Determination of ploidy and nuclear DNA content in populations of Atriplex halimus (Chenopodiaceae)

Nuclear DNA contents were determined by flow cytometry for 20 populations of the perennial C₄ shrub Atriplex halimus L. (Chenopodiaceae) originating from the Mediterranean basin and Fuerteventura (Canary Islands). Two populations were also analysed for chromosome number: one (from Ibiza, Spain), with a 2C nuclear DNA content of 2.40 pg, was shown to be diploid (2 n  = 2 x  = 18), whilst the other (from Sicily, Italy), with 5.11 pg, was tetraploid (2 n  = 2 x  = 36). With respect to nuclear DNA content, two groups of populations were detected, diploids with 2.40–2.44 pg and tetraploids with 4.77–5.13 pg. The diploid populations were mainly from the western Mediterranean (Spain and France) and Fuerteventura, whereas tetraploids were generally, but not exclusively, from more arid areas in North Africa and the eastern Mediterranean. In general, the diploid and tetraploid populations corresponded to the subspecies halimus and schweinfurthii , respectively. For certain populations having morphologies intermediate between those considered typical of these two subspecies, nuclear DNA contents showed them to be tetraploid. There was significant variation in nuclear DNA content among the tetraploid populations, with greater values in the more easterly populations.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 147 , 441−448.     

Genetic structure and diversity in Ramonda myconi (Gesneriaceae): effects of historical climate change on a preglacial relict species

The importance of the Mediterranean Basin as a long-term reservoir of biological diversity has been widely recognized, although much less effort has been devoted to understanding processes that allow species to persist in this area. Ramonda myconi (Gesneriaceae) is a Tertiary relict plant species restricted to the NE Iberian Peninsula. We used RAPD and chloroplast markers to assess the patterns of genetic structure in eight mountain regions covering almost the full species range, to identify the main historical processes that have shaped its current distribution and to infer the number and location of putative glacial refugia. While no cpDNA variation was detected, the species had relatively high levels of RAPD variation. Maximum levels of diversity were found within populations (71%), but there was also a significant differentiation between geographical regions (20%) and among populations within regions (9%). A spatial AMOVA identified three main groups of populations, corresponding to previously recognized centers of endemism and species richness. In addition, we found a marked geographical pattern of decreasing genetic diversity and increasing population differentiation from west to east. Our results support a complex phylogeographic scenario in the Iberian Peninsula of "refugia-within-refugia" and suggest that the higher diversity observed in western regions might be associated with prolonged and more stable climatic conditions in this area during the Quaternary.     

Differential responses to salinity of two Atriplex halimus populations in relation to organic solutes and antioxidant systems involving thiol reductases

Atriplex halimus L. is a xero-halophyte species widespread in the Mediterranean basin. The tolerance to water stress and high salinity of two Atriplex populations from semi-arid (Djelfa) and arid saline (Laghouat) Algerian regions has been investigated in relation with organic solutes and antioxidant systems. Whereas no noticeable difference was observed between the two populations under water stress resulting from withholding watering or PEG treatment, Laghouat plants display significantly higher fresh and dry weights than Djelfa plants when exposed to high salinity. At 300mM NaCl, Laghouat plants exhibit higher concentrations in Na(+), proline and quaternary ammonium compounds, and a higher catalase activity than Djelfa plants. We then analysed the involvement of recently characterized plastidial thiol reductases, peroxiredoxins (Prxs) and methionine sulphoxide reductases (MSRs), key enzymes scavenging organic peroxides and repairing oxidized proteins, respectively. Upon salt treatment (300mM NaCl), we observed higher amounts of PrxQ and over-oxidized 2-Cys Prx in Laghouat than in Djelfa. An increased abundance of plastidial MSRA and a higher total MSR activity were also noticed in Laghouat plants treated with 300mM NaCl compared to Djelfa ones. We propose that mechanisms based on organic solutes and antioxidant enzymes like catalases, peroxiredoxins and MSRs party underlie the better tolerance of the Laghouat population to high salt.     

松杨栅锈菌遗传多样性初步分析

采用ITS-nrDNA-RELP、测序技术、RAPD(随机扩增多态性DNA)分子标记技术,对我国松杨栅锈菌不同地域的5个生理小种11个菌系进行了遗传多样性分化研究.结果表明,该菌在我国的遗传分化与地理来源相关,可分为西部地理群和北方地理群.西部地理群又可分为高山森林生态型(HMF)和平原生态型(WPL).小种遗传分化不一定与致病性分化一致.t检验表明,各生理小种RAPD遗传多样性指数无明显差异,高山森林小种遗传多样性指数(0.5172)略高于平原小种遗传多样性指数(0.5089).核糖体基因转录间隔区高度保守,不适合该菌种内群体遗传多样性分化研究.     

Genetic diversity among Zygophyllum (Zygophyllaceae) populations based on RAPD analysis

Zygophyllum species are succulent plants that are drought resistant and/or salt tolerant, growing under severe, dry climatic conditions. Despite their importance and abundance in the Mediterranean and Middle East regions, there is little information concerning molecular variations among species of this genus. Genetic diversity was assessed, using RAPD primers, of 12 populations of Z. coccineum, Z. album and Z. aegyptium collected from various locations in Egypt and Saudi Arabia. Yong leaves were used for DNA extraction. Genetic distances were calculated using Nei's method. A dendrogram was constructed based on the similarity data matrix by unweighted pair group method using arithmetic averages cluster analysis. Analysis with RAPD markers revealed genetic variation between and within populations of Zygophyllum. Zygophyllum coccineum showed higher levels of genetic variation and more unique alleles than the other species.     

红树植物分子生态与进化研究进展

红树林是热带与亚热带海洋森林和地球湿地生态系统的重要组成部分 ,是多种海洋动物及鸟类栖息繁衍的重要场所 ,在调节全球生态平衡及维持生物多样性方面起着十分重要的作用。有关红树林的生态生物学研究 ,特别是红树林及其生物多样性变化的监测研究 ,红树林的保护与管理已成为热带亚热带海洋及湿地生态学研究的重要内容。海南岛有长达 1 5 2 8ｋｍ的海岸线 ,红树林群落的分布十分广泛。孢粉学证据说明 ,海南岛滨海地区在第三纪时即有红树林出现[1 ] 。现海南岛红树林植物种类有 1 8科 2 6属 34种 ,占中国红树植物种数的 97.1 % [2 ] 。由于…     

Hotspots of diversity in a clonal world--the Mediterranean moss Pleurochaete squarrosa in Central Europe

Diversity patterns of the dioecious haploid Mediterranean moss Pleurochaete squarrosa were analysed from Central and Northwest Europe using nuclear and chloroplast DNA sequencing and enzyme electrophoresis. Across 69 populations, 38 distinct haploid multilocus genotypes (MLGs) were detected, but nearly all populations were clonal. Only five MLGs occurred in more than two regions, and two diversity hotspots were detected. The Kaiserstuhl mountains in Southwest Germany harboured 34 MLGs, 25 being endemic within Central Europe. Levels of linkage disequilibrium and population structure in Kaiserstuhl populations were similar to levels and structure in sexually reproducing populations in the Mediterranean Basin. In the Moselle-Nahe area, some 250 km north, a comparably high allelic diversity, but no evidence of recombination, was detected. Genetic diversity measures were significantly lower than estimates obtained in the Mediterranean Basin and a G _ST of 0.89 signified extreme population differentiation. Mantel tests identified a positive correlation on genetic and geographical distance for distances up to 50 km. Seven nrITS and three cpDNA haplotypes were detected, their geographical structure mirroring enzyme data set results. Comparative analysis with Mediterranean data demonstrated multiple recolonization of Central Europe from both the Iberian Peninsula and the Balkans. A suture zone of genotypes was detected along the border of Belgium/France and Germany. Despite P. squarrosa having haploid spore and/or vegetative propagules dispersal, we found patterns of postglacial recolonization of Central Europe comparable with those reported in flowering plants and animals. This study demonstrates the importance of comparative research on population genetics and phylogeography of a diverse range of organisms.     

国产甘草属植物的RAPD分析及其分类学研究

应用RAPD技术,探讨甘草属(G ly cy rrh iza L.)13种1变种30个植物类群的遗传差异和几个争议种的分类地位。从60个随机引物中筛选出14个多态性好的引物进行RAPD实验,DNA片段的二态数据用U PGM A聚类法构建系统发育树。共扩增出250条带,多态性带204条,约占总数的81.7%。聚类结果显示RAPD分子标记构建的系统发育树与经典分类系统一致。甘草属植物具有丰富的遗传多样性,同种内不同居群间的遗传分化较大。黄甘草、胀果甘草、乌拉尔甘草三者亲缘关系较近,平卧甘草与粗毛甘草存在很大的遗传差异,作为独立种较合理。RAPD标记可为甘草属植物的系统分类研究提供分子生物学依据。     

Genetic variation among different populations of Aster tripolium grown on naturally and anthropogenic salt-contaminated habitats: implications for conservation strategies

The sea aster, Aster tripolium L., grows naturally in temperate regions, mainly in the salt meadows close to the coast. The species is also found in naturally and anthropogenically salt-contaminated inland habitats, such as potash mine dumps. The genetic relationships among populations from different habitats and correlations of the genotype with physiological and vegetational parameters were investigated. A. tripolium plants from five different sites close to the seashore on the North Sea island Baltrum, from five different potash mine dumps and, as an outgroup, from the seashore in Japan were probed. DNA was extracted from five plants from each of the 11 A. tripolium populations and analyzed for random amplified polymorphic DNA (RAPD). Altogether 35 polymorphic bands in 51 individuals and 45 different detectable genotypes could be identified. For evaluation of the genetic variation using RAPD bands, the neighbor-joining method, the principal coordinate analysis, and the analysis of molecular variance were applied, resulting in the classification into three genetic groups. A. tripolium plants from different ecological habitats on Baltrum were closely related while the plants growing at the deposit dumps showed a higher genetic diversity. The Japanese population was genetically very different from the German populations. Correlations between phytosociological and soil parameters and the respective genotype were not significant. The results argue for a conservation of anthropogenically salt-contaminated habitats to maintain genetic variability not only on the species level, but also within a species.     

High levels of genetic variability in the moss Ceratodon purpureus from continental Antarctica, subantarctic Heard and Macquarie Islands, and Australasia

The random amplified polymorphic DNA (RAPD) technique, and DNA sequencing of the conserved nuclear ribosomal DNA internal transcribed spacer region (ITS1-5.8S-ITS2), have been used to assess levels of genetic diversity in the moss Ceratodon purpureus from several locations in Australasia, subantarctic Heard and Macquarie Islands, and continental Antarctica. Populations from Heard and Macquarie Islands and from Antarctica maintain high levels of genetic variation. Both within- and among-colony variation were observed at these locations. DNA sequence analysis showed that samples from the Ross Sea region of Antarctica were most closely related to colonies from Casey and Macquarie Island, and that one colony from Heard Island was most closely related to one from Europe. DNA sequence data separated two Australian populations from the Antarctic and subantarctic group on a dendrogram. Detailed RAPD analysis of a single colony from continental Antarctica demonstrated that mutation probably causes the high variability observed in this moss. DNA sequencing and RAPD analysis are complementary techniques for genetic investigation of Antarctic moss populations.Jenny Ninham was an integral part of this research team for several years. Unfortunately she did not live to see these results published.     

RAPD标记研究新疆胡杨五个地理种群的遗传分化

目标：对新疆地区塔里木盆地、准噶尔盆地和吐鲁番盆地的天然胡杨5个地理种群进行研究,科学评价地理隔离和遗传多样性的关系。方法：CTAB法提取DNA,RAPD分子标记分析5个天然胡杨种群的遗传结构。结果：筛选出的10个随机引物总共扩增出133个条带,其中84.96%为多态性,5个地理种群的种间遗传多样性0.0601～0.3081,Shannon’s指数0.2087～0.3332之间,Gst数据表明60.51%的遗传变异存在于种群内。结论：基于Nei’s遗传距离的UPGMA聚类分析显示：塔里木和吐鲁番盆地的胡杨种群相比准噶尔盆地种群有更近的遗传关系,胡杨通过两个途径传入新疆,造成遗传分化的因素主要与胡杨在新疆特殊地理环境下的发展历史及生态适应有关。     

Genetic structure of the widespread and common Mediterranean bryophyte Pleurochaete squarrosa (Brid.) Lindb. (Pottiaceae) - evidence from nuclear and plastidic DNA sequence variation and allozymes

The Mediterranean Basin as one the world's most biologically diverse regions provides an interesting area for the study of plant evolution and spatial structure in plant populations. The dioecious moss Pleurochaete squarrosa is a widespread and common bryophyte in the Mediterranean Basin. Thirty populations were sampled for a study on molecular diversity and genetic structure, covering most major islands and mainland populations from Europe and Africa. A significant decline in nuclear and chloroplast sequence and allozyme variation within populations from west to east was observed. While DNA sequence data showed patterns of isolation by distance, allozyme markers did not. Instead, their considerable interpopulation genetic differentiation appeared to be unrelated to geographic distance. Similar high values for coefficients of gene diversity (G(ST)) in all data sets provided evidence of geographic isolation and limited gene flow among populations (i) within islands, (ii) within mainland areas, and (iii) between islands and mainland. Notably, populations in continental Spain are strongly genetically isolated from all other investigated areas. Surprisingly, there was no difference in gene diversity and G(ST) between islands and mainland areas. Thus, we conclude that large Mediterranean islands may function as 'mainland' for bryophytes. This hypothesis and its implication for conservation biology of cryptogamic plants warrant further investigation. While sexually reproducing populations were found all over the Mediterranean Basin, high levels of multilocus linkage disequilibrium provide evidence of mainly vegetative propagation even in populations where sexual reproduction was observed.     

Fasciola hepatica: identification of molecular markers for resistant and susceptible Pseudosuccinea columella snail hosts

Protein electrophoresis, RAPD-PCR and nuclear rDNA ITS sequencing were performed to search for genetic differences between Pseudosuccinea columella snails susceptible and resistant to Fasciola hepatica infection. Of the 21 enzymatic loci analyzed in both populations, none of them exhibited neither within- or between-group variation. Such an absence of enzyme polymorphism support the hypothesis of selfing as the "prevalent" mating system for this hermaphroditic species. Conversely, the RAPD profiles displayed clear differences between susceptible and resistant isolates for 17 of the 26 primers tested while no within-group variation was detected. rDNA ITS sequence analysis from snails of each isolates showed only two bases that differed between groups accounting for a 0.17% of variation confirming that susceptible and resistant snails belong to the same species. This is the first time that a genetic variation using RAPD markers is demonstrated between susceptible and resistant lymnaeid snails vis-a-vis of F. hepatica infection in absence of experimental selection.     

Evidence for massive clonal growth in the invasive weed Fallopia japonic a (Japanese Knotweed)

Clonal growth in introduced populations of Japanese Knotweed ( Fallopia juponica ) in Britain was assessed using RAPDs (Randomly Amplified Polymorphic DNA). A total of 150 British samples was analysed for genetic variation using ten arbitrary decamer primers, and compared with data from 16 samples of other introduced populations from Europe and the U.S.A. All samples produced an identical multi-primer RAPD profile. Accepting that RAPD profile identity need not equate to genet identity, based on the sensitivity of these markers for detecting genetic diversity in related taxa and on the absence of male fertile individuals of this species in Britain, we interpret this result as consistent with the presence of a single, exceptionally widespread clone. This clone must represent one of the world's largest vascular plants.     

Large‐scale longitudinal gradients of genetic diversity: a meta‐analysis across six phyla in the Mediterranean basin

Biodiversity is the diversity of life at all scales, from genes to ecosystems. Predicting its patterns of variation across the globe is a fundamental issue in ecology and evolution. Diversity within species, that is, genetic diversity, is of prime importance for understanding past and present evolutionary patterns, and highlighting areas where conservation might be a priority. Using published data on the genetic diversity of species whose populations occur in the Mediterranean basin, we calculated a coefficient of correlation between within‐population genetic diversity indices and longitude. Using a meta‐analysis framework, we estimated the role of biological, ecological, biogeographic, and marker type factors on the strength and magnitude of this correlation in six phylla. Overall, genetic diversity increases from west to east in the Mediterranean basin. This correlation is significant for both animals and plants, but is not uniformly expressed for all groups. It is stronger in the southern than in the northern Mediterranean, in true Mediterranean plants than in plants found at higher elevations, in trees than in other plants, and in bi‐parentally and paternally than in maternally inherited DNA makers. Overall, this correlation between genetic diversity and longitude, and its patterns across biological and ecological traits, suggests the role of two non‐mutually exclusive major processes that shaped the genetic diversity in the Mediterranean during and after the cold periods of the Pleistocene: east‐west recolonization during the Holocene and population size contraction under local Last Glacial Maximum climate in resident western and low elevation Mediterranean populations.     

RAPD analysis of diploid and tetraploid populations of Aronia points to different reproductive strategies within the genus

Plant breeding in black chokeberry (Aronia melanocarpa) is based mainly on seedlings derived from domesticated Russian plants. Previous studies have, however, demonstrated very low levels of phenotypic variation within this gene pool. The present investigation was undertaken in order to study the genetic structure in native populations growing in North America. Random amplified polymorphic DNA (RAPD) marker variation was analysed in eight populations (three or five mother plants/population and five seedlings/mother plant) and compared with the variation in four cultivars and 15 seedlings derived from a Russian plantation. The four cultivars and all the Russian seedlings turned out to have identical RAPD profiles. In the native plant material, there were two types of mother plants: diploid plants that produced very heterogeneous offspring and tetraploid plants that produced homogeneous offspring. Partitioning of variability based on Shannon's diversity index attributed approx. 22% of the variation to the among-population level in diploids, compared to approx. 55% in the tetraploids. However, the diploid populations and the tetraploid populations did not differ significantly in within-population variation. These results prompted a second set of RAPD analyses, which were carried out on offspring obtained through open pollination of the initially examined material when growing in an experimental field. The analyses showed that tetraploid plants produced tetraploid offspring that, with few exceptions, were identical, indicating apomixis, whereas offspring of diploid plants were diploid or triploid, and highly heterogeneous, indicating outcrossing. Presumably, the tetraploid form of Aronia is an allopolyploid, with A. melanocarpa as one of the parents.     

燕麦草（Arrhenatherum elatius）多倍体复合体的等位酶多样性研究

对欧洲及地中海地区燕麦草复合体２７个居群的等位酸电泳调查表明,燕麦草复合体维持比较高的等位酶多样性（Ｈｅ＝０．４４７,Ａ＝３．２９）,亚种间遗传分化较小（Ｇ（ＳＴ）＝０．０５３）;在四个亚种内,也维持着比较高的多样性（Ｈｅ：０．３２５—０．５３３）,各亚种内的基因多样度主要存在于居群之内,居群间分化较小．四倍体的基因多样性高于二倍体的．燕麦草复合体内居群间基因流较高,表明燕麦草繁育方式主要为风媒远交．对Ｎｅｉ氏标准遗传距离的ＵＰＧＭＡ聚类结果表明,四倍体是从二倍体有鳞茎的ｓｓＰ．ｂａｅｔｉｃｕｍ中产生的．     

中华水韭遗传多样性的RAPD分析

采用RAPD方法对珍稀濒危植物中华水韭(Isoetes sinensis)4个自然居群的48个样品进行了DNA多态性分析。从60个随机引物中筛选出14个有效引物,共产生124条DNA片段,其中72条为多态性条带,总的多态位点百分率(PPB)为58．06％。各居群间多态位点百分率差异显著(0．81％-12．90％)。AMOVA分析结果表明,4个居群间基因分化系数Фst=0．5894,即遗传变异中有相当一部分来源于群体间(58．94％)。日益缩小的种群规模而导致的居群内近交和遗传漂变的发生以及居群间有限的基因交流可能是中华水韭目前遗传结构的主要成因。鉴于目前中华水韭居群内个体数偏少、遗传多样性较低的现状,建议对其进行就地保护并保护尽可能多的生境,对不同自然居群内的个体进行植株相互移栽和育苗移栽,以提高不同居群间的基因交流,尽可能地保护中华水韭的遗传多样性。     

Determination of genetic diversity among Indian isolates of Rhizoctonia bataticola causing dry root rot of chickpea

Genetic diversity among 27 isolates (23 from chickpea and 4 from other host crops) of Rhizoctonia bataticola representing 11 different states of India was determined by random amplified polymorphic DNA (RAPD), internal transcribed spacer restriction fragment length polymorphism (ITS-RFLP) and ITS sequencing. The isolates showed variability in virulence test. Unweighted paired group method with arithmetic average cluster analysis was used to group the isolates into distinct clusters. The clusters generated by RAPD grouped all the isolates into six categories at 40% genetic similarity. High level of diversity was observed among the isolates of different as well as same state. Some of the RAPD (OPN 4, OPN 12, and OPN 20) markers clearly distinguished majority of the isolates into the area specific groups. The ITS I, 5.8rDNA and ITS II regions of 11 isolates representing different RAPD groups were amplified with primers ITS 1 and ITS 4 and digested with seven restriction enzymes. The restriction enzymes DraI, MboI, RsaI, and AluI were found to be suitable for differentiating the isolates into five categories by showing isolate specific ITS-RFLP patterns. The isolates were variable in their nucleotide sequences of the ITS regions. This is the first study on genetic diversity among chickpea isolates of R. bataticola.     

Phytoextraction of cadmium by four Mediterranean shrub species

The possibility of remediating contaminated soils though the use of high biomass-generating, native plant species capable of removing heavy metals is receiving increased attention. The cadmium (Cd) accumulation capacities of the native Mediterranean, perennial shrubs Atriplex halimus, Phyllirea angustifolia, Rhamnus alaternus and Rosmarinus officinalis were tested by growing transplanted specimens in a pine bark compost substrate (pH 5.6) contaminated with 100 mg Cd kg(-1). After 70 days, only R. alaternus showed reduced growth. The increase in biomass seen in all the test species enhanced the phytoextraction of Cd. However, the species behaved as metal excluders, except for the halophyte A. halimus, which behaved as an indicator plant. In this species the leaf Cd concentration reached 35 mg Cd kg(-1), with the shoot responsible for some 86% of total Cd accumulation. Atriplex halimus showed the highest bioconcentration factor (BCF) (0.36) and leaf Cd transport index (1.68); consequently, this species showed the highest Cd phytoextraction capacity.