Assessment of Genetic Diversity and Identification of Informative Molecular Markers for Germplasm Characterization in Caribbean Stylo (Stylosanthes hamata)

Caribbean stylo (Stylosanthes hamata) is a tropical fodder and cover crop. Along with four other Stylosanthes species (S. scabra, S. humilis, S. viscosa, S. guianensis), it was introduced in India. It became well adapted in certain parts of the country and has been recommended for the improvement of range and degraded lands. A collection of 63 S. hamata accessions was fingerprinted with RAPID, ISSR and STS markers. Though the mean discriminating power of these marker systems ranges from 0.65 to 0.71, high values of marker index (2.91), resolving power (14.92) and effective number of patterns per assay unit (50.65) makes ISSR as a better marker system in comparison to other two markers used in this study. Thirteen RAPD and eleven STS primers could differentiate a maximum of 42 and 17 accessions, respectively, whereas two ISSR primers produced distinct fingerprints of all the S. hamata accessions. Mean genetic similarities of accession ranged from 0.83 (ISSR) to 0.91 (RAPD). Two RAPD, two STS and four ISSR primers generated a set of 12 diagnostic markers which could be useful for germplasm characterization and management.     

DNA Pooling: a tool for large-scale association studies

DNA pooling is a practical way to reduce the cost of large-scale association studies to identify susceptibility loci for common diseases. Pooling allows allele frequencies in groups of individuals to be measured using far fewer PCR reactions and genotyping assays than are used when genotyping individuals. Here, we discuss recent developments in quantitative genotyping assays and in the design and analysis of pooling studies. Sophisticated pooling designs are being developed that can take account of hidden population stratification, confounders and inter-loci interactions, and that allow the analysis of haplotypes.     

微卫星DNA与生化标记分析对长爪沙鼠群体遗传分析的比较

目的比较生化标记和微卫星DNA标记方法对长爪沙鼠群体遗传分析的可靠性。方法应用27个生化位点和13个微卫星DNA位点,采用已建立的生化标记和微卫星DNA标记分析方法对国内2个长爪沙鼠群体进行遗传分析,计算并比较两种方法测得的各群体遗传参数。结果生化基因位点中有13个位点在整体中呈现遗传多态性,多态率为48.1%;微卫星位点中有11个位点在整体中表现出多态性,多态率均为84.6%。两种方法测得的平均有效等位基因数趋于一致,微卫星DNA的多态位点百分率和平均杂合度均明显高于生化标记方法。但生化标记和微卫星DNA检测对两个长爪沙鼠群体的遗传多样性差异反映一致,所反映的群体平衡状况也基本一致。结论生化标记分析和微卫星DNA方法均可较好地反映长爪沙鼠群体遗传结构。     

湖栖鳍虾虎鱼微卫星DNA标记的开发与群体遗传多样性分析

为研究雷州半岛湖栖鳍虾虎鱼(Gobiopterus lacustris)遗传多样性,对湖栖鳍虾虎鱼雌雄性腺进行转录组测序,采用MISA软件进行微卫星分析,共获得25 452个微卫星标记,其中包含14 708个单碱基重复类型,6 175个2碱基重复类型,3、4、5和6碱基重复类型数目分别为4 223、327、15和4。随机选取50个微卫星位点设计引物,能够扩增出清晰稳定条带的有39对,其中,11个位点表现出不同程度的多态,28个位点呈现单态。利用11个具有多态性的微卫星位点分析湖栖鳍虾虎鱼在廉江市高桥镇红树林保护区、湛江东海岛、雷州市附城镇和雷州市九龙山红树林国家湿地公园4个野生群体中的遗传多样性及遗传结构,11个微卫星位点呈现出不同程度的多态性,等位基因数(Na)2～15,平均等位基因为(6?3.9)个,有效等位基因数(Ne)、平均观测杂合度(Ho)和期望杂合度(He)分别在1.919～2.485、0.343～0.465和0.381～0.483之间,平均多态信息含量(PIC)为0.348～0.465。Hardy-Weinber平衡分析显示,4个群体的大部分位点未偏离平衡。在每个群体中进...     

糯玉米种质品质性状鉴定和SSR标记遗传多样性分析

对165份来源不同的糯玉米农家种和自交系的穗粒性状和淀粉品质性状进行了鉴定,并利用60对SSR标记进行了遗传多样性分析。结果表明,165份糯玉米种质穗长、秃顶长、行数、行粒数和穗粗变异较大,粗淀粉含量、支链淀粉含量和淀粉糊化特性RVA特征谱带值各指标变异丰富。60 对SSR引物在165份材料间共检测到281个等位基因变异,PCR扩增片段大小介于90～690bp,每对引物检测到2～9个等位基因,平均为4.68个;每对SSR 引物的多态信息量( PIC) 在0.332～0. 860之间,平均为0. 690。利用UPGMA 聚类分析方法将供试种质自交系分为3类,划分结果基本符合品系的来源情况,生产应用的多数糯玉米自交系材料与我国西南地区糯玉米地方品种材料具有较远的亲缘关系。显示出165份糯玉米种质具有丰富的遗传多样性,可为糯玉米杂优利用和遗传改良提供遗传基础。     

Population Genetic Structure and Demographic History of Atrina pectinata Based on Mitochondrial DNA and Microsatellite Markers

The pen shell, Atrina pectinata, is one of the commercial bivalves in East Asia and thought to be recently affected by anthropogenic pressure (habitat destruction and/or fishing pressure). Information on its population genetic structure is crucial for the conservation of A. pectinata. Considering its long pelagic larval duration and iteroparity with high fecundity, the genetic structure for A. pectinata could be expected to be weak at a fine scale. However, the unusual oceanography in the coasts of China and Korea suggests potential for restricted dispersal of pelagic larvae and geographical differentiation. In addition, environmental changes associated with Pleistocene sea level fluctuations on the East China Sea continental shelf may also have strongly influenced historical population demography and genetic diversity of marine organisms. Here, partial sequences of the mitochondrial Cytochrome c oxidase subunit I (COI) gene and seven microsatellite loci were used to estimate population genetic structure and demographic history of seven samples from Northern China coast and one sample from North Korea coast. Despite high levels of genetic diversity within samples, there was no genetic differentiation among samples from Northern China coast and low but significant genetic differentiation between some of the Chinese samples and the North Korean sample. A late Pleistocene population expansion, probably after the Last Glacial Maximum, was also demonstrated for A. pectinata samples. No recent genetic bottleneck was detected in any of the eight samples. We concluded that both historical recolonization (through population range expansion and demographic expansion in the late Pleistocene) and current gene flow (through larval dispersal) were responsible for the weak level of genetic structure detected in A. pectinata.     

名贵易混淆植物性药材的DNA分子遗传标记鉴定研究进展

名贵易混淆药材的伪品和掺假品较为常见,采用常规的方法较难鉴别.DNA分子遗传标记鉴定具有取样量小、减少贵重样品损消耗、鉴定结果准确、灵敏性高等特点.本文以人参、西红花、天麻、当归等药材为代表,对近年来DNA分子遗传标记技术在名贵易混淆植物性药材鉴定中的研究情况予以综述.     

Molecular Genetic Markers for Identification of Rhodococcus erythropolis and Rhodococcus qingshengii

Microbiology - The application of restriction analysis of amplification products of the genes rpoC and alkB, encoding the synthesis of the DNA-dependent RNA polymerase β'-subunit and...     

微卫星标记对资源猪群的遗传分析和连锁图谱构建

在猪数量性状位点的定位研究中,标记的使用和图谱的构建是很重要的。本研究从猪的第4、6、7、8和13染色体上选取39个微卫星标记,在来源于约克夏和梅山214头猪组成的资源群中,分析了遗传特征并构建了图谱。研究表明,平均等位基因数、平均观察杂合度(Ho)和平均多态信息含量(PIC)在F1和F2代中分别为:3.2,0.528,0.463和3.2,0.496,0.447。结果表明大多数微卫星标记位点表现为中高度杂合性。在资源群体中,平均有信息减数分裂数是217.4(44-316),而各染色体上两性平均图谱的长度分别是:172.3cM(SSC4),168.7cM(SSC6),191.7cM(SSC7),197.3cM(SSC8),178.3cM(SSC13)。与USDA-MARC的参考图谱相比,标记位点的顺序相同,但长度均较长。雌雄两性图谱相比,第4和第6染色体上雌性图谱长于雄性图谱;而在另外3条染色体上,则雄性图谱长于雌性图谱。结果显示了标记位点在资源猪群的遗传特征和遗传关系,其连锁图谱可用于今后的QTL定位。     

Species Detection and Identification in Sexual Organisms Using Population Genetic Theory and DNA Sequences

Phylogenetic trees of DNA sequences of a group of specimens may include clades of two kinds: those produced by stochastic processes (random genetic drift) within a species, and clades that represent different species. The ratio of the mean pairwise sequence difference between a pair of clades (K) to the mean pairwise sequence difference within a clade (θ) can be used to determine whether the clades are samples from different species (K/θ≥4) or the same species (K/θ<4) with probability ≥0.95. Previously I applied this criterion to delimit species of asexual organisms. Here I use data from the literature to show how it can also be applied to delimit sexual species using four groups of sexual organisms as examples: ravens, spotted leopards, sea butterflies, and liverworts. Mitochondrial or chloroplast genes are used because these segregate earlier during speciation than most nuclear genes and hence detect earlier stages of speciation. In several cases the K/θ ratio was greater than 4, confirming the original authors'' intuition that the clades were sufficiently different to be assigned to different species. But the K/θ ratio split each of two liverwort species into two evolutionary species, and showed that support for the distinction between the common and Chihuahuan raven species is weak. I also discuss some possible sources of error in using the K/θ ratio; the most significant one would be cases where males migrate between different populations but females do not, making the use of maternally inherited organelle genes problematic. The K/θ ratio must be used with some caution, like all other methods for species delimitation. Nevertheless, it is a simple theory-based quantitative method for using DNA sequences to make rigorous decisions about species delimitation in sexual as well as asexual eukaryotes.     

Miscanthus: Genetic Diversity and Genotype Identification Using ISSR and RAPD Markers

Due to the limited number of molecular studies focused on European gene pool investigation, it is necessary to perform plant material recognition. Eighteen accessions of three Miscanthus species, namely, M. × giganteus, M. sinensis, M. sacchariflorus were evaluated with the use of molecular marker systems such as: inter simple sequence repeats (ISSRs), random amplified polymorphic DNA (RAPD), and by estimation of ploidy level based on flow cytometry. As a result, only one ISSR primer (ISSR1) and three RAPD primers (RAPD1, RAPD2, RAPD4) were required to identify all genotypes. Moreover, the use of the above mentioned molecular markers enable the proper species recognition of the interspecific hybrid M. × giganteus “Floridulus,” which has been previously mislabeled as M. floridulus. The highest genetic similarity coefficient (0.94) was observed between M. × giganteus clones, which indicates that the genetic diversity within this species was very low. Whereas M. sinensis genotypes represented a relatively wide diversity with similarity coefficient of 0.58. Cluster analysis using UPGMA grouped the 18 accessions in three clusters according to species affiliation including relabeled M. × giganteus “Floridulus,” which proved to be closely related to M.  × giganteus. Similar groupings were evident in the PCoA analysis.     

Forensic DNA Analysis of Pacific Salmonid Samples for Species and Stock Identification

Identification of salmonid tissue samples to species or population of origin has been conducted for over 20 forensic cases in British Columbia. Species identification is based on published sequence variation in exon and intron regions of coding genes. Identification of source populations or regions is carried out using microsatellite and major histocompatibility complex allele frequency data collected from populations throughout the species range and with standard genetic stock identification (GSI) methods. Regional contributions to mixture samples are estimated using maximum likelihood mixture analysis and classification of individual genotypes is carried out with Bayesian methods. DNA has been obtained successfully from salmon scale samples, fresh, frozen and canned tissue samples and bloodstains in clothing. Results from DNA analyses have been instrumental in a number of convictions. A major benefit has been cost savings resulting from the number of guilty pleas entered after disclosure to the defendant of results from genetic testing. In two cases, GSI analysis resulted in exoneration of suspects under investigation for possible illegal sales of Fraser River sockeye salmon by substantiating their claim that the fish originated from the Skeena River watershed. DNA analysis has generally corroborated the species and stock identification carried out by fishery officers, but has revealed that species identification of samples from sources such as restaurants and fish plants can be erroneous. Forensic DNA analysis has facilitated the conviction of those who purchase fish not caught under the authority of licence, thus bringing those who buy fish illegally as well as those involved in illegal harvest and sales within the scope of law enforcement.     

Genetic Markers and Quantitative Genetic Variation in Medicago Truncatula (Leguminosae): A Comparative Analysis of Population Structure

Two populations of the selfing annual Medicago truncatula Gaertn. (Leguminoseae), each subdivided into three subpopulations, were studied for both metric traits (quantitative characters) and genetic markers (random amplified polymorphic DNA and one morphological, single-locus marker). Hierarchical analyses of variance components show that (1) populations are more differentiated for quantitative characters than for marker loci, (2) the contribution of both within and among subpopulations components of variance to overall genetic variance of these characters is reduced as compared to markers, and (3) at the population level, within population structure is slightly but not significantly larger for markers than for quantitative traits. Under the hypothesis that most markers are neutral, such comparisons may be used to make hypotheses about the strength and heterogeneity of natural selection in the face of genetic drift and gene flow. We thus suggest that in these populations, quantitative characters are under strong divergent selection among populations, and that gene flow is restricted among populations and subpopulations.     

Genetic Stock Identification of Chum Salmon in the Bering Sea and North Pacific Ocean Using Mitochondrial DNA Microarray

A newly developed DNA microarray was applied to identify mitochondrial (mt) DNA haplotypes of more than 2200 chum salmon in the Bering Sea and North Pacific Ocean in September 2002 and also 2003, when the majority of maturing fish were migrating toward their natal river. The distribution of haplotypes occurring in Asian and North American fish in the surveyed area was similar in the 2 years. A conditional maximum likelihood method for estimation of stock compositions indicated that the Japanese stocks were distributed mainly in the north central Bering Sea, whereas the Russian stocks were mainly in the western Bering Sea. The North American stocks were abundant in the North Pacific Ocean around the Aleutian Islands. These results indicate that the Asian and North American stocks of chum salmon are nonrandomly distributed in the Bering Sea and the North Pacific Ocean, and further the oligonuleotide DNA microarray developed by us has a high potential for identification of stocks among mixed ocean aggregates of high-seas chum salmon.     

Development of Microsatellite Markers for Japanese Scallop (Mizuhopecten yessoensis) and Their Application to a Population Genetic Study

Abstract The Japanese scallop (Mizuhopecten yessoensis) is one of the main fishery products in Japan, but with the expansion of culture operations of the Japanese scallop, various problems have been encountered including high mortality, poor growth, poor seed production, and so on. Moreover, there is concern that many years of cultivation may have affected the genetic structure of the scallop population. To approach these problems and concerns, we developed microsatellite markers as a molecular tool for population genetic studies. By using 4 microsatellite markers as well as a mitochondrial marker, we investigated the genetic structure of samples from the islands of Hokkaido (14 populations) and Honshu (Tohoku, 3 populations) in Japan, and south Primorye (4 populations) in Russia. All the populations sampled had high genetic diversity (average expected heterozygosity, 0.7011 to 0.7622; haplotype diversity, 0.6090 to 0.8848), and almost all showed a tendency of homozygote excess, which was significant in 2 populations. Hierarchical analysis of molecular variance tests based on the microsatellite and mitochondrial markers indicated that the 3 geographic regions were genetically divergent from one another, with little evidence of divergence within regions. Homogeneity in allele frequency distributions between natural and cultured scallops and allele frequency stability over a period of 2 decades indicated that the culturing operations have probably not had a substantial effect on the genetic structure of the populations.