Abstract:

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.' cultivar was more originative than ‘Oha.' cultivar from Japan; the results of cluster analysis of genetic distance(D_ij²) indicated that ‘San.', ‘Aut.', and other four cultivars were further evolved. The mean values of the absolute total length(ATL), relative total length(RTL), index of relative length(IRL), total morphological percentage(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.

Key words: Ginkgo biloba germplasm, karyotype evolution, asymmetrical karyotype coefficient, genetic distance