Two groups of tandemly repeated DNA fragments have been isolated and cloned from the Oryza officinalis genome (W 1278). These fragments have been sequenced and are 374 and 367 bp long. They were compared with an element previously isolated from another O. officinalis accession. They are 76 and 92% homologous to the latter and show 78% homology between themselves. The two types of elements are interspersed within large blocks of tandemly organized units. Their copy number is in the range of 200 000 units. This sequence was present only in wild rice accessions with a CC genome. However, this apparent specificity is even more restricted, since it was absent from some O. officinalis accessions and from the allotetraploid species of the CCDD type. Use of digestions with 4-bp restriction enzyme cutters and analysis on denaturing polyacrylamide gels revealed polymorphism that might be used to map the repeats in the genome as well as to establish the relationship between accessions. Finally, hybridization of the repeated sequence to DNA prepared from the eight available O. sativa – O. officinalis monosomic addition lines revealed that the elements are located on two alien chromosomes. This suggests that these elements have at least some restricted chromosome specificity.Key words: satellite DNA, rice, monosomic addition lines, RFLP, evolution.
Production and characterization of Brassica napus–Raphanus sativus monosomic addition lines mediated by the synthetic amphidiploid “Raphanobrassica”