Isolation, screening, and characterization of plant growth enhancing endophytic bacteria from halophytic Heliotropium curassavicum L. collected from salt stress areas of Srikakulam, Andhra Pradesh

Abstract

Farmers use excessive chemical fertilizers to boost crop productivity to meet growing agricultural demands. However, this practice is costly and environmentally hazardous. Sustainable increase in crop yield can be achieved through alternatives like microbial-based fertilizers. In the quest to identify plant growth-promoting endophytic bacteria, the present study was carried out and selected unexplored halophytic plant Heliotropium curassavicum L. Thirteen endophytic bacterial strains were isolated from both aerial and root portions of H.curassavicum. These isolates were tested for salt tolerance, enzyme production, and synthesis of growth-promoting secondary metabolites, like Indole-3-acetic acid (IAA) and phosphate solubilization . Most of the isolates belonged to the Bacillus family, exhibiting varying Gram staining and biochemical reactions. The majority are Gram-positive bacteria, non-motile, spore formers, and exist in two cells or chains. All isolates could tolerate up to 10% NaCl concentration and a temperature of 42°C. Based on phenotypic, bio-chemical characteristics, isolate HCR3 showed promising properties in synthesizing IAA and phosphate solubilization abilities. The isolate HCR3 grew well upto 10% NaCl concentration and also 42°C temperature. Based on molecular characterization by using 16S rRNA gene-based analysis HCR3 isolate was identified and belonged to the Genus Pseudomonas with the highest similarity index with Pseudomonas khazarica sp. HCR3 showed IAA production of 37µg ml-1, had a phosphate solubilization ability of 3.5 ppm, and recorded protease activity on gelatin medium. The findings highlight the potential of HCR3 and other strains from halophytic H. curassavicum L. to enhance plant growth through secondary bioactive metabolites, offering eco-friendly solutions for sustainable agriculture.