影响披碱草属植物遗传分化和亲缘关系的地理因素分析

用微卫星标记法对产自中国青藏高原和蒙古高原地区9种披碱草属（Elymus L．）植物的40个居群进行遗传变异和亲缘关系分析,居群问遗传相似系数为0．020～0．957,居群间遗传距离与地理因素关系密切。以垂穗披碱草（Elymus nutctns Griseb．）为例,采用二维和三维Mantel检验,对遗传距离和地理因素间的关系（纬度、经度和海拔）作进一步分析,结果表明,地理位置（纬度和经度）是影响垂穗披碱草居群微卫星遗传差异的最重要因素（R=0．478;P＜0．05）,其次是海拔（R=0．258;P＞0．05）。单一地理位置因素（纬度或经度）与遗传距离的相关性并不明显,但从单一地理位置因素与遗传距离的相关系数、可信度区间来看,纬度对遗传分化的影响程度大于经度。     

青藏高原垂穗披碱草遗传变异的地理因素分析

采用等位酶标记对我国青藏高原地区垂穗披碱草的9个种群进行遗传变异和系统关系分析.结果表明,不同种群间遗传距离范围在0.010 6-0.377 8,种群间遗传距离和地理环境关系密切.采用聚类分析和二维、三维Mantel检验,对青藏高原垂穗披碱草(Elymusnutans Griseb.)不同种群间遗传距离与环境条件的关系(纬度、经度和海拔)进一步分析发现,海拔和地理位置(纬度和经度)均明显影响垂穗披碱草种群遗传差异.种群间遗传距离和海拔(R=0.476 8)、地理位置(R=0.447 1)均呈现显著正相关,种群间遗传距离随着海拔、地理位置差距的增大而增加,但海拔是影响其遗传结构的最重要因素,其次是经纬度.     

垂穗披碱草与达乌里披碱草基因组细胞遗传学比较

采用顺序FISH-GISH技术,12个重复序列探针,包括9个三核苷酸简单重复序列、2个卫星DNA重复序列pSc119.2和pAs1以及5S rDNA,通过重复序列的物理定位对达乌里披碱草和垂穗披碱草基因组中部分重复序列的分布特征进行了比较分析,为进一步研究垂穗披碱草和达乌里披碱草的物种形成及演化提供新的分子细胞遗传学证据。结果表明:(1)所有的序列在这2个物种的染色体上都能产生可检测的杂交信号,且在2个物种中(AAC)_(10)、(ACT)_(10)、(CAT)_(10)都表现为共分布,(AAG)_(10)与(AGG)_(10)表现为近似共分布;2个物种的H基因组除5S rDNA序列外,其他序列都产生强烈且丰富的杂交位点,St与Y基因组不同重复序列探针的荧光位点数目有所差别,表现为5S rDNA、pSc119.2、(AAC)_(10)、(CAT)_(10)、(ACT)_(10)、(CAC)_(10)探针的信号位点较少或无信号,其余的探针信号位点稍多。(2)达乌里披碱草的第2对染色体上具有(AAC)_(10)、(CAT)_(10)、(ACT)_(10)的杂交位点、第6对染色体上具有(CAC)_(10)的杂交位点,而在垂穗披碱草的St基因组中未观察到上述序列杂交位点;达乌里披碱草St基因组仅有第4对染色体的端部具有pSc119.2杂交位点,而在垂穗披碱草St基因组中的pSc119.2杂交位点位于第5对染色体长臂的间隔区;相对于达乌里披碱草,垂穗披碱草St和Y基因组染色体含有更多的重复序列杂交位点。(3)达乌里披碱草的H/Y基因组间易位在不同材料间是稳定存在的,达乌里披碱草基因组相对稳定,不同材料间H基因组重复序列杂交信号多态性高于St和Y基因组;垂穗披碱草基因组的变异较大,不同材料间St和Y基因组重复序列杂交信号多态性高于H基因组。研究认为,垂穗披碱草和达乌里披碱草的H基因组均起源于布顿大麦,St基因组可能起源于不同的拟鹅观草属物种;与达乌里披碱草相比垂穗披碱草St与Y基因组可能具有更高的染色体结构变异性,而垂穗披碱草St与Y基因组变异较大的原因可能是与同区域分布的含StY基因组的物种发生了种间渗透杂交。     

异叶泽兰的遗传多样性和居群历史动态研究

异叶泽兰属于菊科泽兰属,是该属分布海拔相对较高的植物,分布在青藏高原东部和横断山海拔1700~3000 m的地区。该文利用ycf6-psbM和rpl32-trnL两个叶绿体DNA(cpDNA)片段以及核DNA片段ITS(nITS)作为分子标记,研究了异叶泽兰的遗传多样性及其分布特征,探讨了其居群历史动态。结果表明:(1)叶绿体片段联合分析结果显示,异叶泽兰在物种水平遗传多样性水平不高,单倍型多态性指数(H_d)为0.656,核苷酸多态性(π)为0.00161;而ITS的基因型多态性指数(H d)为0.687,核苷酸多态性(π)为0.00235。(2)cpDNA和nITS分析结果均显示,异叶泽兰居群水平总的遗传多样性大于居群内平均遗传多样性,遗传变异主要发生在居群间,居群间存在明显的遗传分化(cpDNA:G_st=0.679,N_st=0.655,F st=0.655;nITS:G_st=0.543,N_st=0.370,F_st=0.584),但是由于N_st值小于G_st值,因此异叶泽兰的分布不具有明显的谱系地理结构。(3)基于单倍型地理分布以及Network分析推测,横断山区南部(川西南-滇西北)和云南中部可能是异叶泽兰在第四纪冰期时的两个避难所,中性检验和失配分析的结果支持异叶泽兰在冰期后未发生过居群扩张。     

利用RAPD分析披碱草属、鹅观草属和猬草属模式种的亲缘关系

利用随机扩增多态性DNA（RAPD）技术对小麦族披碱草属、鹅观草属和猬草属3个属的模式种进行了基因组DNA多态性分析。42个引物产物的290条谱带中,257条（88.62%)表现出多态性,说明披碱草属、鹅观草属和猬草属3个属的模式种间具有丰富的遗传多样性。利用290个RAPD标记,计算材料间Nei氏遗传相似性系和遗传距离,在NTSYS程序中利用UPGMA进行聚类。结果表明,Elymus sibiricus种不同居群间的遗传差异较小,遗传距离在0.097-0.180之间。E.sibiricus,Roegneria caucasica和Hystrix patula的种间遗传差异明显,遗传距离在0.458-0.605之间。H.patula与E.sibiricus的亲缘关系较近。R.caucasica与E.sibiricus的亲缘关系较远。     

披碱草属野生居群表型多样性及其与环境关系研究

以来自8省区38个披碱草属野生居群的22个表型性状为调查对象,利用变异系数及多样性指数法对性状内和性状间及种间的表型变异进行分析,并对表型性状与地理气象因子间的关系进行相关性分析,用平均聚类法对38个居群进行分类,以揭示不同来源披碱草属种质资源表型多样性。结果显示:(1)营养器官性状中旗叶至穗基部长变异系数最高(44.695%),穗部性状中的每穗小穗数变异系数最高(77.005%)。(2)披碱草、麦宾草、圆柱披碱草与老芒麦这4个种间总体平均多样性指数为0.920～1.560,披碱草最高,麦宾草次之,圆柱披碱草最低。(3)表型性状变异受海拔、经度及年均温的影响较大。(4)UPGMA聚类结果将所有材料分成4组,披碱草属植物性状的表型特征没有严格按地理距离而聚类。研究表明,披碱草属植物野生种质材料具有丰富的表型多样性,表型性状与环境之间关系密切,采集过程中应尽量保持居群的完整性,最大程度地保护中国披碱草属牧草的遗传多样性。     

青海高原披碱草属种间天然杂种的细胞学鉴定

利用重复序列探针染色体荧光原位杂交（FISH）和基因组原位杂交（GISH）技术,对采自青海高原披碱草属种间天然杂种进行细胞学鉴定,同时结合物种分布及形态学特征,共揭示6种不同天然杂种的类型。第一类为垂穗披碱草（Elymus nutans Griseb.）和鹅观草属（Roegneria C.Koch）物种间的天然杂种,染色体数为35,染色体组成为StStYYH;第二类为垂穗披碱草和达乌力披碱草种（Elymus dahuricus Turcz.ex Griseb.）间杂种,染色体数为42,染色体组成为StStHHYY;第三类为达乌力披碱草和老芒麦（Elymus sibiricus L.）种间杂种,染色体数为35,染色体组成为StStHHY;第四类为垂穗披碱草和糙毛以礼草（Kengilia hirsuta Keng）种间杂种,染色体数为42,染色体组成为StStYYHP;第五类为垂穗披碱草和大颖草（Kengilia grandiglumis Keng）种间杂种,染色体数为42,染色体组成为StStYYHP;第六类为糙毛以礼草和赖草（Leymus secalinus（Georgi） Tzvel.）种间杂种,染色体数为35,染色体组成为StYPNsXm。研究结果为进一步研究披碱草属种间杂交渐渗提供了重要参考资料;同时鉴定出的天然杂种可以作为潜在的种质资源在牧草或生态草育种中加以利用。     

珍稀濒危植物阜康阿魏的遗传多样性及遗传结构

明确珍稀濒危小种群阜康阿魏(Ferula fukanensis)的遗传多样性和遗传结构,是对其制定有效的保护和管理策略的基础和前提。本研究基于10对多态性好且可以稳定扩增的SSR引物对来源于3个居群87个珍稀濒危植物阜康阿魏的遗传多样性和遗传结构进行分析。结果显示：小种群的阜康阿魏具有相对较高的遗传多样性,居群间Nei’s基因多样性指数(h_S)为0.514,总的Nei’s基因多样性指数(h_T)为0.516,观测杂合度(H_o)为0.881,期望杂合度(H_e)为0.512,香农信息指数(I)为0.836,多态位点百分率(P_PB)为100%,遗传分化程度较低(F_st=0.007),95.9%的变异发生在居群内,遗传距离与地理距离无显著相关性,66.7%的居群遭遇了遗传瓶颈。结果表明,阜康阿魏遗传变异丰富,有较高的进化潜力。结合该种野外种群现状,建议建立保护区,开展就地保护,并加强引种和人工繁育等迁地保护措施,辅助阜康阿魏保育。本研究可为阜康阿魏植物资源保护提供理...     

野生垂穗披碱草种质的醇溶蛋白遗传多样性分析

用酸性聚丙烯酰胺凝胶电泳(A-PAGE) 对采集自中国新疆、青海、四川、西藏四省区的33份垂穗披碱草Elymus nutans材料进行醇溶蛋白分析,获得下述结果:（1）供试材料共分离出38条带纹,多态率达92.10%。4个电泳分区（α、β、γ、ω）的平均Shannon指数为0.55,Nei-Li遗传相似系数（GS）变异范围为0.36~0.93,平均值为0.63。这些结果说明供试野生垂穗披碱草材料具有较为丰富的醇溶蛋白遗传多样性。（2）对所有材料的聚类分析和主成分分析发现,在GS值为0.67的水平上供试材料可聚成7个类群,绝大部分来自于相同或相似生态地理环境的材料聚成一类,即醇溶蛋白图谱类型与材料的生态地理环境具有一定的相关性。（3）基于Shannon 多样性指数估算了5个垂穗披碱草地理类群内和类群间的遗传分化,发现类群内遗传变异占总变异的42.94 %,而类群间的遗传变异占总变异的57.06 %。这可能与该草以自花传粉为主的繁育系统有关。（4）对各地理类群基于Nei氏无偏估计的遗传一致度的聚类分析表明,各地理类群间的遗传分化与其所处的地理生态环境具有较高的相关性。 .     

利用SSR标记对垂穗披碱草和老芒麦进行物种鉴定和遗传变异分析

垂穗披碱草(Elymus nutans)和老芒麦(Elymus sibiricus)皆为花序下垂类披碱草属物种,高海拔地区的E.sibiricus的部分变异类型也具有小穗紧密排列等特征,与E.nutans在形态学性状上具有较多的交叉,造成野外种质资源采集时进行直接的田间鉴定存在困难。本研究利用12对小麦族SSR引物对8份垂穗披碱草和10份老芒麦种质进行遗传变异和物种鉴定分析,UPGMA聚类分析表明供试材料明显可依据物种差异划分成两大类,主向量分析(PCo A)与聚类分析的结果保持一致。种质间遗传相似系数分析和分子方差分析(AMOVA)也表明种间变异远高于种内。另外,本研究筛选出3对引物,ESGS79和ESGS155能够在垂穗披碱草材料中扩增出特异性条带,Xgwm311能够在老芒麦材料中扩增出特异性条带,这3对引物能够作为区分垂穗披碱草和老芒麦的依据,为野外种质资源的收集以及田间育种工作提供指导。     

Intra-population genetic diversity of two wheatgrass species along altitude gradients on the Qinghai-Tibetan Plateau: its implication for conservation and utilization

A fluorescence-based AFLP fingerprinting was applied to investigate genetic diversity in 22 natural populations of two wheatgrasses from Qinghai-Tibetan Plateau at different altitudes: the hexaploid Elymus nutans Griseb and the tetraploid E. burchan-buddae (Nevski) Tzvelev (Poaceae). Five selective primer combinations used in this study generated a total of 637 AFLP fragments across all the samples, with 612 fragments in E. nutans and 570 in E. burchan-buddae. About 45% of the scored fragments were <200 bp and about 13% of the fragments were >400 bp. Results showed that genetic diversity within populations of the two Elymus species increased gradually with the increase in altitudes from the lowest sampling sites (2800 m) and reached a plateau at the medium altitudes, and then started to decrease with the increase in altitudes. Regression analysis demonstrated a clear pattern between the expected heterozygosity (H _e) or Shannon index (I) and altitude variation, where the highest H _e values (0.3449 for E. nutans and 0.3167 E. burchan-buddae) and I values (0.5123 and 0.4759) were expected at the altitudes 3399 m and 3418 m across all sampling sites, respectively for E. nutans and E. burchan-buddae. In other words, higher genetic diversity was observed in populations occurring at the medium altitudes (3200–3600 m) than those at the low and high altitudes for the two Elymus species. Principal coordinate analysis (PCA) did not show clear association between genetic relationships of populations and their occurrences at a particular altitude. The above results suggest that efforts for conservation and utilization of two wheatgrasses species should focus more on populations occurring at the medium altitudes.     

Genetic variation and geographical divergence in Elymus nutans Griseb. (Poaceae: Triticeae) from West China

Elymus nutans Griseb. as an important forage grass and gene pools for improving cereal crops, widely distributes in west China. However, little is known about its genetic and geographical patterns. Inter-simple sequence repeat (ISSR) markers were applied to assess genetic diversity and geographical divergence among 63 E. nutans accessions from west China. The cluster analysis separated the accessions into several groups with geographical origins. The molecular variance analysis (AMOVA) showed that the proportion of variance explained by within- and among-geographical group diversity was 43.2% and 56.8%, respectively. Based on pairwise genetic distances (Φ_ST) between geographical groups, the relationships were congruent with the cluster of accessions. The distinct geographical divergence of E. nutans was revealed between Qinghai-Tibet Plateau and Xinjiang. The ecogeographical conditions such as climate and mountain ranges and elevation behaved as the crucial factors for genetic divergence. Furthermore, the study also indicated that Qinghai-Tibet Plateau might be the diversity differentiation center of E. nutans. The result will facilitate the breeding program and germplasm collection and conservation.     

Population structure affected by excess gene flow in self-pollinating Elymus nutans and E. burchan-buddae (Triticeae: Poaceae)

Seed-mediated gene flow can considerably affect population genetic structure of strictly self-pollinating species, but little is known on the extent and nature of such gene flow among pastoral plant populations. Molecular fingerprints provide a powerful tool to address the relevant issues. Genetic structure of 22 populations of two self-pollinating pasture species, Elymus nutans and E. burchan-buddae, collected from various altitudes of the Qinghai–Tibetan Plateau was studied using fluorescence-based amplified fragment length polymorphism technique. Analysis of molecular variance revealed 42.97% and 37.63% among-population variation for the two Elymus species, respectively, indicating that the majority of the total variation presented within populations. This result contradicts the common genetic variation pattern for a selfing plant species: lower genetic variation within populations. Further analysis suggested higher level of gene flow among populations within the same region than among different regions across the sampled area for the two Elymus species. STRUCTURE analyses of the Elymus populations indicated an evident admixture genetic structure, particularly among neighboring populations from the same region, supporting the hypothesis of considerable seed dispersal among populations. The excess within-region gene flow of E. nutans and E. burchan-buddae might be caused by grazing animals that promote seed dispersal when moved around the pastoral lands during foraging. The among-population gene flow promulgated by grazing animals may promote the maintenance of genetic diversity in the pasture species, particularly in small and fragmented populations within a given region.     

Assessing genetic diversity of Elymus sibiricus (Poaceae: Triticeae) populations from Qinghai-Tibet Plateau by ISSR markers

Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population structure in eight populations of Elymus sibiricus L. from the southeast of Qinghai-Tibet Plateau of China. Of the 100 primers screened, 13 produced highly reproducible ISSR bands. Using these primers, 193 discernible DNA fragments were generated with 149 (77.2%) being polymorphic, indicating considerable genetic variation at the species level. In contrast, there were relatively low levels of polymorphism at the population level with the percentage of polymorphic bands (PPB) ranging from 44.04 to 54.92%. The mean gene diversity (H_E) was estimated to be 0.181 within populations (range 0.164–0.200), and 0.274 at the species level. A high level of genetic differentiation among populations was detected based on Nei's genetic diversity analysis (33.1%), Shannon's index analysis (34.5%), Bayesian method (33.2%) and AMOVA analysis (42.5%). No significant statistical differences (analysis of molecular variance [AMOVA], P = 0.08) in ISSR variation were found between the sample collection regions. However, among populations (42.5% of the variance) and within populations (57.5% of the variance), there were significant differences (P < 0.001). Populations shared high levels of genetic identity. This pattern of genetic variation was different from that for most of inbreeding Triticeae species reported. In addition, a geographical pattern of population differentiation, where the populations from south and north of sampling sites were clearly separated from each other, was revealed by both the cluster and principal coordinates analyses. Generally, the result of this study indicates that E. sibiricus contains high molecular variation in its populations. The implications of these results for the conservation of the species are discussed.     

青藏高原地区山生柳遗传多样性研究

利用叶绿体非编码区片段研究分布于青藏高原地区的山生柳居群遗传多样性,对未来山生柳生态环境和青藏高原地区物种丰富度的保护具有指导意义。该研究设计并筛选出cpDNA引物5'trnG2G-3'trnG(UUC)和5'rpS12-rpL20,用扩增出的片段和对应的联合片段进行后续的遗传多样性分析。结果表明:通过山生柳的联合片段检测到35种单倍型,单倍型多态性0.626,核苷酸多态性0.000 85。中性检验Tajima’s D(-2.286 70,P0.01)和Fu’s Fs(-5.298 05,P0.02)都是显著负值,推测山生柳个体数近期经历过扩张。AMOVA分析显示,居群内和居群间遗传变异分别为93.70%和6.30%,表明居群内的变异是山生柳遗传变异的主要来源。居群间遗传分化程度中等偏低(FST=0.063),基因流(N_m)为7.439,说明山生柳各居群的基因交流非常频繁,不同地理居群间存在一定的基因流动。遗传分化系数N_(ST)(0.075)大于GST(0.068)和基于遗传距离和单倍型的UPGMA聚类分析,表明山生柳12个居群分为4组且与居群的地理分布没有明显相关性。山生柳是进行有性繁殖还是无性繁殖主要受环境因素的影响,居群内变异是山生柳遗传变异性的主要来源,居群间基因交流频繁。     

Molecular variation and population structure in Elymus trachycaulus and comparison with its morphologically similar E. alaskanus

Random amplified polymorphic DNA (RAPD) markers were used to determine the levels and pattern of molecular variation in four populations of Elymus trachycaulus, and to estimate genetic similarity among different populations of E. trachycaulus from British Columbia and the Northwest Territories and one population of Elymus alaskanus from the Northwest Territories. Based on 124 RAPD bands (loci), mean percent polymorphic loci for E. trachycaulus (P_P) was 67.4% (a range 41.2% to 86.3%), and mean gene diversity (H_e) for E. trachycaulus species was 0.23 (range 0.18 to 0.27). The total genetic diversity was 0.32. Differentiation among populations was 31% (F_ST = 0.31) with most of the genetic variation found within populations (69%). This pattern of genetic variation was different from that reported for inbred species in general.The authors are very grateful to Michael Bond for excellent Laboratory assistance, to Dr. Mary Barkworth for her encouragement. This study was supported by a Natural Science and Engineering Research Council (NSERC) discovery grant and by a Saint Marys University Internal grant to G.S.     

北沙柳群体遗传多样性和遗传结构分析

以内蒙古北沙柳(Salix psammophila)国家种质资源库内9个群体(P1~P9)288个无性系为实验材料,利用TP-M13-SSR技术,选取22对具有多态性EST-SSR北沙柳引物,采用毛细管电泳对PCR产物进行检测,分析北沙柳遗传多样性、分化程度和群体遗传结构,为北沙柳种质资源库遗传管理、无性系鉴定、品种选育、遗传改良和构建指纹图谱提供理论依据。结果显示:(1)22对EST-SSR引物共检测到222个等位基因,各位点平均等位基因数(A)为10,四倍体基因型丰富度(G)和特异基因型(G1)总和分别为1 460和802个,平均特异基因型比率(P1)和种质鉴别率(P2)分别为45.86%和13.21%。(2)9个群体平均等位基因数(A)为7.475,基因型丰富度(G)为15.586,观察杂合度(Ho)和期望杂合度(He)分别为0.577和0.638。以期望杂合度He为标准,北沙柳群体遗传多样性水平最低的是P1和P9。(3)北沙柳群体遗传分化系数仅为0.02,AMOVA分子变异分析显示,北沙柳群体大部分遗传变异来自群体内(97%),群体间变异仅为3%。(4)三维主成分、聚类和Structure群体遗传结构分析显示,9个群体被划分为2个组,Mantel检验表明北沙柳遗传距离与地理距离极显著相关(r=0.684 P0.001)。研究表明,北沙柳种质资源具有丰富的遗传多样性,这是其具有耐旱、耐寒、耐高温、耐沙埋和抗风蚀等适应性较强的分子基础;北沙柳的遗传变异集中在群体内;分布区群体呈现由中心向边缘群体扩张分化的趋势。     

Effects of landscape structure on genetic diversity of Geum urbanum L. populations in agricultural landscapes

Plant species in fragmented populations are affected by landscape structure because persistence within and migration among inhabited patches may be influenced by the identity and configuration of surrounding habitat elements. This may also be true for species of the semi-natural vegetation in agricultural landscapes. To determine the effect of landscape elements we analyzed Wood Avens (Geum urbanum L.) populations within three 4×4 km² agricultural landscapes in Germany, Switzerland and Estonia, which differ in levels of land use intensity and habitat fragmentation. Genetic variation was determined in 15 randomly selected populations in each landscape using 10 microsatellite loci. The landscape structure was assessed at two circles around each population, with radii defined by the range limits of spatial genetic autocorrelation. Multiple regression analysis was used to determine the influence of landscape structure variables for inter- and intrapopulation genetic diversity. Gene diversity was equally high in Germany (H_e=0.27) and Switzerland (H_e=0.26) but lower in Estonia (H_e=0.16). A high overall inbreeding coefficient (F_IS=0.89) was found, as expected for a selfing breeding system in G. urbanum. Genetic differentiation among populations was high (overall F_ST=0.43, 0.48, and 0.45 in Estonia, Switzerland and Germany, respectively), and did not differ among the three landscapes. Only a moderate influence of individual land use types on genetic diversity within and among populations was found with some idiosyncratic relationships. Genetic variation within populations was correlated to the amount of hedgerows positively in Estonia but negatively in Switzerland. The study demonstrates that the distribution of individual land use types affects the genetic pattern of a common plant species. However, different variables were identified to influence the genetic structure in three different landscapes. This indicates a major influence of landscape-specific land use history and stochastic processes determining gene flow and plant population structure.