中文摘要：

低能离子注入技术作为生物物理诱变的一种新型技术,在园艺植物育种方面具有很大的应用潜力,但其诱变的分子机理目前知之甚少。文章对Fe＋离子注入诱变的白洋淀红莲（Nelumbium speciosum Willd）突变体及其对照的基因组进行RAPD研究,并将突变体和对照在辐射敏感位点的条带进行克隆测序及DNA序列分析。在已优化好的RAPD体系下扩增,从110条随机引物中筛选出了10条可以稳定扩增出显著特异条带的引物,引物多态性为9.09%。将这10条引物扩增出的辐射敏感位点的条带进行克隆测序,并进行序列比对。结果显示：突变体的总碱基突变频率为0.87%,6个突变体的碱基突变频率存在着差异;碱基突变类型包括碱基的颠换、转换、缺失、插入,在检测到的159个碱基突变中,单碱基置换的频率（61.01%）高于碱基插入或者缺失的频率（38.99%）,在碱基置换中,转换的频率（44.65%）是颠换频率（16.35%）的2.7倍,其中C/T之间的转换所占比例最大,A→G和A→T也具有较高的替换频率;构成DNA的4种碱基均可以被离子束辐照诱变发生变异,除了没有C→G的置换外,每一种碱基都可以被其他的几种碱基所置换,但是胸腺嘧啶（T）具有较高的辐射敏感性。通过对碱基突变位点周边序列的分析发现,嘌呤突变位点的周围嘌呤碱居多,嘧啶突变位点的周围嘧啶碱居多。研究结果为揭示低能离子注入诱变作用分子机理提供了依据。

英文摘要：

Ion implantation,as a new biophysically mutagenic technique,has shown a great potential for horticultural plant breeding.Up to date,little is known about the mutation mechanism of ion implantation at the DNA level.To reveal the mutation effect of Fe＋ ion implantation on Baiyangdian red lotus,the random amplified polymorphic DNA（RAPD） was used,and then the bands of mutants and the control in the radiation-sensitive sites were cloned to be sequenced for comparing their DNA sequences.The results indicated that the total base mutation rate of mutants was 0.87%,and there was different in the six mutants.The types of base changes included base transition,transversion,deletion,and insertion.Among the 159 base changes detected,the frequency of single base substitutions（61.01%） was higher than that of base deletions and insertions（38.99%）,and the frequency of base transitions（44.65%） was 2.7 times of that of the base transversions（16.35%）.The transitions between C and T accounted for largest proportion,A→G transitions and A→T transversions were also present at high frequency.Adenine,thymine,guanine or cytosine could be replaced by any of other three bases,except that there was no C → G substitution.However,thymine was more sensitive to the irradiation than other bases.In our study,we found many purine bases around the purine mutational sites,and many pyrimidine bases around the pyrimidine mutational sites.These will further help us to understand the mechanism of mutagenesis by ion implantation.