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Ramazan Çakmakçı, Metin Turan, Nurgul Kıtır,

Adem Güneş, Emrah Nikerel,

Bahar Soğutmaz Özdemir, Ertan Yıldırım,

Murat Olgun, Bülent Topçuoğlu, Şefik Tüfenkçi,

Mehmet Rüştü Karaman, Leyla Tarhan and

Negar Ebrahim Pour Mokhtari

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67274

#### **Abstract**

Free-living plant growth-promoting rhizobacteria (PGPR) have favourable effect on plant growth, tolerance against stresses and are considered as a promising alternative to inorganic fertilizer for promoting plant growth, yield and quality. PGPR colonize at the plant root, increase germination rates, promote root growth, yield, leaf area, chlorophyll content, nitrogen content, protein content, tolerance to drought, shoot and root weight, and delayed leaf senescence. Several important bacterial characteristics, such as biological nitrogen fixation, solubilization of inorganic phosphate and mineralization of organic phosphate, nutrient uptake, 1-aminocydopropane-1-carboxylic acid (ACC) deaminase activity and production of siderophores and phytohormones, can be assessed as plant growth promotion traits. By efficient use, PGPR is expected to contribute to agronomic efficiency, chiefly by decreasing costs and environmental pollution, by eliminating harmful chemicals. This review discusses various bacteria acting as PGPR, their genetic diversity, screening strategies, working principles, applications for wheat and future aspects in terms of efficiency, mechanisms and the desirable properties. The elucidation of the diverse mechanisms will enable microorganisms developing agriculture further.

**Keywords:** PGPR, wheat, abiotic stress, enzymes, nitrogen fixation

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
