An Arbuscular Mycorrhizal Fungus Specifically Associated with Mycoheterotrophic Seedlings of Gentiana zollingeri (Gentianaceae) is Isolated and Identified as Conspecific or Closely Related to Dominikia aurea (Glomeraceae)
Ryota Kusakabe1* and Masahide Yamato2
1 Graduate School of Horticulture, Chiba University
2Faculty of Education, Chiba University
Gentiana zollingeri (Gentianaceae) is a green herbaceous plant that depends on a specific group of arbuscular mycorrhizal (AM) fungi for carbon sources during the underground growth after seed germination (initial mycoheterotrophy). In this study, we isolated the specific AM fungus dominant in mycoheterotrophic seedlings of G. zollingeri from a soil core collected near a flowering G. zollingeri in its habitat. The isolate was identified as conspecific or closely related to Dominikia aurea (Glomeraceae) by spore morphology and molecular phylogeny. SSU rDNA sequences of the isolate corresponded to the dominant mycobiont of G. zollingeri seedlings, and VTX159 and VTX166 in the MaarjAM database. Since VTXs in the MaarjAM were defined as clusterings at a 97% sequence similarity threshold for the partial SSU rDNA, the affiliation into two OTUs suggests a high intragenomic variation for the SSU rDNA. Both VTXs have been detected in several mycoheterotrophs such as Burmanniaceae and Triuridaceae in previous studies, which suggests that the isolate is one of the cheating susceptible AM fungi. These VTXs have also been obtained from a wide range of plants in various ecosystems and matched the sequences of AM fungi that are dominant in Japanese temperate forests. Accordingly, it is suggested that some mycoheterotrophic plants, including seedlings of G. zollingeri, may target AM fungi with a broad host range and ubiquitous distribution as stable carbon sources.