甘蓝型油菜与黑芥双倍体减数分裂的原位杂交分析

In situ hybridization analysis on meiosis of Brassica napus and Brassica nigra amphiploids

【目的】探明植物杂种后代减数分裂异常与花粉败育之间的关系。【方法】通过甘蓝型油菜与黑芥种间杂交和基因组加倍,获得芸薹属三基因组双倍体,采用基因组原位杂交方法,观察三基因组双倍体花粉母细胞的减数分裂规律。【结果】与单倍体相比,双倍体花粉育性得到一定恢复,但可育花粉的比例较低,只有10%-20%。基因组原位杂交结果显示,双倍体花粉母细胞减数分裂终变期染色体以形成同源二价体为主,但也有部分染色体形成四价体或六价体。四价体有3种形式：B基因组染色体形成的四价体、AC基因组染色体形成的四价体及B与AC基因组之间形成的异配四价体。减数分裂后期Ⅰ染色体均等分离的细胞占总数的70%左右,在第2次减数分裂期也观察到非正常分裂如非四分孢子、微核等现象。【结论】减数分裂过程中的染色体异常行为可能是导致花粉育性不高的重要原因;虽然不正常的减数分裂导致花粉育性下降,但双亲染色体的异源联会可为双亲遗传物质的交换提供条件。

【Objective】This study investigated the relationship between abnormal meiosis and pollen fertility of plant hybrid offspring.【Method】Trigenomic amphiploids between Brassica napus and Brassica nigra were obtained by interspecific hybridization and genome doubling.Genomic in situ hybridization（GISH）was carried out to observe chromosome behavior in meiosis of pollen mother cells（PMC）of the amphiploids.【Result】Pollen fertility of the amphiploids was determined and majority of pollen grains was sterile with fertile ratio of 10%-20%.Multivalents were formed as quadrivalents and hexavalents at diakinesis.The quadrivalents included autosyndetic quadrivalents of B genome,AC genomes and allosyndetic quadrivalents betwee B and AC genomes.The hexavalents also appeared in amphiploids at very low frequencies.Total chromosomes were segregated equally at about 70% PMCs at anaphase Ⅰ.At the end of second stage of meiosis,non-tetrads and micro-nucleus were also observed.Some abnormalities including chromosome bridges and laggards were observed at low frequency in some PMCs at anaphaseⅡ/Ⅱ.【Conclusion】The non-diploidized cytological behavior of these amphiploids contributed to their low fertility.Although abnormal meiosis decreased pollen fertility,heterologous recombination improved exchange of genetic materials between parents.