Additional Hosts and an Efficient Purification Procedure for Four Viroids

Abstract

Additional hosts of potato spindle tuber viroid (PSTV), citrus exocortis viroid (CEV), chrysanthemum stunt viroid (CSV), and chrysanthemum chlorotic mottle viroid (ChCMV) are reported. Chrysanthemum morifolium is a new host of PSTV (both mild and severe strains) and CEV. Both viroids reach high concentrations in chrysanthemum. Tomato (Lycoperiscon esculentum ''Rutgers'') and Gynura aurantiaca are new hosts of CSV; and C. zawadskii is a new host of ChCMV. PSTV and CEV were purified from these hosts, labeled in vitro with 125I and identified by RNA fingerprinting analysis. Comparisons of fingerprints of these viroids from several hosts confirmed a previous report that the nucleotide sequence of viroid RNA is not determined by the host plant. An efficient purification procedure for PSTV, CEV and CSV is described. Yields of 10-50 times greater than those of published procedures for PSTV were obtained. Additional evidence for the viroid nature of ChCMV and its symptomless strain were obtained by demonstrating infectivity following fractionation in 5-15% polyacrylamide gels.