Cytology And Technology Of Chromosome Doubling Of Populus Adenopoda Mazim

Populus adenopoda Mazim is a native tree in south China that grows in mountain area and used to produce timber. There was little research on its genetic improvement. It is almost in wild state. In order to meet the increasing requirement of wood production in south China, it is necessary to make a genetic improvement program on Populus adenopoda. In this paper, cytological genetics and technology of triploid breeding based on chromosome doubling were carried out. All results are as following:1. Microspore mother cell's meiosis of Populus adenopoda would start in 24hs when flower branches were cultured in water. It took 84hs to finish the process of meiosis. Flower buds' morphological characters changed according to the process of microspore mother cell's meiosis. Different meiosis stages were found not only in different clones, in floral branches from the same clone, but also in buds from the same floral branch and different anthers in the same bud. Maybe asynchronous meiosis was a kind of mechanism to adapt to rainy environment where they grew.2. The meiosis stages of megaspore and microspore had close correlation during their development. When the meiosis of megaspore mother cell (MMC) reached leptone, microspore mother cell had developed into tetrad. When male gamete developed into mononuclear, the megaspore mother cell arrived at bouquet stage. So according to the corresponding correlation between male gamete and female gametes, the meiosis stage of MMCs could be determined through screening that of pollen mother cells (PMCs) in the same environmental condition.3. The embryo sac of Populus adenopoda Mazim is Polygonum type. One-nucleate embryo sac formed at 3h after pollination. At 8h after pollination, the nucleate separated into two new nucleus undergoing mitosis and formed two-nucleate embryo sac which developed into four-nucleate embryo sac in 4h. A mature embryo sac would come into being in 20hs after pollination. An egg cell fused with one of sperms developed into a zygote, which took place in 44hs after pollination. The optimal pollination period was that the stigma lobed at 180℃ and excreted mucilage.4. Preliminary research on pollen chromosomes doubling by colchicine was carried out. The highest frequency of 2n pollen was only 20%, which may be result from the asynchrony of the PMC meiosis. Further studies on pollen chromosome doubling were needed.5. The technology of triploid induction through direct treating female gamete or inflorescenceswith colchicine after pollination based on the timely discrimination of megaspore meiosis stage and the optimal time of pollination was build. A number of hybrids were obtained, and their chromosome number would be screened in future.