THE INFLUENCE OF RIBOSYL-DHT AND DHT ON T HE REPLICATION OF PVX AND ON THE ACTIVITY OF THE PVX-INDUCED RNA-DEPENDENT RNA-POLYMERASE

Ribosylized 2,4-dioxo-hexahydro-1,3,5-triazine (= Ribosyl-DHT = 5,6-di hydro-5-dihydro-5-azauridin) inhibits PVX (potato virus X) in tissue d iscs of Nicotiana tabacum L. ''Samsun'' at considerably lower concentr ations than DHT. For this reason, ribosyl-DHT is supposed to be the ac tual antiviral active form of DHT. But in an in-vitro-replication syst em, ribosyl-DHT did not inhibit the PVX-induced RNA-dependent RNA-Poly merase. DHT inhibited this enzyme only at relatively high concentratio ns. These results suggest that the PVX-induced RNA-dependent RNA polym erase is neither specifically inhibited by ribosyl-DHT nor by DHT in t he replication cycle of PVX. - In contrast to infiltration of tissue d iscs, spraying intact plants with ribosyl-DHT did not give higher leve ls of PVX inhibition than spraying with DHT.