Assessment the important PGPR features of isolates used in biofertilizers Barvar2, Biosuperphosphate, Supernitroplus and Nitroxin

Quality control of biofertilizers has several aspects that attention to properties of plant growth promoting of bacteria which used in biofertilizers as part of their quality control is taken into consideration. In this study, four kinds of biofertilizer commonly used in the Iran, including Nitroxin, Supernitroplus, Biosuperphosphate (industrial biotechnology company mehre Asia) and Barvar2 (produced in Greenbiotech Company) were selected and examined. Isolates used in Biofertilizers Ba1 and Ba2 from Barvar2, Bio1, Bio2, Bio3 and Bio4 of Biosuper phosphate, SN1 and SN2 of Supernitroplus and N1, N2, N3, N4 and N5 of Nitroxin were evaluated for the solubilizing ability of organic and inorganic phosphates, auxin and siderophore production, and K release in both qualitative and quantitative methods. The results showed that the Ba1 strain with a maximum ratio of diameter of the clear zone to the colony (3.26 mm) and phosphate solubilizing (606.4 mg/l) in both qualitative and quantitative methods, had the maximum ability to dissolve insoluble inorganic phosphate compound Ca3(PO4)2 compared with other treatments. However, Ba2, another strain of Barvar2, with mineralizing ability of 62.23 mg/l had the greatest ability in phosphate mineralization. The isolates used in Nitroxin had good results for production of auxin and siderophore. So, maximum production of auxin and siderophore were observed in N4 (15.13 mg/l) and N3, respectively. Isolate N3 produced largest orange zone in qualitative assay and 124.54 µm siderophore in quantitative methods, respectively. The isolates, Ba1 and Bio1 had highest ability to release potassium from the Muscovite and Biotite respectively compared with other treatments. In view of the PGPR features, Biofertilizers Barvar2 and Nitroxin had a better situation. Biofertilizer Biosuperphosphate was in the next order but isolates used in Supernitroplus had the weakness results.