orchid-associated bacterial communities of two Platanthera spp.

A consensus is emerging that besides the plant-fungus symbiosis in arbuscular and ectomycorrhizal plants, endophytic and rhizosphere bacteria also enhance plant fitness via tripartite interactions. Assuming that bacterial associations are just as important for the obligate mycorrhizal family Orchidaceae, little is known about orchid associated bacteria (OAB). In this multiyear, rangewide study, we examined the OAB communities of two terrestrial orchids, Platanthera cooperi and Platanthera praeclara, representing widely disparate North American ecosystems. We asked whether congeneric orchids recruit a core bacterial community, and whether community composition can be linked to phenology, population size, or habitat soil. Genomic DNAs from roots of seedling, vegetative, and reproductive plants and from soil were subjected to high throughput sequencing of the V4 and V5 regions of the 16S nrDNA.