High endophytic diversity associated with roots of Cattleya milleri, an endemic orchid from rupestrian grasslands of the “Quadrilátero Ferrífero”, a Brazilian savanna hotspot area in Minas Gerais

Abstract Cattleya milleri is a microendemic orchid of iron-rich rupestrian grasslands in the Brazilian savanna hotspot. It is under critical threat due to illegal collections and habitat destruction. As endophytic and mycorrhizal fungi have potential application during C. milleri propagation and conservation, we investigated its root fungal community. C. milleri roots were sampled in five natural sites and at a greenhouse. Fungal root endophytes were isolated for cultural characterization and molecular ITS (Internal Transcribed Spacer) identification. Total DNA was extracted from root endorhiza and rhizosphere to ITS amplification and sequencing. Sixteen fungal isolates were clustered in 6 Operational Taxonomic Units (OTUs), while endorhizal and rhizospheric sequences were clustered in 327 OTUs. Endorhiza richness (OTUs number) ranged from 25 to 89 OTUs, and rhizosphere presented 56 OTUs. Cluster analysis showed high divergence between natural and greenhouse environments, but a small distance among natural samples. Four phyla, 48 orders, 81 families, and 94 genera were annotated. The putative role of 134 OTUs was annotated, and 24 genera were endophytes, 2 mycorrhizas, 33 pathotrophs, 40 saprotrophs and 17 symbiotrophs. Three orders containing endophytes (Capnodiales, Hypocreales, and Pleosporales) and one containing mycorrhizae (Sebacinales) occurred in all sites. The mycorrhizae Tulasnella occurred in all natural samples. The presence of only two mycorrhizal taxa suggested the mycorrhizae may limit C. milleri distribution. However, many fungi can be recruited from the environment as non-mycorrhizal endophytes. Considering their abundance and role in orchid development, Pleosporales, Tulasnella , and Sebacinalles may be considered for C. milleri propagation and conservation.