Macromolecular syntheses in germinating conidia and basidiospores of Heterobasidion annosum (original) (raw)
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Double-stranded RNA transmission through basidiospores of Heterobasidion annosum
Mycological Research, 2004
A search for double-stranded RNA (dsRNA) was conducted among 106 isolates of the pathogenic basidiomycete Heterobasidion annosum. Of these isolates, 47 were tissue isolates from fruit bodies and 59 were isolated from decayed wood. Nucleic acids were extracted from freeze-dried mycelia and dsRNA was separated by cellulose CF-11 chromatography and confirmed by digestions with specific nucleases. dsRNA was present in 19 and 14 % of the tissue and wood isolates, respectively. From five of the fruit bodies containing dsRNA basidiospores were investigated and 10-84% of the germinated basidiospores contained dsRNA. On high nutrient media, the germination frequency of basidiospores was reduced by presence of dsRNA in the fruit body (P<0.05) ; germination frequencies were 34 and 78% for spores from fruit bodies with and without dsRNA, respectively. The same trend was present also on low nutrient media, although not statistically significant ; germination was 3 and 10 % for spores from infected and dsRNA free fruit bodies, respectively. Transmission of dsRNA in H. annosum from mycelia into basidiospores together with the lowered germination frequency are likely to play a significant role in the life cycle of the fungus. The relative importance of different transmission routes for dsRNA in H. annosum is discussed.
Basidiospore viability and germination in ectomycorrhizal and saprotrophic basidiomycetes
Mycological Research, 1993
Spores of the ectomycorrhizal basidiomycetes Rhizopogan rubescens and Suillus tomentosus were induced to germinate and stained with fluorescent stains FDA and DAPI to assess germinability and viability. Basidiospores of several saprotrophic species including Pleuratus astreatus, Marasmius areades, Agaricus brunnescens, Coprinus quadrifidus and Conocybe lactea were also assayed for comparison. Nearly all spores of both the ectomycorrhizal and saprotrophic fungi contained intact nuclei. The percentage of R. rubescens and S. tamentasus spores that stained with FDA increased throughout the study. Peaks in FDA staining corresponded with germination events which occurred every 9 to 13 days. The FDA staining in spores of P. astreatus and M. oreades was high and corresponded with high rates of germinability. Germination and FDA staining of the other saprotrophic species were variable. In ectomycorrhizal and several saprotrophic species FDA staining was unreliable as an indicator of viability but served as a good predictor of dormancy. Non-fluorescent vital and nuclear stains were compared with the fluorescent stains and gave similar results. Equations for estimating viability, dormancy, and activation of spores are presented.
Electron microscopy studies of basidiosporogenesis in Agaricus brasiliensis
Mycologia, 2012
The objective of this work was to study the basidiosporogenesis and the intraspecific variation in the number of basidiospores produced per basidium in Agaricus brasiliensis with transmission (TEM) and scanning electron microscopy (SEM). A. brasiliensis produces predominantly tetrasporic basidia, but this trait may vary depending on the strain. For certain strains, such as CS2 and CS7, the frequency of bisporic and trisporic basidia was similar to, or greater than, that of tetrasporic strains. These results suggest that some strains of A. brasiliensis may be amphithallic; however, this behavior is variable and strain dependent. The development of basidia and basidiospores occurs asynchronously during basidiocarp production. The basidiospore cell wall is composed of three distinct layers and presents variable thickness. The conspicuous presence of lipid bodies also was observed in the basidiospores, while nuclei, mitochondria, vacuoles and dolipore septa could be visualized only in the basidia. The basidiospores generally are produced free but also may be enveloped by an extracellular matrix with unknown chemical composition. The presence of connection hyphae linking the basidia was observed for the first time in A. brasiliensis. This characteristic, so far not reported for other fungi, may represent a specific strategy of A. brasiliensis for exchanging nuclei and other cell material between basidial cells during basidiosporogenesis.
Mycological Research, 1994
Conidiospores of the deuteromycetous fungi, Metarhizium anisopliae, Paecilomyces fumoso-roseus and Verlicillium lecanii harvested from young (2-3 d old) Petri plate cultures germinated more rapidly than those taken from older cultures, including those still in an exponential phase of spore production. Also germ tube lengths were proportionately longer for conidia taken from younger cultures.
Fungal Ecology, 2008
Although spore dispersal is the predominant mode of spread in fungi, the functional ecology of offspring (spore) size and shape has received little attention. We investigated the relationship between spore size (volume) and shape and various life history parameters among 303 European polypore species. In an analysis of variance, basidiocarp size, nutritional mode (parasitic vs. saprotrophic) and host (conifer vs. deciduous) accounted for a significant part of the variation in spore size. Species producing large basidiocarps also produce large spores, parasites produce larger spores than saprotrophs, and species colonizing deciduous trees generally produce larger spores than those colonizing conifers. There was a correlation between spore size and shape, with larger spores being more spherical. The most important factors accounting for variation in spore shape were rot type (white rot vs. brown rot) and nutritional mode, with white rot species and parasites having more spherical spores compared to brown rotters and saprotrophs.
Growth and sporulation responses of Basidiobolus to changes in environmental parameters
Transactions of the British Mycological Society
The growth, asexual and sexual reproduction of pathogenic and saprophytic isolates of Basidiobolus haptosporus were studied. Isolates were recovered from amphibian, reptile and wallaby dung, and from woodlice and clinical specimens from the horse. Saprophytic isolates grew poorly or not at all at 40°C. A pathogenic isolate showed modest growth at this temperature; reproduction in this isolate was favoured by temperatures about 5°higher than for saprophytic isolates. All forms of biological activity investigated were favoured by slightly acid conditions; however, activity was possible over a wide range of pH values. Conidium production ceased at water potentials lower than around-11 to-16 bar; zygospore formation continued under relatively dry conditions and down to-39 bar. All isolates grew minimally at potentials around-48 to-56 bar. Visible light stimulated conidium production but exerted no observable effect on zygospore formation.
Physiological specialization of Heterobasidion annosum on conifer hosts
Canadian Journal of Botany, 1989
Eight conifer hosts belonging to five conifer species were inoculated in vitro with conidial suspensions of eight isolates of Heterobasidion annosum from Washington and California. The conifer trees were represented in inoculation tests by 1 cm diameter branch disks of 0.7 cm thickness. The ability of H. annosum to colonize dying woody tissue was assessed in terms of the number of conidiophores produced on the disks, measured 2 to 3 weeks after inoculation. Analysis of variance showed that there was a great range in conidiophore production with most of this variation attributable to host differences rather than to differences between the pathogen isolates. A second analysis involving four Tsuga heterophylla trees and five isolates showed similar results. In both the interspecific analysis with eight trees and the intraspecific analysis with four T. heterophylla trees, there were significant differential interactions between the isolates and the trees. This indicated that physiologic...