Objective After screening, the functional gene composition and growth-promoting potential of the indole-3-acetic acid (IAA)-producing strains were analyzed to provide microbial resources for the development and utilization of biofertilizers.
Methods Screening of IAA-producing pakchoi (Brassica chinensis L.) rhizosphere microorganisms were carried out in 96-well microculture plates using Salkowski reagent, followed by secondary quantitative screening of the strains with high IAA production trait. The isolates were identified by morphological, physiological and biochemical experiments and 16S rDNA sequencing, and the growth promotion potential of them were assayed by phosphorus solubilization, siderophore production, 1-amino-1-cyclopropanecarboxylic acid (ACC) deaminase production and biofilm production. The growth promotion effects of the strains were verified by pot experiments. A preliminary analysis of growth promotion mechanism of the strain was conducted at the genome level.
Results JB0319 was identified as Bacillus velezensis and the IAA yield of JB0319 was up to 30.05 μg mL-1. The strain possessed high capacity of phosphorus solubilization, siderophore production, ACC deaminase production and biofilm production. The result of pot experiments showed that inoculation with JB0319 significantly increased the plant height, fresh weight, root length, root diameter and number of leaves of pakchoi by 17.06%, 96.42%, 125.77%, 50.56% and 33.33%, respectively. Whole-genome sequence analysis of JB0319 revealed a total of 57 genes related to growth promotion.
Conclusion JB0319 can be used as promising PGPR, providing valuable microbial resources for the development of biofertilizers.
DownLoad: