| The rosebush and the lily of the valley were planted in ancient Egypt and Syria before three thousands years according to historical materials. The earliest recordation about flower planting in China is that the Wu Guo's king-fu chai had ever constructed the phoenix tree garden to planted a great deal of flowers and trees at hui ji, China.Flower industry has become the one of the livingest industry of the world. The flower breeding has been gotten more and more recognition by plant breeders because of the development of economy and the stimulation of market. It promotes the continued development of flower breeding that the people's request for new varieties and high character. Breeders have bred a great deal of new flower varieties by taking routine cross breeding, radiation breeding, tissue culture breeding, polyploidy breeding, and spaceflight breeding etc. . Especially since 1990s, with the development of molecular biology and genetic engineering technique, it has become a study hotspot using transgenic technique breed new varieties. We can get anticipatory new materials (new varieties) of plants cultivated after the target gene is inducted directly into plant cell or tissue. They provide a more effective new method for direct breeding of flower. There are several tens kinds of flowers have gotten transgenic plants at present.Chrysanthemum is one of the ten famous flower originated in China with two thousands years history. And the earliest words recordation about chrysanthemum was in Li Ji. Chrysanthemum is not only population in China, but also far and wide in many countries of world. There are 7000 varieties of chrysanthemum in the world and more than 3000varieties in China, but abundance resources of chrysanthemum haven't been made full use. One cause is that most of them bloom regularly about November; a few of them bloom at summer or early autumn. Another factor is that most of varieties blooming early have small flowers and a little kinds and colors. The flowering time is the key for the development of chrysanthemum on some aspects. Most of breeders in the world are engaged in researches of flower color, flower shape, adverse-resistance in breed of chrysanthemum. The treatment of illumination as a normally method for changing flowering time with high cost and ark for strict technique but does not fit all kinds of chrysanthemum. This is one of the reasons for cut chrysanthemum is lack ofabundant kinds in the market of at present. In order to overcome the difficulties of flowering time, Li Hongjian in Nan Jing agricultural university began breed new varieties of cut chrysanthemum at 1986 with routine hybridization method, which varieties cover many flower shape and color with breeding more than hundred varieties of chrysanthemum, but the problem of chrysanthemum's flowering time is not been solved completely. There are several difficulties in the traditional breeding methods, such as the great uncertainty, the highly difficult hybridization, the longer breeding periods and the difficulty of breaking up gene linkage. The excellent target genes can be transferred directly if you adopt transgenic method and take the foreign gene into chrysanthemum and make the flowering time of it produce anticipate changes. Furthermore, the advantages of more stability and shorter breeding even enriched the hereditary resources by this method.The flowering time of plants is controlled by genes according to other researches. The expression of the genes is modulated by environmental factors and the growth status of cell itself. Environmental factor modulate the grnes of flowering time depend on photoperiod and jarovization. Some plants are sensitive to the length of illumination, and they are divided into the long-day plant and the short-day plant depend on flowering must undergo a certain long-day or a certain short-day. Some plants' flowering must under go a certain time induction of lower temperature, and the promotive effect of lower temperature is named jarovization. The other plants can flower without... |
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