BACILLUS ISOLATES FROM THE SPERMOSPHERE OF PEAS AND DWARF FRENCH BEANS WITH ANTIFUNGAL ACTIVITY AGAINST BOTRYTIS-CINEREA AND PYTHIUM SPECIES

A range of isolation procedures including washing, sonication and incu bation in nutrient broth were used separately and in combination to ob tain potential bacterial antagonists to Botrytis cinerea and Pythium m amillatum from the testae and cotyledons of peas and dwarf French bean s. Heat treatment was also used to bias this selection towards spore-f orming bacteria. Ninety-two bacterial isolates were obtained, 72 of wh ich were provisionally characterized as species of Bacillus. Four of t hese Bacillus isolates (B3, C1, D4 and J7) displayed distinct antagoni sm in vitro against Botrytis cinerea and P. mamillatum when screened u sing dual culture analysis. Further characterization of these antagoni sts using API 50CHB biochemical profiling identified isolate D4 as Bac illus polymyxa and isolates B3, C1 and J7 as strains of B. subtilis. r n vitro screening techniques, using cell-free and heat-killed extracts of liquid cultures against Botrytis cinerea, demonstrated the product ion of antifungal compounds by these four Bacillus antagonists. With e ach isolate the antifungal activity was found not to be either exclusi vely spore-bound nor released entirely into the medium but present in both fractions. The antifungal compounds produced by these isolates we re shown to be heat-stable. Their identification, production and relea se require further study for exploitation as biocontrol systems.