二、四倍体青花菜花粉母细胞减数分裂比较

Comparison of pollen mother cells meiosis in diploid and autotetraploid broccoli

观察二、四倍体青花菜花粉母细胞减数分裂过程并对分裂各时期参数进行统计分析。结果表明,同源四倍体花粉母细胞减数分裂过程与二倍体相比,中期Ⅰ染色体构型复杂,有多价体、四价体、三价体、二价体和单价体;中期Ⅰ及中期Ⅱ有部分染色体没有排列在赤道板上;后期Ⅰ及后期Ⅱ出现落后染色体、染色体桥及断片;后期Ⅱ和末期Ⅱ有染色体不同步分离及不等分裂的现象;四分体时期还出现二分体、三分体、含微核的异常四分体及多分体。同源四倍体花粉母细胞减数分裂平均异常频率高达31.5%,二倍体则只有10.2%的细胞表现异常,说明同源四倍体遗传稳定性比二倍体差,减数分裂不正常是同源四倍体青花菜育性降低的细胞学原因。

Pollen mother cells （PMC） meiosis and relevant parameters of diploid and autotetraploid broccoli were studied comparatively. Results showed that the PMC meiosis of autotetraploid was similar to the diploid except some particularities. In metaphase Ⅰ , multivalent, quadrivalent, trivalent, bivalent and univalent were observed and some of the chromosomes were found not to rank on the metaphase plate and so did in metaphase Ⅱ cells. In anaphase Ⅰ and anaphase Ⅱ cells, there were lagging chromosomes, chromosome bridge and fragment. During anaphase Ⅱ and telophase Ⅱ , chromosome segregation was not synchronous or equal, At tetrad stage, dyad, triad, tetrad with micronucleus and polyad appeared. The emergence frequency of abnormal phenomena in each stage of meiosis in autotetraploid and diploid were 31.5% and 10. 2% respectively, which indicated that the genetic stability of autotetraploid was lower than that of diploid broccoli and it was the cytologic reason of fertility reduction of autotetraloid broccoli,