Ectomycorrhizal Fungal Inoculation of Sphaerosporella brunnea Significantly Increased Stem Biomass of Salix miyabeana and Decreased Lead, Tin, and Zinc, Soil Concentrations during the Phytoremediation of an Industrial Landfill

Fast growing, high biomass willows (Salix sp.) have been extensively used for the phytoremediation of trace element-contaminated environments, as they have an extensive root system and they tolerate abiotic stressors such as drought and metal toxicity. Being dual mycorrhizal plants, they can engage single or simultaneous symbiotic associations with both arbuscular mycorrhizal (AM) fungi and ectomycorrhizal (EM) fungi, which can improve overall plant health and growth. The aim of this study was to test the effect of these mycorrhizal fungi on the growth and trace element (TE) extraction potential of willows. A field experiment was carried out where we grew Salix miyabeana clone SX67 on the site of a decommissioned industrial landfill, and inoculated the shrubs with an AM fungus Rhizophagus irregularis, an EM fungus Sphaerosporella brunnea, or a mixture of both. After two growing seasons, the willows inoculated with the EM fungus S. brunnea produced significantly higher biomass. Ba, Cd and Zn were found to be phytoextracted to the aerial plant biomass, where Cd presented the highest bioconcentration factor values in all treatments. Additionally, the plots where the willows received the S. brunnea inoculation showed a significant decrease of Cu, Pb, and Sn soil concentrations. AM fungi inoculation and dual inoculation did not significantly influence biomass production and soil TE levels.

Draft Genome Sequence of the Ectomycorrhizal Ascomycete Sphaerosporella brunnea

Sphaerosporella brunnea is a pioneer ectomycorrhizal fungus with facultative saprophytic capacities. Here, we sequenced the genome of S. brunnea strain Sb_GMNB300, which is estimated at 51.6 Mb in size with 872 assembled contigs accounting for 12,597 predicted coding genes. This genome will be useful for comparative studies of Pezizales ectomycorrhizal symbioses.

Antifungal activity in culture filtrates of the ectomycorrhizal fungus Pisolithus tinctorius

The ectomycorrhizal fungus Pisolithus tinctorius secreted a metabolite that lysed hypha and conidia and inhibited the germination of conidia in a range of phytopathogenic fungi. The optimum incubation period for the production of the metabolite by P. tinctorius in liquid culture was 42–56 days. Dilutions of the culture filtrate with fresh medium caused a gradient of inhibitory effects. For hyphal lysis the minimum ratio of culture filtrate to medium for complete growth inhibition was 5:1 for Rhizoctonia praticola and Truncatella hartigii and 3:1 for Sphaerosporella brunnea. At higher dilutions, the hyphae that formed were short celled and highly branched; many hyphae lysed. Conidial germination was completely inhibited at a ratio of 5:1 for both Fusarium solani and T. hartigii, 3:1 for a North American isolate of Brunchorstia pinea (NA), 1:1 for a European isolate of B. pinea (EU), and 1:3 for two strains of Cochliobolus sativus (0910, 0912). Conidial lysis was seen for T. hartigii at a ratio of 5:1 and at a ratio of 1:1 for B. pinea (EU) and C. sativus (0910). Characterization of the cell-free culture filtrate through the separate additions of D-glucose and an adsorbent, activated charcoal, showed that hyphal lysis and conidia germination inhibition did not result from a depletion of carbohydrates from the growth medium but from the presence of some substance adsorbed by charcoal. Key words: Pisolithus tinctorius, allelopathy, antifungal metabolite, hyphal lysis, mycorrhizosphere.

Biotrophic associations between lodgepole pine seedlings and postfire ascomycetes (Pezizales) in monoxenic culture

Twenty-two species of postfire ascomycetes belonging to the order Pezizales were screened for biotrophic interactions with roots of lodgepole pine (Pinus contorta Dougl.). Biotrophic associations ranged from pathogenicity to mycorrhizal symbiosis, but most species tested did not show any affinity for roots. Pyropyxis rubra (Peck) Egger and Rhizina undulata Fr. were aggressive pathogens that infected the vascular cylinder and killed the seedlings. Tricharina praecox (Karst.) Dennis var. intermedia Egger, Yang & Korf also had some ability to infect the vascular cylinder, but usually did not kill the seedlings. Geopyxis carbonaria (A. & S.) Sacc. and Trichophaea hemisphaerioides (Mont.) Graddon invaded the cortex, forming complex intracellular structures, but did not penetrate the vascular cylinder. They may form mutualistic associations under certain conditions. The only confirmed mutualistic species was Sphaerosporella brunnea (A. & S.) Svrcek & Kubicka, which formed ectendomycorrhizae. Anthracobia maurilabra (Cooke) Boud. and A. tristis (Bomm., Rouss. & Sacc.) Boud. appear to be primarily root-surface inhabitants with limited capacity to infect cortical tissues through breaks in the epidermis. Gyromitra infula (Schaef.) Quél. penetrated the epidermis but was unable to overcome host defences against pathogenic infection.