Distribution and diversity of culturable phlorizin-resistant bacteria from apple rhizosphere soil in different planting years

Abstract:

[Objective] The experiment was designed to screen bacteria that could tolerate phlorizin and then study the diversity and composition of microbial community of phlorizin-resistant bacteria, which were isolated from the rhizosphere of Malus baccata in different years. Through the study, we aimed to find the potential efficient phlorizin-degrading strains and provide a scientific basis for understanding of the mechanism of continuous cropping obstacles in apple and to overcome or reduce the losses caused by it. [Methods] The phlorizin-resistant bacteria were isolated from five different years’ soils using phlorizin as the sole carbon source. The amplified rDNA restriction analysis (ARDRA) and 16S rRNA gene sequences and phylogeny analysis were employed to identify taxonomic status of phlorizin-resistant bacteria, while the distribution and diversity of the microbial community and its relationship with the physicochemical parameters were analyzed by bioinformatics analysis. [Results] A total of 103 distinct bacterial strains belonging to 13 genera were obtained from apple rhizosphere soil and they could be divided into 18 groups at 65% similarity. Bacillus, Pseudomonas and Novosphingobium were dominant genera. The result showed that rhizosphere soil which was continuously planted for 3 years had the highest diversity and the community composition of phlorizin-resistant bacteria was similar for those continuously planted for 15, 20, 25 years. Pearson analysis exhibited phlorizin-resistant bacteria had a certain correlation with the physicochemical parameters (P<0.05). The redundancy analysis (RDA) also indicated that ferulic acid was an important factor affecting phlorizin-resistant bacterial community structure. [Conclusion] The genetic diversity of phlorizin-resistant bacteria was abundant, and correlations were revealed between the phlorizin-resistant bacteria community structure and soil physicochemical factors. Ferulic acid was an important factor that could influence the community structure of phlorizin-resistant bacteria. This study provides some useful information for alleviating apple continuous cropping obstacles to some extent.