| There were 14 species in Hemerocallis Genus on world, and about 11 species were distributed in China. It was played very important roles in landscape and gardening. Hence, germplasm collection, protection, evaluation and new germplasm creation for Hemerocallis is one of the most active areas in horticulture. In this thesis, the author contributed the results of genetic diversity analysis and intraspecies crossing. The main results as follows:1. The 21 samples of germplasm were clustered into four groups based on Euclidean distance with SAS6.1 and SPSS11.5 software. H. dumortierii and H. esculta were in the first group, H. nana, H. minor, H. middedorffii, H. forrestiii, H. plicata, H. x hybrida cv. JinWaWa, H. hybrida cv. ChongBangNaiYouJuan, H.×hybrida cv. ZiHong XiaoJiuBei, H. flava, and H. fluva were in the second group. H. middendorfii cv .ZR, H. middedorffii cv. JH, H.×hybrida cv. MZ, H.×hybrida cv. Lovely Lady, H.middendorfii cv. NingMengNaiYouJuang, H. Middedorffii cv. Kunming XingHuang were included in the third group. The last one has only one varity H. fulva var. kwanso.2. The pollen morphological and surface ornamental feature from 26 germplasm were been observed and patterns were compared based on ornamentation of SEM (scanning electron microscope). The results show that the pollen grains of daylily are generally ellipsoid or long ellipsoid with mono-furrow and reticulate sculptures. The furrow of pollen reaches to the two poles. Apertures of reticulate sculptures are erose or approximately rotundity with different width. The granules look like rugby or wart and are closely arranged to reticulate spine. The widths of spine are from 0.9 to 1.4 (um). The phylogenetic relationships between 26 germplasm were analysis based on the pollen morphology. It was shown that that H. citrina, H. lilioasphode, H. fulva, and H. fulva var. kwanso had a closer relationship, and next is H. flava, H. nana, and H. middendorffii. The far most groups is only one cultivar'MoZi'. The cultivars of"ZiRong"and"GaoNingMeng"have a closer pollen morphological and surface ornamental feature with H. fulva, H. nana and H. middendorffii than to H. citrina and H. lilioasphode.3. The genetic diversity and relationship have been analyzed based on genetic similarity coefficients and polymorphism rates with ISSR-PCR markers. The genetic distance among the different species ranged from 0.01226 to 0.4941, and Shannon (I) was 0.3597. The average genetic distances among species is 0.3241. The closest relationship were exited in H. lilioasphode, and H. citrina, And then is among H. citrina, H. fulva, H. dumortierii, H. fulva var. kwanso and H. nana. The Nei'Similarity coefficients and genetic distances were calculated by TFPGA and the dendrogram of 12 species and 1variation in the genus of daylily (Hemerocallis) was constructed with UPGMA. It was indicated that the germplasm of daylily included can be divided into five groups, and such result was similar to the conclusion based on plant morphologies and pollen ornamentation. Interestingly, there was a trend that the genetic distance various depend on flower shape and colour of daylily, and the genetic distance is going further gradually from yellow to orange, to purple and black purple.4. The new germplasm were created based on intraspecies crossing and the molecular identification by ISSR-PCR markers and 9 selections were made both among crosses, and plants within cross based on the plants morphological characters, such as plant heights, flowering durations, flower types and colors, etc..5. In the northern of subtropical area, evergreen plants for ground coverage are more perfect in the winter time. In this research, 4 germplasm of daylily with vigorous growth in winter were selected, which lived through -10.7℃in 2006 winter in Nanjing area. There were daylily varieties or species,'Chongban Naiyoujuan','Ningmeng Naiyoujuan', Hemerocallis lilioasphodelus and varity of H 148-27 from H. middendorffii.
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