Antarctic and Sub-Antarctic microoganisms as promoters of vegetable growth and antimicrobial producers for the development of natural biopesticides

Abstract

The antimicrobial activity of psychrophilic and/or psycho-tolerant microorganisms can be used in the prevention/treatment of diseases that affect different regional crops or as an alternative to chemicals that are harmful to the environment. On the other hand, plant growth promoting bacteria (PGPB) belong to a group of beneficial microorganisms, capable of promoting the growth of plants and, in turn, protecting them from certain diseases. PGPBs stimulate plant growth through direct mechanisms that ensure the bioavailability of nutrients, such as biological nitrogen fixation, phosphate solubilization, phytohormone production, etc. Indirect mechanisms usually occur outside the plant and are associated with the production of siderophores, antimicrobial compounds and competition for ecological niches. In this work, the psycho-tolerant bacteria isolated from Antarctic and sub-Antarctic soils identified as Burkholderia gladioli, Serratia proteamaculans and Pseudomonas yamanorum were studied in vitro to demonstrate direct and indirect mechanisms for promoting plant growth in plants. They were then selected based on the results obtained to study them in vivo in soybean crop plants. Serratia proteamaculans was able to produce siderophores, indole acetic acid and solubilize phosphates. Burkholderia gladioli and Pseudomonas yamanorum were only able to solubilize phosphates. No formation of hydrocyanic acid was observed in the isolates. In vitro antagonistic activity of Burkholderia gladioli, Serratia proteamaculans and Pseudomonas yamanorum was evaluated against different phytopathogenic microorganisms, where a strong inhibition of was observed against bacteria of the genus Xanthomonas, Erwinia, Acidovorax and Pseudomonas as well as fungal genus Fusarium, Penicillium, Macrophomina, Phomopsis, Geotrichum and Diplodia. Considering these results, Serratia proteamaculans was selected, as it was shown to have characteristics of PGPB, with the potential to improve plant growth and to Burkholderia gladioli as a biocontrol agent, due to its broad spectrum of inhibition against fungi that affect soybean cultivation. Both were evaluated in vivo in soybean plants.