Using superior plant growth-promoting microorganisms through bioprospecting to create inoculants for peanut (Arachis hypogaea L.) farming

Experiments with pot-grown plants are among the most common in plant research. In this study, we isolated plant growth-promoting bacteria (PGPB) from the rhizosphere soils and root nodules of peanut plants grown under greenhouse conditions, and evaluated their PGP properties to select elite strains as inoculants. The isolates were characterized for the following PGP activities: phosphate (P) solubilization, auxin and siderophore production, fluorescence emission, and nodule formation capacity. Isolates were also identified through 16S rRNA gene sequencing. A total of 90 isolates were obtained and characterized, belonging to five genera: Burkholderia, Bacillus, Brevundimonas, Dyella and Leifsonia. Among these, B. cepacia and B. territorii were the most abundant species, exhibiting the highest levels of auxin and siderophore production, as well as superior P solubilization. Furthermore, nodule isolates demonstrated more intense PGP activities than free-living isolates from rhizosphere soils. This is the first report documenting the nodulation capacity of the genus Dyella, and further studies targeting the nifH gene will be necessary to confirm its nitrogen-fixing ability. The in vitro screening provided sufficient evidence for further in vivo peanut growth-promoting tests of both Burkholderia and Dyella isolates. Such agricultural applications could enhance peanut yields while reducing environmental pollution. Key words: Peanut, biofertilizers, promoting rhizobacteria, characterization, soil and root nodule.