青黑杨杂种三倍体花粉母细胞减数分裂染色体行为及其花粉变异研究

Meiotic chromosome behavior of pollen mother cells and pollen variation in triploid hybrid between section Tacamahaca and sect. Aigeiros of Populus

【目的】本研究通过分析青黑杨杂种三倍体的花粉母细胞减数分裂特征和配子变异规律,为进一步利用三倍体种质作为中介材料进行杨树染色体工程育种奠定基础。【方法】本研究以雌配子染色体加倍来源的‘哲引3号杨’ב北京杨’杂种三倍体WT-21及杂种二倍体WD-2雄株为材料,基于醋酸洋红染色压片观察,比较分析了两者花粉母细胞减数分裂染色体行为及花粉形态变异。【结果】(1)无论是三倍体杂种WT-21还是二倍体杂种WD-2,其花粉母细胞减数分裂染色体行为均非常丰富,存在高频率的染色体提前分离、落后染色体、微核等异常现象,反映了亲本基因组间较强的异质性。(2)WT-21和WD-2花粉母细胞减数第二次分裂过程均存在平行纺锤体、融合纺锤体、三极纺锤体等异常定向,而且在WT-21中还发生胞质提前分裂,共同导致减数分裂产物中二分体、三分体等的产生。(3)三倍体WT-21的花粉空瘪率达44.55%,高于二倍体WD-2;WT-21饱满花粉的直径显著大于WD-2,从花粉直径分布可推测出WT-21能产生少量未减数花粉;WT-21的花粉生活力为(1.08±0.44)%,显著低于二倍体WD-2(28.67%±2.04%)。【结论】由于倍性效应和杂合性的双重影响,青黑杨杂种三倍体的花粉母细胞减数分裂存在复杂的染色体行为,并对配子发育造成影响;利用三倍体的花粉进行授粉,可能获得非整倍体和四倍体后代,为杨树染色体操作奠定基础。

[Objective]Recently,techniques for induction of triploid hybrids between section Tacamahaca and sect.Aigeiros of Populus have been developed and a number of triploid germplasms were produced.However,reproductive developmental characteristics on these triploids are still in lack,which restrains their potential in sexual utilization.This study analyzed meiotic feature of pollen mother cells(PMCs)and pattern of gametic variation in a triploid hybrid,to lay a foundation for chromosomal engineering breeding of Populus using triploids as intermediate materials.[Method]In this study,meiotic chromosomal behaviors of PMCs and pollen morphological variation between a male triploid hybrid WT-21,which derived from hybridization of induced 2 n female gametes of P.pseudo-simonii×P.nigra‘Zheyin3#’and P.×beijingensis,and a male diploid hybrid WD-2 from the same combination were compared by the squashed technique with aceto-carmine.[Result](1)Whether for WT-21 or for WD-2,we observed the kinds of meiotic chromosomal behaviors,such as precocious chromosome migration,lagging chromosomes and micronuclei,reflecting high heterogeneity between parental genomes.(2)Misorientation of spindles during the second meiotic division,including parallel spindles,fused spindles and tripolar spindles,were found both in WT-21 and WD-2 and premature cytokinesis was produced in WT-21,which resulted in formation of dyads and triads in meiotic products.(3)In WT-21,44.55%pollen grains were shrunken,which was higher than that of WD-2.Compared with WD-2,diameter of spherical pollen grains in WT-21 was significantly bigger than that of WD-2.From pollen diameter distribution,we could presume that the WT-21 could produce a small number of unreduced pollen grains.Pollen germination test showed that the germination rate of WT-21 was(1.08±0.44)%,which was significantly lower than that of the WD-2(28.67%±2.04%).[Conclusion]Affected by both ploidy effect and heterozygosity,there are complex meiotic chromosomal behaviors during PMC meiosis in triploid hybrids,which would influence gametic development.Pollination with pollen of triploids would produce aneuploid and tetraploid offspings,laying the foundation for chromosome manipulation of Populus.