Plant Growth Promoting Response of Zinc Solubilizing Bacteria Bacillus tequilensis

Abstract

Zinc is a nutritive element for the growth of the plant, but its bioavailability in soil is frequently restricted. This study aimed to isolate, characterize, and optimize zinc solubilization by bacterial isolates of the rhizosphere of Finger Millet (Eleusine coracana L.) grown in Kaprada Taluka, Valsad District, Gujarat, India. A total 25 bacteria were isolated; from these isolates, 10 exhibited significant zinc solubilization on ZnO-supplemented Bunt and Rovira agar medium. The most potent isolate ZB9, showed the highest zinc solubilization potential (182 μL L-1) with a reduction in pH to 4.8. Furthermore, other plant growth-promoting (PGP) traits as indole acetic acid production (43 μg/mL), phosphate solubilization (92 μg/mL), hydrogen cyanide and ammonia production, were assessed. Optimization studies determined the ideal conditions for maximum zinc solubilization, including 0.1% ZnO, dextrose as a source of carbon, ammonium sulfate as a source of nitrogen, pH 6.0, incubation temperature 35°C, and 0.2% NaCl salinity. Molecular level identification through 16S rRNA sequencing of the isolate confirmed ZB9 as belonging to the Bacillus tequilensis. This study highlights the potential of ZB9 as a biofertilizer to improve zinc bioavailability and enhance plant growth and nutrient quality in Finger Millet cultivation.