REGULAR ARTICLE Isolation of ACC deaminase producing PGPR from rice rhizosphere and evaluating their plant growth promoting activity under salt stress Himadri Bhusan Bal & Lipika Nayak & Subhasis Das & Tapan K. Adhya Received: 26 May 2012 / Accepted: 30 July 2012 / Published online: 15 August 2012 # Springer Science+Business Media B.V. 2012 Abstract Aims Bacteria possessing ACC deaminase activity re- duce the level of stress ethylene conferring resistance and stimulating growth of plants under various biotic and abiotic stresses. The present study aims at isolat- ing efficient ACC deaminase producing PGPR strains from the rhizosphere of rice plants grown in coastal saline soils and quantifying the effect of potent PGPR isolates on rice seed germination and seedling growth under salinity stress and ethylene production from rice seedlings inoculated with ACC deaminase containing PGPR. Methods Soils from root region of rice growing in coastal soils of varying salinity were used for isolating ACC deaminase producing bacteria and three bacterial isolates were identified following polyphasic taxono- my. Seed germination, root growth and stress ethylene production in rice seedlings following inoculation with selected PGPR under salt stress were quantified. Results Inoculation with selected PGPR isolates had considerable positive impacts on different growth parameters of rice including germination percentage, shoot and root growth and chlorophyll content as compared to uninoculated control. Inoculation with the ACC deaminase producing strains reduced ethyl- ene production under salinity stress. Conclusions This study demonstrates the effective- ness of rhizobacteria containing ACC deaminase for enhancing salt tolerance and consequently improving the growth of rice plants under salt-stress conditions. Keywords Growth promoting rhizobacteria . Coastal rice soils . ACC deaminase . Polyphasic taxonomy . Salinity stress . Ethylene production Introduction Plant growth-promoting rhizobacteria (PGPR), free- living soil bacteria thriving in the plant rhizosphere, have been studied as plant growth promoters for in- creasing agricultural productivity (Lucy et al. 2004). PGPR can either directly or indirectly facilitate growth of plants (Glick 1995). Indirect stimulation of plant growth includes mechanisms by which the bacteria prevent phytopathogens from inhibiting plant growth and development (Raaijmakers et al. 2009) while di- rect stimulation may include providing plants with Plant Soil (2013) 366:93–105 DOI 10.1007/s11104-012-1402-5 Responsible Editor: Bernard Glick. Electronic supplementary material The online version of this article (doi:10.1007/s11104-012-1402-5) contains supplementary material, which is available to authorized users. H. B. Bal : L. Nayak : S. Das : T. K. Adhya Laboratory of Soil Microbiology, Division of Crop Production, Central Rice Research Institute, Cuttack, 753006 Odisha, India Present Address: T. K. Adhya (*) School of Biotechnology, KIIT University, Bhubaneswar, 751024 Odisha, India e-mail: adhyas@yahoo.com