Isolation, Characterization and Screening of Bacillus spp. from Rhizosphere Soils of Black Gram (Vigna mungo L.)

Abstract

The present study entitled “Isolation, characterization and screening of Bacillus spp. from rhizosphere soil of black gram (Vigna mungo L.)” was conducted to identify efficient plant growth-promoting Bacillus strains that can be developed as potential bioinoculants for sustainable black gram cultivation. A total of 25 rhizosphere soil samples were collected from black gram fields in Raichur and Kalaburagi during 2024-25. Twenty-five Bacillus isolates were purified and subjected to morphological and biochemical characterization. The isolates grown on Nutrient Agar were found to be Gram-positive, motile, endospore-forming rods. Biochemical tests revealed that all isolates were positive for methyl red and catalase tests, 14 were positive for starch hydrolysis, and 11 for urease test, whereas all were negative for indole test. Plant growth-promoting traits of the isolates showed that IAA production ranged from 5.06 to 8.44 µg/ml, with isolate BR-15 recording the highest level. Phosphate solubilization zones ranged from 13.11 to 17.30 mm, where BR-15 exhibited maximum solubilization. In ammonia production, one isolate was strongly positive (+++), four were moderate (++), and three were negative. Eight isolates displayed antifungal activity against Fusarium sp., with isolate BR-15 showing the highest antifungal activity (62.50%). Overall, BR-15 demonstrated superior PGP and biocontrol attributes, indicating its strong potential as an efficient bioinoculant for enhancing black gram productivity.