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. Inl'ectivity 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 lrom 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/m!. 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 LJ. 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 ::i distinct potexvirus. The present cryptogram for DVX is