Hot spots of DNA instability revealed through the study of somaclonal variation in rye

RAPD analysis was performed to assess DNA variation among rye plants regenerated from immature embryos and inflorescences. From the studied plants, 40% showed at least one variation, and the number of mutations per plant was quite high, ranging from 1 up to 12. On some occasions (2.9% of the scored bands) the modified band was observed in only one plant or in several but originated from the same callus (variable band). In other cases (5.25%) the same band varied in several plants obtained from different calli. We call these hypervariable bands and they could vary between plants belonging to different cultivars and/or with different origins, inflorescences or embryos. Thus, they must originate through independent mutational events. We assume that. these bands represent hypervariable regions of the rye genome and so detect hot spots of DNA instability. Some of these bands proved to be unique sequences, others were present in a low copy number while the remaining ones were moderately or highly repetitive.