Figure 4.

B. rapa rRNA genes are dominant over B. oleracea in both natural and synthetic lines of tetraploid B. napus. RNA isolated from B. oleracea, B. rapa, or the tetraploids was subjected to S1 nuclease protection assay using a B. rapa probe (lanes 2–6) or a B. oleracea probe (lanes 7–11). B. rapa transcripts were readily detected in the tetraploids (lanes 4–6). No B. oleracea transcripts were detected in natural B. napus (lane 8), but trace amounts were detected in the synthetic lines (lanes 10 and 11). DNA sequencing reactions were loaded as size markers in lanes 1 and 12.