ABSTRACT

Attempts were made to isolate, characterize and evaluate plant growth promotional activity of Bacillus in maize (Zea mays L.) during 2023-2024 at the Department of Microbiology, UAS, Dharwad. A total of fifty Bacillus isolates were obtained from the rhizosphere soil of maize and sorghum crops collected from Dharwad and Gadag districts of Karnataka. These isolates along with reference strain Bacillus cereus IAM12605A98 were subjected for morphological, biochemical and functional characterization. Morphological characterization revealed that the cells of all the isolates as rod shaped, Gram positive and endospore former. With respect to functional characterization, the reference stain was found to be efficient. Among the native isolates, BSD29 isolate fixed maximum amount of nitrogen (5.76 mg of N/g of C), released highest amount of Pi (18.21 μg/ml after 7th DAI) from TCP broth, and also released highest amount of K from Aleksandrov’s broth (23.80 μg /ml after 7th DAI) and was observed as strong HCN producer. The isolate BMN9 produced maximum amount of IAA (26.98 g IAA/ml of broth) and GA (8.16 g/25 ml of broth) and solubilization of zinc (4.7 mm dia). Three isolates namely BMN9, BSD29, BMY41 exhibited maximum amount N2 fixation, solubilization of P, K and Zn and production of IAA, GA, HCN and siderophore were selected for further studies. With regard to biochemical characterization, three isolates were positive for catalase, oxidase, citrate utilization, gelatin liquefaction and casein hydrolysis tests. Three potent isolates were further tested under pot experiment to assess their performance on the growth of maize. The native Bacillus isolate BSD29 performed better with respect to plant growth parameters and recorded maximum nutrient concentration in maize under pot culture studies.