| Tree peony is one of Chinese endemic flowers with long history of cultivation. Tree peony breeders in our country have released hundreds of varieties after a long-term efforts, which greatly have enriched the tree peony variety group and been used in landscape gradually and widely. However, almost parents materials in breeding are from Subsect Vagiatea, rarely Subsect Delavayanae. Recently, staffs of Ex-situ Conservation Center located in Luoyang have released many excellent distant hybridization progenies bred by Subsect Vagiatea and Subsect Delavayanae. This paper chose37distant hybrids in Ex-situ Conservation Center (27intersubsect hybrids and10intrasubsect hybrids) and20parents varieties as the materials, and investigated on their morphological characters, pollen morphology and chromosome karyotype and uses numerical taxonomy to analyze the distance of characters and cases. The paper aimed at identifying the inheritance of tree peony distant hybridization and providing reference for future hybrid work. The main conclusions are as follows:1. Pollen deformity rate of the intersubsect hybrids is high and the germination rate is very low. On the contrary, pollen deformity rate of the intrasubsect hybrids is low and the germination rate is high. Pollen morphology of the57varieties are almost ultra-subprolate, except that’Ye Guang Bei’is subprolate. Most of the intersubsect hybrids pollen grain size are smaller than their parents, and the extine sculpture are consistent with the male parent in most cases. The pollen grain size of intrasubsect hybrids is inbetween or bigger than parents’. Two obvious different extine sculpture types appear at the same time on some varieties’pollen.2. Hybridization progenies present some tendencies on heredity of main ornamental characteristics: when female parent is single form varieties, the progenies’flowers gradually develop towards more advanced flower form in condition of the male parents flower whorls increasing. Heredity of the flower colors does not present obvious father-side trend or mother-side trend. The white color has weaker heritability comparing with other colors, while yellow is stronger. Petal suffused with blotches at the base is dominant compared with petals no blotches. Discs texture and hair-covered or not carpels are linked in heredity process. And the leathery discs and the hair-covered carpels are dominant characters. Flower diameter and leave type agree more with their female parents, but the leave type is also highly correlated with the discs texture.3. The chromosome numbers of57materials are all10and diploid. The length of them is in the range of7.80-22.00μm, the arm ratio is in1.85～2.59, and the asymmetry index of karyotype is in59.25%～65.65%. On the whole, karyotype of them is relatively symmetrical. Three karyotype formula are found:(1) K (2n)=10=4m+4sm+2st;(2) K (2n)=10=6m+2sm+2st, this type occurs most frequently;(3) K (2n)=10=8m+2st. Karyotype type are all2A and chromosome satellite is not found.4. R-cluster analysis based on selected39characters shows that these characters remain independent decentralized state rather than clustered into some distinct categories, few of characters are pairwise correlation. Q-cluster analysis based on intersubsect hybrid groups shows some hybrids of the same parents are in one group, some are not. Most of the male parents are in distant relatives with P. lutea. Except ’Cai Pan Xian Rui’, the left24hybrids may be true hybrids of the intersubsect. Q-cluster analysis based on Subsect Vagiatea suggests most of the hybrids owning a common parent can gather in one group. Principal component analysis based on33morphological characters demonstrates that there are11principal components totally. Among the11principal components, reproductive organs were seleceted to represent main morphological characters. Thus, these reproductive organ characters possibly play a more important role in the classification and identification of tree peony varieties. |
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