Abstract
In this study, we aimed at examining the potential to stimulate growth in Pennisetum clandestinum using four isolated bacterial strains from soils obtained from a Colombian tropical silvopastoral system. We previously identified genetically the strains and characterized two plant growth promotion activities. We found that the four bacterial strains were phylogenetically associated with Klebsiella sp. (strains 28P and 35P), Beijerinka sp. (37L) and Achromobacter xylosoxidans (E37), based on partial 16S rRNA gene sequencing. Moreover, the in vitro biochemical assays demonstrated that the strains exhibited some plant growth promotion mechanisms such as 1-aminocyclopropane-1-carboxylic acid deaminase activity and indole compound synthesis. Notably, bacterial inoculation under greenhouse conditions showed a positive influence on P. clandestinum growth. We found a significant (p < 0.05) effect on root and shoot length, and shoot dry weight. Shoot length increased by 52% and 30% with 37L and 35P, respectively, compared to those without inoculation treatment. Similarly, the use of 37L and 28P raised shoot dry weight values by 170% and 131%, respectively. In root development, inoculation with strains 37L and E37 increased root length by 134% and 100%, respectively. Beijerinckia sp. 37L was the most effective of the four strains at increasing P. clandestinum biomass and length.
Highlights
The sustainable production of pastures has become a fundamental challenge for the livestock sector where research with plant growth-promoting rhizobacteria as a viable solution, has nearly not been reported
Identification of bacterial strains: Through 16S rDNA sequence analysis, we found that strain 28P and strain 35P have homology with bacteria belonging to the genus Klebsiella, strain 37L with bacteria belonging to the Beijerinckia genus, and strain E37 with the Achromobacter genus
Screening of in vitro plant growth promotion (PGP) activities: We observed that the only bacterium capable of using ACC as a nitrogen source was Beijerinckia sp. strain 37 L
Summary
The sustainable production of pastures has become a fundamental challenge for the livestock sector where research with plant growth-promoting rhizobacteria as a viable solution, has nearly not been reported. Methods: We previously identified genetically the strains and characterized two plant growth promoting activities. We evaluated the growth-promoting effect of the strains in Kikuyo grass under greenhouse conditions. The in vitro biochemical assays demonstrated that the strains exhibited some plant growth promoting mechanisms such as 1-aminocyclopropane-1-carboxylic acid deaminase activity and indole compound synthesis. Bacterial inoculation under greenhouse conditions showed a positive influence on P. clandestinum growth. We found a significant (P < 0.05) effect on root and shoot length and shoot dry weight. Shoot length increased by 52 % and 30 % with 37L and 35P compared to those without inoculation treatment. Inoculation with strains 37L and E37 increased root length by 134 % and 100 %, respectively. 37L was the most effective of the four strains at increasing P. clandestinum biomass and length Conclusion: Beijerinckia sp. 37L was the most effective of the four strains at increasing P. clandestinum biomass and length
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