Mechanisms and kinetics for the degradation of paclobutrazol and biocontrol action of a novel Pseudomonas putida strain T7

Abstract The present study explores biodegradation kinetics and process optimization of plant growth retardant from triazole group paclobutrazol (PBZ; C15H20ClN3O) mol. wt. 293.79 g mol−1) in a batch experiment. A gram-negative rod-shaped bacterium T7 was isolated from PBZ applied agricultural field by enrichment technique and characterized as Pseudomonas putida strain T7. Strain was tested for PBZ biodegradation and plant growth-promoting characteristics. Results revealed that strain T7 utilizes PBZ as a carbon and energy source and showing degradation up to 98.30% on the 15th day. First-order degradation kinetics and a linear model were well fitted and showing a maximum t1/2 value on 9th day. Biodegradation optimization by Box Behnken design (BBD) of Response surface methodology (RSM) showed maximum degradation at pH 7.0, 31 °C temperature, and 2 ml inoculum size (8 × 109 CFU ml−1). The bacterium was also able to solubilize Zn, K, and PO4 and produced a copious amount of IAA, HCN, and Ammonia. The biocontrol activity against plant pathogens like Fusarium oxysporum (MTCC–284), Colletotrichum gloeosporioides (MTCC 2190), Pythium aphanidermatum (MTCC – 1024), Tropical race–1 (TR -1), and Tropical race – 4 (TR-4) showed the great antagonistic effect. Hence, this strain can be employed as an effective bio-agent for eco-friendly cleanup strategies and pathogen suppressive agents in paclobutrazol contaminated soil.