基于相关序列扩增多态性分子标记的桂花栽培品种演化分析

Evolution analysis of sweet osmanthus(Osmanthus fragrans) cultivars based on sequence-related amplified polymorphism molecular marker

为了进一步揭示桂花栽培品种的演化历程,为桂花育种工作提供借鉴,采用相关序列扩增多态性分子标记技术和毛细管电泳技术,对45份桂花材料进行遗传多样性和群体结构分析,以木犀属中最为原始的牛矢果(Osmanthus matsumuranus)为外部群体,构建桂花栽培品种系统发生树,计算不同演化水平两性花品种的比例,分析桂花性别系统进化情况。结果显示:10对高多态性引物共检测到137个多态性位点,平均每对引物13.7个位点,多态性信息含量为0.202 8~0.302 7;Nei遗传多样性指数为0.220 3~0.350 2;Shannon多样性信息指数为0.348 3~0.519 3。45份桂花材料分为7个亚群和1个混合群体,亚群间遗传分化明显,基因交流较少。系统发生树表明,桂花栽培品种演化历程大致分为10个阶段,大部分银桂品种和四季桂品种最先形成,雄性丹桂品种最晚形成,其他品种处于演化的中间阶段。两性花品种比例随着演化水平的增高呈现逐渐降低的趋势,证明桂花的雄全异株性别系统是雌雄同花演化为雌雄异株的中间状态。此外,桂花花色连续变异可能受到多个CCDs家族同源基因突变的影响,而遗传漂变导致新等位基因丢失,这可能是野生桂花罕见橙红色个体的原因。

Sweet osmanthus(Osmanthus fragrans)is one of the top ten famous native horticultural plants in China.According to different flowering seasons,flower colors and inflorescence types,the cultivars are divided into four groups:O.fragrans Asiaticus Group,O.fragrans Albus Group,O.fragrans Luteus Group and O.fragrans Aurantiacus Group.Despite long-term cultivation of Osmanthus,little information was recorded on the formation of so many cultivars.O.fragrans Asiaticus Group was considered as the most primitive cultivars,and the ones with light color flowers formed earlier,then followed by deep color flowers.The cluster results based on various types of molecular markers were quite different from traditional classification system,indicating diversity of phenotypic traits might account for a tiny part of the whole genetic diversity of sweet osmanthus.However,at present,few studies can give evidence to further understand the evolution process of sweet osmanthus cultivars.In this study,to further understand the evolution theory,a rooted phylogenetic tree for the cultivars of sweet osmanthus was constructed based on population structure analysis through sequence-related amplified polymorphism(SRAP)technology.Forty-five cultivars were used as plant materials;O.heterophyllus,O.fordii,O.cooperi“Yujie”and O.cooperi“Xuegui”were used as controls,and O.matsumuranus was used as an outgroup.Ten pairs of SRAP primers with high polymorphism were applied to amplify DNA of all samples,and the fragments were examined by capillary electrophoresis.POPGENE1.32software was applied to analyze genetic diversity and genetic differentiation.Structure2.34software was used to analyze population structure and divide cultivars into subgroups.Nei’s genetic distance among subgroups was calculated by NTSYSpc,then applied to construct a rooted phylogenetic tree by MEGA6.The rate of hermaphrodite flower cultivars on each level of the phylogenetic tree was calculated to understand the sexual system evolution.Moreover,the genetic mechanism of flower color variation for sweet osmanthus was further speculated based on the result.