INHIBITION OF INFECTIVITY OF POTATO-VIRUS X BY FLAVONOIDS

Infectivity of potato virus X (PVX) in Chenopodium quinoa was strongly inhibited (80%) by low concentrations (< 1-mu-g ml-1) of quercetin. Morin and 3-O-methylgalangin were also strong inhibitors. Methoxylation of quercetin reduced the inhibitory effect. Quercetin did not induce resistance, did not affect symptom development, had no direct viricidal effect and did not affect multiplication of PVX in infected leaf discs. Quercetin did not reduce infectivity when applied either before or after PVX inoculation. When PVX-RNA was used as inoculum, quercetin stimulated infectivity by 75%. It is proposed that quercetin interferes with an interaction between PVX coat protein and a host receptor essential for infection.