Biocontrol Activity of Volatile-Producing<i>Bacillus megaterium</i>and<i>Pseudomonas protegens</i>against<i>Aspergillus flavus</i>and Aflatoxin Production on Stored Rice Grains

Abstract

In our previous study, three bacterial strains, <i>Bacillus megaterium</i> KU143, <i>Microbacterium testaceum</i> KU313, and <i>Pseudomonas protegens</i> AS15, were selected as effective biocontrol agents against <i>Aspergillus flavus</i> on stored rice grains. In this study, we evaluated the inhibitory effects of the volatiles produced by the strains on <i>A. flavus</i> growth and aflatoxin production on stored rice grains. The three strains significantly reduced mycelial growth of <i>A. flavus</i> in dual-culture assays compared with the negative control strain, <i>Sphingomonas aquatilis</i> KU408, and an untreated control. Of these tested strains, volatiles produced by <i>B. megaterium</i> KU143 and <i>P. protegens</i> AS15 markedly inhibited mycelial growth, sporulation, and conidial germination of <i>A. flavus</i> on agar medium and suppressed the fungal populations in rice grains. Moreover, volatiles produced by these two strains significantly reduced aflatoxin production in the rice grains by <i>A. flavus</i>. To our knowledge, this is the first report of the suppression of <i>A. flavus</i> aflatoxin production in rice grains using <i>B. megaterium</i> and <i>P. protegens</i> volatiles.