Narrow mycorrhizae and large non-mycorrhizal fungal diversity associated with roots of Cattleya milleri, an endemic and endangered orchid from a rupestrian hotspot in the “Quadrilátero Ferrífero” of Minas Gerais - Brazil

Abstract

Abstract The threatened orchid Cattleya milleri is a microendemic orchid of a Brazilian savanna hotspot. As endophytes and mycorrhizae may improve its propagation and conservation, we investigated its root fungal community. Cattleya milleri roots were sampled in five natural sites and at a greenhouse. Fungal root endophytes were isolated for characterization and molecular ITS (Internal Transcribed Spacer) identification. Total DNA was extracted from endorhiza and rhizosphere for ITS amplification and sequencing. Sixteen fungal isolates were clustered in 6 Operational Taxonomic Units (OTUs) and endorhizal and rhizospheric sequences were clustered in 327 OTUs. Endorhiza presented from 25 to 89 OTUs, and rhizosphere 56 OTUs. Cluster analysis showed high divergence between natural and greenhouse fungal communities, but similarity among natural samples. From the 94 genera, 24 were annotated as endophytes, two mycorrhizas, 33 pathotrophs, 40 saprotrophs, and 17 symbiotrophs based on the FunGuild database. Endophytes of the orders Capnodiales, Hypocreales, Pleosporales, and mycorrhizae of Sebacinales occurred in all sites. The mycorrhizae Tulasnella occurred in all natural samples. The interaction with only two mycorrhizal taxa may limit C. milleri distribution. However, the recruitment of many non-mycorrhizal endophytes is essential to natural development. Pleosporales, Tulasnella, and Sebacinalles may be considered for C. milleri propagation and conservation