西南地区乡土杨树遗传变异的SRAP分析

采用SRAP分子标记技术对西南地区11种乡土杨树共333份样本的遗传变异进行分析,7对引物组合共扩增出215条带,其中多态性条带158条,多态性条带百分率为73.49%,表明11种乡土杨树间存在广泛变异。AMOVA分析结果显示,种间遗传变异分量为10.84,占总变异的48.70%,遗传差异达极显著水平(P0.001)。种间的遗传相似系数变幅在0.8199~0.9607之间,平均遗传相似系数为0.8983。聚类结果表明,昌都杨和藏川杨之间的遗传差异最小,大叶杨和三脉青杨之间的遗传差异最大。本研究结果为西南地区乡土杨树基因资源的保护、开发和利用提供了一定的科学理论依据。     

基于cpDNA和rDNA ITS片段分析西南地区青杨派杨树的系统发育与进化关系

西南地区青杨派杨树种质资源丰富,可为杨树遗传改良提供珍贵的基因资源,但树种之间形态学差异细微,该研究以山杨作为外类群,测定了西南地区及其他地区杨属青杨派17个种(杂种)共36份样本的3个叶绿体片段(atpF-atpH、trnL-F和matK)和核糖体ITS片段,并对其进行系统发育分析,以探讨西南地区青杨派树种的系统进化关系。结果表明:(1)在所有样本中,3个叶绿体片段atpF-atpH、trnL-F、matK的长度分别为605~634bp、957~1 010bp、819bp,3个片段拼接后的联合序列包含29个变异位点和15个信息位点;ITS片段对齐后的长度为646bp,变异位点19个,信息位点17个。(2)基于叶绿体联合序列和ITS片段的杨属青杨派树种的平均遗传距离分别为0.001 3和0.003 6。叶绿体联合片段的MP和Bayes系统树树型基本一致,青杨派树种可以划分为2组,第1组由青杨、三脉青杨、大青杨和辽杨构成;第2组中的小叶杨、小青杨、川杨、德钦杨、昌都杨、乡城杨、康定杨、西南杨、滇杨和藏川杨不能有效区分,且均与缘毛杨的遗传关系较近。(3)基于ITS的系统树与叶绿体联合片段构建的系统树差异不大,仅在于第2组中的小青杨与小叶杨、川杨等差异明显,与第1组中的树种紧密聚拢。     

基于ISSR的硬叶兜兰居群遗传多样性研究

利用ISSR标记对7个硬叶兜兰居群160个体扩增,10对引物共扩增出101个条带,其中多态性条带97个,种水平上的多态性条带比率(PPB)达96.02%,香侬指数(I)为0.488 9,Neis基因多样性指数(H)为0.332 4。居群水平的遗传参数,多态性条带比率(PPB)为33.51%,香侬指数(I)为0.194 3,Neis基因多样性指数(H)为0.133 2。总的遗传多样性(H_T)为0.323 9,个体遗传多样性(Hs)达到0.133 2。AMOVA结果揭示居群间遗传分化大,居群间基因流N_m为0.349 2。居群间的Neis遗传距离0.148 1~0.4385。基于UPGMA聚类,在遗传距离为0.327时,7个居群聚为两支,第一支由古林箐和马固、田坝、夹寒箐和杨柳井居群组成,第二支由斗咀和小坝子居群组成,聚类关系反映居群间遗传分化与地理距离无显著相关性。     

色季拉山不同海拔高度的藏川杨种群遗传多样性的研究

为研究青藏高原海拔变化与藏川杨遗传多样性和群体遗传结构的关系,以青藏高原东南部色季拉山分布的藏川杨群体为材料,用24对微卫星标记对其进行遗传分析。在469个个体中共检测到126个等位基因,每个位点的平均等位基因数(Na)为5.25;多态性位点百分率(PPL)为100%,期望杂合度(He)在高、低海拔的群体中都处于较高水平,分别为0.48和0.49;分子方差分析(AMOVA)的结果表明,种群间分化占总变异的6.38%,遗传变异主要集中在群体内不同个体之间;基因分化系数(FST)为0.02,也证实群体分化处于较低水平,而检测到群体间的基因流动(Nm)处于较高水平,为9.89。上述结果表明,海拔因素未对生长在色季拉山高低海拔的藏川杨群体造成地理隔离,从而产生种群分化;在此地区藏川杨遗传背景一致,藏川杨种质资源的保存无需考虑海拔的差异。本研究结果为研究高海拔适应机制材料的选择提供了很大的便利,并为藏川杨的可持续利用与保护提供了一定的理论依据。     

濒危植物长叶榧群体遗传多样性的RAPD分析

借助随机扩增多态DNA方法,分析了中国特有的濒危植物长叶榧的遗传多样性和遗传分化．结果表明：12个随机引物在9个长叶榧自然群体180个样品中可检测到180个可重复位点,其中多态位点119个．长叶榧物种水平的遗传多样性较高,多态位点百分率（P）为66．11％,Shannon信息指数（,）为0．3087,Nei指数（h）为0．2015;而群体水平的遗传多样性较低,P、I和h分别平均为23．76％、0．1221和0．0813．AMOVA分子变异显示,42．57％变异来源于群体内,57．43％变异来源于群体间,群体间的遗传分化系数（Gst）为0．5965,群体间的遗传分化程度高．长叶榧群体间的基因流很低,为0．3382．瓶颈效应、群体隔离和群体间基因流低等因素都加剧了长叶榧群体间的遗传分化．9个长叶榧群体间的平均遗传距离为0．1630．通过UPGMA进行聚类,可将9个长叶榧群体分为浙江和福建两大类群．建议在迁地保护时应尽量避免在群体之间实施种质迁移．     

濒危植物扇脉杓兰野生居群遗传多样性的AFLP分析

扇脉杓兰(Cypripedium japonicum)是一种珍稀的地生兰。为了探索并制定针对性的保护措施,采用AFLP分子标记技术对现存于浙江省的6个扇脉杓兰天然居群进行了遗传多样性和遗传结构的研究。筛选出的7对引物共扩增出377条清晰条带,多态性比率为20.95%。居群总Nei基因多样性指数为0.0512,其中居群内基因多样性为0.0247,居群平均Shannon多态性信息指数为0.0417,群体间总遗传分化系数为0.5178,基因流为0.4655,表明扇脉杓兰居群的遗传多样性较低,居群间出现一定程度的遗传分化。UPGMA聚类和Mantel检测分析结果表明,居群间的地理位置与遗传距离之间不存在显著相关性(r=0.16,P=0.242)。基于本研究结果并结合扇脉杓兰的生物学特性,初步提出了相应的保育策略。     

内蒙古扁蓿豆遗传多样性的ISSR分析

应用ISSR分子标记对分布于内蒙古不同地区的扁蓿豆(Medicago ruthenica)8个地理种群进行了遗传多样性研究.结果表明:扁蓿豆具有较高的遗传多样性;15个引物共扩增出363个位点,物种水平上Nei s基因多样性指数为0.198 9,Shannon多样性指数为0.303 7;种内总基因多样性为0.308 6,种群内基因多样性为0.198 9,64.45%的遗传变异存在于种群内,35.55%的遗传变异存在于种群间,种群间的遗传分化系数为0.355 5,基因流为0.906 4,8个种群间基因交流较少,遗传分化较强.UPGMA遗传距离聚类结果表明,生态地理条件相似的种群优先聚集.     

云南木兰科48种野生植物资源的遗传多样性研究

为了解云南省木兰科(Magnoliaceae)野生植物资源的遗传多样性,利用ISSR分子标记技术对48种木兰科野生植物资源进行研究。结果表明,10对引物共扩增出151条带,均为多态性条带,多态性条带百分率为100%。总的观测等位基因数(N_a)为2.000 0,有效等位基因数(N_e)为1.564 5,Nei’s基因多样性指数(H) 0.337 9,Shannon’s信息指数(I)为0.510 1。总的基因多样性指数(H_t)为0.368 0,属间基因多样性指数(D_(st))为0.251 9,占68.4%,基因分化系数(G_(st))为0.684 0,基因流(N_m)为0.231 0。UPGMA聚类分析将48种木兰科植物划分为7个类群,各类群并非按照属聚在一起,而是不同属植物相间分布,长喙厚朴(Magnolia rostrata)、素黄含笑(Michelia flaviflora)和球花含笑(M. sphaerantha)可能为云南省木兰科植物中的原始种。48种木兰科野生植物总体具有较高的遗传多样性,但属间遗传变异较高,基因流较小,存在遗传漂变的风险,聚类结果与刘玉壶的分类系统存在分歧,这从分子水平为木兰科植物间的起源、进化与分类提供了重要依据。     

西南地区麻疯树天然种群遗传多样性的等位酶变异

为了揭示麻疯树(Jatropha curcas)天然种群的遗传多样性和遗传结构, 采用聚苯烯酰胺凝胶垂直平板电泳技术, 对采自四川、云南、贵州3个省的10个麻疯树天然种群的叶片样本进行了同工酶分析。7个酶系统10个位点的检测结果表明: 麻疯树种群水平上的遗传多样性较高, 每位点平均等位基因数为2.428 6, 多态位点百分率为97.14%, 平均期望杂合度为0.396 4。种群间遗传分化系数为0.041 3, 种群间总的基因流较高, 为5.808 9, 种群间遗传一致度较高(Shannon信息指数为0.921 7- 0.995 3)。非加权类平均法(UPGMA)聚类结果显示, 10个种群的遗传距离与地理距离相关性不显著。麻疯树天然种群具有较低程度的遗传分化、较高的基因流, 种内及种群内多样性丰富, 这为麻疯树优良品种的选育提供了良好的遗传基础。     

濒危特有种掌叶木的微卫星遗传多样性研究

掌叶木居群具有较丰富的遗传多样性,该研究利用9对微卫星(SSR)分子标记揭示了掌叶木(Handeliodendron bodinieri)的遗传多样性。结果表明:观测等位基因数(Na)平均为3.903,有效等位基因数(Ne)平均为2.545,期望杂合度(He)平均为0.521,Shannon’s多态性信息指数(I)为0.962,PIC平均值为0.465。掌叶木的自然分布居群有相对较高的遗传多样性,但由于人为破坏等因素导致该群体濒危,而濒危并不是因为遗传多样性降低而造成的。居群间的遗传分化为掌叶木8个居群间的遗传一致度为(GI=0.849~0.970),遗传距离为(GD=0.032~0.164)。基于Nei’s遗传距离用UPGMA法对掌叶木居群进行聚类,Nei’s的基因分化系数为(G_(st))为0.027,平均Nei标准遗传分化系数(G'_(st)N)为0.031,平均Herick’s标准遗传分化系数(G'_(st)H)为0.064,基因流(N_m)为3.368。AMOVA分析结果表明:掌叶木居群间变异占3%,居群内变异占97%,居群内的遗传分化大于居群间的分化。利用Mantel检测发现,居群间的遗传距离与地理距离显著正相关(r=0.299,P0.05)。该研究结果为掌叶木生物多样性和资源保护与利用提供了更充分的科学依据。     

Study of genetic relationships and phylogeny of the native Populus in Southwest China based on nucleotide sequences of chloroplast trnT–trnF and nuclear DNA

Unique historical factors and ecological conditions make Southwest China a natural distribution and variation center for trees of the genus Populus in China. However, little is currently known about the native poplars occurring in this region, and considerable doubt still exists regarding the classification and evolutionary relationships of poplar species. In this study, nuclear and chloroplast DNA (cpDNA) sequences were utilized to determine the genetic relationships and phylogeny of Populus species in Southwest China. The results suggest that P. pseudoglauca belongs to the section of Tacamahaca. Further, P. schneideri may be a natural hybrid of P. kangdingensis and P. cathayana and, thus, it should likely not be regarded as a variety of P. kangdingensis, as in the existing classification system. In addition, cluster analyses showed that P. gonggaensis may be derived from a cross between species of section Leucoides and P. cathayana or P. schneideri of section Tacamahaca, although it is still doubtful whether P. gonggaensis can be regarded as a separate species, due to its narrow distribution range. The parents of the Luding poplar may be P. yunnanensis and P. lancifolia. P. butuoensis showed a close affinity to species of section Leucoides and had a close relationship with P. gonggaensis or P. lasiocarpa. However, further research is needed in order to appropriately classify these as species or varieties. The incongruence between phylogenetic trees based on nuclear- and chloroplast-DNA sequence data may be due to the different inheritance patterns between nuclear- and cpDNA genome.     

Responses to drought stress in two poplar species originating from different altitudes

Cuttings of Populus kangdingensis and Populus cathayana, originating from high and low altitudes in the eastern Himalaya, respectively, were examined during one growing season in a greenhouse to determine their responses to drought stress (soil moisture decreased from 100 to 55 or 25 % field capacity). Compared to control plants grown under 100 % field capacity, those poplars grown under 55 and 25 % field capacity possessed lower increases in height and stem diameter, and higher contents of soluble sugars, free proline, malondialdehyde (MDA) and hydrogen peroxide, and higher activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR). Compared with P. cathayana with greater leaf area, P. kangdingensis with greater root/shoot ratio exhibited lower MDA and H₂O₂ contents, higher soluble sugar and free proline contents, and higher activities of CAT, SOD, POD, APX and GR. These results suggested that P. kangdingensis was more drought tolerant than P. cathayana.     

Genetic diversity of <Emphasis Type="Italic">Caragana</Emphasis> species of the Ordos Plateau in China

Plants of the genus Caragana (Fabaceae) are dominant shrub species of high ecological and economic importance on the Ordos Plateau in China. Due to natural environmental variability and anthropogenic impacts, Caragana pastures have experienced severe degradation, which has decreased their carrying capacity. In this study, we investigated the genetic diversity of eight Caragana species (C. purdomii, C. opulens, C. stenophylla, C. intermedia, C. korshinskii, C. roborovskyi, C. tibetica and C. brachypoda) on the Ordos Plateau by using ISSR markers. The results reveal high genetic diversity of all the species, with the percentage of polymorphic bands (PPB) reaching 100%. However, interspecific differences in genetic diversity within the genus were significant, as indicated by higher levels of genetic diversity of C. stenophylla, C. tibetica, C. intermedia, C. korshinskii and C. roborovskyi (PPB > 86%) when compared to the C. brachypoda with the lowest genetic diversity (PPB = 42.86%). Caragana brachypoda showed the lowest genetic similarity with and largest genetic distance from other taxa of the genus. Caragana tibetica had higher genetic diversity than C. roborovskyi. A large genetic distance was found between C. roborovskyi and C. tibetica, although the two species belong to Ser. Tragacanthoides and grow in a semidesert area. Such differences in genetic structure may be the reason for large areas occupied by C. tibetica, whereas C. roborovsky has rather limited distribution in the semidesert area. Caragana intermedia had high genetic diversity and a large genetic differentiation between intraspecific populations implying strong adaptability of the species to environmental fluctuations and selection capabilities. There was an obvious gene flow between C. intermedia and C. korshinskii, suggesting possible hybridization between these species is consistent with ecological variability, which may be important characteristics of Caragana plants in terms of molecular variation in the ecotone of Ordos plateau. Our results provide a molecular basis for sustainable management, utilization and conservation of Caragana plants on the Ordos plateau.     

基于SSR标记的大明松天然群体遗传多样性分析

大明松是广西和贵州特有的高山松类,具有很高的经济价值和生态价值,其自然种群长期没有得到充分的保护和利用,不利于该树种长期稳定发展。为了合理保护和开发利用大明松天然遗传资源,该文利用12个SSR分子标记对大明松3个天然群体进行遗传多样性研究,分析其群体间的遗传分化和基因流,为该物种的保护策略提供参考。研究结果表明:(1)12对引物共检测到37 个等位基因,多态位点百分率为100%。每个位点平均观察等位基因数(Na)为3.08,平均有效等位基因数(Ne)为1.68, 不同位点间有效等位基因数差异较大; 每个位点平均观察杂合度(Ho)为0.35,平均期望杂合度(He)为0.40,平均多态信息含量(PIC)为0.31。(2)3 个群体的Shannon''s多样性指数变化范围为0.48～0.65,Nei''s基因多样度的变化范围为0.27～0.39,与其他近缘种松类相比遗传多样性偏低。群体平均观察杂合度为0.40,平均期望杂合度为0.33,平均有效等位基因数为1.58。群体间基因分化系数(Gst)为0.10,群体间的遗传分化水平较低,大部分变异均存在群体内。群体间的基因流(Nm)为2.74,说明大明松群体间的基因交流比较充分。该研究可为大明松生物多样性保护提供重要参考依据,为科学利用大明松资源打下基础。     

Population Genetic structure ofPotentilla fragariodes var.major (Rosaceae) in Korea

The genetic diversity and population structure of eighteenPotentilla fragariodes var.major (Rosaceae) populations in Korea were determined using genetic variations at 22 allozyme loci. The percent of polymorphic loci within the enzymes was 66.7%. Genetic diversity at the species level and at the population level was high (Hes = 0.203; Hep = 0.185, respectively), whereas the extent of the population divergence was relatively low (G_ST = 0.069). F_IS, a measure of the deviation from random mating within the 18 populations, was 0.075. An indirect estimate of the number of migrants per generation (Nm = 3.36) indicated that gene flow was high among Korean populations of the species. In addition, analysis of fixation indices revealed a slight heterozygote deficiency in some populations and at some loci. Wide geographic ranges, perennial herbaceous nature and the persistence of multiple generations are associated with the high level of genetic variation. AlthoughP. fragariodes var.major usually propagated by asexually-produced ramets, we could not rule out the possibility that sexual reproduction occurred at a low rate because each ramet may produce terminal flowers. Mean genetic identity between populations was 0.983. It is highly probable that directional movement toward genetic uniformity in a relatively homogeneous habitat operates among Korean populations ofP. fragariodes var.major.     

Genetic structure of Japanese Chattonella marina (Raphidophyceae) populations revealed using microsatellite markers

Chattonella marina var. antiqua and C. marina var. marina (Raphidophyceae) are red tide‐forming, harmful phytoplankton species. We investigated the genetic diversity and genetic relationship among the populations using microsatellite markers to identify putative sources of C. marina var. antiqua and C. marina var. marina in Japanese coastal populations. A positive correlation between genetic divergence and geographical distance (isolation by distance) was recognized for C. marina var. antiqua. The C. marina var. antiqua populations were established throughout a geological time scale, and genetic divergence had progressed in each population with gene flow depending on geographic distances. In contrast, isolation by distance was not observed for C. marina var. marina populations, and the genetic divergence among populations was extremely high. The Tokyo Bay population of C. marina var. marina, which was first recognized in 2008, had many private alleles but was related to the Kagoshima Bay population. The Tokyo Bay population may have been established by several invasions from the Kagoshima Bay population and other regions.     

The influence of seed dispersal mechanisms on the genetic structure of tropical tree populations

Seed dispersal mechanisms should have a direct impact on the genetic structure of populations. Species whose seeds are dispersed near the maternal plant (e.g. gravity or wind dispersal) or species whose seeds are deposited in clumps or patches should have more fine-scale genetic structure than species whose seeds are dispersed singly by mobile animals. Furthermore, due to the overlap of seed shadows, species with high adult densities should have less genetic structure than species with lower densities. Allozyme analyses of three tropical tree species belonging to the moist tropical forest of Barro Colorado Island, Republic of Panama, were used to describe variation in the scale and intensity of genetic structure within their populations. The genetic structure of seedlings and immature trees in the low-density, wind-dispersed species (Platypodium elegans) was the coarsest and strongest whereas genetic structure in a population of Swartzia simplex var. ochnacea (high density, bird-dispersed) was both the finest and the weakest. The genetic structure of Alseis blackiana, a high-density, wind-dispersed species was intermediate in both degree and scale. In P. elegans and A. blackiana, which had J shaped size distributions, the significant genetic structure seen in the smaller and intermediate diameter classes disappeared in the largest diameter class. The loss of genetic structure was not observed in S. simplex, a species with a more even size distribution.     

Volatile Organic Compound Analysis of Host and Non-Host Poplars for <Emphasis Type="Italic">Trypophloeus klimeschi</Emphasis> (Coleoptera: Curculionidae: Ipinae)

Trypophloeus klimeschi Eggers was first discovered in Xinjiang Province and had strong selection specificity for Populus alba var. pyramidalis Bunge. There was an outbreak of this beetle in the northwest shelter forest of China, resulting in significant economic losses and loss of ecological benefits. Based on a prior long-term field investigation, T. klimeschi had a different extent of injuries for different ages of P. alba var. pyramidalis and other Populus in the same area were not selected by T. klimeschi. To further explore the specificity volatile compounds, this study involved selecting host and non-host trees to analyse the volatile chemical profile of host and non-host poplars of T. klimeschi. The main volatile compounds of the host poplar P. alba var. pyramidalis for different physiological statuses and those of three other non-host poplars (P. alba L., P. tomentosa Carr., and P. dakuanensis Hsu) were analysed through solid-phase micro extraction (SPME) coupled with thermal desorption and gas chromatography-mass spectrometry (GC-MS). The major compound groups were aldehydes, esters, alcohols, ketones, phenols, terpenes and alkanes. Comparative analysis of the changes in the different physiological stages of P. alba var. pyramidalis and other non-host Populus volatile substances was conducted, and the results showed that 2-hydroxy-benzaldehyde, nonanal, decanal, 2-methyl-butanal, (Z)-3-hexen-1-ol benzoate, methyl benzoate, methyl salicylate, geraniol and salicyl alcohol might act as attractants for T. klimeschi, and 2-hexenal, hexanal, 2-cyclohexen-1-one, caryophyllene, eugenol, benzyl alcohol, and eucalyptol could be deterrents for T. klimeschi. These experiments may lead to the optimisation of a synthetic lure that may be used to detect and monitor T. klimeschi.     

EVOLUTION OF POPULUS NIGRA (SECT. AIGEIROS):INTROGRESSIVE HYBRIDIZATION AND THE CHLOROPLAST CONTRIBUTION OF POPULUS ALBA (SECT. POPULUS)

Restriction site variation in chloroplast DNA and nuclear ribosomal DNA was examined in 16 accessions from the Salicaceae comprising ten species of Populus and one outgroup species of Salix. Forty-nine restriction site mutations in the chloroplast DNAs were used to generate one most parsimonious phylogenetic tree. This tree indicates that all varieties of P. nigra (black poplars of sect. Aigeiros) have a chloroplast genome, maternally inherited, derived from the clade including the white poplars (P. alba and segregate species of sect. Populus) and divergent from the American cottonwoods of their own section. Twenty-one restriction site mutations in the nuclear ribosomal DNAs generated a single most parsimonious phylogenetic tree that indicates that the nuclear genome ofP. nigra is distinct from both the white poplars and American cottonwoods. The incongruity of these independent molecular phylogenies provides evidence for an unusual origin of the black poplars. Populus alba or its immediate ancestor acted as the maternal parent in a hybridization event with the paternal lineage of P. nigra. Subsequent backcrosses to the paternal species gave rise to the extant P. nigra with a chloroplast genome of P. alba and the nuclear genome of the paternal species. These hybridization and introgression events must have pre-dated the divergence of the black poplar varieties. The biphyletic nature of the P. nigra genomes suggests that dependency on one class of molecular or morphological markers or the merging of the two kinds of data sets to derive accurate estimates of true phylogenies could be misleading in plants.