Exploration of phyto-beneficial traits of halophilic rhizobacteria isolated from the mangrove halophyte Avicennia marina

Abstract

The salinity of the soil exerts an adverse effect on plant development and yield. However, amid saline stress, certain halophilic bacteria enhance the growth of plants. In this investigation, the mangrove halophyte Avicennia marina’s (A. marina) rhizosphere soil was used as the source for the isolation of halophilic bacteria. The isolates’ growth capacity at different pH, salinity, temperature, and polyethylene glycol (PEG) was assessed, and it was found that 56% showed growth in media supplemented with 2–7.5% NaCl; 50% showed efficient growth at pH 6–8, 62% grow optimally at temperature 25–35 °C, and about 88% showed growth in media with 5% PEG. The isolates possess growth-promoting traits evidenced by nitrogen fixation (18%), ammonia production (31%), phosphate solubilization (88%), zinc solubilization (44%), and indole acetic acid (IAA) (88%) production. The isolates can produce extracellular enzymes, viz., protease (88%), amylase (62%), cellulase (56%), and lipase (31%). The bacterial isolate S1B1 that displayed maximum plant growth-promoting traits was selected as the potent and subjected to plant growth promotion studies. The potent isolate S1B1 enhances Solanum lycopersicum’s germination under different salinity compared to untreated seeds with germination of 64% at the maximum concentration of 2% NaCl. The potential halophilic plant growth-promoting rhizobacteria (PGPR) isolate was determined as Rossellomorea aquimaris (R. aquimaris) by 16s rRNA analysis. The results demonstrated that R. aquimaris recovered from the rhizosphere of halophyte A. marina found possible applications for enhancing plant development and productivity in salinity-affected soils.