三種野生菸草間體細胞雜種染色體配對的研究

Abstract

三種單倍體菸草N. plumbaginifolia (n＝10), N. otophora (n＝12)與N. sylvestris(n＝12)的原生質體融合後，再生出許多不同的P＋S及O＋S染色體組組合的體細胞雜種，但得不到P＋O組合的雜種；而N. plumbaginifolia與N. otophora的原生質體融合，只得到PPO及PPPPOO的雜種，顯示這兩種菸草的染色體組間有相當程度的不相容性。同一癒合組織分化出來的植株，有時染色體套數、數目、或構造不同，是為嵌合細胞系。染色體構造的變異包括中節融合、染色體轉座及染色體片段等。當P與O染色體組同時存在時，染色體容易發生變異。三種單倍體菸草的染色體在減數分裂時幾乎不配對，表示同一染色體組內的染色體間不具同源性。PS雜種約有兩個二價體，OS雜種則只有0.6個二價體，而PPSS及OOSS雜種也多呈二價體，顯示三種菸草之間的親緣關係相當疏遠。由此推論，本研究所用的三種菸草皆是二倍體而不是同源或異源四倍體。

Several somatic hybrid plants of different P + S and O + S genome constitutions were regenerated through protoplast fusion of haploid Nicotiana plumbaginifolia (n=10), N. otophora(n=12), and N. sylvestris(n=12), but no P+O hybrids appeared. Only P P O and P P P P O O hybrid plants were obtained through fusion of N. plumbaginifolia with N. otophora protoplasts. There exist chimeric cell lines derived from spontaneous chromosome doubling and from variations in chromosome number and structure such as aneuploidy, centric fusion, translocation, and appearance of chromosome fragments etc. As P and O genomes exist in the same nucleus, chromosomes of the P genome show variation easily. Haploids of the three species show univalents at diakinesis and metaphase I, indicating that there is no homology among chromosomes within each of these genomes. There are about two bivalents in P S hybrid, 0.6 in O S hybrid, and nearly complete bivalent formation in P P S S and O O S S hybrids, indicating that the three species are phyletically distant. Thus, the Nicotiana species used in this study are diploid, rather than allo- or autopolyploid as has been suggested by other investigators.