Fatemeh Saadat Nasri - Department of Microbiology, Kerman Branch, Islamic Azad University, Kerman, Iran.
Farokh Rokhbakhsh-Zamin - Department of Microbiology, Kerman Branch, Islamic Azad University, Kerman, Iran.
Nadia Kazemipour - Department of Microbiology, Kerman Branch, Islamic Azad University, Kerman, Iran.

Introduction and Objectives: Biofertilizers constructed by obtained bacteria from rhizosphere of plants are good alternative for chemical fertilizers. Helianthus annuus is an important strategic oilfield crop. The aim of this research was to isolate beneficial plat growth promoting rhizobacteria and evaluation their effects on vegetative stage of Helianthus annuus in pot experiment. Materials and Methods: Sampling was performed from rhizospheric soils of different fields in Kerman district. Different bacterial strains were isolated from rhizospheric samples. Direct mechanisms were carried out as zinc and phosphate solubilization, nitrogen fixation, ammonia production as well as evaluation of their resistance to environmental stress. Molecular characterization using 16R rRNA sequences was used to identify the selected isolate. A pot experiment was also conducted to investigate the effects of selected PGPR isolate on the growth of Helianthus annuus. Results: Strain numbers of isolates were considered as IAUK2301-2330. All of selected strains were resistant to the different temperatures between 25-42oC as well as having normal growth in salt concentrations between 5-7 and PH=4-8. Maximum phosphate solubilization efficiency was 350 and related strain was selected for further experiments. Molecular characterization using 16R rRNA sequences suggested the identity this isolate as Agrobacterium tumefacience strain IAUK2307. Pot experiment by this strain revealed meaningful plant growth promoting traits in seedling stage on shoot height, root length and dry weight of Helianthus annuus. Conclusion: According to the In vitro and in vivo results, Agrobacterium tumefacience IAUK2307 may have a good potential for field experiments before usage as the new biofertilizer.

Agrobacterium tumefacience IAUK2307, PGPR, Phosphate solubilization, Pot experiment, Helianthus annuus L