Influence of rice cultivars on soil bacterial microbiome under elevated carbon dioxide

Abstract

Elevated CO2 concentration (eCO2) may stimulate plant growth and influence the soil microbial community, but questions remain for whether microbial responses to elevated CO2 would vary by different CO2-responsive plants. We thus attempted to elaborate the changes of soil microbiome to different rice cultivars under the eCO2 condition. Two rice cultivars, i.e., the CO2-tolerant cultivar, Wuyunjing23 (WYJ23), and the CO2-sensitive one, Yandao 6 (YD6), were grown under eCO2 and ambient CO2 (aCO2) conditions. The contents of dissolved organic carbon (DOC) and nitrogen (DON) in soil were measured. Real-time qualitative PCR (qPCR) and high-throughput sequencing techniques were employed to characterize the bacterial community. Furthermore, co-occurrence network analysis was applied to reveal the ecological interactions among bacterial taxa. No significant differences were found among all treatments in terms of bacterial population, alpha-diversity indices, and bacterial community structure. However, the topological parameters of ecological networks highlighted the distinct co-occurrence patterns among treatments. YD6 under eCO2 led to more links, lower modularity, and greater centralization degree compared to that under aCO2. Opposite trends of those parameters were observed for WYJ23 under eCO2 compared to that under aCO2. Besides, more Proteobacteria and Acidobacteria served as keystone taxa in the CO2-sensitive cultivar treatments, compared to those in WYJ23, implying the different influences of rice cultivars on the microbial ecological network. Different rice cultivars under eCO2 did not influence the alpha- and beta-diversity of the soil bacterial community, but changed the co-occurrence network of the community. More attention should be paid to the assembly mechanisms of the soil microbial microbiome when evaluating the impacts of productive crops on the soil-plant ecosystem under the eCO2 condition.