2 CIRCULAR SINGLE-STRANDED DNAS ASSOCIATED WITH BANANA BUNCHY TOP VIRUS

Nucleic acids extracted from partially purified banana bunchy top viru s (BBTV) consisted of 20 Kb DNA, 0.9-1.1 Kb DNA and 0.3 Rb RNA. Partia lly purified BBTV preparations predigested with DNase and RNase before particle disruption and nucleic acid isolation yielded only the 0.9-1 .1 Kb DNA, but no corresponding nucleic acid band was obtained in tota l nucleic acid isolated from healthy banana tissue. Analysis of two BB TV cDNA clones showed that clone 1 consisted of 287 nucleotides and cl one 2 contained a 1.0 Kb DNA insert. Clone 1 is not part of clone 2. W hen two pairs of primers, each pair in opposite orientation were used to amplify BBTV DNA by PCR using the total DNA from diseased banana ti ssues or DNA encapsidated in BBTV particle as the template, a DNA prod uct of 1.1 Kb Nas generated by both, results indicating that the BBTV DNAs are circular. Additional results suggested chat BBTV contained at least two circular ssDNAs designated BBTV cssDNA I (containing clone 1 nucleotide sequence) and BBTV cssDNA II (containing clone 2 nucleoti de sequence).