Efficacy of Plant Growth Promoting Rhizobacteria in In Vitro Inhibition of Xanthomonas axonopodis pv. Glycines and Prevention of Bacterial Pustules of Soybean in the Field

Twelve different plant growth promoting rhizobacteria (PGPRs) belonging to Pseudomonas fluorescens and Bacillus subtilis were tested for their efficacy against bacterial pustules of soybean (Glycine max) caused by Xanthomonas axonopodis pv. glycines both in laboratory and field conditions. PGPR-10 (P. fluorescens), PGPR-3 (B. subtilis), PGPR-4 (B. subtilis) and PGPR12 (P. fluorescens) showed maximum bacterial growth inhibition in vitro (more than 30mm inhibition zone) and increased seed germination (more than 92%). Highest seed germination (above 95%) occurred with the treatment of PGPR-4 (B. subtilis), PGPR10 (P. fluorescens), PGPR-1 (B. subtilis), PGPR-7 (P. fluorescens), PGPR-11 (P. fluorescens) and PGPR-5 (B. subtilis), while plant vigor increased with PGPR-12 (P. fluorescens), PGPR-5 (B. subtilis), PGPR-11 (P. fluorescens) and PGPR-3 (B. subtilis). Under field conditions, PGPR-12 (P. fluorescens) and PGPR-5 (B. subtilis) resulted in decrease of per cent disease index and increase in plant yield compared to other PGPR strains.