Inhibition of tomato bushy stunt virus infection using a quercetagetin flavonoid isolated from Centaurea rupestris L.

Flower and leaf extracts of Centaurea rupestris L. and also the flavonoid quercetagetin 3'-methylether isolated from these extracts revealed a strong antiviral activity when inoculated simultaneously with tomato bushy stunt virus in two Nicotiana species. Almost complete reduction of local lesion number resulted from these inoculations in N. glutinosa. A similar effect was observed in inoculated leaves of N. megalosiphon causing the absence of systemic infection in 40% of treated plants. The antiphytoviral activity was not a consequence of induced resistance, inhibition of virus multiplication, suppression of symptom development or direct virus inactivation. Results presented in this paper suggest that the flavonoid may interfere with the initiation of virus infection.