波斯小麦×节节麦杂种F_1直接形成双二倍体的细胞遗传学研究

Cytogenetic Study on the Formation of Amphiploids in the F_1 Hybrids of Triticurn carthlicum Nevskivar and Aegilops tauschii Cosson

波斯小麦(Triticum carthlicum,AABB)与节节麦(Aegilops tauschii,DD)杂交,杂种 F_1出现可育性。不同组合的自交结实率21.25—39.72%。细胞学研究表明,可育性是由于杂种 F_1通过两种途径形成了未减数配子:第一,一部分花粉母细胞第一次分裂消失,只发生第二次分裂。即21条染色体集中到赤道面上之后,姊妹染色单体均等分离并移向两极,形成体积均等的二分体,二分体直接发育成未减数配子。第二,细胞质提前分裂,形成再组核。在第一次分裂的后期Ⅰ和末期Ⅰ,21条染色体向细胞中央移动形成再组核,同时细胞质提前分裂,形成体积不等的二分体,其中大子细胞含全套或大部染色体,再经正常的第二次分裂发育成两个未减数配子。未减数配子受精后形成双二倍体。

The fertile F_1 hybrids(2n=21)between Triticum carthlicum Nevski var.darginicum(AABB)and various accessions of Aegilops tauschii Cosson(DD)had theseed-set ranging from 21.25 to 39.72 percent.Cytological observations showed thatthere were two mechanisms on the formation of unreduced gametes which related with thefertility of the F_1 hybrids.(1)A part of the PMC's omitted the process of the firstmeiotic division and only undergone the second meiotic division.At metaphase,21univalents moved to metaphase plate and had two clearly visible chromatids like those atmitotic metaphase.Those univalents divided equationally at anaphase and produced sym-metrical dyads that matured into functional pollen grains.(2)First division restitution(FDR)with premature cytokinesis resulted in a asymmetrical dyad composed of oneanucleate cell and one cell with the restitution nucleous which included all chromosomes.A normal second division of the dyad followed to produced a triad of two unreducedmicrospores and one anucleate cell with a little cytoplasm.Amphiploids originated by theunion of unreduced gametes.