Studies On The Main Cultivars Fingerprints And Genetic Mapping Of Ginkgo Biloba L.

Ginkgo biloba L. is the only extant representative of Ginkgoales, and has high economic and scientific values.11 seed traits of 44 Ginkgo cultivar were studied. The results showed that the variances of weight traits were great while the variances of shape traits were low. The lowest value of weight variance (weight per seed, 12.95%) was still significantly higher than that of shape traits (nut width, 12.95%). The results of classification by principle analysis method differed greatly from those by traditional method.The genetic diversity of the 44 cultivars was analyzed by RAPD and ISSR methods. 74 polymorphic loci were detected and the average effective number of alleles, the average Nei's gene diversity, and the average Shannon's information index were 1.6343, 0.3636, and 0.5373 respectively. The polymorphic locus percentage of RAPD and ISSR were 24.6% and 17.2% respectively. The genetic diversity revealed by ISSR method was higher than that by RAPD method, while the standard errors of the parameters estimated by ISSR were lower. The relative relationship of the cultivars concluded by cluster method with molecular data was different from that concluded by seed traits.A Ginkgo linkage map was constructed in a mapping panel with 95 megagametophytes. 1220 RAPD and 110 ISSR primers were screened, and 131 RAPD and 7 ISSR primers were polymorphic. 196 segregated markers were generated, among which 181 markers segregated in a 1 present to 1 absent ratio. Through multipoint linkage analysis, 164 markers were assigned to 12 different linkage groups. It covered a total genetic distance of 1742.2cM. The average distance between markers was 10.82 cM, and the maximum distance covered by a single linkage group was 261.2cM while the minimum was 62.4 cM. It was estimated that the Ginkgo genome genetic distance was 2200.73 cM.The sequences of Ginkgo ITS region were sequenced in a 10 sample set. The entire ITS and 5.8S rDNA gene region was 1224-1226 bases long with an ITS1 of 821-823bp, an ITS2 of 241bp and a 5.8S of 162bp. 28 variable sites were detected among which 6 sites were parsimonious informative.An evolutionary tree containing 18 taxons was reconstructed using 8 gene sequence data (minus 3rd codon position transition information), which convered 3 plant genomes, by maximum parsimony method. The results showed that conifers were the closest relatives of Ginkgo with gnetales being nested within conifers, and cycads were the most primitive in gymnosperms. The results were supported by high bootstrap values.