黄瓜同源三倍体创制及减数分裂行为观察

Creation and Meiosis Studies of Autotriploid in Cucumber

采用常规杂交法研究黄瓜二、四倍体杂交过程中亲本育性、授粉组合及亲本基因型对杂交结实率的影响,并利用减数分裂制片法对获得的黄瓜同源三倍体进行了花粉母细胞减数分裂行为的观察。结果显示:(1)同源四倍体自交结实率比较低(13.0%～14.5%),可能与其花药内所包含的正常花粉粒比例小及花粉管萌发长度较短有关。(2)二、四倍体杂交组合的结实率很低(0.26%～1.02%),但在两种配组方式之间存在着明显差异,即以同源四倍体黄瓜为父本和二倍体黄瓜为母本的杂交结实率比较高,反之则杂交结实率比较低。(3)在二、四倍体杂交过程中,二、四倍体的基因型对杂交结实率的影响较大,以杂交双亲同属一个基因型的杂交效果较好。(4)同源三倍体花粉母细胞减数分裂过程与二倍体基本相同,但存在较高频率的染色体异常行为:中期I染色体构型复杂,在大多数花粉母细胞中可观察到单价体、二价体、三价体的存在;中期Ⅰ和Ⅱ有少数染色体游离于赤道板外;后期Ⅰ和后期Ⅱ常出现落后染色体、染色体桥及细胞分裂不同步现象,其最终结果导致了不正常四分体和不可育配子的形成。(5)同源三倍体花粉粒的平均可染率和萌发率分别为18.8%和11.3%。研究结果表明,黄瓜二、四倍体正反交能直接获得同源三倍体材料;同源三倍体花粉母细胞减数分裂异常导致不育配子的形成是引起其育性低的细胞学原因;同源三倍体的部分育性为通过同源三倍体的回交来选育初级三体系奠定了基础。

The effects of fertility of parents, pollination combination and genotype of parents on seed-setting in hybridization between autotetraploid and diploid were analyzed with conventional cross method,and the meiosis of pollen mother cells （PMCs） in autotriploid cucumber was also studied using meiotic analysis. The results showed： （1）The low seed-sets （13.0%-14.5%） of the autotetraploidy combinations may be attributed to the presence of more abnormal pollen in the anthers or length of pollen tube. （2）The seed-sets of cross combinations between autotetraploid and diploid were very low （0.26 %- 1.02%）, but there were obvious different seed-settings between the two mating methods. If the autotetraploid cucumber was used as the male parents and the diploid as the female parents, higher seed-sets were found in the hybridized combination. However,the seed-sets in the combinations were lower if the diploid cucumber was used as male parents. （3）Besides,the effect of genotype of parents on production of autotriploid was biggish; the average percentage of autotriploid production was higher when autotetraploid and diploid were belonging to same genotype. （4）The PMCs meiosis of the autotriploid was similar to the diploid. However, the higher frequency of abnormality was observed in autotriploid. Variable chromosome configurations, e. g. univalent and trivalent were observed in most PMCs of the autotriploid at metaphase I ~ In additional, some of the chromosomes were found not to rank at metaphase plate in metaphase I and metaphase II cells. At ana- phase I and anaphase U ,chromosome lagging, bridges and asynchronization were frequently observed as well, which led to formation of abnormality tetrad and inviable gametes. （5）The average percentages of pol- len dryration and pollen germination were 18.8~ and 11.3~ ,respectively. These findings indicate that au- totriploid could obtain directly from autotetraploid by diploid crosses. The decrease in fertility is due to ir- regularities of chromosome behavior during meiosis with the formation of imbalanced and non-viable gam- etes in autotriploid cucumber. Meanwhile, autotriploid was partially fertile which established groundwork for the selection of the primary trisomic cucumber by autotriploid backcross method.