芍药属组间杂种‘Bartzella’的减数分裂观察

Meiotic observation on‘Bartzella’,an intersectional hybrid of Paeonia

【目的】芍药属组间杂种大部分为三倍体,普遍高度不育,极少获得杂交后代。‘Bartzella’是个观赏性好且有少数杂交后代的组间杂种,减数分裂染色体行为观察可为揭示其极低可育性的形成机制提供参考。【方法】以‘Bartzella’花药为材料,用压片法观察花粉母细胞减数分裂的染色体行为。【结果】(1)‘Bartzella’的花粉母细胞在中期Ⅰ形成大量单价体,后期Ⅰ产生不同类型的染色体非整倍分离,占比高达89.13%。(2)减数第1次分裂中,染色体桥和断片出现在27.20%的花粉母细胞中;减数第2次分裂中,比例升到47.68%。(3)中期Ⅱ的纺锤体定位异常较普遍,融合纺锤体占27.06%,三级纺锤体占12.84%。(4)减数分裂产物中包含高达72.41%的二分体和13.43%的三分体,其产生未减数配子所占比例约为67%。【结论】减数分裂中染色体非整倍分离以及染色体片段缺失可能是‘Bartzella’高度不育的重要原因。融合纺锤体、三级纺锤体以及减数分裂Ⅱ结束时胞质分裂异常可导致未减数配子形成。大量的未减数配子可使‘Bartzella’在多倍体育种中具有一定潜力,但倍性间杂交障碍可能限制其杂交亲和性。

[Objective]Most intersectional hybrids in Paeonia are triploids and generally sterile,producing a small number of hybrid offspring.Observing the meiotic chromosome behaviors of‘Bartzella’,an intersectional hybrid with high ornamental value and several hybrid offspring,can provide insight into the formation mechanism of its low fertility.[Methods]The study utilized the anthers of‘Bartzella’as materials to observe the meiotic chromosome behaviors of pollen mother cells(PMCs)through the squash method.[Results](1)In metaphaseⅠ,a significant number of univalents were formed in‘Bartzella’PMCs.In anaphaseⅠ,various types of chromosomal aneuploid segregation were observed,accounting for up to 89.13%.(2)During the first meiotic division,chromosome bridges and fragments were found in 27.20%of the PMCs;during the second meiotic division,this percentage was increased to 47.68%.(3)In metaphaseⅡ,spindle positioning abnormalities were relatively common,with fused spindles accounting for 27.06%and tripolar spindles accounting for 12.84%.The meiotic products included up to 72.41%of dyads and 13.43%of triads,which could generate unreduced gametes accounting for about 67%.[Conclusion]Chromosome aneuploidy segregation and loss of chromosome segments during meiosis may be the primary causes of the high sterility of‘Bartzella’.Fused spindles,tripolar spindles,and abnormal cytokinesis at the end of second meiotic division may result in the production of unreduced gametes.The significant number of unreduced gametes might give‘Bartzella’the potential polyploid breeding.However,interploidy hybridization barriers could restrict its hybrid affinity.