大理茶遗传多样性和大苞茶起源机制的研究
赵东伟
学位类型硕士
导师杨世雄
2010-11
学位授予单位中国科学院研究生院
学位专业植物学
摘要栽培植物的野生近缘种和野生型是育种的宝贵资源,同时,栽培起源也是当今研究的热点问题之一。野生茶树是商品茶育种的珍贵种质,有着重要的经济价值,然而近年来在市场利益的驱动下却遭到了严重破坏,大理茶(Camellia taliensis)是其中的主要代表。除了存在野生居群外,大理茶在云南茶区还被长期驯化利用,有着一定量的半栽培和栽培居群。在至今无法确认广泛种植的茶(C. sinensis)的野生型是否存在的背景下,大理茶的野生和不同驯化类型兼备,使得它成为研究茶树栽培起源不可多得的材料。本研究从发表的37对微卫星引物中筛选出14对引物,对大理茶的16个野生、4个半栽培和5个栽培居群共579个个体进行了居群遗传学和比较遗传多样性方面的研究,以期揭示大理茶的生存和驯化利用现状,为这一资源的保护和可持续利用提供依据。和大理茶同域分布的大苞茶,因其形态特征的不稳定和过渡性,被认为可能是由大理茶和普洱茶杂交形成。本研究利用微卫星标记,对大苞茶的2个居群39个个体、普洱茶的4个居群83个个体以及上述大理茶的材料进行分析,以检验上述杂交假说的真实性。研究表明,野生大理茶具有较高的遗传多样性﹝A(平均等位基因数)= 14.3,Ne(有效等位基因数)= 5.7,HE(无偏杂合度)= 0.666,I(香农信息指数)= 1.753,AR(等位基因丰富度)= 7.2,PPB(多态位点百分数)= 100%﹞。K对策、祖先类群的遗传基础、一定的居群间基因流和种间杂交渐渗的存在,是它维持较高遗传多样性的重要原因。野生大理茶居群间具有较高水平的基因流(Nm = 1.197)和较低的遗传分化﹝GST(遗传分化系数)= 0.147;FST = 0.173﹞;AMOVA分析表明,大量的遗传变异(81%)存在于居群内。这和其他长寿命木本植物相似,表明大理茶可能在很大程度上继承了其祖先居群的遗传结构特点。Mantel检测显示,居群间的遗传距离和地理距离间的相关性是极显著的(r = 0.372,P = 0.001),符合距离隔离的模型。基于个体基因型的贝叶斯分析将所有居群分为两组,在一定基础上可能反应了居群分化的现状。然而这种分析结果与基于遗传距离的聚类以及实际地理分化不完全一致,这种状况可能是由人类活动所造成。采集和破坏活动使得大理茶居群内的基因型发生一定规模、非随机的丧失,对该种的遗传结构产生了复杂而深远的影响。野生(AR = 4.651)、半栽培(AR = 5.091)和栽培型(AR = 5.132)大理茶之间不存在遗传多样性的显著性差异(P > 0.05)。长寿命木本植物的遗传基础难以快速改变和较高的基因流(Nm = 1.281)可能导致了这一现象的形成。对云南云县同地的栽培和野生居群的典型分析显示,栽培居群的遗传多样性(AR = 7.1)显著高于野生居群(AR = 5.9)(P < 0.05)。栽培的大理茶在一定程度上和茶、大苞茶发生种间基因交流,而野生居群较少具备这种种间基因交流的便利条件,同时受到人类活动破坏致使其基因型丧失是这一差异出现的可能原因。通过子房室数变异统计和基因型分析检验了大苞茶是大理茶和普洱茶杂交后代的假说。大苞茶的子房为3、4、5室,没有稳定的、占据绝对优势的子房室数,这体现了它形态特征上的过渡性和镶嵌性。其等位基因绝大部分(99.1%)和大理茶、茶相同,只有1个特有等位基因。聚类分析中它和大理茶聚为一支。研究结果部分支持上述杂交起源的假说。大苞茶可能由杂交和不对称渐渗现象共同作用形成,大理茶是其亲本的可能性很大。通过推论,认为普洱茶或许是其另一个亲本,然而这需要更多的材料和手段来验证。同时,大苞茶作为“种”的真实性值得商榷。
资助项目Camellia taliensis (W. W. Smith) Melchior, a member of Camellia sect. Thea, is an indigenous species in local natural forest and has a long cultivative history in western Yunnan and its neighborhood, where the domestications of this species in different historical periods and in different ways can be found. C. taliensis is an important contributor to the formations of tea landraces by hybridization and introgression. In the present study, 14 microsatellite loci screened from 37 loci were used to explore the genetic diversity about this species with 579 samples from 25 populations (16 wild populations, 4 semi-cultivated populations and 5 cultivated populations). At the same time, the potential hybrid speciation of C. grandibracteata, was investigated using 39 individuals from 2 populations, along with C. taliensis and C. sinensis var. assamica (83 individuals from 4 populations) by the same microsatellite markers. C. taliensis had a moderate high level of genetic diversity (A = 14.3, Ne= 5.7, HE = 0.666, I = 1.753, AR = 7.2, PPB = 100%). This may result from several factors including K-strategy, genetic background, gene flow between populations, hybridization and introgression among species. Between wild populations of C. taliensis, the gene flow was moderate high (Nm = 1.197), and genetic variation was less than 20% (GST = 0.147, FST = 0.173), which was similar to other research results of long-lived woody plants, and reflected the genetic structure of its ancestry to same extent. There was a high significant correlation between geographic distance and Nei’s genetic distance (r = 0.372, P = 0.001) of populations, which accorded with isolation by distance model. Inferring from Bayesian clustering of genotypes, all individuals of C. taliensis were divided into two groups, conflicting with the result based on Nei’s genetic distance and real geographic distribution, which suggested there were heavy and non-random influences by human practices. According to allelic richness, there were no significant differences (P > 0.05) between wild (AR = 4.651), semi-cultivated (AR = 5.091) and cultivated (AR = 5.132) populations of C. taliensis, which suggested that the genetic background of long-lived woody plant was not easy to be changed, and there were moderate high gene flow between populations. However, there was a significant difference (P < 0.05) between wild (AR = 5.9) and cultivated (AR = 7.1) populations distributed in the same place in Yun county, Yunnan province, which may result from the hybridization and introgression of species in the tea garden and anthropogenic damages to the wild population. The hypothesis of hybrid origin of C. grandibracteata was tested by morphological and microsatellites analyses. Compared with other species, the locules in ovary of C. grandibracteata are variable, which showed a morphological intermediate and mosaic. Except one private allele, Ninety-nine percent alleles of C. grandibracteata were shared with these of C. taliensis and C. sinensis var. assamica. And C. grandibracteata was nested in the cluster of C. taliensis in the UPGMA tree. Conclusively, our results supported the hypothesis of hybrid origin of C. grandibracteata partly. The speciation of C. grandibracteata was derived from hybridization and asymmetrical introgression potentially. It is possible that C. taliensis was one of its parents, but it still needs more evidences to prove that C. sinensis var. assamica was another parent.
语种ch
文献类型学位论文
条目标识符http://ir.kib.ac.cn/handle/151853/16018
专题昆明植物所硕博研究生毕业学位论文
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赵东伟. 大理茶遗传多样性和大苞茶起源机制的研究[D]. 中国科学院研究生院,2010.
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