Identification of the DNAs of the ectomycorrhizal fungusTricholoma bakamatsutake using specific oligonucleotide probes and PCR primers

Partial nucleotides of the 18S rDNAs ofTricholoma bakamatsutake were sequenced and compared with those of six ectomycorrhizal fungi and a tree. Two probes, Probes 1 and 2, and a pair of primers were designed based on the variable positions in this region. The DNAs ofT. bakamatsutake were isolated from the colonized mycelia in the soil, field-collected fruit-bodies and artifically cultured mycelia. Hybridization with Probe 1 and PCR-amplification with the primers differentiated these DNAs of this fungus from those of eight ectomycorrhizal fungi and two tree species.     

Hierarchical neighbor effects on mycorrhizal community structure and function

Theory predicts that neighboring communities can shape one another's composition and function, for example, through the exchange of member species. However, empirical tests of the directionality and strength of these effects are rare. We determined the effects of neighboring communities on one another through experimental manipulation of a plant‐fungal model system. We first established distinct ectomycorrhizal fungal communities on Douglas‐fir seedlings that were initially grown in three soil environments. We then transplanted seedlings and mycorrhizal communities in a fully factorial experiment designed to quantify the direction and strength of neighbor effects by focusing on changes in fungal community species composition and implications for seedling growth (a proxy for community function). We found that neighbor effects on the composition and function of adjacent communities follow a dominance hierarchy. Specifically, mycorrhizal communities established from soils collected in Douglas‐fir plantations were both the least sensitive to neighbor effects, and exerted the strongest influence on their neighbors by driving convergence in neighbor community composition and increasing neighbor seedling vigor. These results demonstrate that asymmetric neighbor effects mediated by ecological history can determine both community composition and function.     

Degradation of 14C-labelled lignin and dehydropolymer of coniferyl alcohol by ericoid and ectomycorrhizal fungi

The ability of ericoid and ectomycorrhizal fungi to utilize ¹⁴C-labelled lignin and O¹⁴CH₃-labelled dehydropolymer of coniferyl alcohol as sole C sources has been assessed in pure culture studies. The results indicate that ericoid mycorrhizal fungi are more effective in degrading lignin than ectomycorrhizal fungi. Amongst the ectomycorrhizal fungi the facultative mycorrhizal fungus Paxillus involutus degraded lignin more readily than those which are normally considered to be obligately mycorrhizal fungi such as Suillus bovinus and Rhizopogon roseolus. The importance of these lignin degrading capabilities is discussed in relation to the predominance of specific mycorrhiza forms along a gradient of increasing organic matter and hence lignin content of soil.     

Effects of Mineral Structure and Microenvironment on K Release from Potassium Aluminosilicate Minerals by Cenococcum geophilum fr

K-bearing minerals with enormous reserve in the world, were not easy to provide the available K nutrient element for plant direct uptake because of the slow K release rate. With the potential potassium-solubilizing microorganisms, the slow K release rate from minerals would be improved significantly. In this work, Cenococcum geophilum Fr, one of the most common ectomycorrhizal fungi in boreal to temperate regions, was adopted to dissolve K-bearing minerals for K release. Five kinds of potassium aluminosilicate minerals were tested by bioleaching experiments in pure culture, including feldspar, nepheline, biotite, muscovite and illite. The available and unavailable potassium amounts in minerals before and after bioleaching were measured and compared with each other. The effect of mineral structure on the potassium solubilization efficiency by Cenococcum geophilum Fr. was discussed. Furthermore, the microenvironment formation between fungi and mineral surface to enhance the K release rate was investigated through detecting K, Al, Si concentrations and metabolites amounts (polysaccharide and organic acids) in microenvironment and external environment, respectively. Experimental results demonstrated that Cenococcum geophilum Fr. was a potential candidate of potassium solubilizing microorganisms, and both mineral structure and microenvironment have significant effects on the K release rate.     

Determination of chitin in fungi and mycorrhizal roots by an improved HPLC analysis of glucosamine

A method to measure chitin content in fungi and ectomycorrhizal roots with high-performance liquid chromatography (HPLC) was developed. Measurements of fluorescence of 9-fluorenylmethylchloroformate (FMOC-CI) derivatives of glucosamine were made on acid hydrolysates of pure chitin, chitin-root mixtures and fungal-root mixtures. The method was applied on 5 isolates of ectomycorrhizal fungi, and ectomycorrhizal and non-mycorrhizal Pinus sylvestris roots. Interference from amino acids was removed by pre-treatment of samples with 0.2 N NaOH. This pre-treatment did not reduce the recovery of chitin, nor did plant material affect the recovery of chitin. The HPLC method was compared with a colorimetric chitin-method by measurements on root-fungal mixtures, with known fungal content. The HPLC method gave estimates of fungal biomass which were equal to the expected while the colorimetric method showed values significantly (p<0.001) lower than the expected. The present chitin method offers a sensitive and specific tool for the quantification of chitin in fungi and in ectomycorrhizal roots.     

Fungal content of ectomycorrhizal tips: comparison among 13 tree species

To better understand soil carbon cycling in forest ecosystems, we studied the proportion of fungal sheath area (FSA) in the cross-sectional ectomycorrhizal area in 13 tree species. Ectomycorrhizal samples were collected from subalpine and temperate forests in Japan. The FSA values were in the range of 12% to 56% across all tree species, tree ages, and fungal species. In Abies firma and Quercus serrata, the FSA values were larger in mature trees than in seedlings, whereas no such differences were found in Pinus densiflora and Fagus crenata. In broad-leaved trees, because the plant tissue radii lay within a narrow range, the FSA was affected mainly by the fungal sheath thickness. In conifers, however, the plant tissue radii varied widely among genera, so the FSA was affected by both the plant tissue radius and the fungal sheath thickness. Our findings suggest that the fungal content of ectomycorrhizal tips differs among tree species and fungal species, so that both parameters must be considered in studies of forest carbon cycling. The estimates revealed that data gathering in each type of forest leads to more accurate estimates of the biomass of fungi in ectomycorrhizal tips.