Genetic And Evolutionary Study Of Epimedium From Southwest China

The genus Epimedium involving in 56 populations 18 species, including 15 species from Southwest China and 3 species collected from Germany, were systematic studied with taxonomy, cytology, isozyme, hybridization and pharmic composition analyses. The results were as follows:A new species, E. yingjiangense, with 24 chromosomes from Yingjiang, Guizhou is described and published. Numerical taxonomy indicates that all species in the genus were separated easily in the dendrogram. In Section Diphyllon (from Southwest China), Series Brachycerae in the dendrogram was a distinct group based on the results of numerical taxonomy.The karyomorphology of 18 Epimedium species showed that the chromosome numbers of all species are 2n=2x=12, except E. yingjiangense 2n=4x=24. Tetraploid in the genus Epimedium was reported for the first time. All the Epimedium species, investigated in the present work, have a uniform karyotype with two types of chromosome, metacentric and submetacentric, except E. leptorrhizum and E. sagittatum, of which the sixth pair of chromosomes were subteleocentric. A secondary constriction was commonly found on the proximal side of the short arm of the chromosome pair 1 or 2. The karyotype symmetry of all investigated species was relatively primitive 1A,2A or 3A.The 45S and 5S rDNA loci were physically located by FISH for the first time. Several features of 45S and 5S rDNA loci distribution in the genus Epimedium can be discerned:(a) Chromosomeâ… andâ…¡of all fourteen species examined, except for E. shuichengense, hosted one pair of 45S rDNA sites, respectively. Most of the 45S rDNA sites gave clear signals and were positioned in the distal regions of the short arms, (b) All species studied of section Diphyllon were found with one pair of 5S rDNA sites localized in the interstitial regions of the long arm of chromosomeâ…£, and the two species of section Epimedium, E. alpinum and E. pubigerum, with two pairs of 5S rDNA sites localized in the interstitial regions of the long arm of chromosomeâ…£andâ…¤, respectively. (c) In section Diphyllon, all species of small flower taxa, except E. shuichengense, have three pairs of 45S rDNA sites, obviously more than species of big flower taxa, except E. davidii, with two pairs of 45S rDNA sites. (d)Based on the 45S and 5S rDNA distribution patterns and other chromosomal morphological characteristics, six pairs of chromosomes can be unambiguously identified in all fourteen Epimedium species.Analysis of flavonoids and icariin contents showed that the natural populations of E. acuminatum, E. wushanense, E. sagittatum reach the standard of the flavonoids and icariin contents by CCP (2005), their contents of flavonoids and icariin more than 5% and 0.5%, respectively, except the cultivated population of E. acuminatum. There are highly significant differences of the flavonoids and icariin contents among different species or populations, but no significance among E. acuminatum samples collected in July and in October.Genetic diversity using isozyme variation at 11 loci for six enzyme systems (EST, GLU, PGM, PRX, GPI, and SOD) showed the mean number of alleles per locus (Ap) varied small, ranging from 2.09 to 2.73. The mean percentage of polymorphic loci (P) of 18 species varied highly, ranging from 72.73% to 100%. The mean expected heterozygosity (He) ranged from 0.229 to 0.479 of 36 populations studied. Intrapopulational genetic diversity (HT) was 0.5981 while interpopulational genetic diversity (Hs) was only 0.3534. Obvious grouping of populations according to taxonomic species was found in the cluster analysis, suggestting that the species studied were independent, with a clear boundary.The hybridization was studied by self-cross, infra-populational cross, inter-populational cross of the same species and interspecific cross. Self-pollinations of nine populations indicated high incompatibility (at most 6.76%, usually 0% in capsule-set). Interspecific cross-pollinations showed high crossabilities in any cross combination(15.38%-92.44% in capsule-set), and the F1 seeds obtained high germination rates (>20%). The F1 hybrids of three interspecific cross combinations were raised to mature. The morphology, karyomorphology of somatic cell, and meiosis of PMCs of these F1 plants showed that they were all highly fertile (>76.10% in pollen viability), there were few structural differences in chromosomes among species, and most of them with 6 bivalents at MI of meiosis in PMCs were same with their parents. Simultaneously, abnormal chromosomal behaviors occurred in minority, such as chromosome bridge, unequal segregation of chromosome number, lagging chromosome, micronuclei and so on.