Cercospora leaf spot is one of the most important widespread and
destructive fungal diseases affecting sugar beet. The ability of most Cercospora
isolates to cause disease is correlated with cercosporin toxin production. The yellow
toxin first called (GF) for Gelben Fraktion, but now called (Cal) for Cercosoor«
beticola toxin.ln vitro preliminary experiments showed the ability of some Cercospora
isolates to form red and yellow pigments in culture media. Applying pigments
exogenously to leaves, showed its toxIcity to sugar beet (Bets vulgaris L.), whereas,
carcosporin necr08is lesions were similar to that lesions induced by the natural fungal
infection. Factors influencing cercosponn In cullure have been studied. Results
indicated that PDA medium was the most favorable medium for overall growth.
Comparison of measured amounts of cercosporin produced on,different media
confinned that malt medium was the most favorable tor (CST) production in all tested
isolates, on which the highest level of cercosporin was harvested. Ught also plays an
important role in growth, sporulation and toxin accumulation. The present study was
concemed with the role of cercosporin toxin in inducing sugar beet leaf spot as well as
the impact of bacterial toxin degradation as antimicrobial agent in disease control. The
most efficient degraders were isolates of Xanthomona3 campestris pv. pruni or
zinnia6.