Uncovering the mycorrhizal community of two Habenaria orchids in South Africa

Abstract

Southern Africa is a biodiversity hotspot for a variety of orchids, including Habenaria. However, we know very little about the orchid mycorrhizae that are associated with these orchids. To bridge this gap, we compared the community of orchid mycorrhizae that are associated with two indigenous Habenaria species, H. barbertoni and H. epipactidea, using a high-throughput sequencing platform. We selected these two orchids because their distribution zones overlap in South Africa. Furthermore, H. barbertoni is endangered, whereas H. epipactidea is not. We hypothesised that the mycorrhizal diversity and composition linked with the roots of these two orchids would overlap, but that some distinct fungal taxa would exist, and these distinct fungi would include unusual taxa. Analyses of the DNA sequence data revealed that the two orchids shared 35 fungal OTUs. Twenty-four and seventeen OTUs were exclusively detected in the roots of H. barbertoni and H. epipactidea, respectively. Mycorrhizal fungi from the rust lineage Atractiellales (Atractiellomycetes, Pucciniomycotina) were only detected in the roots of the endangered H. barbertoni, which represents the first report of these fungi associated with orchids outside of the Andean rainforest. Our findings increase knowledge of the diversity of mycorrhizae associated with indigenous orchids on the African continent.