水杉栽培居群的遗传多样性研究

Genetic Diversity of Cultivated Populations of Metasequoia glyptostroboides

利用RAPD技术,对9个水杉(Metasequoia glyptostroboides)栽培居群的遗传多样性进行了初步研究.用10 bp的随机引物16条,共扩增出103个位点,其中37个为多态位点,占35.92%.各居群的多态位点百分率在16.50%～33.01%之间.POPGENE version 1.31软件处理结果如下:居群的Shannon's信息指数为0.1930.遗传距离在0.0130～0.0650之间,遗传一致度在0.9370～0.9871之间.AMOVA分析结果显示遗传变异主要存在于居群内,占89.05%,居群之间有一定的分化.上述结果表明水杉栽培居群的遗传多样性略低于自然居群,涵盖了自然居群近80%的遗传多样性.由此可以确认栽培水杉的种源是经过混合的,它们在相当程度上代表了自然居群的遗传多样性水平.采自潜江的9株丛枝水杉(Metasequoia glyptostroboides var.caespitosa)没有扩增出特有位点,将其视为一个居群根据遗传一致度作UPGMA聚类分析时,该居群和湖北的3个居群及南京(NJ)、成都(CD)居群聚在一起;单株聚类时丛枝水杉也没有聚成独立的一支,而是比较分散,因此不支持将丛枝水杉作为水杉的一个变种的分类处理.从亲缘关系上看,丛枝水杉应当归属于湖北潜江蚌湖种子园(BH)和湖北潜江广华(GH)居群,这与其分布现状也是吻合的.

Random amplified polymorphic DNA markers were used for initial evaluation of genetic diversity within and among nine cultivated populations of Metasequoia glyptostroboides. The sixteen primers （ 10 bp） produced 103 loci, of which 37 （35.92%） were polymorphic. Percentage of polymorphic loci per population varied between 16.50% and 33.01%. As analyzed by POPGENE version 1.31, the data from the cultivated populations had Shannon＇s iuformation index of 0.1930. The genetic distance varied between 0.0130 and 0.0650. The genetic identity varied between 0.9370 and 0.9871. AMOVA analysis indicated that 89.05% of total variation was due to difference within the populations, which showed that there was a little differentiation among populations. The genetic diversity of cultivated populations was slightly lower than that of natural populations, covering nearly 80% of the genetic diversity of natural populations of Metasequoia glyptostroboides, So it was true that the original seeds of cultivated populations of Metasequoia glyptostroboides were mixture from different individuals and populations in its original distributed regions. To some extent, it represented the genetic diversity level of the natural populations. No individual-specific loci were found in nine individuals of Metasequoia glyptostroboides var. caespitosa from Qianjiang of Hubei Province. UPGMA dendrogram of ten populations based on genetic distance showed that the population of Metasequoia glyptostroboides var. caespitosa clustered with populafions of Hubei, Nanjing （NJ） and Chengdu （CD）. UPGMA dendrogram of 90 individuals based on Nei＇s genetic identity showed that the nine individuals of Metasequoia glyptostroboides var. caespitosa were not clustered together, which did not support the taxonomical treatment that Metasequoia glyptostroboides var. caespitosa was a variety of Metasequoia glyptostrobohtes. In respect to genetic relationship, Metasequoia glyptostroboides var. caespitosa belongs to the populations from Banghu Seeds Garden （BH） and Guanghua （GH）, Qianjiang City, Hubei Province, which is consistent with their current distribution pattern.