芜菁的诱导同源四倍体减数分裂分析

细胞学上芜菁 (Brassicarapa)为正常的二倍体 ,具有 1 1的联会和 1 - 1的染色体分离。它的花粉母细胞 (PMC’s )在小孢子发生过程中的减数分裂前期 (M1 )无“B染色体” ,也无任何次级缔合。用 0 0 2 %的秋水仙碱水溶液处理 6h对多倍体的诱导形成明显。诱导出的同源四倍体构型中无联会基因 ,而成 1或 2次交叉的二价体、三价体和四价体。从多倍体逆转的有趣现象中发现 ,4 6 7%的诱导多倍体后来恢复成二倍体。不平衡的染色体分离普遍存在于诱导出的同源四倍体中 ,这就是导致生存能力不同的异常配子体出现的主要原因。异常配子体的结合 ,在芸苔属 (Brassica)现存种的演化中起到了重要作用

Meiotic Analyses in the Induced Autotetraploids of Brassica rapa

Cytogenetically B.rapa (2n) exhibited as normal diploid with 1/1 synapsis and 1-1 chromosomal disjunction.Its PMC's witnessed no "B chromosomes",neither any secondary associations were observed during microsporogenesis,at M1.Six hours treatment with 0.02% aqueous colchicine was effective for polyploidy induction.Meiotic configurations in the induced autotetraploids were asyndetics,one-or-two chiasmatic bivalents,trivalents and quadrivalents.Interesting phenomena of polyploid reversal is discovered,among the induced polyploids 46.7% revoked into diploids.Imbalance chromosomal disjunction was common in the induced autotetraploids,which mostly gave rise to aberrant gametes,with different viability.The union of such gametes aberrant has played an important role in the evolution of the present day Brassica species.