银杏特异种质核型进化趋势

Karyotype Evolution Trend in Ginkgo biloba Special Germplasms

首次以银杏幼叶为试材,采用压片法,对来自中国、美国、法国、日本及荷兰的21个特异种质的核型及进化趋势进行研究。结果表明:染色体数目均为2n=2x=24=4m+8sm+12st;染色体相对长度组成(RLF)种质间差异较大,并有普遍加长的趋势;平均臂比(MAR)、长度比(LR)及核型不对称系数(As.K.c)能较好地反映其进化水平,‘垂乳银杏’较原始,中国的‘叶籽银杏’比日本的‘叶籽银杏’更原始;遗传距离(Dij2)聚类发现,‘圣克鲁斯’、‘金秋’等6个种质更为进化。染色体绝对总长度(ATL)、相对总长度(RTL)、相对长度系数(IRL)、总形态百分比(TM)、平均臂比(MAR)、长度比(LR)和As.K.c的均值分别为7·64μm、8·33%、1·00、28·96%、2·94、2·71和71·04%。对银杏的细胞遗传学及进化进行探讨。

In Ginkgo biloba, significant morphological variations, such as tree form, leaf shape, and leaf colour etc. exist in current 21 germplasms from different countries. The karyotype and evolution trend of 21 G. biloba special germplams from China, USA, France, Japan and Holland were firstly studied by method of squash with the young leaves as test materials in this paper. The analysis results showed that： the karyotype of all 21 germplasms could be described as 2n = 2x = 24 = 4m ＋ 8sm ＋ 12st;the relative length formula（RLF） differs greatly among germplasms and appears a lengthening trend of chromosomes; the evolution level of G. biloba can be better reflected by the mean arm ratio（MAR） ,length ratio（LR） and asymmetrical karyotype coefficient（ As. K. c, % ）, ‘Tit＇ cultivar was more originative, and the Chinese ‘Yez.＇ cuhivar was more originative than ‘ Oha. ＇ cuhivar from Japan; the resuhs of cluster analysis of genetic distance（ Dij^2） indicated that ‘San.＇, ‘Am.＇, and other four cuhivars were further evolved. The mean values of the absolute total length（ ATL）, relative total length（ RTL）, index of relative length（ IRL）, total morphological pewentage（TM）, MAR, LR and As. K. c of chromosomes are 7.64 μm, 8.33%, 1.00,28.96% ,2.94, 2.71 and 71.04%, respectively. The cytogenetics and evolution of G. biloba were discussed in this paper.