Preliminary Investigations on Selection of Synergistic Halotolerant Plant Growth Promoting Rhizobacteria for Inducing Salinity Tolerance in Wheat

Halotolerant bacteria having 1-aminocyclopropane-1-carboxylate (ACC)-deaminase activity were isolated from wheat rhizosphere and further screened for their plant growth promoting potentials in planta by using wheat as test crop under salinity stress. ACC-deaminase activity ranged from 85 to 399 nmol α-ketobutyrate mg hr of these rhizobacteria. In absence of L-tryptophan, out of 25 rhizobacteria, 16 were able to produce IAA equivalents while nine did not produce auxins as IAA equivalents. Production of IAA equivalents ranged from 1.45 to 12.32 μg mL in absence of L-tryptophan. While, in the presence of L-tryptophan, all the 25 rhizobacteria produced auxins as IAA equivalents and it ranged from 3.10 to 34.76 μg mL. Out of 25 rhizobacterial isolates, seven isolates were recognized as plant growth promoting rhizobacteria (PGPR) which were statistically significant for improving growth of wheat under saline conditions. These seven halotolerant PGPR were tested for their compatibility of growth and synergism with each other. Out of 7, only three isolates were found synergistic and they showed abilities to coexist. Sequencing of rrs (16S rRNA) gene of these PGPR strains and phylogenetic analysis confirmed that these 3 PGPR strains are Bacillus cereus strain Y5, Bacillus sp. Y14 and Bacillus subtilis strain Y16. It is concluded that rhizobacteria varying in ACC-deaminase activity differentially respond to influence plant growth under salinity stress.