ORIGINAL ARTICLE Plant growth-promoting activities of fluorescent pseudomonads, isolated from the Iranian soils P. Abbas-Zadeh • N. Saleh-Rastin • H. Asadi-Rahmani • K. Khavazi • A. Soltani • A. R. Shoary-Nejati • Mohammad Miransari Received: 22 November 2008 / Revised: 3 September 2009 / Accepted: 28 September 2009 / Published online: 15 October 2009 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2009 Abstract Fluorescent pseudomonads are among the most influencing plant growth-promoting rhizobacteria in plants rhizosphere. In this research work the plant growth- promoting activities of 40 different strains of Pseudomonas fluorescens and Pseudomonas putida, previously isolated from the rhizosphere of wheat (Triticum aestivum L.) and canola (Brassica napus L.) and maintained in the microbial collection of Soil and Water Research Institute, Tehran, Iran, were evaluated. The ability of bacteria to produce auxin and siderophores and utilizing P sources with little solubility was determined. Four strains of Wp1 (P. putida), Cfp10 (Pseudomonas sp.), Wp150 (P. putida), and Wp159 (P. putida) were able to grow in the DF medium with ACC. Thirty percent of bacterial isolates from canola rhizosphere and 33% of bacterial isolates from wheat rhizosphere were able to produce HCN. The results indicate that most of the bacteria, tested in the experiment, have plant growth-promoting activities. This is the first time that such PGPR species are isolated from the Iranian soils. With respect to their great biological capacities they can be used for wheat and canola inoculation in different parts of the world, which is of very important agricultural implications. Keywords ACC deaminase Á Auxin Á Plant growth-promoting rhizobacteria (PGPR) Á Pseudomonas fluorescens Á Pseudomonas putida Á P solubilizing activities Á Siderophore Introduction Plant–microbe interactions are among the most important mutual and in the most cases beneficial behavior, deter- mining soil potential productivity and health (Jeffries et al. 2003; Miransari et al. 2007, 2008). Hence, the functioning of soil microbes, indicated in the following, can very much affect the establishment and maintenance of sustainable agricultural strategies: (1) their physiolog- ical and biochemical activities to increase nutrient availability and inhibit soil pathogens, and (2) their alleviating effects on adverse soil conditions such as suboptimal root zone temperature and unfavorable soil pH and salinity (Dey et al. 2004; Miransari and Smith 2007, 2008, 2009). Plant growth-promoting bacteria (PGPR) are rhizo- sphere bacteria, with the ability to stimulate and enhance plant growth through different mechanisms (Kloepper et al. 1989; Glick et al. 1999). These mechanisms include the production of plant growth hormone, auxin (Khakipour Communicated by B. Barna. P. Abbas-Zadeh Á N. Saleh-Rastin Department of Soil Science, Tehran University, Tehran, Iran H. Asadi-Rahmani Department of Soil Science, Soil and Water Research Institute, Tehran, Iran K. Khavazi Á A. R. Shoary-Nejati Department of Soil Biology, Soil and Water Research Institute, Tehran, Iran A. Soltani Department of Soil Biology, Tehran University, Tehran, Iran M. Miransari (&) Department of Soil Science, College of Agricultural Sciences, Shahed University, Tehran, Iran e-mail: Miransari1@gmail.com; Miransari@Shahed.ac.ir 123 Acta Physiol Plant (2010) 32:281–288 DOI 10.1007/s11738-009-0405-1