Characterization of Florescent Pseudomonads for Biological control Efficacy, Plant Growth Promotion and Antibiotic Tolerance

Abstract

A collection of fourteen indigenous Fluorescent Pseudomonads (FLPs) was isolated from diverse crop rhizospheres across different regions of Bihar, and their distinctive characteristics were documented. The differentiation between Pseudomonas aeruginosa and Pseudomonas fluorescens was achieved through pigmentation, fluorescence assessment on King's A media, and growth analysis at 42°C. Among the isolates, nine were identified as P. aeruginosa: FLP strains associated with Rice, Turmeric, Mustard-1, Mustard-2, Okra-G, Pea, Barley, Brinjal, and Chickpea. Meanwhile, five isolates - FLP Wheat, FLP Bean, FLP Mango, FLP Brinjal New, and FLP Cauliflower - were classified as P. fluorescens. Confirmation of these classifications was established through DNA sequencing of the 16s RNA region. These FLP isolates were evaluated against prevalent phytopathogens, including Macrophomina phaseolina, Colletotrichum musae, Fusarium oxysporum f. sp. cubense, and Xanthomonas oryzae pv. oryzae. Notable performance was exhibited by FLP Barley (70.55%) against Macrophomina phaseolina, FLP Okra-G (53.82%) against Colletotrichum musae, FLP Rice (38.58%) against Fusarium oxysporum f. sp. cubense, and FLP Okra-G against Xanthomonas oryzae pv. oryzae. In the context of biocontrol efficacy, FLP Turmeric, FLP Pea, FLP Okra-G, and FLP Mustard-1 showcased superior performance in combatting phytopathogens. Additionally, all FLP isolates, except FLP Cauliflower, exhibited phosphate-solubilizing capabilities, with FLP Brinjal demonstrating the highest solubilization (Phosphate Solubilizing Index of 2.89). Siderophore production was a common trait among the isolates. Compatibility with antibiotics, namely Streptocycline at concentrations of 0.025% and 0.10%, as well as Copper oxychloride at 0.25%, 0.30%, and 0.50%, was assessed. Only FLP Cauliflower exhibited compatibility with both antibiotics across all concentrations. Notably, FLP Rice, FLP Turmeric, and FLP Barley demonstrated positive antibiotic compatibility alongside effective biocontrol potential. In summation, this study unveils the distinct attributes and potential applications of indigenous Fluorescent Pseudomonads (FLPs) isolated from the rhizospheres of diverse crops in Bihar. The identified isolates exhibit promising traits such as disease control, phosphate solubilization, siderophore production, and antibiotic compatibility, thus presenting valuable options for sustainable agricultural practices and disease management.