马铃薯腐烂茎线虫的遗传变异及其与生态因子的相关性

马铃薯腐烂茎线虫(Ditylenchus destructor)是世界范围内广泛分布的检疫性线虫,严重危害多种作物.马铃薯腐烂茎线虫为适应不同的生活环境而发生相应的遗传变异,可以通过不同地理种群之间遗传结构的差异来研究环境生态因子对种群遗传结构的影响.利用简单重复序列区间(inter-simple sequence repeat,SSR)分子标记技术研究了我国马铃薯腐烂茎线虫5个群体的遗传多样性、遗传变异,分析了遗传多样性与生态因子的相关性.研究结果表明,马铃薯腐烂茎线虫具有较高的遗传多样性.在种群水平,安徽省太和县种群的遗传多样性最高,河北省昌黎县的遗传多样性最低;在群体水平,5个群体的遗传多样性大小分别为安徽＞山东＞江苏＞河北＞北京.5个群体间具有较小程度的遗传变异,遗传分化系数(Gs)为0.0725;不同种群间具有频繁的基因交流(Nm=6.3933).相关分析表明马铃薯腐烂茎线虫的Shannon遗传多样性与海拔、经度、纬度、年降雨量等成正相关关系,与年均温、最高温、最低温等成负相关关系;马铃薯腐烂茎线虫的遗传距离与地理距离成正相关关系.研究结果认为马铃薯腐烂茎线虫对低温具有较强的适应性,适于在华北、东北等地生长发育,将加强北方地区马铃薯种苗和种薯的管理,对防止马铃薯腐烂茎线虫进一步扩散蔓延提供指导意义.     

细基江蓠繁枝变种（Gracilaria tenuistipitata var.Liui）群体遗传多样性的ISSR分析

运用ISSR标记对来自深圳、北海和防城港的三个细基江蓠繁枝变种群体进行遗传多样性检测,筛选出的16条ISSR引物共扩增出111条带,引物平均多态位点比例为54.95%。三个群体的多态位点比例深圳群体最高为23.42%,北海群体最低为4.50%;群体平均多态位点比例为11.12%,平均基因多样性（Hs）为0.051 3,表明细基江蓠繁枝变种群体遗传多样性较低。群体遗传分化指数为0.756 5,说明遗传变异主要存在于群体间且群体间的遗传分化水平较高。Mantel检验发现遗传距离与地理距离无关。适应生态环境选择无性繁殖模式可能是细基江蓠繁枝变种群体遗传多样性较低、群体间遗传分化大的重要因素。     

Neutral DNA markers fail to detect genetic divergence in an ecologically important trait

The development of strategies for in situ, ex situ conservation and reforestation of the monkey puzzle tree (Araucaria araucana), a vulnerable tree endemic to southern South America, has led to an interest in the level and distribution of the genetic diversity of the species. Neutral DNA markers (RAPDs) and quantitative genetic techniques were used to characterise genetic heterogeneity within and among populations from throughout the natural range of the species. Both the level and pattern of genetic variation estimated using the different techniques were essentially uncorrelated. An important discrepancy was found with the neutral markers failing to detect an important quantitative genetic divergence across the Andean Range relating to drought tolerance. This study clearly demonstrates the potential problems associated with making recommendations for conserving the genetic resource of threatened species based solely on neutral marker studies. Alternative approaches are discussed, including a stronger focus on ecologically important traits and the potential use of surrogate measures of genetic variability.     

复杂疾病的遗传咨询技术

复杂疾病大面积爆发使人们的生活健康面临着重大挑战。在这一环境下,遗传咨询在人们的生活中占据了越来越重要的地位。依据基因与环境互作共同影响个体健康的原理,咨询者在遗传咨询师的指导帮助下合理解决各种遗传学问题可以有效降低复杂疾病的发病率。目前国内的遗传咨询发展尚处于萌芽期,随着遗传咨询在健康领域的地位上升,该技术在未来将会进一步推广应用。     

分子标记技术在杉木研究中的应用

综述了分子标记技术在杉木种质资源鉴定、群体遗传多样性研究、遗传连锁图谱构建和数量性状位点(QTL)定位及分子标记辅助选择育种等方面的应用进展,指出目前该方面研究存在的问题,并展望了分子标记技术在杉木研究中的应用前景     

Consequences of ex situ cultivation of plants: Genetic diversity, fitness and adaptation of the monocarpic Cynoglossum officinale L. in botanic gardens

Ex situ collections in botanic gardens have great potential in contributing to the conservation of rare plants. However, little is known about the effects of cultivation on the genetic diversity and fitness of garden populations, about genetic changes due to unconscious selection and potential adaptation to the artificial conditions. We compared the genetic variability and fitness of the rare, short-lived perennial Cynoglossum officinale from 12 botanic gardens and five natural populations in Germany. Genetic variability was assessed with eight nuclear microsatellites. Plants were grown in a common garden and performance was measured over 2 years. Mean genetic diversity was very similar in botanic garden and natural populations. However, four of the garden populations exhibited no genetic variability at all. Moreover, the genetic diversity of garden populations decreased with increasing duration of cultivation, indicating genetic drift. Plant performance from natural and garden populations in terms of growth, flowering and seed production was similar and in garden populations only seed mass was strongly related to genetic diversity. Several lines of evidence indicated genetic changes in garden populations in response to cultivation. Seed dormancy was strongly reduced in garden populations, and in response to nutrient addition garden plants increased the size of their main inflorescence, while wild plants increased the number of inflorescences. These changes could be maladaptive in nature and reduce the suitability of garden populations as a source for reintroductions. We suggest that botanic gardens should pay more attention to the problem of potential genetic changes in their plant collections.     

Are hotspots of evolutionary potential adequately protected in southern California?

Reserves are often designed to protect rare habitats, or “typical” exemplars of ecoregions and geomorphic provinces. This approach focuses on current patterns of organismal and ecosystem-level biodiversity, but typically ignores the evolutionary processes that control the gain and loss of biodiversity at these and other levels (e.g., genetic, ecological). In order to include evolutionary processes in conservation planning efforts, their spatial components must first be identified and mapped. We describe a GIS-based approach for explicitly mapping patterns of genetic divergence and diversity for multiple species (a “multi-species genetic landscape”). Using this approach, we analyzed mitochondrial DNA datasets from 21 vertebrate and invertebrate species in southern California to identify areas with common phylogeographic breaks and high intrapopulation diversity. The result is an evolutionary framework for southern California within which patterns of genetic diversity can be analyzed in the context of historical processes, future evolutionary potential and current reserve design. Our multi-species genetic landscapes pinpoint six hotspots where interpopulation genetic divergence is consistently high, five evolutionary hotspots within which genetic connectivity is high, and three hotspots where intrapopulation genetic diversity is high. These 14 hotspots can be grouped into eight geographic areas, of which five largely are unprotected at this time. The multi-species genetic landscape approach may provide an avenue to readily incorporate measures of evolutionary process into GIS-based systematic conservation assessment and land-use planning.     

Effects of flood events on the genetic structure of riparian populations of the grassland plant Origanum vulgare

River regulation results in the disconnection and increased fragmentation of habitats in the river corridor. In this study, we investigated the within-population genetic variability and among-population genetic differentiation of 21 populations of Origanum vulgare along the River Meuse, using dominant AFLP markers, in order to asses the restoration potential of this species in the context of current river restoration efforts. The average observed within-population genetic diversity was high and suggests that river regulation and associated fragmentation of the populations have not strongly affected genetic diversity. The genetic differentiation between populations was high (Φ_ST = 0.24) and can be explained by founder effects, rather than by genetic drift in isolated populations. We also detected a pronounced hierarchic spatio-temporal structure in genetic variation. This structure can be related to the irregular patterns in the flow regime of the River Meuse. Large floods are the major vector of genetic structure, but geographic upstream proximity, probably mediated by small floods, also has an important effect on genetic structure. Three distinct groups of populations were observed, two of which could be related to the extreme flood events of the mid-nineties of last century. Assignment tests revealed occasional long-distance seed dispersal with extreme flood events and local colonisation with more regular floods. Our study species optimally took benefit of the opportunities offered by the river restoration programme, with a strong colonisation after floods, and illustrates the need for maintaining river dynamics to conserve and restore genetic diversity.     

Microsatellite analysis of genetic population structure of the endangered cyprinid Anaecypris hispanica in Portugal: implications for conservation

The endangered fish species Anaecypris hispanica is restricted to eight disjunct populations in the Portuguese Guadiana drainage. The genetic structure of these populations was studied in order to determine levels of genetic variation within and among populations and suggest implications for conservation of the species. Based on five microsatellite loci, the null hypothesis of population homogeneity was tested. Tests for genetic differentiation revealed highly significant differences for pairwise comparisons between all populations, and substantial overall population subdivision (F_ST=0.112). All sampled populations contained unique alleles. Our findings indicate marked genetic structuring and emphasise limited dispersal ability. The high levels of genetic diversity detected within and among A. hispanica populations suggest, however, that the observed fragmentation and reduction in population size of some populations during the last two decades, has impacted little on levels of genetic variability. Data imply that most A. hispanica populations should be managed as distinct units and that each has a high conservation value containing unique genetic variation. It is argued that geographic patterns of genetic structuring indicate the existence of eight management units.     

小麦抽穗期和株高的辐射遗传效应

以两个小麦品种为材料,用０、２０、３０、４０ｋｒａｄ的１３７Ｃｓ和６０Ｃｏγ射线辐照,探讨其抽穗期和株高的辐射遗传效应,比较两种辐射源的差异。结果表明：１３７Ｃｓ和６０Ｃｏγ射线均能诱发早熟和矮秆突变,辐射遗传效应显著并相似。说明两种辐射源均可采用,但性状的平均表现与遗传方差、遗传变异系数、遗传力、遗传进度、相对遗传进度等遗传参数值随品种、辐照剂量和辐射世代的不同而异。诱变效果较好的品种是７７中－２８８２,剂量为３０ｋｒａｄ;在Ｍ２、Ｍ３代的辐射遗传效应明显。     

Improving Genetic Engineering Secondary Education Through a Classroom-Ready Online Resource

Genetic engineering has long been used in food production in the United States. However, consumers' science literacy in genetic engineering is poor. Teacher knowledge, time, and resources are lacking in science curriculums on genetic engineering. Through interviews conducted with six high school agriculture teachers we show how a new online resource, The Journey of a Gene, addresses these barriers to help improve their knowledge and increase time spent on genetic engineering. The positive outcomes support funding for genetic engineering education. Education is key to help consumers make informed purchasing decisions and societal decisions about advancing genetic engineering research.     

Challenges and opportunities of genetic approaches to biological conservation

I discuss future challenges and opportunities in genetic approaches to biodiversity conservation. Resolving taxonomy uncertainties and identifying diverged evolutionary units within species are both bedevilled by a plethora of definitions: the challenge for the conservation community is to come to an agreed definition of species and for a unit within species for conservation purposes. For genetic management in the wild, the main challenge is to apply well-established genetic principles to management, especially of fragmented populations. Fears about outbreeding depression are preventing rational use of gene flow for genetic rescue; predicting the risk of outbreeding depression is the most important unmet scientific challenge in the field. The major challenge in genetic management of captive populations of threatened animal species is to institute explicit management to minimize genetic adaptation to captivity, so that reintroduction success is maximized. The development of low cost genome sequencing offers many research opportunities and challenges. For example, there are opportunities to identify genes involved in speciation and a major challenge is to devise molecular tests to predict reproductive isolation between populations. Genomics offers opportunities to provide higher precision estimate for many parameters of importance to conservation. A major challenge is to devise means to assess, on a genome-wide basis, genetic diversity that is important to adaptive evolution. There is a challenge to develop simple inexpensive means to monitor genetic diversity of species on a global scale. Many of the most important practical challenges concern application of current genetic knowledge to the management of threatened species.     

山西芝麻种质资源SSR遗传多样性及群体结构分析

为探明山西芝麻种质资源的遗传特性,本研究利用30对简单重复序列标记(SSR)对71份山西芝麻种质资源进行遗传多样性分析及群体结构分析。结果表明,30对SSR标记共检测到144个等位基因位点,平均每个SSR标记4.800个等位基因;有效等位基因数在1.058~5.149之间,平均2.805个;Shannon指数变幅为0.128~1.813,平均为1.096;Nei's遗传多样性指数变幅为0.055~0.806,平均为0.558;多态性信息含量变幅为0.053~0.783,平均为0.515。基于SSR标记对参试材料进行聚类分析,遗传相似系数为0.21~0.67,在遗传相似系数0.27处将参试材料分为6个类群;基于SSR标记对参试材料进行群体结构分析,将参试材料划分为5个组群。综上所述,山西芝麻种质资源间遗传差异相对较高,具有丰富的遗传多样性,在今后芝麻种质资源创制利用中,加大山西芝麻种质资源的开发与利用,可为芝麻品种遗传改良和优异基因发掘奠定良好的基础。     

Low impact of present and historical landscape configuration on the genetics of fragmented Anthyllis vulneraria populations

Decreasing habitat fragment area and increasing isolation may cause loss of plant population genetic diversity and increased genetic differentiation between populations. We studied the relation between the historical and the present landscape configuration (i.e., patch area and patch connectivity), and the present management of calcareous grassland fragments on the one hand, and the within and between population genetic structure of 18 Anthyllis vulneraria populations on the other hand. Despite the long-time fragmentation history and the mainly selfing breeding system of the species, we detected very low genetic differentiation (Φ_st = 0.056) among habitat fragments and no significant isolation-by-distance relation. Average within fragment genetic diversity measured as molecular variance and expected heterozygosity, were relatively high (16.46 and 0.28, respectively), and weakly positively correlated with the current fragment area, most likely because larger fragments contained larger populations. We found no effects of the historical landscape configuration on the genetic diversity of the populations. Our data suggest that the consequences of habitat fragmentation for genetic differentiation and genetic diversity of A. vulneraria are relatively minor which is very likely due to the historical high levels of seed exchange among fragments through grazing and roaming livestock. This study provides indirect evidence that nature management by grazing not only positively affects habitat quality but that it might also mitigate the genetic consequences of habitat fragmentation. From the conservation point of view, this study illustrates the importance of grazing and of the regular transport of livestock between fragments to prevent the long-term effects of fragmentation on the genetic diversity of the populations studied.     

EST-SSR分析云南茶树资源的遗传多样性和亲缘关系

利用EST-SSR标记对云南134份茶树资源遗传多样性和亲缘关系进行了分析。30对引物共检测到等位位点127个,平均每对引物产生423个;共检测到263个基因型,平均每对引物所扩增的基因型有88个;遗传多态性信息含量平均达0501,高于其它地区的相关研究结果,表明云南茶树资源具有丰富的遗传多样性。资源间的平均遗传距离和相似系数分别为0413和0597,说明资源间的遗传差异比较大,遗传基础较宽。聚类可将134份资源划分为4大组。8个种群间的遗传相似系数变异范围为0753～0981,平均遗传相似系数为0891,表明不同种群间的遗传差异比较小。云南茶树资源间亲缘关系的揭示为今后茶树资源保存和新品种选育提供了一定理论依据。     

利用SRAP和ISSR标记分析广东茶树种质资源的遗传多样性

利用EST-SSR标记对云南134份茶树资源遗传多样性和亲缘关系进行了分析。30对引物共检测到等位位点127个,平均每对引物产生423个;共检测到263个基因型,平均每对引物所扩增的基因型有88个;遗传多态性信息含量平均达0501,高于其它地区的相关研究结果,表明云南茶树资源具有丰富的遗传多样性。资源间的平均遗传距离和相似系数分别为0413和0597,说明资源间的遗传差异比较大,遗传基础较宽。聚类可将134份资源划分为4大组。8个种群间的遗传相似系数变异范围为0753～0981,平均遗传相似系数为0891,表明不同种群间的遗传差异比较小。云南茶树资源间亲缘关系的揭示为今后茶树资源保存和新品种选育提供了一定理论依据。     

Relative effects of road mortality and decreased connectivity on population genetic diversity

Roads can have two important effects on populations that impact genetic variation: reduced gene flow and reduced abundance. Reduced gene flow (“barrier effects”) due to road avoidance behavior or road mortality can lead to reduced genetic diversity because genetic drift is enhanced in fragmented populations. Road mortality can also reduce population abundance (“depletion effects”) whenever road-caused mortality outpaces recruitment, also lowering diversity even when barrier effects are inconsequential. Although roads are expected to affect both genetic diversity and fragmentation, most research focuses only on fragmentation. Furthermore, in studies that do investigate road effects on genetic diversity, correlations are usually attributed to barrier effects and little attention is paid to the potentially confounding influence of mortality-caused depletion effects. Here we investigate the relative importance of barrier and depletion effects on genetic diversity of populations separated by a road by performing coalescent simulations wherein these two road effects are varied independently. By simulating wide ranging rates of migration and population decline, we also determine how the importance of these forces changes depending on their relative magnitude. We show that the vast majority of potential variation in genetic diversity is governed by depletion (mortality) rather than barrier effects. We also show that unless migration is sufficiently high and population decline due to mortality is sufficiently low, increasing migration across roads will generally not recoup genetic variation lost due to road mortality. We argue that the genetic effects of road-mediated mortality have been underappreciated and should be more often considered before prioritizing road-mitigation measures.     

Agronomic and genetic characterization of wild emmer wheat (<Emphasis Type="Italic">Triticum turgidum</Emphasis> subsp<Emphasis Type="Italic">. dicoccoides</Emphasis>) introgression lines in a bread wheat genetic background

During a long evolutionary history across a range of environmental conditions in the Near East Fertile Crescent, wild emmer wheat (Triticum turgidum subsp. dicoccoides) has accumulated a wealth of genetic diversity and adaptations to multiple biotic and abiotic stress conditions. The joint effects of the domestication and subsequent selection in man-made agro-ecosystems have considerably reduced the genetic variation in cultivated crop species as compared to their wild progenitors. The wild emmer gene pool harbors a rich allelic repertoire for improving numerous agronomically important traits. A set of advanced wild emmer wheat introgression lines (ILs) was previously established on a bread wheat genetic background. It combines genetic diversity from the wild progenitor as well as the genetic background of the cultigen. Based on field evaluations, the set of ILs (divided hierarchically into different families based on the genetic background) has exhibited high phenotypic variance in agronomically important traits. Analyses of variance ?(ANOVA) have shown that the effect of the hierarchical genetic factors was significant in the vast majority of the traits. Similarly, characterizations by molecular markers of known traits have shown that the genetic profile differs between ILs from different genetic backgrounds. Multivariate principal component analysis has revealed interesting associations between vegetative and reproductive traits and illustrated the impact of some of these traits on ILs distribution in the PC1 and PC2. The exploitation of the wild emmer wheat ILs as a tool for reintroduction of alleles that were lost during domestication and possible implications for wheat breeding are discussed.     

Level and Transmission of Genetic Heterozygosity in Apricot (Prunus armeniaca L.) Explored Using Simple Sequence Repeat Markers

In this study, 17 peach simple sequence repeat (SSR) sequences were used in the exploration of the genetic heterozygosity level of several apricot cultivars from Spain, France, Greece, and the USA, and 23 descendants. The genotypes can be classified in three groups as a function of their genetic heterozygosity (1) local cultivars from Murcia (Spain) (‘Gitanos’ and ‘Pepito del Rubio’) and several descendants from crosses among these cultivars, with very low genetic heterozygosities (less than 0.30); (2) cultivars from France and Spain (‘Moniquí’, ‘Currot’ and ‘Bergeron’) and several descendants, with intermediate levels of genetic heterozygosity (around 0.45); and (3) cultivars ‘Orange Red’ and ‘Goldrich’ from North America and ‘Lito’ from Greece, with the remaining descendants, having genetic heterozygosities higher than 0.50. The results showed the high increase of genetic heterozygosity in the case of descendants from complementary crosses. The use of cultivars from North America could increase greatly the genetic heterozygosity in the Spanish apricot breeding programs, enlarging the genetic variability of the local cultivars. On the other hand, in the case of transgressive crosses among local Spanish cultivars, the increase of genetic heterozygosity was much lower.     

Widespread selective sweeps affecting microsatellites in Drosophila populations adapting to captivity: Implications for captive breeding programs

Many threatened species are being maintained in captivity to save them from extinction, often with the eventual aim of reintroduction. The objective of genetic management in captivity is to ‘freeze’ evolution i.e. to avoid genetic adaptation to captivity and to retain genetic diversity. Most current genetic management of threatened species addresses the latter, but does not explicitly address the former. The theory underlying current genetic management and its practical implementation assumes neutrality of loci. However, genetic adaptation in captive populations may cause non-neutral behavior at neutral loci due to selective sweeps (hitchhiking) caused by rapid allele frequency changes at linked fitness loci. We compared changes in microsatellite genetic diversity at eight non-coding loci with neutral predictions in 23 pedigreed captive populations of Drosophila melanogaster maintained with effective sizes of 25 (eight replicates), 50 (6), 100 (4), 250 (3) and 500 (2) for 48 generations. Loss of microsatellite heterozygosity was significantly faster (by 12%) than predicted by neutral theory, as assessed by regressing proportion of heterozygosity retained on pedigree inbreeding coefficients. Further, greater than neutral changes were observed for both variances in allele frequencies across replicates (by 25%), and for temporal changes in allele frequencies (by 33%). All eight microsatellite loci showed signals of selectively-driven changes. Rather than having their evolution ‘frozen’, captive populations are undergoing major genome-wide selective sweeps that affect not only fitness loci but linked neutral loci. Captive genetic management for threatened species destined for reintroduction requires modification to explicitly minimize genetic adaptation to captivity.