Morphology and cytogenetics of F-3 progenies from intergeneric hybrids between Brassica juncea and Orychophragmus violaceus

Plant morphology and cytogenetics of progenies from intergeneric hybrids be tween Brassica juncea and Orychophragmus violaceus were studied. The progen ies comprised three F-3 populations derived from three mixoploid F-2 plants with different morphology and chromosome numbers. The following results we re obtained. (1) The differences in plant morphology were maintained among the three F-3 populations. (2) All F-3 plants were mixoploids, mainly compo sed of cells with serial chromosome numbers in certain ranges. In plants wi th similar serial numbers, the cells with the highest three chromosome numb ers accounted for 66-89% of the total cells. (3) In mitotic metaphase sprea ds, it was possible to differentiate some large and more darkly stained chr omosomes which showed a later chromatid separation than the others. Lagging chromosomes and micronuclei were often observed in anther-wall cells. (4) In pollen mother cells (PMCs) at diakinesis and metaphase I, some large and more: darkly stained bivalents and univalents were easily distinguished, a nd the chromosomes composing these bivalents segregated later than the othe rs. Various segregation patterns were observed at anaphase I. At both anaph ase/telophase I and II, some large and darkly stained chromosomes lagged be tween or were included in polar groups or daughter nuclei. (5) The differen tiable large and darkly stained chromosomes in mitotic and meiotic cells we re conceived as of O. violaceus origin. Differences in timing between the p arental chromosomes during mitotic and meiotic divisions very likely contri bute to the complete and partial separation of parental genomes proposed to occur in the B. juncea x O. violaceus hybrids.