Aluminium polyphosphate complexes in the mycorrhizal basidiomyceteLaccaria bicolor: A27Al-nuclear magnetic resonance study

The techniques of ²⁷Al- and ³¹P-nuclear magnetic resonance (NMR) spectroscopy were used to investigate the interactions of aluminium with intracellular ligands within the mycelium of the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton (S238). The vegetative mycelium was grown on medium containing 0.5 mM AlCl₃ for 0.5 to 3 d. The ²⁷Al-NMR spectra showed that aluminium was rapidly taken up and accumulated into polyphosphate complexes in the vacuole. Comparison with Al-polyphosphate complexes obtained in vitro on model systems indicated that Al forms at least three mixed-solvation complexes with Pi and polyphosphates, that there is more than one complex present under any set of conditions, and that the equilibrium between these complexes shifts dramatically with Al concentration in the medium. The high phosphate concentrations in the growth medium favoured the accumulation of the Al-polyphosphate complexes. When mycelium containing Al-polyphosphate complexes was transferred to Al-free nutrient solution for 9 d, the Alpolyphosphate complexes were not remobilized. The sequestration of Al in the polyphosphate complexes could therefore make a significant contribution to the protection of mycorrhizal plants against aluminium toxicity.Abbreviations NMR nuclear magnetic resonance - PolyP polyphosphate(s) - PP₁ terminal phosphate of PolyP - PP₃ middle phosphate of PolyP We thank Prof. Daniel Canet (Laboratoire de Méthodologie RMN, University of Nancy I, Vandceuvre-lès-Nancy, France) for his constant encouragement and Christine Delaruelle for skilled technical assistance in growing the fungal cultures. This work was supported by a research grant from the Commission of the European Communities (STEP-CT90-0059, Role of Ectomycorrhiza in Stress Tolerance of Forest Trees) to F.M. and a travel grant from the Institut National de la Recherche Agronomique to I.K.; R.C. is a recipient of a Postdoctoral Fellowship from the Natural Sciences and Engineering Research Council of Canada.     

Fruiting of ectomycorrhizal basidiomycetes on unburned and prescribed burned hard-pine/hardwood plots after drought-breaking rainfalls on the Allegheny Mountains of southwestern Virginia

A headfire upward along the crest to the peak of a foothill during February 1988 had been prescribed to lower the possibility of a wildfire during the dry season on the Jefferson National Forest. Some surface litter plus annual and perennial stems on one-half of a stand of Pinus pungens/P. rigida had been destroyed. Subsequent development of ectomycorrhizal sporophores of basidiomycetes was recorded regularly within equal areas of burned and unburned portions and within a nearby unburned stand of P. virginiana. Each plot had a few ectomycorrhizal hardwoods, mainly Quercus spp. First fruiting was noted under burned P. pungens 3 weeks after a general rain in mid-July and after 4 weeks under both. By the end of November, when fruiting ceased, 138 separable taxa had been collected of which 95 had been identified. A list of the fungi and data on current and previously reported host associations, occurrence on each of the substrates, times and frequencies of fruiting, periodicity of genera, and variations in weather conditions are presented.     

Arbuscular fungi and mycorrhizae (Glomales) of the Hel Peninsula,Poland

In the years 1985–1989, the occurrence of arbuscular fungi and mycorrhizae on the Hel Peninsula (Poland) was investigated with the help of 45 soil and root samples collected under 20 plant species of eight families. Except for Zea mays, the other plant species were from uncultivated sites. All soil samples contained spores of arbuscular fungi, of which about 45% were of the genus Glomus. Acaulospora spp. preferred members of the Cupressaceae. Spores of Gigaspora occurred rarely and only in two plant families. Glomus spp. were most frequently associated with plants of the Rosaceae, and species of Scutellospora were found at markedly higher frequencies among roots of plants of the Gramineae and Cupressaceae. A total of 29 spore-forming species and Glomus tenue (a fungus recognizable by its distinctive infections) were found. The most frequently recovered fungus, Glomus tenue, was present in roots of 56.8% of examined plants. Of the spore-forming fungi, the most frequently isolated spores were those of Scutellospora dipurpurascens, then Glomus constrictum, Acaulospora 61, and Glomus microcarpum. The overall spore density in examined samples averaged 99.8 in 100 g dry soil in the range 1 to 547, and was highest in a sample taken from around roots of Festuca arundinacea. The dominant fungi forming spores in sampled soils were Glomus constrictum, Glomus microcarpum, and Scutellospora dipurpurascens. The average species density was 3.9 in 100 g dry soil in the range 1 to 10, and was highest in Corynephorus canescens, Rosa canina, and Thuja occidentalis. Levels of colonization by arbuscular fungi ranged from 0.0 to94.0% (mean 23.3%) of the root length and were highest in Festuca arundinaceae and Zea mays.     

The impact of wildfire on vesicular-arbuscular mycorrhizal fungi and their potential to influence the re-establishment of post-fire plant communities

Wildfires are a typical event in many Australian plant communities. Vesicular-arbuscular mycorrhizal (VAM) fungi are important for plant growth in many communities, especially on infertile soils, yet few studies have examined the impact of wildfire on the infectivity of VAM fungi. This study took the opportunity offered by a wildfire to compare the infectivity and abundance of spores of VAM fungi from: (i) pre-fire and post-fire sites, and (ii) post-fire burned and unburned sites. Pre-fire samples had been taken in May 1990 and mid-December 1990 as part of another study. A wildfire of moderate intensity burned the site in late December 1990. Post-fire samples were taken from burned and unburned areas immediately after the fire and 6 months after the fire. A bioassay was used to examine the infectivity of VAM fungi. The post-fire soil produced significantly less VAM infection than the pre-fire soil. However, no difference was observed between colonization of plant roots by VAM fungi in soil taken from post-fire burned and adjacent unburned plots. Soil samples taken 6 months after the fire produced significantly more VAM than corresponding soil samples taken one year earlier. Spore numbers were quantified be wet-sieving and decanting of 100-g, air-dried soil subsamples and microscopic examination. For the most abundant spore type, spore numbers were significantly lower immediately post-fire. However, no significant difference in spore numbers was observed between post-fire burned and unburned plots. Six months after the fire, spore numbers were the same as the corresponding samples taken 1 year earlier. All plants appearing in the burned site resprouted from underground organs. All post-fire plant species recorded to have mycorrhizal associations before the fire had the same associations after the fire, except for species of Conospermum (Proteaceae), which lacked internal vesicles in cortical cells in the post-fire samples.     

Decoloration of azo dyes by three whiterot fungi: influence of carbon source

Two strains of Phanerochaete chrysosporium and a local isolate of white-rot fungus, if pre-cultured in a high nitrogen medium with glucose, could decolorize two azo dyes (Amaranth and Orange G) and a heterocyclic dye (Azure B). When starch was used in the pre-cultivation medium, decoloration of Orange G occurred if the medium also contained 12mM NH₄Cl, whether or not veratric acid was present. In medium containing 1.2mM NH₄Cl and veratric acid, greater decoloration occurred with one strain of P. chrysosporium and the local isolate. In preculture medium with cellulose and 1.2mM NH₄Cl, decoloration by the local isolate was enhanced but not that by the other strains.The authors are with the Department of Microbiology, Soochow University, Shih Lin, Taipei, Taiwan     

Effect of lignin-related phenols and their methylated derivatives on the growth of eight white-rot fungi

When various lignin-related para-phenolic benzoic acids, para-phenolic cinnamic acids, para-phenolic phenylpropionic acids, the corresponding unsubstituted and 4-O-methylated derivatives, and 4-hydroxyl substituted benzaldehydes were tested on the growth of eight white-rot fungi, methylation of the 4-hydroxy substituent resulted, in most cases, in increased inhibition of fungal growth. This effect was most notable with monomethoxylated compounds. When the aromatic ring contained additional methoxyl substituents, the toxicity of the 4-O-methylated derivative was less pronounced. Marked inhibition of fungal growth was also observed with aromatic compounds lacking a para-substituent. Higher concentrations of aromatic aldehydes were manifestly more toxic than the corresponding carboxylic acid.J.A. Buswell is with the Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong. K.-E.L. Eriksson is with the Department of Biochemistry, The University of Georgia, Athens, Georgia, 30602, USA.     

Ecology of Microbial Saprophytes and Pathogens in Tissue Culture and Field-Grown Plants: Reasons for Contamination Problems In Vitro

This review compares published surveys of microbial populations in plant tissue and cell cultures with the microbial saprophytes and pathogens found on field grown plants and microbial populations in the laboratory environment. From this comparison and the measured reduction in contamination after improvements in working practices in the laboratory, conclusions can be drawn about the importance of the explant and the laboratory as sources of contamination.

Mechanisms of pathogenicity in vitro are described to explain why bacteria, fungi, and yeasts that are not pathogenic to plants in the field become pathogens in plant tissue cultures. Conversely, plant metabolism and its effect on the tissue culture environment are described to explain why prokaryotes, viruses, and viroids that cause disease in the field can stay latent in vitro.

Detection methods for latent contaminants in plant tissue cultures are summarized, and the strategies and methods for prevention or treatment of contamination are discussed.     

The ability of 16 ectomycorrhizal fungi to increase growth and phosphorus uptake of Eucalyptus globulus Labill. and E. diversicolor F. Muell.

The effectiveness of 16 fungal isolates in forming ectomycorrhizas and increasing the growth and phosphorus uptake of Eucalyptus globulus Labill. and E. diversicolor F. Muell. seedlings was examined in the glasshouse. Seedlings were grown in yellow sand at 2 phosphorus levels (4 and 12 mg P kg^-1 sand). At the time of harvest (100 days), the non-inoculated seedlings and seedlings inoculated with Paxillus muelleri (Berk.) Sacc. and Cortinarius globuliformis Bougher had a low level of contamination from an unknown mycorrhizal fungi. Seedlings inoculated with Thaxterogaster sp. nov. and Hysterangium inflatum Rodway had developed mycorrhizas of the superficial type whereas Hydnangium carneum Wallr. in Dietr., Hymenogaster viscidus Massee & Rodway, Hymenogaster zeylanicus Petch, Setchelliogaster sp. nov., Laccaria laccata (Scop. ex. Fr.) Berk., Scleroderma verrucosum (Vaillant) Pers., Amanita xanthocephala (Berk.) Reid & Hilton, Descolea maculata Bougher and Malajczuk and Pisolithus tinctorius (Pers.) Coker & Couch formed typical pyramidal ectomycorrhizas. The dry weight of non-inoculated and inoculated E. globulus seedlings at 12 mg P kg^-1 sand did not differ, whereas several isolates caused growth depression of E. diversicolor. By contrast, at 4 mg P kg^-1 sand growth increases ranged from 0–13 times above that of non-inoculated seedlings. P. tinctorius produced the largest growth increase on both eucalypt species. In general, isolates which developed more extensive mycorrhizas on roots produced the largest growth responses to inoculation. Isolates which increased plant growth also increased phosphorus uptake by the plant. Seedlings inoculated with L. laccata and S. verrucosum retained more phosphorus in their roots than plants inoculated with the other fungal isolates.