Response of the rhizosphere prokaryotic community of barley (Hordeum vulgare L.) to elevated atmospheric CO(2) concentration in open‐top chambers

The effect of elevated atmospheric CO (2) concentration [CO (2)] on the diversity and composition of the prokaryotic community inhabiting the rhizosphere of winter barley (Hordeum vulgare L.) was investigated in a field experiment, using open‐top chambers. Rhizosphere samples were collected at anthesis (flowering stage) from six chambers with ambient [CO (2)] (approximately 400 ppm) and six chambers with elevated [CO (2)] (700 ppm). The V4 region of the 16S rRNA gene was PCR‐amplified from the extracted DNA and sequenced on an Illumina MiSeq instrument. Above‐ground plant biomass was not affected by elevated [CO (2)] at anthesis, but plants exposed to elevated [CO (2)] had significantly higher grain yield. The composition of the rhizosphere prokaryotic communities was very similar under ambient and elevated [CO (2)]. The dominant taxa were Bacteroidetes, Actinobacteria, Alpha‐, Gamma‐, and Betaproteobacteria. Elevated [CO (2)] resulted in lower prokaryotic diversity in the rhizosphere, but did not cause a significant difference in community structure.