Effectiveness of elevated CO2 mediating bacterial communities in the soybean rhizosphere depends on genotypes

Soil microbial community responses to elevated CO2 (eCO2) occur mainly indirect via CO2-induced plant growth stimulation, leading to quantitative as well as qualitative changes in rhizodeposition and plant litter; these can also be dependent on plant cultivar. The CO2-induced response of rhizospheric microbes is likely to act eco-functions as well. In order to investigate the interactive effects, an OTC (open top chamber) experiment was performed using 4 soybean cultivars (i.e. Xiaohuangjin, Suinong 8 hao, Suinong 14 and Heinong 45) grown in a Mollisol under ambient CO2 (390 ppm) and eCO2 (550 ppm), respectively. Rhizosphere soils were collected at the R5 stage for DNA extraction and subsequent high-throughput sequencing. PCoA (principal coordinate analysis) result showed that eCO2 changed the soil microbial communities. Analysis of the genera abundance (read numbers) with a two-way ANOVA showed that the genera of Gaiellales_uncultured, Acidimicrobiaceae_uncultured, Arthrobacter, Catelliglobosispora, Bryobacter, Bradyrhizobium, Ensifer, Pedomicrobium, Xanthomonadales_uncultured, Roseiflexus, Flavisolibacter, Chitinophagaceae_uncultured, 480-2_norank, Gitt-GS-136_norank and 288-2_norank in the rhizosphere were significantly affected by CO2, and the CO2-induced responses of genera of Pseudomonas, Escherichia-Shigella and RB41_norank were dependent on cultivars. There were 8 genera, i.e. Acidimicrobiales_uncultured, Iamia, Blastococcus, Nitrosomonadaceae_uncultured, Escherichia-Shigella, Bacillus, 480-2_norank, GR-WP33-30_norank being significantly mediated by soybean cultivars. This study revealed, for the first time, the abundance of microorganisms on the genus level being affected by eCO2 in the soybean-planted Mollisol, which may be associated with soil nutrient cycling and plant productivity.