Biosynthesis and purification of indole-3-acetic acid by halotolerant rhizobacteria isolated from Little Runn of Kachchh

Abiotic stresses are increasing globally at an alarming rate. On the contrary, demand for food is ever increasing with the rise in population and salts stress has been the major one reported to affect photosynthetic machinery and thereby reduce growth and yield. Halo-tolerant plant growth promoting rhizobacteria that have ability to work under salt stress and promote plant growth along-with enhanced synthesis of secondary metabolites including phytohormones (Indole Acetic Acid (IAA) and volatile compounds is being widely studied. The present work describes isolation, characterization and identification of IAA, producing halotolerant PGPR from Cumin cyminum rhizosphere cultivated in saline areas of Kachchhh, Gujarat, India. Initially, the IAA secreting ability was assessed for 20 bacterial isolates and three potential isolates that had ability to synthesize IAA under saline conditions (2% w/v NaCl) were selected for further studies. The cultures were identified as Bacillus subtilis, Rheinheimera sp. and Rhizobium sp. by partial sequencing of 16S rRNA gene, the nucleotide sequences has been submitted to NCBI, GenBank. The IAA producing ability under salt stress was assessed for all three cultures and was observed to be 250. 0.1 mu g/ml, 220. 0.1 mu g/ml and 200. 0.1 mu g/ml for Rheinheimera sp. Rhizobium sp. and Bacillus subtilis respectively. The total estimation of IAA biosynthesis by Rheinheimera sp. was done by TLC and HPLC of extracted IAA and reference indolic compounds. This is the first time that Rheinheimera sp. is the being selected for IAA production and development of Halo-tolerant PGPR for field based studies and applications.