Homoeological relationships between the f chromosome of Brassica rapa and the e chromosome of Brassica oleracea.

Eight plants of the putative double monosomic addition line (DMAL, 2n =20) were developed by crossing a monosomic chromosome addition line of radish [f(A)-type monosomic addition line (MAL) (2n =19)] carrying the f chromosome of Brassica rapa (2n =20, AA) with another [e(C)-type MAL (2n =19)] having the echromosome of Brassica oleracea (2n =18, CC). The homoeological relationships between the two alien chromosomes were investigated by morphological, cytogenetic and random amplified polymorphic DNA (RAPD) analysis. Seventeen morphological traits that were not present in the radish cv. `Shogoin' were observed in both MALs and these traits were substantially exhibited in DMAL plants. At the first metaphase of pollen mother cells (PMCs), the two parental MALs showed a chromosome configuration of 9II + 1I, demonstrating impossibility of recombination between the R and the added chromosomes. The DMALs formed 10II in approximately 73% of PMCs, with one bivalent showing loose pairing between two chromosomes differing in size. In an attempt to identify the two MALs by RAPD-specific markers using 26 selected random primers, 13 and 20 bands were specific for the f(A)-type and the e(C)-type MALs, respectively; 12 bands were common to both MALs (26.7%). In conclusion, the f chromosome of B. rapa is homoeologous to the e chromosome of B. oleracea . The genetic domain (genes) for 17 morphological traits are linked to each homoeologous chromosome bearing 27% of the corresponding RAPD markers. [ABSTRACT FROM AUTHOR]