Metagenomic Insights into Rhizosphere Microbial Communities in Annual Bluegrass Putting Green Turf.

There is an increasing interest in understanding plant-associated microbial communities and how these microorganisms may be utilized to improve plant health.  However, this research has largely been limited to agronomic systems and little is known about the microbial constituents in other economically important specialty crop systems, such as turfgrass.  The objective of this study was to perform a community-wide assessment of the fungi, bacteria and archaea inhabiting the rhizosphere of annual bluegrass (Poa annua L.) putting green turf.  Three separate field studies were sampled for this research that consisted of (1) plots receiving different potassium treatments; (2) plots receiving two different nitrogen regimes; and (3) plots established to examine rhizosphere microbial communities over time.  Following DNA extractions, organism-specific rDNA regions from fungi (ITS) and bacteria and archaea (16S) were PCR amplified.  Amplicons were sequenced in multiplexed reactions on the Illumina MiSeq platform and data was analyzed with QIIME (Quantitative Insights into Microbial Ecology).  Numerous OTUs (operational taxonomic units) were identified from all studies, ranging from 1.5 x 10⁵ to 8.3 x 10⁵ OTUs.  Archaea, bacteria and fungi were identified from all samples.  Alpha diversity metrics showed that microbial diversity was high in all studies, though archaea/bacteria always displayed higher diversity than fungi. A core microbiome of six OTUs was present across all samples and in all studies.  For example, an unnamed member of the archaea in the Cenarchaeales was recovered from all samples. This data demonstrates that the rhizosphere of P. annua turf is diverse, and that certain microorganisms are consistently found inhabiting this environment.  Using this data, microbes of interest can now be targeted, to better understand the functional and biological role they may play in the rhizosphere of P. annua turf.