Abstract
This work aims to characterize the bioactive molecules produced by an antagonistic
Bacillus
sp. strain BCLRB2 isolated from healthy leaves of olive tree against
Rhizoctonia solani
and
Sclerotinia sclerotiorum
. The bacterial strain isolated showed a high and persistent antifungal activity against the two pathogens. The free-cell supernatant showed also a high antifungal activity against
R. solani
and at a lower extent against
S. sclerotiorum
. The partial purification of the antifungal substances with methanol gradient applied to C18 column binding the
Bacillus
BCLRB2 culture supernatant showed that the 20% and 60% methanol fractions had a high and specific activity against
S. sclerotiorum
and
R. solani
, respectively. The mass spectrometry identification of the compounds in the fraction specifically active against
S. sclerotiorum
revealed the presence of bacillomycin D C16 as a major lipopeptide. The fraction specifically active against
R. solani
contained bacillomycin D C15 and 2 unknown lipopeptides. The 80% methanol fraction had a moderate and a broad spectrum activity against the two pathogens and consisted from two iturin D (C13 and C14) as a major lipopeptides.