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Abstract  The effect of various media formulations on in vitro ectomycorrhizal synthesis of identified fungal strains with European aspen (Populus tremula L.) was tested in Petri dishes. Pre-grown seedlings were transferred to various nutrient media and inoculated with Paxillus involutus isolates using modified sandwich techniques. Mycorrhiza formation was evaluated macroscopically and further confirmed by microscopic examination of semi-thin sections for anatomical features of the mantle and the Hartig net. Standard media formulations did not support successful ectomycorrhiza formation because of either very poor plant survival (below 20%) or impaired fungal growth. The inclusion of micronutrients and vitamins in a Melin Norkrans (MMN)-based medium increased plant survival rate to above 60% and supported successful mycorrhizal synthesis. P. involutus isolates formed mycorrhizas with a characteristic Hartig net restricted to the epidermis. Mantle density and thickness varied depending on the isolate. In a follow-up experiment, the adapted medium supported successful ectomycorrhiza formation by various Laccaria and Hebeloma isolates. Our results show that an exogenous supply of vitamins and micronutrients in the medium was a prerequisite for successful mycorrhization of P. tremula in vitro in Petri dishes. [ABSTRACT FROM AUTHOR]

Abstract  The bog sedge Kobresia myosuroides is among the first ectomycorrhizal (EM) plants forming dense pads on receding glacier forefronts of the Austrian Alps. This is the only Cyperaceae species known to form EM. To date, little is known about fungal species involved in these EM associations. Therefore, the main aim of this study was to detect EM fungal communities of K. myosuroides (1) by describing mycorrhizal morphotypes (MT) and (2) by identifying the mycobionts by rDNA internal transcribed spacer (ITS) sequencing. Furthermore, seasonal dynamics of Kobresia mycobionts were investigated. Sampling was performed in all four seasons (also under snow cover) during the years 2005 and 2006 at the Rotmoos glacier forefront, a well-characterized alpine primary successional habitat in the Austrian alps (2,300 m above sea level). The degree of EM infection of K. myosuroides roots was high (95%). Ten MTs were described and sequences of 18 fungal taxa were obtained. This was the highest mycobiont diversity ever reported for this plant. Cenococcum geophilum was the most abundant mycobiont (37–46%) and shared dominancy with Sebacina incrustans (16–44%) and Tomentella spp. (7–37%). Tomentella (including Thelephora) was the most species-rich mycobiont genus with five taxa, followed by Cortinarius, Inocybe, and Sebacina with two taxa each and one Hebeloma species. Other ascomycete mycobionts beside C. geophilum were Helvella sp., Lecythophora sp., and one Pezizales species. Due to high interannual differences in the EM fungal community, no significant seasonal changes could be detected. The importance of fungal mycobionts in alpine habitats is discussed. [ABSTRACT FROM AUTHOR]

Abstract  Dwarf willows (e.g. Salix herbacea) are among the earliest ectomycorrhizal (EM) plants colonising primary successional sites such as glacier forefronts in the Tyrolean Alps. EM of S. herbacea were sampled at the Rotmoos glacier forefront (Ötz Valley, Austria) three times a year during the growing season and once a year during winter when plants were covered with snow in 2005 and 2006. EM were investigated using morphological methods and by sequencing the rDNA ITS region. The degree of EM mycorrhization was high throughout both years (93%). We distinguished 21 EM morphotypes and identified 19 fungal species. Cenococcum geophilum, Sebacina spp., Tomentella spp. and Cortinarius spp. dominated the mycobiont community of S. herbacea. The observed species richness in this about 150-year-old soil was at least 59% of the estimated species richness. Fungal communities differed significantly between consecutive years, and spatial heterogeneity was high. These differences made it difficult to detect seasonal impacts. Abundances of C. geophilum EM increased throughout the 2-year sampling period. Sebacina incrustans EM were very abundant in 2005, but nearly disappeared in 2006, whilst its fruitbodies were still frequent in the sampling area. This suggests that the mycorrhizae were displaced from the roots by an outcompeting species, whereas the mycelium was still present in the soil. [ABSTRACT FROM AUTHOR]

Abstract   Polygonum viviparum is one of the first ectomycorrhizal (EM) plant species colonising primary successional sites at the Rotmoos glacier forefront (Tyrolean Alps, Austria). On a site with soil development of about 150 years (2,400 m above sea level), mycobionts of P. viviparum were identified by morphotyping and fungal ribosomal deoxyribonucleic acid internal transcribed spacer sequencing. For studying seasonal dynamics and spatial heterogeneity, ectomycorrhizae were sampled on five plots during all seasons. P. viviparum root tips were always EM. In total, 18 mycobiont taxa of the following genera were identified: Cenococcum (1), Cortinarius (2), Helvella (1), Inocybe (3), Russula (1), Sebacina (2), Thelephora (2) and Tomentella (6). All were non-specific EM partners of EM plants. As early as 2 weeks after spring snow melt, EM were well developed, vital and showed high mycobiont diversity. The relative abundance of senescent root tips was lowest in spring and increased throughout the year, with a maximum in winter (frozen soil). Thus, mycobiont growth and physiological activity obviously start when soil is still under snow cover: We speculate that water availability is one important initiation factor for mycorrhizal development under snow cover, when temperatures still range around the freezing point. Irrespectively of the season, most abundant mycobionts at this primary successional site belonged to the genera Tomentella, Sebacina and Cenococcum, also in frozen soil. Spatial heterogeneity was high when considering species composition and diversity indices. Overall mycobionts species richness was restricted at this site, probably because of the limited availability of fungal partners. We regard the presence/absence of fungal partner and limiting abiotic impacts of the environment as key factors for the symbiotic status of P. viviparum. [ABSTRACT FROM AUTHOR]