Researches On Molecular Genetics Basis Of Seed Nucleus' Variation Of The Ancient Ginkgo Trees In Suizhou And Anlu

Ginkgo biloba L.,belonging to Ginkgoaceae and Ginkgo,is one of the oldest remained tree species in gymnosperm and known as "living fossil".China is the native land of Ginkgo biloba and there are abundant ancient Ginkgo tree resources.Suizhou and Anlu of Hubei Province are two of the main concentrated distribution regions of ancient ginkgo trees in China.In this paper,based on of Fuhuimin's recearches about seed nucleus' characteristics and nutritional components' content of the ancient ginkgo trees in Suizhou and Anlu,the genetic variation of the ancient ginkgo trees here were studied by using ISSR molecular markers.Major results were as follows:(1) A total of 145 bands were amplified using 9 ISSR primers to the genome DNA of those 120 Ginkgo seed samples.Of these bands,116 were polymorphic,and the percentage of polymorphic bands(PPB) was 80.00%.At the total level,Nei's gene diversity(H_E) was 0.269,Shannon's information index was 0.401.It showed that seeds of ginkgo trees here had high genetic variation.(2) Percentage of polymorphic bands(PPB),observed number of alleles per locus (A_O),effective number of alleles per locus(A_E),Nei's gene diversity(H_E) and Shannon's information index(H_O) were used to reveal genetic variation within the 4 types populations.It showed that the variation extent decresased in sequence of Meihe type＞Maling type＞Yuanzi type＞Fozhi type.Among the four types,G_ST was 0.228,φST was 2.46%.This showed that the genetic variation was mainly distributed within types.(3) UPGMA cluster of 120 individuals was made based on Genetic similarity(GS). UPGMA cluster of these trees was also made based on seed nucleus' characteristics. Correlation analysis between two kinds of cluster showed that there was no significant correlation between morphological markers and ISSR molecular markers.(4) 6 ISSR primers which could amplify more bands were screened out from the 9 polymorphic ISSR primers.These effective primers were used to analyze the genetic variation of 100 seed samples of 10 ancient Ginkgo trees at individual level.As a result, 97 bands were generated,of which 90 bands were polymorphic based on haploid data and 39 bands were polymorphic based on diploid data,the percentage of polymorphism bands were 92.78%and 40.21%respectively.Heterozygosity test showed that the average number of heterozygous loci was 55 and the average heterozygosity was 56.91%.The highest heterozygosity was 68.04%,and the lowest was 45.36%.These results indicated that high heterozygosity existed in the Ginkgo trees in Suizhou and Anlu.Genetic variation at individual level was:PPB=55.16%,HE=0.203,H_O=0.300.Among the 4 seed nucleus types,G_ST was 0.139 andφST was 16.71%.(5) According to the amplification results with the 6 ISSR primers to the 10 Ginkgo individuals,similar but not exactly the same dendrograms were generated through molecular genetic clustering at haploid level and diploid level.The duster based on haploid level was more accurate than that based on diploid level,so the former was more credible than the latter.