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Subject: Microbiology × Author: Bikramjeet Singh × End date: 2023 × Start date: 2020 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Isolation and characterization of bacterial endophytes with antagonistic potential against Rhizoctonia solani
    (Punjab Agricultural University, Ludhiana, 2021) Bikramjeet Singh; Pratibha Vyas
    The present study was carried out with the aim to select bacterial endophytes from Stevia rebaudiana with biocontrol potential against a broad host range phytopathogen Rhizoctonia solani. A total of 22 morphological distinct bacterial endophytes were isolated from the leaves of Stevia rebaudiana collected from the Herbal Garden, PAU Ludhiana and Hara Agro Centre Nursery, Ludhiana, Punjab. Of 22 bacterial endophytes, eight isolates (36%) showed antagonistic activity against R. solani with a growth inhibition ranging from 12.5 to 40% in dual plate assay. Three isolates SR1EB1 SR1EB11 and SR2EB5 exhibited more than 25% growth inhibition of R. solani. The inhibition in fungal biomass by the three antagonistic bacteria singly or in combinations varied from 61.3 to 86.6% in liquid medium. The effect of antagonistic bacterial endophytes on the ultrastucture of R. solani studied by scanning electron microscopy showed stripping of the fungal hyphae leading to the accumulation of debris in the presence of antagonistic bacterial isolates. In addition to antagonistic activity, the isolates also exhibited tricalcium phosphate solubilization, zinc solubilization, auxin production, ammonia production, cellulose hydrolysis and starch hydrolysis. All the three isolates were tested negative for the production of siderophores and hydrogen cyanide. Based on morphological features, biochemical tests and MALDI-TOF-MS analysis, the isolates were identified as Ochrobactrum gallinifaciens SR1EB1, Alcaligenes faecalis SR1EB11 and Bacillus licheniformis SR2EB5. Maize seeds inoculated with the antagonistic bacterial endophytes singly or in combinations showed vigour index ranging from 351 to 695. An increase of 37.1 to 64.4% in root length, 27 to 40% in shoot length and 20.5 to 47.1% in dry weight over uninoculated control in maize in soil infested with R. solani was observed with the three antagonistic bacterial endophytes and their combinations in pots. Disease control varied from 66.7 to 83.3% in bacterial treatments with R. solani. The study has led to the selection of three bacterial endophytes Ochrobactrum gallinifaciens, Alcaligenes faecalis and Bacillus licheniformis strains as potential biocontrol agents against Rhizoctonia solani. This is the first study on the bacterial endophytes from Stevia rebaudiana leaves with antagonistic activity against Rhizoctonia solani. As a future line of recommendation, the formulation containing the consortium of Ochrobactrum gallinifaciens, Alcaligenes faecalis and Bacillus licheniformis may be developed and tested in maize to control Rhizoctonia solani infection in field conditions.