EFFECT OF SOME BACTERIAL ANTAGONISTS ON GROWTH AND MYCOTOXIN PRODUCTION OF FUSARIUM GRAMINEARUM AND F.CULMORUM ISOLATES

The impact of mycotoxin contamination of foodstuffs and feedstuffs on human and animal health is well documented. Trichothecene mycotoxins are metabolic compounds produced by various Fusarium species such as F.graminearum, F. culmorum, F. sporotrichioides, F. poae and F. equiseti on different grains like wheat, oats or maize. The most significant thrichothecenes produced by fusaria are T-2 toxin, HT-2 toxin, diacetoxyscirpenol (type A) and nivalenol, deoxynivalenol, 3- and 15-acetyldeoxynivalenol (type B). Deoxynivalenol (DON), mainly synthesized by F. graminearum and F. culmorum (that produce Fusarium Head Blight disease = FHB), is the most common trichothecene contaminant of wheat, and appears to play an important role in the aggressiveness of both species toward wheat. In order to prevent the contamination of the cereals with mycotoxigenic fungi, various strategies were developed (cultural practices: tillage, crop rotation; use of fungicides, resistant cultivars or biological control agents = BCAs). Because of the low efficacy of fungicides to control members of the Fusarium head blight Complex, the selection of highly efficient antagonists is of great interest for the specialists all over the world. Environmental friendly, the use of BCA is an important additional strategy that can be used as part of an integrated management of FHB. For this reason, the aim of our work was to select potential microbial antagonists that are able to inhibit the growth of Fusarium graminearum and F.culmorum, and to prevent the presence of DON on wheat. 37 Fusarium spp. strains were used in experiments and the in vitro aggressiveness of these isolates was determined. Twelve fungal strains with differences in the aggressiveness potential and DON biosynthesis were selected and used for interactions with eight bacterial strains isolated from compost or soil. Four out of the eight bacterial strains used were selected based on their high inhibitory activity against all the fungal isolates. Specific microscopically modifications of hyphae were observed at the edge of fungal colonies near the antagonist. The effect of the bacterial antagonists on DON accumulation in specific culture medium was also checked by TLC method. The results showed the possibility to use one or more bacterial strains as a tool for the biological control of FHB agents that survives in crop residues.