ANTIFUNGAL ACTIVITY OF <i>Bacillus</i> sp. E164 AGAINST <i>Bipolaris sorokiniana</i>

Abstract

Spot blotch caused by Bipolaris sorokiniana is an important disease of wheat in warmer and humid weather conditions, whose control relies mainly on chemical antifungal agents. The purpose of this work were to isolate bacteria strains with antifungal activity against B. sorokiniana; to select the best inhibitor and to evaluate the best growth conditions for the antifungal production; and to test it´s action in vivo. The bacterial strains were pre-screened against four B. sorokiniana isolates on plates containing Sabouraud maltose agar. The isolate that showed the best result was grown on different culture media, cells were filtrated and the filtrates were tested against B.sorokiniana on plates with PDA medium. The in vivo test was done on wheat seeds, infected with B. sorokiniana isolate on a chamber with controlled temperature. Bacillus E164 was chosen among the 86 bacterial isolates tested against the phytopathogen. The filtrate from Bacillus E164 grown on tryptic casein soy broth (TSB) and straw culture media showed a similar degree of inhibition against the phytopathogen, the same result was not observed with malt extract broth media. The filtrate culture showed activity similar to control being submitted to temperatures from 50- 90ºC. The in vivo test with isolate E164 caused morphological effects on wheat plants with a significant root length reduction. Control exerted by Bacillus E164 over B. sorokiniana isolates was relevant in vitro, nevertheless the influence and importance of the metabolites produced must be elucidated for the application in vivo.