Paclobutrazol Biodegradation of Native Bacteria in Mango Orchards in Mekong Delta, Vietnam

Background: Paclobutrazol (PBZ), a plant growth regulator, is usually used to promote off-season flowering in mango orchards in the Mekong Delta, Vietnam. Several studies demonstrated that PBZ degradation in the soil takes several months and its residue effects to the soil environment and consequently to the plants and microorganism community. The objective of this study was to identify native bacteria that can biodegrade PBZ in the soil of mango orchards. Methods: Soil samples were collected in thirty mango orchards in Vietnam’s Mekong Delta. One gram of soil was mixed with distilled water and injected into a PBZ culture medium. After culturing, bacterial colonies were isolated and transferred onto the TSA medium in order to characterize morphological and biochemical assays and to evaluate PBZ biodegradation ability. Four strains of bacteria, which had high PBZ biodegradation, were identified and evaluated PBZ biodegradation ability. Additionally, 16S rDNA region was sequenced. Result: The results of identification indicated that the four high PBZ biodegradation bacterial strains related to Pseudomonas fluorescens, Pseudomonas nitroreducens, Burkholderia cepacia, Acinetobacter seifertii. After 30 days, the content of paclobutrazol biodegradable by these bacteria was 36.51%, 36.23%, 34.19% and 33.56%, respectively, at an initial concentration of 60 ppm.