基于ITS分析云南光叶桑和钦州长果桑在桑属中的亲缘关系及分化时间

An Analysis on Phylogenetic Relationship and Divergence Time of Yunnan Guangye Sang and Qinzhou Changguo Sang in Morus Genus Based on ITS Sequence

云南光叶桑、钦州长果桑在形态分类学上均属同一桑种Morus macroura。通过PCR扩增2份地方品种资源材料的ITS序列并分析序列差异及构建系统进化树,阐明各自在桑属中的遗传分化关系。2份材料的ITS序列长度均为576 bp,其中:云南光叶桑的G+C含量为59.90%,碱基序列45位A变G,560位T变G,与昆明奶桑(Morus macroura)、荥经川桑(Morus notabilis)、云南毛叶奶桑(Morus macroura var.mawa)、云南长穗桑(Morus wittiorum)、云南奶桑(Morus macroura)、雅安华桑(Morus cathayana)同在第Ⅰ类群,有较近的亲缘关系;钦州长果桑的G+C含量为59.72%,碱基序列45位为A,560位T变G,与云南华桑(Morus cathayana)同在第Ⅱ类群,有较近的亲缘关系。应用松散分子钟方法估算云南光叶桑与荥经川桑、雅安华桑、云南长穗桑的分化时间为8.23 Ma,钦州长果桑与云南华桑的分化时间为9.67 Ma,二者起源的地质年代是新第三纪中新世与上新世之交,是为了抵御地球寒冷、旱化,向南、向山地迁移形成的物种。

Yunnan Guangye Sang and Qinzhou Changguo Sang belong to the same mulberry species,Morus macroura,in morphological taxonomy.In this study,the ITS sequences of both local variety materials were PCR amplified,analyzed on their sequence difference,and used to construct phylogenetic trees for elucidation of their inheritance and divergence behavior in the Morus genus.The ITS sequence of both materials is 576 bp.However,the G＋C content in Yunnan Guangye Sang is 59.90%,and A has been replaced by G at nucleotide 45 and T by G at nucleotide 560.It has close phylogenetic relationship with Kunming Nai Sang（Morus macroura）,Yingjing Chuan Sang（Morus notabilis）,Yunnan Maoyenai Sang（Morus macroura var.mawa）,Yunnan Changsui Sang（Morus wittiorum）,Yunnan Nai Sang（Morus macroura）,and Ya’an Hua Sang（Morus cathayana）,all of which belong to group Ⅰ in the constructed phylo-genetic tree.The G＋C content in Qinzhou Changguo Sang is 59.72% with A at nucleotide 45 and with substitution of T by G at nucleotide 560.It has close phylogenetic relationship with Yunnan Hua Sang（Morus cathayana）,both of which belong to group Ⅱ in the constructed phylogenetic tree.Estimation by loose molecular clock method showed that the divergence time of Yingjing Chuan Sang,Ya’an Hua Sang,and Yunnan Changsui Sang is 8.23 Ma,and that of Qinzhou Changguo Sang and Yunnan Hua Sang is 9.67 Ma.The geologic age of their origination was the transient time between the Miocene epoch and the Pliocene epoch in Neogene Period.They are the species evolved in the migration towards southern and hilly areas to resist cold and arid environment of the earth.