【文章內容簡介】 的，*老師是中國農業(yè)科學院蔬菜花卉研究所的在讀博士，*老師在科研工作勤勞、謙遜和務實的作風是我在今后學習和工作的楷模，作畢業(yè)設計的這幾個月里，他及時了解實驗的進展情況，并提出寶貴的建議，為我提供實驗所用的藥品和器材，使我的論文得以順利完成，在這里我真誠的向他說一聲：謝謝您*老師！ 在此我還要感謝生命科學學院的指導教師**老師，謝謝她在百忙之中抽出時間來修改我的論文，使得文章變得精煉嚴謹。 我還要感謝蔬菜所生物技術室的***、***兩位老師，他們也對本實驗提出了寶貴的、建設性的意見和建議。感謝原子能所的*老師， 通過交流，了解了很多關于包埋和切片的技巧，對實驗有很大幫助。除此之外，還有生物技術室的其他師哥師姐們，他們?yōu)槲覡I造了一個融洽的氛圍，平時也給我很多幫助，這里一并感謝。另外還要感謝**老師，謝謝他為我們聯系實習單位。文獻1：Twelve primer binations were used for the AFLP fingerprints, and 251 polymorphism bands obtained in this study. The polymorphism rate was relatively low (%) paring to the results from between cabbage subspecies of Brassica oleracea, which reflected that the head cabbage landraces are very similar in genotypes and have a relatively low diversity level among the genotypes analyzed. PIC has been used in marker parison studies concerning the analysis of level of our work, Relatively lower PIC values ( the average was ) also suggest that B. oleracea L. captatal cultivars represents a genetically low diverse population. The pairwise genetic diversity analysis which showed the much lower genetic distance () within cabbage landraces than that between cabbage and outgroup subspecies() strongly support the above conclusion as well.The UPGMA dendrogram tree of all accessions showed that Group I in present study is a distinct group of old latematuring landraces. Most of the landraces from North of China , Russia and Ukraine fall into this group, but the landraces from Northeast and Northwest of China were mingled. This result suggest that landraces from North of China have relatively relationship to that from their East Europe neighbor countries. The misalignment of other Northeast or Northwest geographical originated latematuring landraces showed a significant implication that these landraces was probably minglecrossed and evolved after head cabbage being introduce into different part of China. The fairly high gene flow(Nm=) in population analysis (Table 4)also strongly support this implication. Another important observation of this study was the clustering together of the morphologically contrasting genotypes of landraces from south of China in group II. Unlike the old latematuring landraces in group I, The morphotypes of the south of china originated landraces in group II are varing from pointhead to drumhead or earlymaturing to latematuring, but they did fall into the same group with high genetic similarity. The incongruity between morphological and molecular data may implied that there were no more signifant genetic distance between these main economical traits in cabbage cultivars than geographical origin diversity. The morphological groups analysis showed that the genetic distance of between groups() was not significantly greater than the average diversity of within earlymaturing groups（） and latematuring groups(). The low gentic distance between the early and late maturing groups implied that most polymorphisms in present study do not contribute to the phenotypic variation, which indicates that only a few genes are involved in causing the clear economical traits. This may also explain why the different morphotypes from South of China and other countries could clustered into group II together. Jinzaosheng(SO9), Jixinganlan(SO2) and Beijingzaoshu(SO8) are the most monly applicated earlymaturing breeding materials in China. In our study, they have high genetic similarity to typical Europe earlytype Golden acre(OE5), Copenhagen Market(OE4) which also were regarded as the elite foreign breeding materials. This result evidently confirmed the narrow genetic diversity of main cabbage breeding material in previous study by Fang (2000). Latematuring round and Flatballed Cabbages are the oldest group of heading cabbages and the earliest planted ecotype in China according to the historical document in China. This type of cabbage have ever been the most popular old cultivars in China and formed many cultivars in different region. With the aim of allocating the different geographical origin populations of this type of cabbage landraces in more defined groups, earlymaturing types were excluded for further analysis. The genetic diversities within populations of China were greater than other Countries populations but no significant genetic distance between Northeast, Northwest and South of China populations reflected both in genetic identity or genetic distance analysis. This result revealed that genetic diversity of latematuring in China had fairly greater genetic diversity for future cabbage breeding programs.One of the most valuable observation of this study was that the Russia and Ukraine population has closer relationships to North China populations and relatively farer relationships to other Europe country and Africa populations. This result based on molecular data confirmed the historical document’s record on latematuring cabbage cultivars which were introduced into china from Russia both from Northeast and Northwest of China. Though some of the historical document extrapolated that latematuring cabbage may introduced from Hollad or Other west Europe Countries through South of China　to North of China, here in our study, It was evidently that old latematuring landraces had much closer relationships to Russia and Ukraine populations than the west Europe countries populations. Even the latematuring landraces from South of China and East Asia countries had a closer relationships to Russia and Ukraine populations than to west Europe Countries populations. Considering of the fairly large diversity within