Suillus hypogaeus: First record of a truffle Suillus.

Suillus (order Boletales) is a diverse genus of epigeous, mushroom-forming fungi native to temperate forests across the Northern Hemisphere; however, some species are also present in areas where Pinaceae has been introduced in the Southern Hemisphere. Unlike the closely related genus Rhizopogon, there are no described hypogeous, sequestrate species of Suillus. Here, we describe Suillus hypogaeus, the first known species of the genus with hypogeous, sequestrate sporocarps. Collections were made on Marys Peak in Benton County, Oregon, USA, at an elevation of 800 m in forests dominated by Pseudotsuga menziesii var. menziesii. The peridium is white, quickly staining pink to purple-reddish where bruised or cut. The gleba is pale yellow when young, becoming purple with maturity, and the basidiospores are obovoid, light yellow in KOH, and amyloid in Melzer's reagent. Multilocus molecular phylogenetic analyses support the placement of S. hypogaeus among the Larix specialists in the spectabilis group of Suillus. Although Larix and Pseudotsuga are sister genera, Larix does not occur on Marys Peak or elsewhere in western Oregon. Suillus hypogaeus, therefore, represents both an independent origin of the hypogeous, sequestrate sporocarp within the Boletales and an independent host shift between Larix and Pseudotsuga within the genus Suillus.

Ectomycorrhizal communities of ponderosa pine and lodgepole pine in the south-central Oregon pumice zone.

Forest ecosystems of the Pacific Northwest of the USA are changing as a result of climate change. Specifically, rise of global temperatures, decline of winter precipitation, earlier loss of snowpack, and increased summer drought are altering the range of Pinus contorta. Simultaneously, flux in environmental conditions within the historic P. contorta range may facilitate the encroachment of P. ponderosa into P. contorta territory. Furthermore, successful pine species migration may be constrained by the distribution or co-migration of ectomycorrhizal fungi (EMF). Knowledge of the linkages among soil fungal diversity, community structure, and environmental factors is critical to understanding the organization and stability of pine ecosystems. The objectives of this study were to establish a foundational knowledge of the EMF communities of P. ponderosa and P. contorta in the Deschutes National Forest, OR, USA, and to examine soil characteristics associated with community composition. We examined EMF root tips of P. ponderosa and P. contorta in soil cores and conducted soil chemistry analysis for P. ponderosa cores. Results indicate that Cenococcum geophilum, Rhizopogon salebrosus, and Inocybe flocculosa were dominant in both P. contorta and P. ponderosa soil cores. Rhizopogon spp. were ubiquitous in P. ponderosa cores. There was no significant difference in the species composition of EMF communities of P. ponderosa and P. contorta. Ordination analysis of P. ponderosa soils suggested that soil pH, plant-available phosphorus (Bray), total phosphorus (P), carbon (C), mineralizable nitrogen (N), ammonium (NH4), and nitrate (NO3) are driving EMF community composition in P. ponderosa stands. We found a significant linear relationship between EMF species richness and mineralizable N. In conclusion, P. ponderosa and P. contorta, within the Deschutes National Forest, share the same dominant EMF species, which implies that P. ponderosa may be able to successfully establish within the historic P. contorta range and dominant EMF assemblages may be conserved.

Relationships between Swiss needle cast and ectomycorrhizal fungus diversity.

Swiss needle cast (SNC) is a disease specific to Douglas-fir (Pseudotsuga menziesii) caused by the ascomycete Phaeocryptopus gaeumannii. Here we examine characteristics of the EM fungus community that are potentially useful in predictive models that would monitor forest health. We found that mean EM density (number of colonized root tips/soil core) varied nearly 10-fold among sites of varying levels of SNC, while mean EM fungus species richness (number of species/soil core) varied by about 2.5 times. Strong relationships were found between EM and SNC parameters: EM species richness was positively correlated with both Douglas-fir needle retention (R(2) = 0.93) and EM density (R(2) = 0.65); EM density also was significantly correlated with Douglas-fir needle retention (R(2) = 0.70). These simple characteristics of the EM fungus community could be used to monitor forest health and generate predictive models of site suitability for Douglas-fir. Based on previous findings that normally common EM types were reduced in frequency on sites with severe SNC, we also hypothesized that some EM fungi would be stress tolerant-dominant species. Instead, we found that various fungi were able to form EM with the stressed trees, but none were consistently dominant across samples in the severely diseased areas.

Structural characteristics of root-fungus associations in two mycoheterotrophic species, Allotropa virgata and Pleuricospora fimbriolata (Monotropoideae), from southwest Oregon, USA.

All members of the Monotropoideae (Ericaceae), including the species, Allotropa virgata and Pleuricospora fimbriolata, are mycoheterotrophs dependent on associated symbiotic fungi and autotrophic plants for their carbon needs. Although the fungal symbionts have been identified for A. virgata and P. fimbriolata, structural details of the fungal-root interactions are lacking. The objective of this study was, therefore, to determine the structural features of these plant root-fungus associations. Root systems of these two species did not develop dense clusters of mycorrhizal roots typical of some monotropoid species, but rather, the underground system was composed of elongated rhizomes with first- and second-order mycorrhizal adventitious roots. Both species developed mantle features typical of monotropoid mycorrhizas, although for A. virgata, mantle development was intermittent along the length of each root. Hartig net hyphae were restricted to the host epidermal cell layer, and fungal pegs formed either along the tangential walls (P. fimbriolata) or radial walls (A. virgata) of epidermal cells. Plant-derived wall ingrowths were associated with each fungal peg, and these resembled transfer cells found in other systems. Although the diffuse nature of the roots of these two plants differs from some members in the Monotropoideae, the structural features place them along with other members of the Monotropoideae in the "monotropoid" category of mycorrhizas.

Taxonomy of the Rhizopogon vinicolor species complex based on analysis of ITS sequences and microsatellite loci.

We are re-addressing species concepts in the Rhizopogon vinicolor species complex (Boletales, Basidiomycota) using sequence data from the internal-transcribed spacer (ITS) region of the nuclear ribosomal repeat, as well as genotypic data from five microsatellite loci. The R. vinicolor species complex by our definition includes, but is not limited to, collections referred to as R. vinicolor Smith, R. diabolicus Smith, R. ochraceisporus Smith, R. parvulus Smith or R. vesiculosus Smith. Holo- and/or paratype material for the named species is included. Analyses of both ITS sequences and microsatellite loci separate collections of the R. vinicolor species complex into two distinct clades or clusters, suggestive of two biological species that subsequently are referred to as R. vinicolor sensu Kretzer et al and R. vesiculosus sensu Kretzer et al. Choice of the latter names, as well as morphological characters, are discussed.