Differential Impacts on Bacterial Composition and Abundance in Rhizosphere Compartments between Al-Tolerant and Al-Sensitive Soybean Genotypes in Acidic Soil

In this study, two soybean genotypes i.e . aluminum-tolerant Baxi 10 (BX10) and aluminum-sensitive Bendi 2 (BD2) were used as plant materials and the acidic red soil was used as growth medium. The soil layers from the inside to the outside of the root are: rhizospheric soil after washing (WRH), rhizospheric soil after brushing (BRH) and rhizospheric soil at two sides (SRH), respectively. The rhizosphere bacterial communities were analyzed by high-throughput sequencing of V4 hypervariable regions of 16S rRNA gene (16S rDNA) amplicons via Illumina MiSeq. The results of alpha diversity showed that the BRH and SRH of BX10 were significantly lower on community richness than that of BD2, while the WRH existed no significant difference between BX10 and BD2. Among the three sampling compartments of the same soybean genotype, WRH had the lowest community richness and diversity while existed the highest coverage. Beta diversity analysis results displayed no significant difference for any compartment between the two genotypes, or among the three different sampling compartments for any same soybean genotype. However, the relative abundance of major bacterial taxa specifically nitrogen-fixating and/or aluminum-tolerant bacteria was significantly different in the compartments of the BRH and/or SRH at phylum and genus levels depicting genotype dependent variations in rhizosphere bacterial community. Strikingly, as compared with BRH and SRH, the WRH within the same genotype (BX10 or BD2) always had an enrichment effect on rhizosphere bacteria associated with nitrogen-fixation.