Introduction Aspergillus Candida Penicillium Geomyces Leucosporidium 2007 Cystofilobasidium Mrakia 2004 2001 2003 Aspergillus Trichoderma 2001 Rhizoctonia carotae 1996 1969 1990 1987 1987 Fibulorhizoctonia 1996 Fibularhizoctonia Rhizoctonia carotae R. centrifuga 1948 Athelia Rhizoctonia solani Thanatephorus 2007 F. carotae Athelia arachnoidea 1996 1976 A. arachnoidea 1996 Corticium centrifugum 1986 1984 1980 C. centrifugum Athelia Butlerelfia eustacei 1980 Fibulorhizoctonia psychrophila F. psychrophila Materials and methods Strains and growth conditions F. psychrophila Daucus carota Athelia arachnoidea Populus  Fibulorhizoctonia carotae Aspergillus niger 1996 1988 F. psychrophila A. niger 2004 F. psychrophila F. psychrophila A. niger Schizophyllum commune 1979 Aspergillus 2004 F. psychrophila F. psychrophila Athelia arachnoidea F. carotae Powdered wood was obtained by grinding wood shavings of a storage crate in a coffee grinder until a fine powder was obtained. Of this powder, 1 g was added to 1.5 g agar and 100 ml water and autoclaved to prepare solid media. The crude arabinoxylan preparation was a gift from Latenstein (Nijmegen, The Netherlands) and is in fact a waste stream of a protein and starch extraction process from wheat. Molecular biology methods 1990 F. carotae A. arachnoidea Enzyme assays F. psychrophila Aspergillus niger p d p d p d p d p 2 3 p Results and discussion Taxonomy Fibulorhizoctonia psychrophila 1 Fig. 1 Fibulorhizoctonia carotae Athelia arachnoidea Fibulorhizoctonia psychrophila a b c  Mycelium ad 9°C cotoneum, albidum, ad 18°C cremeum, avellaneum vel brunneum, velutinum vel crustosum. Liquor exsudatus brunneus. Sclerotia presentia vel absentia, irregularia, in statu maturitate subfusca a liquore exsiccata. Hyphae hyalinae vel subfuscae, (2.5–)3–6 μm. Septa fibulatae vel afibulatae. Cellae sclerotiorum doliformes, tenui-tunicatae vel crasse-tunicatae, hyalinae vel fuscae. Fungus psychrophilus, ad temperaturas −3° ad 21°C crescens. Typus: CBS 109695 Colonies at −3 to 9°C are cottony, rather high and reaching the lid of the Petri dish, white. Margin raised, rather dense. At increasing temperatures the mycelium grows less high and becomes nearly velvety at 18°C and nearly crustose at 21°C. At 12° the centre of the colony is cream-coloured, at 15°C becoming Light Cinnamon Drab to Avellaneous (Munsell 7.5YR6/2, 10YR6/2, 10 YR6/3). At these temperatures exudate droplets are not present. At 18°C the colony is low, nearly velvety, Ochraceous Tawny (7.5YR5/8) caused by exudate drops and at 21°C there is hardly any growth; the mycelium is crustose and Cinnamon Brown to Prouts Brown (5YR4/3, 5YR4/4), and finally Mummy Brown. Sclerotia are generally not produced within 6 weeks, but have occurred in a tube; they start as white semiglobose pustules, generally up to 1 mm diameter, aggregated, often fusing, and producing a brown exudate, which dries in, leaving a dark brown sclerotium, up to 5 mm diam, finally Mummy Brown. Marginal hyphae at −3 to 3°C are irregular, rather long-celled, with swellings and granular contents, thin-walled, (2.5–)3–6 μm wide, swellings up to 12 μm wide. Clamps present, not abundant. Branching at various angles, sometimes a constriction is present at the base of the side branch. At 6°C and above the hyphae are regular, thin- to firm-walled, 2.5–6(–7.5) μm wide, contents hyaline to pale brownish, with abundant clamps, especially at the wider hyphae, but the narrower hyphae (2.5–3.4–4 μm) generally have clampless septa. Cell wall hyaline, but irregular brownish encrustations present at some hyphae, probably dried exudate. Aerial mycelium regular, thin- to firm-walled, (2.5–)3.2–6.5 μm wide, with hyaline to brownish contents. Most septa with clamps; clamps regular, but sometimes of the medallion type. Cardinal temperatures: minimum below −3°C, optimum range between 9 and 12°C, maximum 20°C. Holotype: CBS 109695 (IMI 395943), also preserved dried in herb. CBS. Mycobank number: MB501325. Rhizoctonia Tulasnella Ceratobasidium Thanatephorus Athelia 1996 Epulorhiza Rhizoctonia Fibulorhizoctonia F. carotae F. psychrophila F. psychrophila F. carotae Athelia arachnoidea Athelia 1948 F. carotae F. psychrophila 2 A. arachnoidea F. psychrophila 2 F. psychrophila A. arachnoidea A. carotae F. psychrophila Fig. 2 Fibulorhizoctonia psychrophila Fibulorhizoctonia carotae Athelia arachnoidea  F. psychrophila F. carotae Athelia arachnoidea F. psychrophila F. psychrophila 2 F. psychrophila F. carotae A. arachnoidea 2 F. psychrophila F. psychrophila F. psychrophila F. psychrophila F. psychrophila F. psychrophila F. psychrophila F. psychrophila 3 F. psychrophila F. psychrophila Fig. 3 Fibulorhizoctonia psychrophila a b c  F. psychrophila 3 3 F. psychrophila F. psychrophila F. psychrophila F. psychrophila Aspergillus niger A. niger 2001 A. niger 4 F. psychrophila 4 F. psychrophila A. niger Fig. 4 Fibulorhizoctonia psychrophila Aspergillus a A. niger b F. psychrophila  F. psychrophila 2004 2005 b