A mixotrophy is in question: New data on fungal community associated with photosynthetic terrestrial orchid Goodyera repens

Abstract

The boreal green orchid Goodyera repens is an object of debates on its mycorrhizal symbionts' diversity and nutritional strategy. The study was focused on biodiversity of G. repens mycobionts and root fungal endophytes diversity revealing by direct molecular identification from roots and rhizomes and estimation of its possible partial heterotrophy by 13C/15N stable isotope analysis. Thirteen fungal taxa, predominantly basidiomycetes, both saprotrophs and ectomycorrhizal were detected, and the shared with coniferous tree mycobiont (Russula vinosa) was revealed both in orchid and neighbouring trees roots. The presence of wood and litter decay fungi can indicate the first steps G. repens on mycoheterotrophic pathway. 13C depletion along with 15N enrichment characterizes G. repens as initially mycoheterotrophic- autotrophic species. The similarity of δ15N values with litter saprotroph fungi both with sharp increase in 13C/15N in underground parts need further investigation with particular attention to clonal growth and intraclonal transfer potential and mycobiont diversity.