Screening and characterization of native Pseudomonas sp. as plant growth promoting rhizobacteria in chickpea (Cicer arietinum L.) rhizosphere

Abstract

The search for diverse plant growth promoting rhizobacteria (PGPR) is gaining momentum as efforts are directed to exploit them as low-input biotechnology for sustainable agriculture. In search of efficient PGPR (Pseudomonas sp.) with multiple plant growth promoting (PGP) activities, a total of 35 isolates of rhizobacteria were isolated from 25 soil samples collected from healthy chickpea rhizospheric locations of Punjab (India). Ten isolates of rhizobacteria were characterized as Pseudomonas sp. on the basis of morphological, biochemical and growth promotion activities. PGPRs (Pseudomonas sp.) were screened for growth promotion activities [indole acetic acid (IAA), ammonia (NH 3), hydrogen cyanide (HCN), siderophore, phosphate (P) solubilization, catalase, antibiotic resistance spectra] and seed germination on water agar medium along with reference strain PGPR LK884 (Pseudomonas diminuta). Maximum amount of IAA was produced by PGPR-3 (70.05 µg/ml) followed by PGPR-2 (66.79 µg/ml) as compared to PGPR LK 884 (61.58 µg/ml) in the presence of L-Tryptophan as precursor of IAA. 70% of isolates showed capacity for P solubilization in the range of 5.08 to 13.45 mg/100 ml. Maximum P-solubilization was noticed with PGPR-3 (13.45 mg /100 ml) followed by PGPR-2 (13.15 mg/100 ml). Two isolates of Pseudomonas sp. PGPR-2 and PGPR-3 also produced siderophores, HCN, NH 3 and improved seed germination in kabuli and desi chickpea. Intrinsic antibiotic spectra (IAR) showed 70% of PGPRs (Pseudomonas sp.) resistance to ampicillin (10 µg/ml). Two native isolates of PGPRs (Pseudomonas sp.) PGPR-2 and PGPR-3 with multiple PGP traits can be exploited for plant growth promotion due to their well adaptation in chickpea rhizosphere. Further evaluation of potential isolates for exhibiting their multiple PGP traits on soil plant system is needed to uncover their efficacy.