Hybridization of potato spindle tuber viroid to cellular DNA of normal plants

Molecular hybridization experiments of ¹²⁵I-labeled potato spindle tuber viroid (PSTV) with DNA from uninfected or PSTV-infected tomato plants showed that infrequent DNA sequences complementary to PSTV exist in both uninfected and infected cells. DNA titration experiments revealed that at least 60% of PSTV is represented by sequences in DNA of several normal solanaceous host species. Phylogenetically diverse plants contain sequences related to less of the PSTV. PSTV-infected tomato or Gynura aurantiaca plants did not possess new PSTV sequences at detectable levels. These results support the hypothesis that PSTV may have originated from genes in normal solanaceous plants.