Evaluation of plant-growth promotion characteristics in endophytic bacteria isolated from leaves and stems of some medicinal plants

Abstract

In this study, ninty nine endophytic bacteria were isolated from the mentioned plants. Finally, According to the morphological properties and growth rate, 53 different isolates (13 isolates from each plant) were selected. Results revealed that all the endophytic bacteria were able to produce IAA at 100 mg l-1 L-tryptophan. The production ability of this metabolite in the isolated bacteria from four medicinal plants was different. The most potent bacteria in terms of IAA production were P4, P3 and B1 isolates (with production of 15.31 mg l-1, 11.55 mg l-1 and 12.97 mg l-1, respectively). All of the studied isolates had the ability to dissolve tricalcium phosphate. The highest ability of solubility (646.52 mg l-1) was observed in S5 isolated from Savory. The bacteria isolated from Rosemary had the lowest ability to dissolve tricalcium phosphate. In the present research, all of isolated bacteria were able to produce hydrogen cyanide ranging from low to high amounts. Results of protease production assay showed that all isolates were not capable of growing in Skim milk agar medium. Among the grown isolates, clear zone formation was observed only around the colonies of S1, S4, B9, B12, B3, B11, R7, P6 and P4.