[Effect of elevated O3 on rhizosphere microorganisms of two genotypes of snap bean]

In open top chamber (OTC), elevated atmospheric ozone was simulated to investigate effects of elevated O3 or/and arbuscular mycorrhizae (AM) inoculation on microbial biomass and microbial community structure (MCR) in rhizosphere and hyphosphere of two genotypes (O3-sensitive: S156; O3-tolerant: R123) of snap bean by phospholipid fatty acids (PLFA) method. The objective was to clarify the effect of elevated ozone on rhizosphere microorganism and provide evidence for evaluating the influence of elevated ozone on soil-plant system. The result showed that mycorrhizal colonization rates in two genotypes presented significantly different responses to elevated O3. Relative to ambient O3, mycorrhizal colonization rate of S156 plant decreased at both 50 nL x L(-1) and 80 nL x L(-1) O3, but it only decreased at 80 nL x L(-1) O3 in R123 plant. Biomass of actinomycetes in rhizosphere and Gram-positive bacteria in hyphosphere showed more sensitive to the treatments than others. Actinomycete biomass was significantly affected by plant genotypes, O3 x AM and O3 x AM x genotype, and Gram-positive bacterial biomass was affected O3, AM and AM x genotype. In S156 plant, AM inoculation and elevated O3 affected alone MCR in rhizosphere, and their interaction showed greater effect on MCR than single factor. But elevated O3 only altered MCR in hyphosphere of mycorrhizal plant. In R123 plant, elevated O3 and AM inoculation altered alone MCR in rhizosphere, but their interaction was slight effect on MCR. MCR in hyphosphere was only affected by 80 nL x L(-1) O3. The conclusion of this study was that elevated O3 and AM inoculation can alter alone microbial biomass and community in rhizosphere and hyphosphere, but their interaction depended on sensitivity of host plant to ozone.