easily isolated from surface-sterilized roots of ecto-, ectendo-, endo- and non-mycorrhizal host species, their ecological functions are little understood. Studies of DSE thus far have yielded inconsistent results and only poorly illustrate the role of DSE in their natural habitats. These inconsistencies are largely due to the uncertain taxonomic affinities of the strains of DSE used. In addition, because different strains of a single anamorph taxon seem to vary greatly in function, no clear generalizations on their ecological role have been drawn. This paper reviews the current literature on DSE and the ecology and discusses the need for and direction of future research.     

柔膜菌属(柔膜菌目)新种及中国新记录种

本文对采自中国温带部分省区的柔膜菌属Hymenoscyphus标本进行了研究。文中报道新种一个 —— 井冈柔膜菌Hymenoscyphus jinggangensis,中国新记录种三个,它们是无须柔膜菌Hymenoscyphus imberbis, (参照)闪烁柔膜菌H. cf. nitidulus 以及该属的一个未命名种。新种模式标本保藏在中国科学院微生物研究所菌物标本馆。     

Chromosome numbers of Western Australian species ofVillarsia (Menyanthaceae)

Chromosome numbers are reported for eight of the nine Western AustralianVillarsia species.Villarsia albiflora, V. calthifolia, V. capitata, V. congestiflora, V. lasiosperma, V. latifolia, andV. violifolia are diploid with n=9. Five populations ofV. parnassiifolia are diploid and three are tetraploid (n=18). The morphological, ecological, and breeding-system diversity of the Western Australian species is largely not associated with the tetraploidy or hexaploidy that characterizes otherVillarsia species in eastern Australia and South Africa. The majority of Western AustralianVillarsia species are restricted to the high rainfall zone of southwestern Western Australia, where favorable climatic and edaphic conditions may have existed since mid-late Tertiary times.     

Effect of heavy metal pollution on mycorrhizal colonization and function: physiological, ecological and applied aspects

 High concentrations of heavy metals in soil have an adverse effect on micro-organisms and microbial processes. Among soil microorganisms, mycorrhizal fungi are the only ones providing a direct link between soil and roots, and can therefore be of great importance in heavy metal availability and toxicity to plants. This review discusses various aspects of the interactions between heavy metals and mycorrhizal fungi, including the effects of heavy metals on the occurrence of mycorrhizal fungi, heavy metal tolerance in these micro-organisms, and their effect on metal uptake and transfer to plants. Mechanisms involved in metal tolerance, uptake and accumulation by mycorrhizal hyphae and by endo- or ectomycorrhizae are covered. The possible use of mycorrhizal fungi as bioremediation agents in polluted soils or as bioindicators of pollution is also discussed. Accepted: 23 June 1997