Identification and functional characterization of plant growth-promoting rhizobacteria enhancing growth and nutritional quality of Sorghum bicolor

This study examines the role of plant growth-promoting rhizobacteria (PGPR) in enhancing the growth and nutritional quality of Sorghum bicolor, an essential forage crop for livestock in India. Soil samples were collected from three locations: the Bapatla Agricultural College farm, Agronomy and forage section field CCSHAU, Hisar, resulting in 14, 19 and 27 bacterial isolates. These isolates were screened for plant growth-promoting traits, including phosphorus, zinc, and potassium solubilization. Thirteen isolates demonstrated significant traits, with HTA 1 exhibiting the highest phosphate solubilization index (5.41), indole-3-acetic acid (IAA) production (25 µg/mL), and siderophore production index (3.77). Additional isolates, such as CTA 12, STA 6, and STA 11, displayed notable biosurfactant production, zinc solubilization (5.23), and potassium solubilization (6.17), respectively. Principal component analysis (PCA) was conducted on the 13 isolates based on their growth-promoting characteristics. Quantitative analyses revealed that STA 11 exhibited the highest phosphorus solubilization (184.3 µg/mL) and potassium solubilization (42 µg/mL), STA 6 recorded the highest zinc solubilization (19.7 µg/mL), and STA 15 showed the highest ammonia excretion (15.8 µg/mL). The effect of these promising isolates on sorghum seed germination was evaluated using the between-paper method. A consortium of the four top-performing isolates significantly outperformed individual treatments. Sorghum seeds treated with these isolates under both sterile and non-sterile soil conditions exhibited enhanced morphological, physiological, and biochemical traits compared to the control treatment which does not have any bacterial treatment. This study concludes that PGPR can significantly improve sorghum growth and yield without the application of synthetic fertilizers, offering a sustainable and eco-friendly solution when integrated with natural bioformulations. Their application and effect on the growth of Sorghum, under field conditions should be studied.