Comparative studies on mutated and unmutated strains of Bacillus velezensis for their plant growth promoting activities
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Date
2022
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DRPCAU, PUSA
Abstract
In the present study, mutated and unmutated strains of Bacillus velezensis were screened for their biological traits and plant growth promoting activities. In this regard, total of 12 Bacillus velezensis strains collected from Department of Microbiology, CBS&H, Dr. RPCAU, Pusa, out of which 11 strains were mutated and 1 strain was unmutated. Isolates were subjected to morphological characterization on the basis of colony morphology and microscopic features. Most of the isolated colonies represent to small size, smooth texture, whitish and reddish-brown colonies on nutrient agar. All strains were Gram-positive based on Gram staining and microscopic observations and all strain cells found rod shape. Mutated and unmutated strains of Bacillus velezensis were subjected to biological activities viz., protein solubilization, β-glucan solubilization and biosurfactant production and also screened for plant growing promoting activities viz., Phosphorus solubilization, Zinc solubilization, Potassium solubilization, IAA production, Siderophore production and also studied interaction of mutated and unmutated strains of Bacillus velezensis with phytopathogen Helminthosporium maydis. It has been noted that out of 11mutated isolates except T9 and unmutated strain T0 showed protein solubilization. Mutated strain T3 showed highest protein solubilization index as 4.2±0.03 and protein solubilization efficiency 320±0.03 while T10 strain showed lowest protein solubilization index (2.9±0.04). T5 strain showed highest β-Glucan solubilization index as 4.4±0.04 and unmutated strain T0 showed least solubilization index as 2.1±0.02. The highest yield of crude biosurfactant was shown by T3 mutant as 0.362±0.003 gm/100ml followed by mutant T5 as 0.332±0.004 gm/100 ml. Strain T5 efficiently solubilize phosphorus solubilization as 1.23±0.35 ppm/ml with Phosphorus solubilization index P-SI as 4.1±0.01. The highest (3.1±0.02 ppm/ml, 16.08±0.1 ppm/ml) Zn and K solubilization was recorded for T 1 and T 3 strain, respectively.
Unmutated strain T0 showed highest IAA production as167±1.15µg mg-1 protein. Mutated strain T7 registered highest Siderophore production efficiencyas307.14±0.01%. while T0 strain showed as 176.92±0.01%lowest Siderophore production efficiency. The mutants T3, T5, T6 has shown nearly70-80% inhibition of Helminthosporium maydis. Lactophenol cotton blue staining Resulted in disruption of hyphae with blue colour due to biosurfactant action of B. velezensis on H. maydis.