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Plant growth promoting(PGP)rhizobacteria can improve fertilizer use efficiency,reduced pathogen infection,and improved resistance to abiotic stresses such as drought,mineral deficiency and salinity.In this study,56 dominant nitrogen-fixation bacteria were isolated and screened from rhizosphere and root of potato,including 28 rhizosphere bacteria and 28 endophytic bacteria.Based on the 16S rRNA gene sequences phylogenetic analysis,the most abundant groups of these nitrogen-fixation bacteria belonged to the genera Arthrobacter(14),Microbacterium(8),Pseudomonas(8),and Rhizobium(8).Through the PGP characterization test,we found 28 isolates(50%of the total)were able to solubilize organic phosphate and 7isolates(12.5%of the total)were able to solubilize inorganic phosphate;15 bacteria(26.78%of the total)had the ACC-dearninase activities and Arthrobacter sp.MLS-5-2 had the highest ACC-deaminase(21.068 isolμmol mg protein-1 h-1);48 isolates(85.71%of the total)had the ability to produce IAA and Arthrobacter sp.MLS-1-9 has the highest IAA production(230.16y to pμg ml-1);8 isolates were effective against Fusarium oxysporum and 6 isolates were effective against Fusarium solani.Among the 56 nitrogen-fixation bacteria,Rhizobium sp.MLS-3-7 had the determined four PGP traits and 13 diazotrophic had the determined three PGP traits.These bacteria with multiple PGP traits or the best ablility of one PGP traits showed the potential use for biofertilizer,biostimulant and biocontrol.