| The objective of this research is to study the cross-compatibility between peonies and between peony and tree peony. This study selected some species with superior characteristics to compose cross-combinations. This species includ peony species'Fen Yu Nu','Zi Feng Yu','Hong Pan Tuo Jin'and tree peony species P.ostii.The cross-combination are'Zi Feng Yu'×'Hong Pan Tuo Jin','Fen Yu Nu'×'Hong Pan Tuo Jin','Zi Feng Yu'×'Fen Yu Nu','Fen Yu Nu'×P.ostii.'Zi Feng Yu'×P.ostii..First, the abilities of male hypogonadism were measured by determination of pollen viability and observation of stamen before pollination.After pollination, the cross fertilization of the hybrid embryo development were observed by fluorescence microscopy and cytology respectively. Combining with hybrid seed rate, the barriers and stages of the crossing-hybrid were identified and the cellular mechanism of hybrid incompatibility was clarified. This can offer the most direct theoretical basis to improve the hybrid cross–compatibilities and provide the theoretical direction for peony breeding.1. Definite the abilities of malehypogonadism by determination of pollen viability and Observation of stamen1)Observed and determinated the viability and germination rate of'Fen Yu Nu','Hong Pan Tuo Jin'and P.ostii.with semi-solid agar method before pollination. The results as follows:(1) The pollen can be divided into normal and abnormal pollen grains, the former are cylindrical spherical, larger, with apertures and able to carry out normal germination, belonging to pollen is viable; the latter are ellipsoid, significantly smaller and can not germinate.(2) The rate of viable pollens of'Hong Pan Tuo Jin'and P.ostii. is 92.4% and 91.2% seprately, the average germination rate percentage of po llen can up to 85.1% and 88.0%. So enough maturity pollens, and the pollen does not become obstacles to the cfertilization. (3) But the rate of viable pollen of'Fen Yu nu'are 40-50%, the average germination rate of pollen only can reach to 30%-50% and the number of abnormal pollen can reach to 50% -60%. So there are obstacles in fertilization if'Fen Yu nu'is the male parent. So the hybrid combination of'Zi Feng Yu'×'Fen Yu Nu'was abandoned in the following study. The cytological observation of stamen development in'Fen Yu nu'was carried to find the reason of abnormal pollen.2) Discuss the cause of abnormal pollen from the development processes of small spores and male gametophyte of'Fen Yu Nu'.According to the differences in viability and germination rate of pollen, the development of small spores and male gametophyte were observed and compared between'Fen Yu Nu','Hong Pan Tuo Jin'and P.ostii.The results show that: there are 4 small anther sporangia. Anther wall structure is dicotyledonous type, tapetum is glandular. (1)The meiosis of the mother pollen cells of viable pollen is simultaneous type; tetrads are mostly tetrahedral, slightly symmetrical shape, mature pollen was 2-cells. (2) Microspore mother cell of abnormal pollen can not carry out normal meiosis; the tetrad is fifth and there is chromosomal bridge abnormaly.2. Analyze the cross fertilization by fluorescence microscopy.The fertilization of four crosses was observed within 72 hours after artificial pollination by fluorescence microscopy. There are two states of flowers after hybridization, one keep open and the other is bagged.1) If flowers bagged after hybridization, some pollen tubes can be observed drilling into the ovule in the cross-combination of'Zi Feng Yu'×'Hong Pan Tuo Jin'; pollen tubes drilling into the ovule will be more if flowers keep open.2) The pollen tubes cannot drill into the ovule in the cross-combination of'Zi Feng Yu'×P.ostii and'Fen Yu Nu'×P.ostii and'Fen Yu Nu'×'Hong Pan Tuo Jin'. However a lot of collose was found in papillose cells of stigma, tubes became twisted, swelled or growing at irregular distance on the stigma; few of pollen tubes could enter into styles through stigmas in the cross-combination of'Fen Yu Nu'×'Hong Pan Tuo Jin'.3. Cytological observation of the development process of female parent's embryo and endosperm at the state of nature and after hybridization by paraffin section method. The results showed:1) The development are normal of embryo and endosperm at the natural and hybridization state of'Zi Feng Yu'and'Zi Feng Yu'×'Hong Pan Tuo Jin'. But the whole process is lacked. The form of endosperm developments is nuclear type, including free nuclear stage and cells stage. Endosperm haustorium can be found on the chalazal.2) Disintegrations exists in both pollination and self-pollination status of'Fen Yu nu'and'Zi Feng Yu'×P.ostii. The disintegration of embryo is caused by the disintegration of endosperm. But it may also be caused by the abnormality in the process of double fertilization.4. Compared the setting rate of different treatments in differenthybridizationThis study has couted the seed rate in pollination and self-pollination status of'Fen Yu Nu'and'Zi Feng Yu'respectively. The conclusions were as follows:(1)The seed setting rate of'Zi Feng Yu'is 50%-70% in natural state and increased to 70%-80% after hybridization. (2)The seed setting rate of'Fen Yu Nu'only is 13%-15% in natural state. Although the rate percentage inceased after hybridization but only 20-25. (3)The seed rate percentage of P. lactiflora×P.ostii is zero.These differences are consistent with the cytological observation.The cellular mechanisms are different between different combinations. (1)The combination of'Zi Feng Yu'×'Hong Pan Tuo Jin'exhibited high hybrid compatibility, consistent with cytological observation: A. the pollen viability and germination of'Hong Pan Tuo Jin'are high B. pollen tube could reach to ovule smoothly C. embryo could develop normally. (2)The hybrid incompatibility of'Fen Yu Nu'×'Hong Pan Tuo Jin'was mainly caused by obstacles before fertilization and abortion of hybrid embryos. (3)The hybrid incompatibility of P.lactiflora×P.ostii mainly due to genetic distances and hybridization barriersThese conclusions have laid the foundation for the direction detection hybrid effectively.'Zi Feng Yu'is a good hybrid parent because of high seed rate. While'Fen Yu Nu'is not appropriate parent because of its pollen abortion. |
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