Abstract
Potato spindle tuber viroid (PSTV) RNA, labelled in vitro with 125I, was hybridized in solution to RNA prepared from uninfected and PSTV-infected Rutgers tomato plants and suspension cultures. Following hybridization to RNA from infected plants, 125I-labelled PSTV was converted from its single-stranded form to double-stranded RNA; this conversion did not occur to a significant extent when the 125I-labelled PSTV was incubated with RNA from uninfected tomato plants under identical conditions. Following fractionation of RNA from PSTV-infected tissue with 2 M-LiCl and chromatography on cellulose CF11 columns, the RNA species which hybridizes with the PSTV probe was found to be enriched in those fractions which are also enriched for double-stranded RNA. Fingerprint analysis of hybridized 125I-labelled PSTV following recovery from the hybrids demonstrated that all regions of the viroid are represented in the complementary strands present in these RNA preparations.