Effects of elevated ozone on bacterial communities inhabiting the phyllo- and endo-spheres of rice plants

To explore the effects of elevated ozone (O3) on microbial communities inhabiting phyllo- and endo-spheres of Japonica rice leaves, cultivars Nangeng 5055 (NG5055) and Wuyujing 27 (WYJ27) were grown in either charcoal-filtered air (CF) or elevated O3 (ambient O3 + 40 ppb, E-O3) in field open-top chambers (OTCs) during a growing season. E-O3 increased the values of the Shannon (43-80%) and Simpson (34-51%) indexes of the phyllo-and endo-spheric bacterial communities in NG5055. E-O3 also increased the values of the phyllosphere Simpson index by 58% and the endosphere Shannon index by 54% in WYJ27. Both diversity indexes positively correlated with the contents of nitrogen, phosphorus, magnesium, and soluble sugar, and negatively correlated with the contents of starch and condensed tannins. The leaf-associated bacterial community composition significantly changed in both rice cultivars under E-O3. Moreover, the leaf-associated bacterial communities in NG5055 were more sensitive to E-O3 than those in WYJ27. The chemical properties explained 70% and 98% of variations in the phyllosphere and endosphere bacterial communities, respectively, suggesting a predominant role of chemical status for the endospheric bacterial community. Most variation (57.3%) in the endosphere bacterial community assembly was explained by phosphorus. Gammaproteobacteria and Pantoea were found to be the most abundant class (63-76%) and genus (38-48%) in the phyllosphere and endosphere, respectively. E-O3 significantly increased the relative abundance of Bacteroidetes in the phyllosphere bacterial community and decreased the relative abundance of Gammaproteobacteria in the endophytic community. In conclusion, elevated O3 increased the diversity of bacterial communities of leaf phyllosphere and endosphere, and leaf chemical properties had a more pronounced effect on the endosphere bacterial community.