Isolation, biocontrol potential and Genomic healthy characterization of cyuclic lipopeptide-producing bacteria isolated from capsicum annum Root
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Date
2023
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Department of Microbiology, Faculty of Science, Obafemi Awolowo University.
Abstract
This study isolated fungi from wilted pepper tissues of Capsicum chinense, obtained bacteria from the root of healthy Capsicum annuum plants and characterized both by
molecular methods. It also investigated the direct antagonism potential of the isolated bacteria and their cyclic lipopeptides against the fungal pathogens. The sturdy further
characterized genes responsible for cyclic lipopeptides production, other traits, and the antagonistic potential of the bacteria. These were with a view to providing information on the biological control efficacy of the rhizospheric bacteria against fungal pathogens of
wilted pepper.
Fungi were isolated from the wilted roots and stem regions of C. chinense, and identified through the sequencing of the internal transcribed spacer (ITS) region; while bacteria were isolated from the healthy C. annuum roots, and characterized by 16S rRNA sequencing.
CLP was extracted from isolated bacteria and the direct effect of the crude CLP at concentrations of 50, 25, 10, and 5 µg/mL on the fungal isolates was investigated in vitro.
The in vitro plant growth promotion potential of the bacteria in this study was evaluated. The in vivo plant growth promotion traits and biocontrol potential of the bacteria were determined using potting soil supplemented with 1.5x10⁸ CFU/g of the bacteria. The genome of the bacteria of choice was sequenced and analyzed.
The isolated fungi from the wilted C. chinense plants were all identified as Trichoderma species. Out of the six bacteria isolated from the healthy C. annuum, LPb1-3 had significant antagonistic effects on all the fungal isolates in a Petri dish assay and was identified as Enterobacter cloacae. The diameter of zones of inhibition (mm) of Enterobacter cloacaeLPb1-3 against the fungal pathogens was highest against Trichoderma erinaceum GP6(12.00), Trichoderma asperellum GP3 (11.00) and Trichoderma atroviride GP8 (8.00); xxand least against Trichoderma sp. GP7 (5.00) and Trichoderma atroviride WP4 (5.00), respectively. CLP produced by E. cloacae LPb1-3 had a direct effect on the fungi isolates at all tested concentrations, with the highest diameter of zones of inhibition of 11.33 mm at 25 µg/mL against T. asperellum GP3, and values of 16.67, 10.67, 10.33 and 9.00 mm at 50 µg/mL against Trichoderma sp. GP7, T. erinaceum GP6, T. atroviride WP4 and T.atroviride GP8, respectively. It caused structural damages such as extensive branching, coiling, blackening of the hyphal edge, hyphal digestion, hyphal breakage, hyphal leakage, and vacuolization, to the respective fungal hyphae. E. cloacae LPb1-3 showed successful phosphate solubilization and ammonia production, which could be responsible for the significant improvement in the shoot height, shoot weight and root weight of C. chinense. Interestingly, E. cloacae LPb1-3 reduced the disease severity caused by T. atroviride GP8, T. asperellum GP3 and T. erinaceum GP6 by 55%, 45% and 27%, respectively on C. chinense. Analysis of the bacterium’s genome confirmed the identity of LPb1-3 as Enterobacter cloacae and revealed genes coding for some pivotal secondary metabolites such as NI-siderophore, ladderane, aryl polyene, thiopeptide, and NRP-metallophore.
The study concluded that Enterobacter cloacae LPb1-3 and its CLP efficiently suppressed the mycelial growth of pathogenic Trichoderma strains isolated from C. chinense in direct antagonism assays in vitro. It also improved C. chinense growth and its resilience against the pathogenic Trichoderma strains in vivo
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xx, 159p
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Citation
Aghughu, M.E.(2023).Isolation, biocontrol potential and Genomic healthy characterization of cyuclic lipopeptide-producing bacteria isolated from capsicum annum Root.Obafemi Awolowo University.