Daphne virus X: A potexvirus from daphne

Abstract Daphne virus X (DVX) was found in all specimens of Daphne cneorum L. indexed for virus but was not associated with macroscopic symptoms. Experimental hosts of DVX included 18 species from 6 dicotyledonous families. Infectivity was retained in expressed sap of Nicotiana clevelandii Gray for 5 weeks at c. 20°c, in sap diluted to 10 ‐5 , after heating for 10 min at 80°c. Attempts to transmit DVX with Myzus persicae (Sulz) failed. DVX was purified from N. clevelandii leaves using chloroform: n‐butanol clarification, one cycle of differential, then density‐gradient, centrifugation. Preparations had a 260:280 ratio of 1.22, a sedimentation coefficient of 110 S, and a buoyant density in CsCl of 1.28 g/ml. An antiserum to DVX had a titre of 1:2048. DVX was not serologically related to clover yellow mosaic virus, narcissus mosaic virus, potato virus X, and white clover mosaic virus. The flexuous filamentous particles of DVX had a normal length of 499 nm in negatively stained preparations from D. cneorum flowers. Ultra‐thin sections of pea leaflets systematically infected with DVX contained aggregates of DVX‐like particles as well as unaggregated particles scattered in the cytoplasm. It is proposed that DVX is a distinct potexvirus. The present cryptogram for DVX is */*: */ (6): E/E: S/*.