Fig. 2

Aberrant chromosome behaviors during meiosis in autotetraploid B. rapa. Normal meiosis from leptotene to telophase II in diploid B. rapa. a Leptotene, the chromosomes were shown as thin threads. b Pachytene, homologous chromosomes were completed synapsis. c Diakinesis, chromosomes moderately condensed as bivalents, d metaphase I, bivalents aligned on the equatorial plate. e Anaphase I, homologous chromosomes separated and move toward the opposite poles. f Metaphase II, two groups of condensed chromosomes at equatorial plate. g Anaphase II, chromatids separated each other and move toward the opposite poles of tetrad. h Telophase II, tetrads formation. Abnormal meiosis in autotetraploid B. rapa. A Leptotene, chromosome morphology was similar to diploid B. rapa. B Abnormal pachytene, some chromosomes are not closely juxtaposed with another (red arrow) suggests that synaptonemal complex is incomplete. C Abnormal diakinesis, multivalent (yellow arrow) and univalent (red arrow) were frequently observed. D Abnormal metaphase I, variable numbers of univalent (red arrow) aligned chaotically on the equatorial plate. E Abnormal metaphase I, asynchrony separation of chromosomes (red arrows) were observed. F Anaphase I, homologous chromosomes separated (20/20) and move toward the opposite poles G abnormal anaphase I, homologous chromosomes separated asymmetrically (19/21). H Metaphase II, chromosomes aligned at the equator in each cell. I Abnormal metaphase II, misaligned chromosomes (red arrows) were oriented away from the equatorial plate. J Abnormal anaphase II, lagged chromosome (red arrow) segregated to the poles. K Abnormal anaphase II, unbalanced tetrads with 19 chromosomes (dotted oval). L Abnormal anaphase II, different kinds of meiosis products with pentad. Magnification of homologous chromosomes pairing and synapsis at pachytene. b′ Full synapsis and pairing in diploid B. rapa. B′ partial synapsis and pairing in autotetraploid B. rapa. Red box indicates the zoom-in of configuration. Bar = 10 μm