Isolation and characterization of bacterial endophytes with antagonistic potential against Rhizoctonia solani
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Date
2021
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Punjab Agricultural University, Ludhiana
Abstract
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.
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Citation
Bikramjeet Singh (2021). Isolation and characterization of bacterial endophytes with antagonistic potential against Rhizoctonia solani (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.