Mode of antagonism of Brevibacillus brevis against Botrytis cinerea in vitro

Aims: To assess the activity of Brevibacillus brevis (formerly Bacillus bre vis) Nagano and the antibiotic it produces, gramicidin S, against the plant pathogen Botrytis cinerea. Methods and Results: Germination and growth of Bot. cinerea were assessed i n the presence of B. brevis or gramicidin S in liquid media, on solid media and on leaf sections of Chinese cabbage. Germination was 10-fold more sens itive to gramicidin S than growth. Inhibition of Bot. cinerea was greater i n liquid media compared with on solid media. Activity of gramicidin S again st Bot. cinerea on leaf sections was much lower than in vitro. In vitro inh ibition of Bot. cinerea by B. brevis Nagano was similar to equivalent level s of gramicidin S. Conclusions: Antibiosis, via gramicidin S, is the mode of antagonism exhibi ted by B. brevis Nagano against Bot. cinerea in vitro. Significance and Impact of the Study: The mode of antagonism of B. brevis a gainst Bot. cinerea was elucidated. The differing activity of gramicidin S against Bot. cinerea in vitro and on leaf sections indicates one mechanism by which biocontrol activity may differ between laboratory and field condit ions.