Isolation and identification of Pseudomonas sp. BP16 and its plant growth-promoting traits and effects

Abstract:

[Background] Pseudomonas is well known to inhibit plant pathogenic microorganisms. However, other plant growth-promoting traits are less reported. [Objective] To characterize the plant growth-promoting traits of Pseudomonas sp. BP16, and reveal its growth promoting effect on wheat seedling and potato. [Methods] The strain was isolated through spread and streak plating on medium of inorganic-phosphorus. We identified the taxonomic position based on polyphasic taxonomy and characterized plant growth-promoting traits on selective media or colorimetry. Wheat and potato were plot planted with 3 treatments, the first adding fertilizer containing BP16, second adding null carrier without inoculant, and third not adding any of them. [Results] 16S rRNA gene sequence of BP16 showed the highest similarity to that of P. brassicacearum subsp. neoaurantiaca (99.38%), and yet there were some major differences in physiochemical characters between them. Beside nitrogen-fixation, BP16 also possessed strong capabilities of Ca-phosphate-solubilizing (water-soluble phosphorus in fermentation solution reached 67.15 μg/mL), and production of indole-3-acetic acid (8.93 mg/L), siderophore (2.46 of D/d) and 1-aminocyclopropane-1-carboxylate deaminase. Additionally, BP16 remarkably inhabited the potato late blight, flax fusarium wilt and sunflower sclerotinia pathogens with inhibitory rates of 76.19%, 32.00% and 22.22%, respectively. Compared with the controls, wheat inoculated by BP16 increased plant height, root length, chlorophyll content and biomass. The content of rhizospheric available phosphorus and nitrogen also increased by the range from 8.63% to 83.81%. BP16 significantly enhanced the potato yield. [Conclusion] BP16 represents a new subspecies of P. brassicacearum and has multiple plant growth promoting traits. It can be used as a plant growth promoting agent.

Key words:Plant growth-promoting rhizobacteria, Granule microbial fertilizer, Pseudomonas, Wheat (Triticum aestivum), Potato (Solanum tuberosum)