Enhancement of trichothecene mycotoxins of Fusarium oxysporum by ferulic acid aggravates oxidative damage in Rehmannia glutinosa Libosch.

Rehmannia glutinosa is an important medicinal herb that cannot be replanted in the same field due to the effects of autotoxic substances. The effects of these substances on R. glutinosa in continuous cropping systems are unknown. In the present study, bioassays revealed that R. glutinosa exhibited severe growth restriction and higher disease indices in the FO+FA (F.oxysporum pretreated with ferulic acid) treatment. The increases in the contents of MDA and HO were greater in the FA+FO treatment than in the FA or FO only treatments, respectively. Consistent with this result, the enzyme activities in the seedlings increased with treatment time. To identify the main factor underlying the increased pathogenicity of FO, macroconidia and trichothecene mycotoxins coproduced by FO were separated and used to treat R. glutinosa seedlings. The MDA and HO contents were similar in the seedlings treated with deoxynivalenol and in the FA+FO treatment. Quantification of the relative expression of certain genes involved in Ca signal transduction pathways suggested that trichothecene mycotoxins play an important role in the increased pathogenicity of FO. In conclusion, FA not only directly enhances oxidative damage in R. glutinosa but also increases wilting symptom outbreaks by promoting the secretion of trichothecene mycotoxins by FO.