Evaluation of Population and Properties of PGPB of Endorhizosphere, Rhizosphere and Nonrhizosphere in Pistachio Seedlings

A greenhouse study was conducted to compare population and properties of Plant Growth Promoting Bacteria (PGPB) of endorhizosphere، rhizosphere and nonrhizosphere in pistachio seedlings. After two months، population densities of theses bacteria were determined and purified 33 endorhizosphere، 25 rhizosphere and 23 nonrhizosphere bacteria. Then all the isolates were investigated for producing Indole Acetic Acid (IAA) and N2 fixation، and also rhizosphere and nonrhizosphere isolates were considered from tricalcium phosphate dissolving potency and siderophore producing viewpoint. Results showed that the population of the rhizosphere bacteria (4×104) was more than the population of endorhizosphere (3. 8×105) and that of the nonrhizosphere bacteria (1. 3×106)، and stimulating effect of rhizosphere exudates on the bacteria population was evaluated using R/S which was equal to 31. The frequencies of endorhizosphere، rhizosphere and nonrhizosphere bacteria producing IAA were 48. 5، 60 and 47. 8 % and those of fixing N2 were 27. 3، 64 and 17. 4 %، respectively. All of non-rhizosphere bacteria as well as rhizosphere bacteria were able to solubilize inorganic phosphorous. The results also indicated that 48 % of rhizosphere bacteria and 13 % of nonrhizosphere bacteria were able to produce a few amount of siderophore. Generally the results indicated، rhizosphere exudates and inner tissue of plant not only affected the population density of bacteria in the rhizosphere and endorhizosphere، also incresed frequencies of plant growth promoting of rhizosphere and endorhizosphere bacteria.