Culturable endophytic Z1B4 isolated from Roxb. with stress-tolerance and plant growth-promoting potential.

Endophytes are an important constituent of sustainable agriculture because of their ability to produce a large number of agriculturally important metabolites. A salt-tolerant fluorescent green pigment-producing endophytic bacterium was isolated on 2.5% NaCl-supplemented nutrient agar from the leaf samples of Roxb. The isolate Z1B4 was identified as based on morphological features, fatty acid methyl ester analysis, biochemical tests, and 16S rRNA gene sequencing. Z1B4 showed positive results for tricalcium phosphate solubilization; 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity; and production of auxins, siderophores, hydrogen cyanide, and ammonia. Z1B4 also showed strong antagonistic activity against (MTCC 283), (MTCC 3322), and (MTCC 1362) and exhibited stress tolerance to a wide range of temperature and pH and concentrations of NaCl and calcium salts. Under natural conditions, following inoculation with the isolate Z1B4, a significant increase in the growth of pea and maize test plants in pots was observed compared to that of uninoculated control plants. The rifampicin-resistant mutant Z1B4 was recovered from the roots, shoots, and leaves of the test plants, indicating that the isolated endophytic bacterium can grow well within different plant tissues. The present study indicated that the endophytic bacterium Z1B4 can be used as a bacterial inoculant in stressed environments for sustainable agriculture.