Enhanced detection of viroid-RNA after selective divalent cation fractionation

Treatment of nucleic acid preparations from citrus exocortis viroid infected tissues with Ca2+, Co2+, Mn2+, and Zn2+ results in rapid precipitation of all large RNA molecules and selective precipitation of low-molecular-weight RNA species. Analysis of the viroid-RNA by polyacrylamide gel electrophoresis is greatly enhanced in the absence of any additional treatment with 2 M LiCl. The ratio of circular to linear molecules as well as the relative infectivity of Mn2+ -treated viroid preparations remain unaffected.