DIFFERENTIAL ABUNDANCE OF SIMPLE REPETITIVE SEQUENCES IN SPECIES OF BRASSICA AND RELATED BRASSICACEAE

Six Brassica species, known as the ''triangle of U'', and four species from related genera were characterized by DNA fingerprinting with simple repetitive oligonucleotide probes. Our results show that CT-, TCC-, and GTG-repeat motifs are equally abundant in the genomes of the six Brassica species. In contrast, GATA-, GGAT-, and GACA-multimers are unevenly distributed among different species. As judged from the number and strength of hybridization signals, the highest copy number of all three motifs occurs in Brassica nigra, while the lowest is observed in B. oleracea. The abundance of GATA- and GACA-repeats varies in a coordinate way. The amphidiploid genomes of B. juncea, B. carinata, and B. napus each harbour intermediate amounts of (GATA)4 and (GACA)4-detected repeats as compared to their diploid progenitors, thus supporting the concept of the ''U triangle''. GATA-, GACA-, and GGAT-repeats were also abundant in Eruca sativa and Sinapis arvensis, but not in Raphanus sativus and Sinapis alba. These results support the idea that Brassica nigra is more closely related to Sinapis arvensis than to other Brassica species such as B. rapa and B. oleracea.