Fungal soil communities in a young transgenic poplar plantation form a rich reservoir for fungal root communities

Fungal communities are playing key roles in ecosystem functioning. However, only scarce knowledge exists about their assemblages in roots and soil of biomass plantations. The goal of this study was to analyze fungal family and OTU richness as well as patterns of fungal distribution in their belowground habitats and to gain information on the ectomycorrhizal (ECM) fungal colonization strategy. In a two-year-old plantation, fungal communities in soil and roots of three different poplar genotypes (Populus x canescens, wildtype and two transgenic lines with suppressed cinnamyl alcohol dehydrogenase activity) were analyzed by 454 pyrosequencing using rDNA ITS1 region as the target region. The results were compared with the dynamics of the root-associated ECM community studied by morphotyping/Sanger sequencing in two subsequent years. Fungal species and family richness in soil were surprisingly high in this simple plantation ecosystem with 5944 OTUs (with = 97% sequence identity) and 186 described fungal families indicating the important role of soil communities as fungal reservoir for roots (2399 OTUs and 115 families). The transgenic modification targeted to the phenylpropanoid pathway had no influence on fungal root or soil communities. Fungal families and OTUs were more evenly distributed in soil than in roots, probably as the result of soil plowing before the establishment of the plantation. Analysis of the fungal lifestyles showed that saprophytic, pathogenic and endophytic fungi were the dominating groups in soil, whereas ECMs were dominant in roots (87%). Arbuscular mycorrhizal diversity was higher in soil than in roots. Species richness of the root-associated ECM community, which was low compared to ECM fungi detected by 454 analyses, increased after one year. This increase was mainly caused by ECM fungal species already traced in the preceding year in roots. This result supports the priority concept holding that ECMs present on roots have a competitive advantage over soil-localized ECM fungi.