Analysis on the diversity and plant growth-promoting characteristics of bacteria in rhizosphere of flue-cured tobacco

Abstract:

[Background] The mining of bacterial resources with the capabilities of both nicotine degradation and plant growth-promoting would contribute to soil quality protection and green cultivation. [Objective] To analyze the bacterial diversity in the rhizosphere of flue-cured tobacco and screen the plant growth-promoting bacteria that can degrade high concentration of nicotine. [Methods] Pure culture is applied to isolate nicotine-degradation strains with selective medium. The diversity and phylogeny of rhizobacteria were analyzed by transcription factor amplification (BOXA1R-PCR), 16S rRNA gene sequencing and phylogeny analysis. The PGPR characteristics of the nicotine-degradation strains were screened via determination of indole-3-acetic acid (IAA) production, phosphorus solubility, antimicrobial activity and other indexes. The growth-promoting effect of the isolates were further confirmed by pot experiment. [Results] Totally, 58 strains of nicotine-degradation bacteria were isolated, and 11 typical strains with different BOXA1R-PCR fingerprints were selected for 16S rRNA gene sequencing. Based on the phylogeny analysis, the 58 strains were belonged to four genera including Bacillus, Pseudomonas, Raoultella and Brevundimonas, with Bacillus as the predominant genus. Of the 58 isolates, 48.28% produced IAA, 27.59% were able to dissolve phosphorus, 37.93% could degrade cellulose. Based on the PGPR abilities, three isolates including G2-13, G2-3 and HT2-8 were used to perform pot experiment to further confirm their potential growth-promoting ability. The results showed that when compared to the control, G2-13 could increased the plant height and aboveground fresh weight by 33.05% and 53.32%, respectively. [Conclusion] The tobacco rhizosphere harbors plenty of nicotine-degradation bacterial strains with PGPR capability and have potential application prospects in plant cultivation strains.