Isolation of ACC deaminase producing PGPR from rice rhizosphere and evaluating their plant growth promoting activity under salt stress

Bacteria possessing ACC deaminase activity reduce the level of stress ethylene conferring resistance and stimulating growth of plants under various biotic and abiotic stresses. The present study aims at isolating 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. 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 taxonomy. Seed germination, root growth and stress ethylene production in rice seedlings following inoculation with selected PGPR under salt stress were quantified. 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 ethylene production under salinity stress. This study demonstrates the effectiveness of rhizobacteria containing ACC deaminase for enhancing salt tolerance and consequently improving the growth of rice plants under salt-stress conditions.