Cytogenetical studies on interspecific Fl hybrids between Brassica campestris and B. oleracea were carried out. Hybrid plants were produced by the culture in vitro of excised ovaries. Three types of Fl hybrids were obtained in the cross between diploid B, campestris, and diploid and autotetraploid B. oleracea. The first type plants had 19 chromosomes in root tip cells. The second type plants had 38 chromosomes which were presumably raised by spontaneous chromosome doubling during embryo

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... ent. The third type plants had 28 chromosomes which were produced by the cross, diploid B. campestris X autotetraploid B. oleracea. Mode of the chromosome configurations at the first meiotic division of the first type hybrids was 9II+1 (44.7%). Frequency of tri-, tetra-and pentavalents was 38.6%, 10.3% and 1.3%, respectively. Tetra-and pentavalents were observed for the first time in the present experiment. Chromosome configurations at meiosis of the second type hybrids were mostly 19II (86.7% and 80.0% in two plants). The mode of chromosome configurations at meiosis of the third type hybrids was 9II+10I (40.9%). Frequency of tri-and tetravalents was 38.1% and 1.2%, respectively. Tetravalents were observed for the first time in the present experiment.