Comparison of aqueous seasoning cube solution and nutrient broth as culture media for production of the biocontrol agent Bacillus megaterium in the laboratory, and for suppression of rice grain discolouration in the field

Abstract

Bacillus megaterium is a beneficial bacterium that is used as a biological control agent (BCA) against the fungi Rhizoctonia solani, Fusarium sacchari and Curvularia lunata, which attack rice plants. However, the cost of preparing the bacterium using standard nutrient broth is prohibitively expensive on a large scale. Therefore, a low-cost product (seasoning cube, a common ingredient for cooking) was examined as an alternative nutrient medium. Bacillus megaterium was cultured in either nutrient broth or in dissolved seasoning cube. These cultures were evaluated for their effect on the growth of rice seedlings in the laboratory and to suppress grain discoloration of rice in small-scale field trials. Bacillus megaterium cultured with a seasoning cube was as effective as standard nutrient broth for the growth of rice seedlings in the laboratory. It also suppressed grain discoloration disease of rice in small-scale field trials. Use of a seasoning cube is suitable for culturing B. megaterium and should be recommended to farmers.