摘要
荞麦(buckwheat)属于蓼科(Polygonaceae),荞麦属(Fagopyrum Mill),是一种重要的杂粮兼药用植物。我国的养麦资源十分丰富,在全世界目前已报道并命名的荞麦有23个种,2个亚种和3个变种。细胞遗传学研究表明荞麦属植物存在四倍体和二倍体的染色体倍性变化。我国西南地区是荞麦的起源地之一,但荞麦研究工作起步晚,研究不够深入,对于荞麦的基础性研究如起源、演化和分类还在初始阶段,种间亲缘关系模糊不清,亟待我们进行全面系统的研究。本研究利用荞麦叶绿体matK基因及核基因组中的ITS序列对13种荞麦属植物进行了系统发育重建,并在此基础上结合形态分类系统及细胞学研究结果,获得以下结果：
1.matK基因的研究结果表明：(1)不同的严格一致树都将栽培种和野生种清晰的划分为两大类别,五个主要分支,其自展支持率达到99%；(2)普格野生荞是野生荞麦的进化种；从整个荞麦属植物的进化关系来看,普格野生荞进化地位位于栽培荞麦和野生荞麦之间,很有可能是二者的中间类型；(3)白翅和红翅亲缘关系较远,他们各自具有独立的进化路线,白翅野生养可能是细柄野生荞的一个亚种,而红翅野生荞可能是独立于细柄野生荞而存在的一个隐存种。
2.ITS序列研究结果表明：(1)同一物种的不同克隆并不总是聚在一起,反映了荞麦属植物的ITS序列存在较大的遗传分化,荞麦属植物的分布广、物种类群多,染色体的倍性变化可能导致其存在较大的遗传分化；(2)细胞学水平和分子水平的结果显示汶川野生荞与西昌金荞亲缘关系密切,推测汶川野生荞很可能是金荞的一个地理亚种。
3.根据生命条码可将荞麦属分为两大类群：类群Ⅰ包括栽培种和金荞及其近缘种；类群Ⅱ主要包括野生种(羌彩野生养,普格野生荞,线叶野生荞,细柄野生荞,皱叶野生荞等)。
4. matK与ITS序列分析结果都表明金荞与苦荞的亲缘关系更近。苦荞和野生荞麦之间可能存在一个中间类型,已搜集的材料研究表明普格野生荞可能是栽培种和野生种的过渡种。
5.形态学、细胞学及分子水平的研究均显示白翅野生荞和红翅野生荞区别十分明显,判定二者应该是两个独立的种,可对其进行重命名。
The buckwheat,Fagopyrum of polygonaceae,is considered as one kind of coarse cereals and medicinal plants.China is rich in buckwheat resource,which was reported and named all over the world,including twenty three species,two subspecies and three variants. Cytogenetical study has proved that Fagopyrum existed with both diploid and tetraploid. China especially in southwest is one of the origin of buckwheat,but the research on buckwheat starts late and lacks of investment. The basis research,such as the evolution and the classification of buckwheat is significantly blank;phylogenetic relationship among the species in fagopyrum is undefined,so systematic research is extremely urgent.The classification and relationship of Fagopyrum have been existing controversy.In this study,phylogenetic investigation of thirteen representative buckwheat species which came from southwestern of China has been conducted based on matK gene and ITS sequence,compared with the typoiology classification and cytological analysis.The main results were as follows:
1.The matK sequence analysis indicated that:(1)The bootstrap support of the five leading branches reached 99%.(2)The result of all data analysis showed that Fagopyrum pugense was the evolving species of wild buckwheat. Overviewing the evolutionary relationship of all of Fagopyrum, Fagopyrum pugense was situated in cultivated buckwheat and wild buckwheat,and it may be the intermediate form of the two.(3)With relatively far genetic relationship between F.gracilipes var.odontopterum W and F.gracilipes var.odontopterum R,which had their own independent revolution line,F.gracilipes var.odontopterum W may be one of the subspecies of F.gracilipes (Hemsl.) Dam.et Diels while F.gracilipes var.odontopterum R may be the cryptice that indepent from F.gracilipes (Hemsl.) Dam. et Diels.
2.The ITS sequence analysis indicated that:(1)different clonings did not always cluster together within a species,which reflected that the ITS sequence of the fagopyrum had distinct genetic differentiation.The factor leading great differentiation may be the wide distribution of Fagopyrum,abandent species groups,or the ploidy change of chromosome.(2) The results of the molecular classification and cytological research showed the close relationship between F.wenchuanense and F.cymosum X,so we speculated that the F.wenchuanense may be a geographic subspecies of the F.cymosum.
3.According to DNA barcode,the buckwheat could be divided into two groups:Cluster I contained cultivated species,F.cymosum and its related species; ClusterⅡcontained wild species,F.qiangcai,F.pugense,F.lineare,F.gracilipes and F.crispatifolium,etc.
4.The results of matK and ITS sequence analysis suggested that F.cymosum had much closer genetic relationship with F.tartaricum.An transitional species,which might be Fpugense from this study,could exist between F.tartaricum and wild buckwheats.
5.The results of morphology, cytology and molecular level studies had all shown that the distinct difference between F.gracilipes var.odontopterum W and F.gracilipes var.odontopterum R,therefore,they should be two separate sepecies and should be renamed.
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