Isolation and identification of Trifluralin Degrading bacteria inbean fields

Background and Aim : Herbicides are one of the most important and necessary inputs in thecropping systems of developed countries and play a significant role in the yield of crops in thesecountries. Trifluralin is one of the herbicides applied in the soil, and its residues may beproblematic for post-bean crops. Therefore, it is necessary to study its biodegradation to reducethese risks. The aim of this study was to isolate and identify bacteria degrading Trifluralin in soilscontaminated with this herbicide, based on biochemical, morphological and molecularcharacteristics and to investigate the rate of degradation of Trifluralin by selected strains.Methods : Topsoil containing organic matter was removed from bean fields in Selseleh city usingsterile gloves, and then soil was sampled from a depth of ۰ to ۳۰ cm. For the initial isolation ofsoil bacteria, the nutrient agar medium containing a concentration of ۱۰% the herbicide was used.Results : . In carbon source substitution test using Standard Succinate Medium containing ۵% ofthe herbicide, only ۱۷ bacteria appeared. The isolates were placed in five groups based on thebiochemical tests including gram reaction, Xanthomonadin and fluorescent pigmentationproduction, oxidase, catalase, H۲s from cysteine, Levan production, Tween ۲۰ Hydrolysis Test,and oxidative/fermentative tests. For molecular diagnosis, five representative isolates wereselected and subjected to amplify ۱۶S rDNA gene using ۱۶s F and ۱۶sR primers and sequenced.Sequences were aligned and compared to the NCBI reference sequences.Conclusion : Based on biochemical and molecular tests, the isolates were identified asPseudomonas koreensis, Pseudomonas sp. LuM, Pseudomonas sp. LuM۳, Rhizobium sp. LuM andVariovorax sp. The lowest Minimum Inhibitory Concentration(MIC) and Minimum BactericidalConcentration (MBC) were attributed to Rhizobium sp and Variovorax sp, while the highest MICand MBC belonging to Pseudomonas sp.

کلیدواژه ها:

Herbicide ، MBC ، MIC ،