| Dongzao jujube(Zizyphus jujuba Mill. cv. Dongzao) is regarded as the best late maturing and fresh cultivars of Chinese jujubes. With the rapid development of Dongzao jujube's industry in recent years, such problems as the degradation of fruit quality, trying to be first, blind introduction happened. Three comparison orchards, which located at Zhanhua county in Shandong province, Huanghua and Cangxian county in Hebei province were established in order to probe the cause of fruit degradation and variation of quality. Such indexes as the fruit quality, the fruit stone phenotype, components of fruit nutrients, food sensory evaluation, cold hardiness and photosynthetic physiology were analyzed at these three comparison orchards for 4 years.The paper also carried a jujube cDNA library construction, sequencing and bioinformatics analysis; pollution-free prevention and the feasibility of cross breeding of Dongzao jujube were also studied in this work. Following was the key results in this thesis.1. There was no qualitative difference for Dongzao jujubes of different provenances in the same comparison orchard and in the same year. But the difference of Dongzao jujube between different orchards and different years was significant. This results showed that the phenotypic and fruit quality of Dongzao jujube were mainly contributed by environmental conditions, cultivation and management measures, but not by provenances. Because the long-term effect of mutant and artificial selection, there are still variations for individual plant. The direction of genetic improvement was individual selection not group selection.2. The N/P of the leaf of Dongzao jujube ranges from 11.11 to 13.54, which indicated Dongzao jujube was a kind of vegetation type influenced by the content of N. The contents of N, P, K in Dongzao jujube leaf were stable from July to September, which was the optimal sampling period for nutrition diagnostic.3. Photosynthetic characteristics of Dongzao jujube were greatly influenced by the environment varation, which were different with the sampling time, place and sampling part. The diurnal variation of Pn in Cangzhou region showed obvious asymmetry double curve, while annual change showed a single peak curve, Dongzao jujube was decline photosynthetic rates plant at noon.4. The sudden change of air temperature is an important factor which leads to freezing of Dongzao jujube, so the protection should be based on the actual situation in different areas. Freezing damage which was caused by extreme low temperature even should be to prevented in Dongzao jujube normal region. Blind introduction should be avoided, especially for those places which temperature conditions are not suitable for the cultivation of Dongzao jujube. Some protective measures were necessary for cultivation. There was some difference between different provenances of Dongzao jujube, but no trees suffered from freezing injury under natural situation in Cang County, Hebei Proviance of China.5. The fruit of three different development stages were equally mixed to construct a fruit cDNA library.1060 EST sequences were obtained by one run sequencing from 5' end which was randomly picked from cDNA library.628 Unigenes were obtained after analyzed by cross-matching and CAP3 software. Compared with Uniprot database,534 Unigene sequences were identified with known homologous genes, accounting for 85% of the total number of Unigene. A GO analysis was carried out by ESTPiper, an online software, which resulted that 273 Unigene sequences could be classified in the "molecular function", "biological process" and "cellular component". Some fruit quality related genes, such as MYB transcription factor, Cinnamyl alcohol dehydrogenase, GDP-mannose transporter, and some genes associated with jujube fruit ripening genes, such as the ACC oxidase, superoxide dismutase, heat shock protein, also could be identified. Furthermore, the Unigene sequences were used for EST-SSR analysis, which revealed 147 SSRs in 116 EST sequences. The dinucleotide and trinucleotide repeats were found as the main motif types.6. Based on pollution-free pest control and pollution-free cultivation, "Technical specification for the fruit production of Ziziphus jujube cv. Dongzao at green food AA grade " was compiled, which provides a theoretical basis and working instruction for the pollution-free cultivation of Dongzao jujube.7. There were difficulties in artificial crossbreeding for Dongzao jujube. The main reasons for failure of crossbreeding were asynchronous flowering of the related cultivars, delaying pollination, low fruit-setting rate, very low kernel percentage, embryo abortion, and damage induced by Lygus bug and so on.
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