RESUMO
A natural bacterial isolate from fermented panchagavya named as PG-64, exhibits multiple plant growth-promoting traits. This Gram-negative bacteria was identified as Klebsiella sp. PG-64 by 16S rRNA gene sequencing. The Klebsiella sp. PG-64 has shown production of indole acetic acid (106.0 µg/ml), gibberellic acid (20.0 µg/ml), ammonia (7.12 µmol/ml), exopolysaccharide (2.04% w/v) and phosphate solubilization (106.0 µg/ml). It produced 437 µg/ml IAA with 0.75% (w/v) L-tryptophan supplementation and was increased to 575 µg/ml in a laboratory-scale fermenter. The PG-64 has shown tolerance to abiotic stress conditions like pH (5.0-12.0), temperature (28-46 °C), salt (0.5-10.0% w/v NaCl) and osmotic resistance (1-10% w/v PEG-6000). The PG-64 also produced 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (0.3 ng α-ketobutyrate/mg protein/h) indicating its potential for drought tolerance. Owing to its diverse properties, the effect of Klebsiella sp. PG-64 on Vigna radiata (Mung bean) was examined. The seeds treated with PG-64 culture showed 92% germination with a good seedling vigour index (202). In the pot study, Vigna radiata growth showed 2.23, 1.55, 2.00, 1.65, 1.73, 1.88, 5.00, 5.00, 1.57 times increase in primary root length, dry root weight, root hair numbers, leaf width, leaf numbers, leaf area, fruits number, flower number and chlorophyll content, respectively after 75 days. The application of Klebsiella sp. PG-64 culture resulted in substantial growth enhancement of Vigna radiata. The Klebsiella sp. PG-64 has multiple plant growth-promoting properties along with capabilities to tolerate abiotic stresses, making it a promising liquid biofertilizer contender for various crops.
