Differential responses of the diazotrophic community to aluminum-tolerant and aluminum-sensitive soybean genotypes in acidic soil

Aluminum (Al) is one of the limiting factors for crop production in acidic soil. We aimed to demonstrate how the rhizosphere diazotrophic community responds to two contrasting soybean genotypes, BX10 (Al-tolerant) and BD2 (Al-sensitive), under Al stress at different growth stages. The diversity and abundance of nifH gene in the rhizosphere soils were assessed by denaturing gradient gel electrophoresis (DGGE) and real-time PCR. The results indicated that there were differences in the community structure between BX10 and BD2 at three sampling stages, respectively. Phylogenetic analyses revealed that 3 and 16 non-identical sequences were responsive to BX10 and BD2, respectively, during the whole growth periods. Parts of sequences responsive to BD2 were affiliated with Rhizobium sp. and Azospirillum brasilense, which have the potential to promote plant growth. Dominant diazotrophs varied in different growth stages of both soybean genotypes. Higher nifH abundance was observed in BD2 at seedling stage, whereas that was detected in BX10 at flowering and maturity stages. The diazotrophic community is sensitive and responds differentially to different soybean genotypes adapted to Al stress, as demonstrated by the increased quantity of diazotrophs in BX10 and the stimulation of beneficial diazotrophic bacteria in BD2.

► The diazotrophs responds differentially to Al-tolerant and -sensitive soybeans.
► The quantity of diazotrophs increased in Al-tolerant soybean with plant growth.
► The beneficial diazotrophic bacteria were stimulated in Al-sensitive soybean.