Suillus

Abstract: Nitrogen isotope values (δ15N) are higher in ectomycorrhizal fungi than in their plant hosts but the wide variability in δ15N among sporocarps of different fungal taxa is unexplained. We propose that fungal δ15N reflects sequestration of fungal nitrogen to build fungal biomass, and should accordingly reflect fungal exploration strategies and hyphal properties. To test this, we compared δ15N to exploration types, hyphal hydrophobicity, and the presence of rhizomorphs in ectomycorrhizal species from surveys at four sites in temperate and boreal coniferous forests. Fungi with exploration types of high biomass, such as long-distance (e.g., Suillus), medium-distance mat (e.g., Hydnellum), and medium-distance fringe (e.g., Cortinarius) were 4–7‰ more enriched in 15N than fungi with exploration types of low biomass [medium-distance smooth (e.g., Amanita), short-distance (e.g., Inocybe), and contact (e.g., Hygrophorus)]. High biomass types comprised 79% (Aheden, northern Sweden), 65% (Deer Park, Pacific Northwest, USA), 45% (Stadsskogen, central Sweden), and 39% (Hoh, Pacific Northwest, USA) of ectomycorrhizal species, with these types more prevalent at sites of lower nitrogen availability. Species with hydrophobic hyphae or with rhizomorphs were 3–4‰ more enriched in 15N than taxa with hydrophilic hyphae or without rhizomorphs. The consistency of these patterns suggest that δ15N measurements could provide insights into belowground functioning of poorly known taxa of ectomycorrhizal fungi and into relative fungal biomass across ectomycorrhizal communities.

Abstract: Summary • Ectomycorrhizal fungi (EMF) are critical for pine establishment under primary succession. The species of EMF supporting primary successional pine seedlings on coastal sand dunes and mechanisms for their establishment were investigated. • Fungi were identified from ectomycorrhizal roots using molecular techniques. Field seedlings were collected from forested and nonforested zones. Laboratory seedlings were grown in soils collected from the same zones, and in sterile soils inoculated with fresh and 1-yr-old dry deer fecal pellets. • Suilloid fungi were frequently observed on all seedlings. A diverse group of fungi was available to seedlings in forested zones. A less diverse group of fungi was available to field seedlings in nonforested zones and all laboratory bioassay seedlings. Deer fecal inoculant yielded an average of two EMF per seedling. Both Suillus and Rhizopogon species dominated seedlings inoculated with fresh deer feces, but only Rhizopogon species dominated seedlings inoculated with 1-yr-old feces. • Suilloid fungi are dispersed by deer, produce resistant spore banks and are the principle fungi supporting seedlings on the sand dunes.

Abstract: THE false-truffles (Hymenogastrales) are a group of basidomycetous fungi that produce underground truffle-like basidiocarps. They are generally believed to be independently derived from several mushroom lineages1–4, but extensive morphological divergence often obscures recognition of these phylogenetic connections. Comparisons of mitochondrial DNA now demonstrate a surprisingly close relationship between species of false-truffles in the genus Rhizopogon (Hymenogastraceae) and the mushroom genus Suillus (Boletaceae). The striking morphological differences separating all Suillus species from Rhizopogon imply an acceleration in the rate of morphological change relative to molecular change during the evolution of these false-truffles from their mushroom ancestors. This acceleration can best be explained by rapid morphological divergence resulting from selective pressures which may have acted on a small number of developmental genes.

Abstract: Ectomycorrhizae of jack pine occurring in mature stands, on bare roadsides, and in a recently burned area were compared. Fifty-six fungus associates were identified from sporocarp collections. Species of Elaphomyces, Suillus, Cortinarius, Cantharellus, and hydnums were almost exclusively limited to mature stands. Laccaria proxima, Rhizopogon rubescens. Scleroderma macrorhizon, and Astraeus hygrometricus were typically found on disturbed sites. Visual observations and direct isolations from ectomycorrhizae further indicated that the symbionts differed between the burn site and mature jack pine – lichen woodlands. A majority of the ectomycorrhizae in all sites were nondescript and could not be identified by culturing. Unlike the vascular plants, ectomycorrhizal symbionts were very numerous without any single species or small group of species dominating jack pine root systems. Pure culture syntheses confirmed that Tricholoma flavovirens, T. pessundatum, T. zelleri, Suillus flavovirens, S. albidipes, Cenococc...