Nutritional environment of soil and roots in and around mycelial blocks of an ectomycorrhizal fungusTricholoma bakamatsutake in an evergreen Fagaceae forest

In the evergreen Fagaceae forests of Japan, an ectomycorrhizal fungusTricholoma bakamatsutake forms shiros or developing mycelial blocks. To determine the physiological characteristics of the mycelial blocks, organic acids of the soil and major nutrient elements of the soil and roots were compared at three types of sites: presently colonized mycelial blocks, previously colonized sites behind the blocks, and uncolonized sites in front of the blocks. The upper part of the mycelial blocks showed the following features compared with the uncolonized site: lower pH (5.1), higher concentrations of oxalic and gluconic acids, lower content of total nitrogen, a similar amount of total carbon, reduced total and available phosphorus, higher content of total calcium and lower content of exchangeable calcium. These findings suggested that the activity of the fungus led to soil acidification by the organic acids, an increase in C/N ratio, depletion of phosphorus and accumulation of calcium.     

Aspergillus taichungensis,a new species from Taiwan

Aspergillus taichungensis isolated from a soil sample collected in Taiwan is described as a new species. The new species is characterized by its restricted growth on Czapek's and malt extract agars and its white to light yellow colonies, radiate conidial heads, smooth and often diminutive conidiophores, hemispherical to elongate vesicles with biseriate aspergilla (conidiogenous cells), globose, micro-verrucose conidia and dark brown sclerotia. The species somewhat resemblesA. versicolor, A. terreus andA. flavipes, but differs in cultural and morphological details, and is considered to represent an interface species in the subgenusNidulantes.     

Materials for the fungus flora of Japan (49)

Two interesting microfungi are described as new to Japan:Talaromyces galapagensis (anam.Penicillium galapagense), isolated from soil in Shizuoka; andPenicillium megasporum, isolated from marine sludge in Nagasaki. Some observations are recorded, particularly on ascomatal initials ofT. galapagensis, which are similar to those described forTalaromyces flavus.(48): Kaneko, S., Mycoscience 36: 359–360, 1995.     

Isolation of the facA (acetyl-CoA synthetase) gene of Phycomyces blakesleeanus

A 5.6 kb DNA fragment from the fungus Phycomyces blakesleeanus has been cloned and sequenced. The fragment contains a gene that probably codes for the enzyme acetyl-coenzyme A synthetase (facA). The amino acid sequence deduced for the P. blakesleeanns protein is highly homologous to those of acetyl-coA-synthetases from other organisms. When placed under the control of a constitutive promoter from Aspergillus nidulans, the cloned gene complemented a facA mutation of this organism. In P. blakesleeanns, the expression of facA is induced by acetate.     

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.     

Presence of double‐stranded RNAs and virus‐like particles in the entomopathogenic fungus Metarhizium anisopliae

Nucleic acids from 41 strains of Metarhizium anisopliae, obtained from different parts of the world were extracted and examined by electrophoresis. Strong bands of double‐stranded RNA (dsRNA) were detected in two isolates from Brazil, V215 and V291, which had, respectively, 13 and 9 distinct bands ranging in size from ca. 0.75 to 3.5 kb. Icosahedral virus‐like particles (VLPs) (ca. 33 nm in diameter) were observed by transmission electron microscopy in extracts of these isolates. The VLPs and dsRNA were both absent from a clone of the isolate V291 which had been subcultured successively on solid medium. Bioassays against the aphid Myzus persicae showed no detectable difference in virulence between the clone of V291 which contained dsRNA and the clone that did not.     

The effect of a foliar disease (rust) on the development of Gastrophysa viridula (Coleoptera: Chrysomelidae)

Abstract.

• 1 Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae) and the pathogenic rust fungus Uromyces rumicis (Schum.) Wint. both occur on leaves of Rumex crispus L. and R.obtusifolius L. Individual stages of beetle development, and egg laying, were compared on healthy and infected leaves of each plant species in the laboratory. Oviposition choice was investigated in the field and laboratory.
• 2 Beetles reared on infected leaves of each species had greater larval mortality and slower development than those reared on healthy leaves. Although larvae feeding on infected leaves consumed up to 2.5 times more dry weight than those reared on healthy leaves, they had a lower relative growth rate and pupated at a lower weight. These changes were consistent with the reduced nutritive quality of rust-infected Rumex leaves.
• 3 Fecundity of beetles reared on infected leaves of both species was considerably reduced. Eggs laid by beetles feeding on infected R.crispus leaves also had a reduced viability.
• 4 The beetle developed consistently poorer on healthy R.crispus than on healthy R.obtusifolius throughout its life-cycle. Differences in larval performance were greater between host species than between infected and healthy leaves.
• 5 Oviposition was similar on infected and healthy R.crispus in both the laboratory and field. However, adults consumed less, and laid fewer eggs on infected than on healthy R.obtusifolius. The pattern of egg laying on different aged leaves was affected by rust infection: a greater proportion of eggs was laid on the older, infected leaves, than on the equivalent aged leaves on the healthy plants. Few larvae survived from eggs laid on rusted leaves in the field.

     

Effects of atmospheric SO2 on Azolla and Anabaena symbiosis

The water fern Azolla pinnata R. Br. was fumigated for 1 week with either 25, 50 or 100 nl 1⁻¹ SO₂. The symbiosis of Azolla with Anabaena azollae (spp.) was severely damaged by atmospheric SO₂ even at concentrations as low as 25 nl 1⁻¹, with significant reductions in growth, reduction of C₂H₂, NH₃ assimilation, protein synthesis, and heterocyst development. These disturbances appear to be mainly responsible for the extreme sensitivity of this fern to atmospheric SO₂. Changes in violaxanthin/antheraxanthin and epoxy-lutein/lutein ratios also indicate that free radical products are induced by atmospheric SO₂. These results suggest that the Azolla-Anabaena symbiotic system is a very responsive and reliable lower plant model to study the detailed effects of total sulphur deposition upon the balances between various important plant metabolic processes.     

Selection of Bradyrhizobium strains and provenances of Acacia mangium and Faidherbia albida: Relationship with their tolerance to acidity and aluminium

This work was designed to determine the role of the acidity and aluminium stress in the selection of partners in the Acacia symbioses with relevance to the persistence of the microsymbiont Bradyrhizobium in the soil and the growth and nodulation of the host plant respectively. Fifteen strains of Bradyrhizobium from Acacia mangium and Faidherbia albida formed a very homogenous acid tolerant group as indicated by their ability to grow better in a medium at pH 4.5 than in a medium at pH 6.8. By contrast, a growth experiment using an acid liquid media (pH 4.5), containing different concentrations of aluminium successfully identified strains sensitive to aluminium toxicity and those able to grow even in the presence of 100 M AlCl₃.Our results suggest that high amounts of aluminium in the soil rather than acidity (pH 4.5) were a major soil factor for selection of Bradyrhizobium strains capable of establishing a permanently high population under natural conditions.Unlike the behaviour of the microsymbiont, growth and nodulation of Acacia mangium and Faidherbia albida were not affected by aluminium, even at 100 M, but they might be significantly affected by medium acidity (pH 4.5) depending on plant provenances. It is therefore suggested that ability of the host plant to tolerate acidity stress should be taken into account first when screening effective Acacia-Bradyrhizobium combinations for use in afforestation trials.     

Stellatospora,a new genus of the Sordariaceae

In the course of study of fungi from soil, a new genus and species,Stellatospora terricola, was isolated. The fungus is distinguished from other known genera in having star- or comfit-shaped ascospores with a distinct germ pore. The morphological characters of the genus are considered to resemble those of the Sordariaceae in Ascomycotina.