Isolation and identification of an arbuscular mycorrhizal fungus specifically associated with mycoheterotrophic seedlings of Gentiana zollingeri (Gentianaceae)

Gentiana zollingeri (Gentianaceae) is an initial mycoheterotrophic plant that depends on a specific group of arbuscular mycorrhizal (AM) fungi for carbon source during underground growth after seed germination. In this study, a mycorrhizal fungus dominant in mycoheterotrophic seedlings of G. zollingeri was successfully isolated from a soil core collected from a point close to a flowering G. zollingeri. The AM fungal isolate was identified as conspecific or closely related to Dominikia aurea (Glomeraceae) by spore morphology and molecular phylogeny. Basic Local Alignment Search Tool (BLAST) searches against the MaarjAM database showed that the nuclear small subunit ribosomal DNA sequences of the isolate matched the AM fungal sequences obtained from a wide range of plants in various ecosystems, including several mycoheterotrophs. Thus, it is suggested that the AM fungal isolate is one of the cheating susceptible AM fungi. Furthermore, the sequences corresponded to those of a group of AM fungi dominantly detected in Japanese temperate forests. Accordingly, there is a possibility that mycoheterotrophic plants, including seedlings of G. zollingeri, may target AM fungi with a wide host range and ubiquitous distribution.