Abstract—The effect of plant growth-promoting rhizobacteria (PGPR) on seed germination, seedling growth and yield of field grown maize were evaluated in three experiments. In these experiments six bacterial strains include P.putida strain R-168, P.fluorescens strain R-93, P.fluorescens DSM 50090, P.putida DSM291, A.lipoferum DSM 1691, A.brasilense DSM 1690 were used. Results of first study showed seed Inoculation significantly enhanced seed germination and seedling vigour of maize. In second experiment, leaf and shoot dry weight and also leaf surface area significantly were increased by bacterial inoculation in both sterile and non-sterile soil. The results showed that inoculation with bacterial treatments had a more stimulating effect on growth and development of plants in nonsterile than sterile soil. In the third experiment, Inoculation of maize seeds with all bacterial strains significantly increased plant height, 100 seed weight, number of seed per ear and leaf area .The results also showed significant increase in ear and shoot dry weight of maize. Keywords—Azospirillum, biofertilizer, Maize, PGPR, Pseudomonas. I. INTRODUCTION LANT growth promoting rhizobacteria (PGPR) are a group of bacteria that actively colonize plant roots and increase plant growth and yield [1]. The mechanisms by which PGPRs promote plant growth are not fully understood, but are thought to include: - the ability to produce phytohormons [2], [3]. - asymbiotic N 2 fixation [4] , [5]. - against phytopathogenic microorganisms by production of siderophores, the synthesis of antibiotics, enzymes and/or fungicidal compounds [6], [7], [8] and also - solubilisation of mineral phosphates and other nutrients [9]. Significant increases in growth and yield of agronomical important crops in response to inoculation with PGPR have been reported [10], [11], and [12]. Azospirillum, Pseudomonas and Azotobacter strains could affect seed germination and seedling growth [13]. Kloepper et al. [38] has been shown that wheat yield increased up to 30% with Azotobacter inoculation and up to 43% with Bacillus inoculation. Strains of Pseudomonas putida and Pseudomonas fluorescens could increase root and shoot elongation in canola [14] as well as Ahmad Gholami and Somayeh Nezarat are with Agronomy Dept., Shahrood University of Technology, Shahrood, Iran (e-mail: 1- ahgholami@yahoo.com). wheat and potato [15], [16]. Inoculation of plants with Azospirillum could result in significant changes in various growth parameters, such as increase in plant biomass, nutrient uptake, tissue N content, plant height, leaf size and root length of cereals [11]. Thus it has been shown that Azospirillum and Pseudomonas had the potential for agricultural exploitation and could use as natural fertilizers [17], [18]. However, the effects of these bacteria on growth and yield of some crop plants studied in previous works. But the effects of PGPR on growth parameter from germination to yield were not evaluated simultaneously. The main objective of this research was to determine if PGPR strains could affects on seed germination, growth parameters of maize seedling in greenhouse and also grain yield of field grown maize. II. MATERIAL AND METHODS Six bacterial strains include P.putida strain R-168, P.fluorescens strain R-93, P.fluorescens DSM 50090, P.putida DSM291, A.lipoferum DSM 1691, A.brasilense DSM 1690 were used in this study that conducted at 2005- 2006. Bacterial strains were used as maize seed treatments. Seeds of maize (SC 647) were surface-sterilized with 0.02% sodium hypochlorite for 2 min, and rinsed thoroughly in sterile distilled water. For inoculation seeds were coated with 20% gum arabic as an adhesive and rolled into the suspension of bacteria (10 8 cfu ml -1 ) with perlit until uniformly coated. Germination tests were carried out by the paper towel method. 25 seeds for each treatment with three replications in completely randomized design and incubated in growth chamber at 28°C. After 7 days the number of germinated seeds was counted. Root and shoot length of individual seedling was measured to determine the vigor index with following formula: Vigor index= (mean root length +mean shoot length) × % germination [19]. For the evaluation of maize seedling growth promotion with PGPRs, above bacterial strains were tested in both non- sterile and sterile soils at 2005. The plastic pots had 15cm diameter and capacity to hold 2Kg of soil .For preparation of sterile soil, field soil was autoclaved twice for 20 min at 120°C with a 24 h interval. All treatments (bacterial inoculation × soil condition) arranged in 48 pots i.e., 3 replicates with 14 pots per replication and a double seed per The Effect of Plant Growth Promoting Rhizobacteria (PGPR) on Germination, Seedling Growth and Yield of Maize A. Gholami, S. Shahsavani, and S. Nezarat P World Academy of Science, Engineering and Technology International Journal of Agricultural and Biosystems Engineering Vol:3, No:1, 2009 9 International Scholarly and Scientific Research & Innovation 3(1) 2009 scholar.waset.org/1307-6892/14657 International Science Index, Agricultural and Biosystems Engineering Vol:3, No:1, 2009 waset.org/Publication/14657