PGPR Isolates from the Rhizosphere of Vegetable Crop Momordica charantia: Characterization and Application as Biofertilizer

Abstract

Plant growth promoting Rhizobacteria (PGPR) enhance the plant growth and productivity through wide variety of mechanism. The strains isolated from rhizosphere of Momordica charantia, mainly belonged to Bacillus, Azotobacter, Pseudomonas and Acinetobacter. Nearly 50% isolates of Pseudomonas and Acinetobacter and all the isolates of Bacillus and Azotobacter were able to solubilise tricalcium phosphate. All the isolates were positive for Catalase activity and IAA production except Acinetobacter with 75% isolates were IAA producing. Pseudomonas (100%), Bacillus (80%), Acinetobacter (75%) and Azotobacter (40%) produced ammonia and all the isolates were siderophore producing except Azotobacter. The Bacillus (75%) and Pseudomonas (50%) also produce HCN. Best performers in above plant growth promotion (PGP) traits, isolate of Bacillus (R7), Azotobacter (RS7), Pseudomonas (RS1) and Acinetobacter (R12) evaluated for their effect on plant vigour. The antibacterial activity and plant growth promotion in Pseudomonas (RS1), salt tolerance in Bacillus (R7), and nitrogenase activity (C2H2-reduction) in Azotobacter (RS7) was highest. Pseudomonas (RS1) was most efficient PGPR and Bacillus (R7) most dominant in rhizosphere of bitter melon. Nitrogenase (C2H2- reduction), phosphate solubilisation and growth promotion activities in Bacillus (R7), Azotobacter (RS7) and Pseudomonas (RS1) suggested that these isolates may be used as a biofertilizer for bitter melon.