Accumulation of the flavonoids betagarin and betavulgarin in Beta vulgaris infected by the fungus Cercospora beticola

Abstract

The flavanone betagarin and the isoflavone betavulgarin occur in necrotic lesions resulting from infection of sugarbeet ( Beta vulgaris) leaves by Cercospora beticola. In whole infected leaves from cultivars of varied leaf spot susceptibility, there were significant differences among cultivars in content of both flavonoids, but only betavulgarin content was significantly correlated with a visual rating of disease severity. In lesions, the content of both compounds differed significantly among cultivars, but only betavulgarin content differed with time after disease initiation. At 3 weeks after plants were inoculated with a suspension of fungal spores, lesion betagarin concentrations were 300 to 1050 μg/ml, depending on cultivar, and betavulgarin contents were from 50 to 200 μg/tnl. When compared with data from in vitro bioassays, these amounts appear potentially capable of limiting fungal growth. However, the correlation coefficient between visual rating of disease severity and compound contents per lesion was non-significant for each flavonoid.