[Genomic in situ hybridization in intergeneric hybrids between Raphanus sativus and Brassica oleracea]

Genomic in situ hybridization (GISH) was applied to study the meiosis of F1 plants from intergeneric hybrids between radish (Raphanus sativus, 2n=18, RR) and cabbage (Brassica oleracea, 2n=18, CC). The result showed that its somatic cells had the expected chromosomes, RC, 2n=18; but the pollen mother cells (PMCs) were different. There were three main kinds of PMCs. The first one was RC (2n=18), and the mean chromosome pairing pattern was 14.87I+1.20II+0.04III+0.06IV on Diakinesis. GISH indicated that most bivalents resulted from chromosome pairing between radish and cabbage, and the nine chromosomes of R-genome were separated mostly in the ratio 5/4 and 6/3 at Anaphase, so the chromosome number and components in gametes were not in equilibrium and the gametes were sterile. The second was RRCC (2n=36) with normal chromosome pairing and separation, producing unreduced gametes. And the third was nullisomic of RRCC in PMCs (2n<36) GISH showed that some radish chromosomes were lost in those PMCs, and its gametes had nine cabbage chromosomes and partial radish chromosomes. The mechanism of this chromosome reduplication was discussed in this paper.