Pseudomonas isolation agar

All chemicals used were of analytical grade. Thiobarbituric acid (TBA), trichloroacetic acid (TCA), 1,1,3,3-tetramethoxypropane, Brij-L23, tetramethylmurexide, and L-β-(3,4 dihydroxyphenyl) alanine (L-DOPA) were procured from Sigma Aldrich (St. Louis, MO, USA). Potassium carbonate and copper (II) sulfate were purchased from Thermo Fisher Scientific (Auckland, New Zealand). The microbial media (eosin methylene blue agar (EMB), Pseudomonas isolation agar (PIA), plate count agar (PCA), triple sugar iron agar, and Mueller–Hinton broth (MHB) were acquired from Himedia (Mumbai, India).

Rhizosphere adhering soil samples were collected from ten different locations of green gram cultivating areas of Jorhat district of Assam, located in 26.75°N and 94.22°E of North East India. Sampling sites were selected based on minimal annual precipitation, i.e mainly drought prone areas. Sampling was carried out during the month of October (vegetative growth phase) and February (reproductive growth phase), 2011–2012. Soils were clay loam in texture with pH of 3.5 to 4. The soil samples from each location were combined and passed through 0.2 cm sieve and preserved at 4°C until use. A total of 120 fluorescent pseudomonad colonies were obtained upon growth on King’s B agar (KB) and Pseudomonas isolation agar (Hi Media, Mumbai, India) medium by incubating at 30±2°C for 24 hours The isolates were stored in 20% glycerol stock at −80°C until use.