Inhibitory effects of the carrot metabolites 6-methoxymellein and falcarindiol on development of the fungal leaf blight pathogen Alternaria dauci

The in vitro effects of 6-MM and falcarindiol on the development of Alternaria dauci were analyzed. The results showed that A. dauci was significantly more susceptible to falcarindiol than to 6-MM. Experiments dealing with mixed solutions of 6-MM and falcarindiol indicated additive effects of the metabolites on growth inhibition. Permeabilization of the fungal plasma membrane was observed after falcarindiol treatment. In planta quantification of 6-MM/falcarindiol was performed on inoculated leaves of carrot genotypes. Significantly faster 6-MM production was observed in Bolero (partially resistant to A. dauci) than in Presto (susceptible). The falcarindiol levels were significantly higher in Bolero than in Presto.