A faster inoculation assay for Armillaria using herbaceous plants

Armillaria (honey fungus) is a virulent necrotrophic pathogen that causes Armillaria root disease. Conventional Armillaria inoculation assays use young saplings as hosts and consequently are cumbersome, frequently conducted outdoors, and take many years from establishment to analysis of infection. We have developed and evaluated a faster inoculation assay for Armillaria that uses herbaceous plants as hosts, is carried out in controlled conditions, and reduces experimental durations to 3 months. Plant species of known susceptibility to Armillaria and comparisons between virulent A. mellea and opportunistic A. gallica were used to validate the assay. Mortality and diagnostic symptoms of Armillaria root disease such as epiphytic rhizomorphs and mycelial fans were used to assess levels of infection. We also attempted to reduce assay preparation time by substituting woody inocula with agar inocula, but typical symptoms of Armillaria root disease were only observed on plants infected with woody inocula. Through our assay, we identified five new potential herbaceous hosts of Armillaria: Kniphofia hirsuta, Hordeum vulgare, Lobelia cardinalis, Nicotiana tabacum and Helenium hoopesii – further expanding the extensive list of plants with susceptibility to Armillaria and suggesting infection of herbaceous species may be more widespread than currently acknowledged.     

Lignin-degrading activity of edible mushroom <Emphasis Type="Italic">Strobilurus ohshimae</Emphasis> that forms fruiting bodies on buried sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) twigs

Strobilurus ohshimae is an edible mushroom, and it specifically forms its fruiting bodies on buried sugi (Cryptomeria japonica) twigs. In this research, we studied lignindegrading activity of S. ohshimae. We isolated 18 strains of S. ohshimae from various regions of Japan, and determined their lignin degradation rates on sugi wood meal medium. All the strains of S. ohshimae degraded approximately 6%–12% of sugi lignin in 30 days, and these lignin degradation rates were 1.5–3 times higher than those of Trametes versicolor, which is a typical lignin-degrading fungus. Among the three main lignin-degrading enzymes, activity of lignin peroxidase and manganese peroxidase was not observed, while 4340U/g of laccase was produced in 30 days. To investigate the effect of wood species on lignin degradation by S. ohshimae, the lignin degradation rate and laccase productivity on sugi wood meal medium were compared with those on beech (Fagus crenata). In T. versicolor, both lignin degradation rate and laccase productivity were higher on beech than on sugi. Conversely, in S. ohshimae, lignin degradation rate and laccase productivity were higher on sugi than on beech. Therefore, it was suggested that coniferous lignin is not always difficult to degrade for the fungi that inhabit softwood. Part of this article presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004     

Size matters: What have we learnt from microcosm studies of decomposer fungus–invertebrate interactions?

The ongoing research ‘boom’ in soil ecology has been advanced by a widespread use of laboratory experiments to investigate mechanisms that could not be unravelled with field observations alone. Interactions between soil fungi and invertebrates have received considerable attention due to their trophic and functional importance in belowground systems. Saprotrophic cord-forming basidiomycete fungi are major agents of primary decomposition in woodland ecosystems, where they are also an important source of nutrition for fungal-feeding soil invertebrates. A plethora of microcosm experiments, with their main benefit being that they enable most variables to be kept constant while just a few are manipulated, have provided detailed insights into the ecology of fungus–invertebrate interactions. This review identifies important trends from this body of work (including a meta-analysis of grazing effects on fungal growth and wood decomposition) and explores the extent to which these patterns are supported by the few related experiments conducted in more complex mesocosm and field systems. Grazing in microcosms reduced fungal growth and increased decomposition, but with interaction-specific magnitude, reflecting invertebrate feeding preferences for different fungi. Macro-invertebrates (woodlice and millipedes) had stronger effects than micro- (e.g. nematodes) and meso- (e.g. collembola) invertebrates. This greater grazing pressure generally increased enzyme activities beneath mycelia during interactions in which wood decay was increased. Top-down effects of fungal-feeding can be extrapolated to more complex systems, but only for macro-invertebrates, particularly woodlice. Soil enzyme activity was stimulated, in microcosms and more complex systems, by short-term or low intensity grazing, but reduced when large areas of mycelium were removed by high-intensity grazing. Effects of differential fungal palatability on invertebrate populations are evident in microcosm studies of collembola. These bottom-up effects can be extrapolated more broadly than top-down effects; fungal community dominance determined collembola abundance and diversity, in mesocosms, and woodlouse abundance in the field. Using, as a case study, a series of experiments conducted at a range of scales, mechanisms underlying potential climate change effects on grazing interactions and decomposition are also explored. Biotic effects on decomposer community functioning are heterogeneous, depending on fungal dominance and the density of key macro-invertebrate taxa.     

Morphological features and dietary functional components in fruit bodies of two strains of <Emphasis Type="Italic">Pholiota adiposa</Emphasis> grown on artificial beds

 The morphological features and dietary functional components of two strains (FPF-13 and Oninome-B) of Pholiota adiposa (numerisugitake mushroom) grown on artificial bed blocks were examined. The components examined were chitin, mannitol, trehalose, guanosine 5′-monophosphate, ergosterol, and β-glucan. There was a significant difference in the external shape of the two strains. However, the differences in the contents of functional components between the two strains, as well as between the pilei and stipes of the strains, were small. In both strains the trehalose content was much higher than the mannitol content, in contrast to those of Lentinula edodes. From a commercial point of view, Oninome-B has a clear advantage over other strains of P. adiposa owing to its less removable scale. Received: May 15, 2002 / Accepted: June 10, 2002 Acknowledgment The authors thank Dr. F. Eguchi (Takasaki University of Health and Welfare) for his technical advice on the β-glucan analysis. Part of this report was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001 Correspondence to:K. Shimizu     

Relationship of host recurrence in fungi to rates of tropical leaf decomposition

Here we explore the significance of fungal diversity on ecosystem processes by testing whether microfungal ‘preferences’ for (i.e., host recurrence) different tropical leaf species increases the rate of decomposition. We used pairwise combinations of γ-irradiated litter of five tree species with cultures of two dominant microfungi derived from each plant in a microcosm experiment. The experiment was designed to test whether early leaf decomposition rates differed depending on relationships between the leaf litter from which the fungi were derived (i.e., the source plant) and the leaf substrata decomposed by these fungi in microcosms. Relationships tested were phylogenetic relatedness between the source and substratum leaves, and similarity in litter quality (lignin, N and P) between the source and substratum. We found a significant interaction between microfungi and leaf species (P<0.0001), and differences among the four classes of source–substratum relationships were highly significant (P=0.0004). Combinations in which fungal source leaves were of the same species or family as the substratum, or the fungal source resembled the substratum in quality had marginally faster decomposition than when the fungal source and substratum leaves were mismatched (i.e., unrelated and of dissimilar quality). In some microcosms, a basidiomycete contaminant had a strong additive effect on decomposition of Croton poecilanthus leaves resulting in faster decomposition than with microfungi alone (P<0.0001). Comparisons among leaf–microfungal combinations were made after the effect of the basidiomycete covariate was adjusted to zero. The data on microfungi suggest differential abundance in particular hosts, which contributes to species diversity of decomposer fungi in tropical forests, affects rates of decomposition.     

担子菌遗传转化研究进展

担子菌遗传转化目前主要采用电激法和PEG法。本文着重介绍自第一例担子菌的遗传转化开始,担子菌中转化系统的构建和转化的一般特点;并列出了截止到1996年9月报道的一些实例,说明了担子菌遗转传化的理论价值和应用价值。     

大白口蘑子实体化学成分研究

从担子菌大白口蘑(Tricholoma giganteum Massee)新鲜子实体提取物中首次分离得到5个化合物,它们的结构经各种波谱数据分别鉴定为(22E,24R)-麦角甾-5,7,22-三烯-3β-醇;5α,8α-桥氧-(22E,24R)-麦角-6,22-二烯-3β-醇;(2S,3S,4R,2’R)-2-(2’-羟基二十一碳酰胺基)-三十烷基-1,3,4-三醇;腺嘌呤核苷和烟酸。     

维生素B1对几种担子菌菌丝体生长的影响

配制不同维生素B1浓度的固体培养基,对冠平1号、金针菇、灵芝80103种食用菌进行斜面培养,研究了3种食用菌生长所需的最适维生素B1浓度范围。结果表明:冠平1号菌丝体生长所需的最适维生素B1范围为30～35mg/L;日本金针菇生长的最适维生素B1浓度为30mg/L;灵芝8010生长的最适维生素B1浓度为10～15mg/L。     

Surface properties of the mushroom Strobilurus ohshimae result in food differentiation by collembolan species

The basidiomycete Strobilurus ohshimae has fruiting bodies covered with prominently projecting hair-like cells called cystidia; it is not consumed by the collembolan Ceratophysella denisana but is consumed by Mitchellania pilosa. To explain this difference, we examined the effects of S. ohshimae cystidia on collembolan survival. In the field, several collembolan species, including C. denisana, were found dead on S. ohshimae, whereas no dead M. pilosa were found on the fungus. Survival of M. pilosa on S. ohshimae was 100%. In the laboratory, cystidium destruction experiments showed that the cystidia of S. ohshimae were capable of killing C. denisana on contact. A cystidium contact time experiment revealed that the cystidia were also capable of killing M. pilosa, although M. pilosa could survive when the contact time was short. In the field, M. pilosa frequently fed on the interior of S. ohshimae. Interior feeding may enable M. pilosa to feed on S. ohshimae by reducing contact time with the cystidia. The deadly surface of S. ohshimae deters the surface feeder C. denisana but not the interior feeder M. pilosa, resulting in food differentiation of these collembolans.     

Soil aggregate stabilization by a saprophytic lignin-decomposing basidiomycete fungus I. Microbiological aspects

 We studied the effects of a saprophytic lignin-decomposing basidiomycete isolated from plant litter on soil aggregation and stabilization. The basidiomycete produced large quantities of extracellular materials that bind soil particles into aggregates. These binding agents are water-insoluble and heat-resistant. Water stability of aggregates amended with the fungus and the degrees of biodegradation of the binding agents by native soil microorganisms were determined by the wet-sieving method. The data demonstrated that aggregates supplemented with a source of C (millet or lentil straw) were much more water-stable and resisted microbial decomposition longer than when they were prepared with fungal homogenates alone. Moreover, retrieval of fungal-amended aggregates supplemented with millet during the first 4 weeks of incubation in natural soil exhibited more large aggregate fractions (>2 mm) than the ones supplemented with lentil straw. The possible relationship of the role of basidiomycetes in litter decomposition and soil aggregation is discussed. Received: 27 September 1999