Hibiscus section Furcaria (Malvaceae) in islands of the Pacific Basin

Hibiscus sectionFurcaria includes more than 60 known taxa. The section has a mainly tropical distribution, but a few species penetrate subtropical and temperate regions. Seven taxa are recognized that occur in the islands of the Pacific Basin, five of which are endemic.Hibiscus fijiensis is described and a new combination,Hibiscus brackenridgei subsp.molokaianus, is proposed.     

Wild sunflower diversity in Argentina revealed by ISSR and SSR markers: an approach for conservation and breeding programmes

Wild sunflower Helianthus annuus originates from North America and has naturalised in Argentina where it is considered invasive. The present study attempts to assess the genetic diversity using two different molecular marker systems to study the wild genetic patterns and to provide data applicable to conservation and breeding uses. Ten natural populations sampled throughout the wild range and six inbred lines were studied using inter‐simple sequence repeat (ISSR) and simple sequence repeats (SSR) markers. A total of 64 ISSR bands and 29 SSR alleles were produced from 106 wild and cultivated plants. We found 9 ISSR private bands and 21 SSR private alleles in wild accessions, but no private bands/alleles were found in cultivated sunflowers. Molecular variability in wild populations was approximately 60% higher than in inbred lines. Local wild sunflowers kept considerable diversity levels in comparison with populations in the centre of origin (approximately 70%) and therefore they might possess a potential for adaptive evolutionary change. Analysis of molecular variance (AMOVA) indicated population structure with nearly 20% of genetic variability attributable to between‐population differentiation. Principal coordinate analyses (PCO) grouped wild populations from different geographic locations, and a Mantel test showed low congruence between genetic distance (GD) and geographic distances (GGD); hence, molecular data could not rule out multiple wild introduction events. Low correlations were found between ISSR and SSR GD at individual and population levels; thus, divergent evolutionary groups were not evident in local wild sunflowers. Several genetic diversity criteria were utilised to assign conservation value and certain wild populations emerged as interesting sites for more extensive sampling.     

山羊草属异源多倍体植物基因组进化的ISSR分析

使用31个ISSR引物对山羊草属Aegilops多倍体植物及其祖先二倍体（共23种）的基因组进行了分析,结果表明：与其二倍体祖先种相比,异源多倍体物种的基因组发生了很大变化。在含U基因组的异源多倍体物种中,U基因组相对而言变化很小,而其他基因组则发生了不同程度的变化。这表明当U基因组与其他基因组共存于多倍体物种中时,U基因组表现出较强的“同化效应”。对这些基因组的进化进行了讨论。     

Plant invasions, interspecific hybridization and the evolution of new plant taxa

Interspecific hybridization between a native and an invading plant species, or two invading species, sometimes results in a new, sexually reproducing taxon. Several examples of such taxa have been confirmed by recent molecular and isozyme analyses. Further study of these new taxa, when recognized soon after their origin, should aim to elucidate the factors that influence their subsequent establishment and spread, thus leading to a better understanding of the processes that lead to successful speciation. Plant hybrids formed following a plant invasion provide great potential for the study of ‘evolution in action’.     

An interspecific linkage map of SSR and intronic polymorphism markers in tomato

Despite the collection and availability of abundant tomato genome sequences, PCR-based markers adapted to large scale analysis have not been developed in tomato species. Therefore, using public genome sequence data in tomato, we developed three types of DNA markers: expressed sequence tag (EST)-derived simple sequence repeat (SSR) markers (TES markers), genome-derived SSR markers (TGS markers) and EST-derived intronic polymorphism markers (TEI markers). A total of 2,047 TES, 3,510 TGS and 674 TEI markers were established and used in the polymorphic analysis of a cultivated tomato (Solanum lycopersicum) ‘LA925’ and its wild relative Solanum pennellii ‘LA716’, parents of the Tomato-EXPEN 2000 mapping population. The polymorphic ratios between parents revealed by the TES, TGS and TEI markers were 37.3, 22.6 and 80.0%, respectively. Those showing polymorphisms were used to genotype the Tomato-EXPEN 2000 mapping population, and a high-density genetic linkage map composed of 1,433 new and 683 existing marker loci was constructed on 12 chromosomes, covering 1,503.1 cM. In the present map, 48% of the mapped TGS loci were located within heterochromatic regions, while 18 and 21% of TES and TEI loci, respectively, were located in heterochromatin. The large number of SSR and SNP markers developed in this study provide easily handling genomic tools for molecular breeding in tomato. Information on the DNA markers developed in this study is available at http://www.kazusa.or.jp/tomato/.     

A comparison of genetic variation among wild and cultivated Morus Species (Moraceae: Morus) as revealed by ISSR and SSR markers

In this study, inter-simple sequence repeats (ISSR) ans simple sequence repeat (SSR) markers were used to investigate genetic diversity of 27 mulberry accessions including 19 cultivated accessions (six M. multicaulis, three M. alba, two M. atropurpurea, two M. bombycis, one M. australis, two M. rotundiloba, one M. alba var. pendula, one M. alba var. macrophylla, and one M. alba var. venose) and 8 wild accessions (two M. cathayana, two M. laevigata, two M. wittiorum, one M. nigra and one M. mongolica). ISSRs and SSRs were compared in terms of their informativeness and efficiency in a study of genetic diversity and relationships among 27 mulberry genotypes. SSRs presented a higher level of polymorphism and greater information content. All index values of genetic diversity both markers analyzed using Popgene 32 software indicated that within wild species had higher genetic diversity than within cultivated species. Cultivation may caused the lose of genetic diversity of mulberry compared with wild species revealed by ISSR and SSR markers. The mean genetic similarity coefficients among all mulberry genotypes ascribed by ISSR and SSR matrices were 0.7677 and 0.6131, respectively. For all markers a high similarity in dendrogram topologies was obtained although some differences were observed. Cluster analysis of ISSR and SSR using UPGMA method revealed that the wild species are genetically distant from the domesticated species studied here. The correlation coefficients of similarity were statistically significant for both marker systems used. Principal coordinates analysis (PCA) for ISSR and SSR data also supports their UPGMA clustering. These results have an important implication for mulberry germplasm characterization, improvement, molecular systematics and conservation.     

Genetic diversity of African maize inbred lines revealed by SSR markers

Knowledge of genetic diversity (GD) and relationships among maize inbred lines is indispensable in a breeding program. Our objectives were to (1) investigate the level of genetic diversity among maize inbred lines and (2) assess their genetic structures by applying simple sequence repeat (SSR) markers. Fifty-six highland and mid-altitude maize inbred lines obtained from CIMMYT programs in Ethiopia and Zimbabwe were genotyped using 27 SSR loci. All of the genotypes studied could unequivocally be distinguished with the combination of the SSRs used. In total, 104 SSR alleles were identified, with a mean of 3.85 alleles per locus. The average polymorphism information content (PIC) was 0.58. GD expressed as Euclidean distance, varied from 0.28 to 0.73 with an average of 0.59. Cluster analysis using unweighted pair group method with arithmetic average (UPGMA) suggested five groups among the inbred lines. Most of the inbred lines adapted to the highlands and the mid-altitudes were positioned in different clusters with a few discrepancies. The pattern of groupings of the inbred lines was mostly consistent with available pedigree information. The variability detected using SSR markers could potentially contribute towards effective utilization of the inbred lines for the exploitation of heterosis and formation of genetically diverse source populations in Ethiopian maize improvement programs.     

Genetic diversity of natural Miscanthus sinensis populations in China revealed by ISSR markers

Miscanthus sinensis is a typical perennial C₄ grass in Asia. In the present study, ISSR markers were used to evaluate the genetic variation within and among grass populations that were sampled from the Zhejiang and Guangdong Provinces of China. Based on nine ISSR primers, 206 clear and reproducible DNA fragments were generated. Relatively low levels of genetic diversity were determined among the populations. The coefficient of genetic differentiation among the populations was 0.52, which indicates that 52.3% of the total molecular variance exists among the populations. Such a high level of divergence present among the populations might be caused by the complex topography and variable climatic conditions present in the two provinces. AMOVA revealed that the majority of the genetic variation was within the populations (50.6%). The application of a novel method, which combines geographical coordinates and genetic differentiation to detect barriers for gene flow, allowed us to identify two zones of lowered gene flow.     

利用EST-SSR分子标记检测鹅掌楸种间渐渗杂交

引进物种常与本土近缘种间发生杂交而导致基因渐渗,进而影响本地种的遗传系统。鹅掌楸(Liriodendron chinense)为我国濒危树种之一,鹅掌楸种间杂交可配性高,近10年来随着北美鹅掌楸(L.tulipifera)的大量引种及杂交鹅掌楸的繁殖推广,鹅掌楸种间发生基因渐渗的可能性大大增加。本文以5个包含鹅掌楸、北美鹅掌楸、杂交鹅掌楸的人工混交林为实验群体,每个群体包含19–130个成年个体及60–117个自然更新小苗或半同胞子代,利用EST-SSR(simple sequence repeat based on expressed sequence tag)分子标记对各子代群体进行亲本分析,探究鹅掌楸种间自然交配方式以检测鹅掌楸种间渐渗杂交;同时,以亲子群体等位基因频率的回归系数作为渐渗系数,定量分析鹅掌楸属种间基因渐渗。结果表明:在研究的5个鹅掌楸混生群体中,均检测到种间渐渗杂交,且渐渗杂交的方向与效应大小在不同群体间有差异。研究还发现,各树种基因渐渗程度与其种群个体数有关,种群个体数越多,其渐渗能力越强。据此,我们还探讨了鹅掌楸种质资源保护策略。     

Phylogenetic relationships between Leymus and related diploid Triticeae species revealed by ISSR markers

To investigate the genetic diversity and phylogenetic relationships between polyploid Leymus and related diploid species of the Triticeae tribe, inter-simple sequence repeats (ISSR) markers was used to analyze 41 Leymus accessions representing 22 species and 2 subspecies, together with Pseudoroegneria stipifolia (St), Psathyrostachys fragilis (Ns), Australopyrum retrofractum (W), Hordeum bogdanii, H. chilense (H) and Lophopyrum elongatum (E^e). A total of 376 clear and reproducible DNA fragments were amplified by 29 ISSR primers, among which 368 (97.87%) fragments were found to be polymorphic. 8–18 polymorphic bands were amplified by each polymorphic primer, with an average of 12.69 bands. The data of 376 ISSR bands were used to generate Nei’s similarity coefficients and to construct a dendrogram by means of UPGMA. The similarity coefficients data suggested great genetic diversity in genus Leymus and related diploid Triticeae species, the genetic diversity among the different species more abundant than that of the different accessions. The dendrogram and principal coordinate analysis showed explicit interspecific relationships and demonstrated close phylogenetic relationships between Leymus species and Psathyrostachys.     

Genomic reorganization and disrupted chromosomal synteny in the siamang (Hylobates syndactylus) revealed by fluorescence in situ hybridization

We employed in situ hybridization (“chromosome painting”) of chromosome-specific DNA libraries of all human chromosomes to establish homologies between the human and siamang karyotypes (Hylobates syndactylus, 2n = 50). Numerous intra- and interchromosomal rearrangements have led to a massive reorganization of the siamang karyotype. There have been a minimum of 33 translocations. The 24 siamang autosomes are composed of 60 recognizable segments that show DNA homology to regions of the 22 human autosomes. Only two autosomes have not been involved in translocations. The siamang presents a case, in a primate closely related to humans, in which chromosome morphology and synteny are highly disturbed in a manner similar to that encountered among rodents. © 1995 Wiley-Liss, Inc.     

Genetic diversity of Lilium tsingtauense in China and Korea revealed by ISSR markers and morphological characters

To study the genetic diversity and population structure of Lilium tsingtauense Gilg (Qingdao Lily), we collected 648 samples from 12 sites in China and Korea, and analyzed their Inter-Simple Sequence Repeat (ISSR) molecular markers and morphological characters. ISSR data revealed a relatively high genetic diversity at the species level, with 72.31% polymorphic loci, effective numbers of alleles of 1.437, average expected heterozygosity of 0.231 and Shannon’s information index of 0.369. Considerable genetic differentiation among the natural populations (G_ST = 0.144) and the gene flow (N_m = 1.487) were detected. AMOVA analysis and UPGMA-dendrogram suggested a hierarchical regional structure among populations, and spatial autocorrelation analysis showed a micro-scaled spatial structure. Furthermore, there was a high correlation between morphological characters and genetic parameters obtained from ISSR parameters. There was only a low genetic differentiation among the different morphological types of L. tsingtauence in China. Based on these findings, we recommend in situ and ex situ conservation strategies for the preservation of L. tsingtauense.     

Genome differentiation in Magonoliaceae as revealed from meiotic pairing in interspecific and intergeneric hybrids

The cross compatibility within and between Yulania Spach and Michelia L.(Magnoliaceae) is relatively good and various such hybrids,obtained by conventional artificial hybridization,are available.The aim of the present study was to determine the extent of genome differentiation between the species involved in these crosses through the observation of chromosome pairing during meiosis in pollen mother cells (PMCs) of the hybrids.Chromosome pairing behavior was studied in five species (2n =38) and two interspecific hybrids of Michelia,eight species (2n =38,76 and 114) and 10 interspecific hybrids of Yulania,and three intergeneric hybrids between Michelia and Yulania.The results showed that chromosome pairing was normal with bivalent formation in diploid parental species and in interspecific hybrids.In addition to bivalents,multivalents were encountered in polyploid parental species and polyploid interspecific hybrids.In the intergeneric hybrids between a tetraploid Yulania and two diploid Michelia,19 chromosomes,most likely originating from Michelia,were unable to synapse from zygotene to metaphase I.Meiotic chromosome pairing indicated a high degree of homology between species within Michelia and Yulania and less homology between the genomes of these two genera.The differentiation of morphological characters and the distinctness of natural distribution also support the conclusion that these two genera are likely independent monophyletic groups.This suggests that the two genera were split at early evolution of Magnoliaceae and the overlapping characteristics in external morphology and internal structures of the two genera may be the result of parallel evolution or ancient common ancestry.     

Construction of intersubspecific molecular genetic map of lentil based on ISSR, RAPD and SSR markers

Lentil (Lens culinaris ssp. culinaris), is a self-pollinating diploid (2n?=?2x?=?14), cool-season legume crop and is consumed worldwide as a rich source of protein (~24.0%), largely in vegetarian diets. Here we report development of a genetic linkage map of Lens using 114 F₂ plants derived from the intersubspecific cross between L 830 and ILWL 77. RAPD (random amplified polymorphic DNA) primers revealed more polymorphism than ISSR (intersimple sequence repeat) and SSR (simple sequence repeat) markers. The highest proportion (30.72%) of segregation distortion was observed in RAPD markers. Of the 235 markers (34 SSR, 9 ISSR and 192 RAPD) used in the mapping study, 199 (28 SSRs, 9 ISSRs and 162 RAPDs) were mapped into 11 linkage groups (LGs), varying between 17.3 and 433.8 cM and covering 3843.4 cM, with an average marker spacing of 19.3 cM. Linkage analysis revealed nine major groups with 15 or more markers each and two small LGs with two markers each, and 36 unlinked markers. The study reported assigning of 11 new SSRs on the linkage map. Of the 66 markers with aberrant segregation, 14 were unlinked and the remaining 52 were mapped. ISSR and RAPD markers were found to be useful in map construction and saturation. The current map represents maximum coverage of lentil genome and could be used for identification of QTL regions linked to agronomic traits, and for marker-assisted selection in lentil.     

Highly differentiated populations of the narrow endemic and endangered species Primula cicutariifolia in China,revealed by ISSR and SSR

The perennial herb Primula cicutariifolia Pax is an endangered and endemic species with narrow distribution in eastern Anhui and Zhejiang provinces of China. In this study, the levels of genetic variation and the pattern of genetic structure in five natural populations of P. cicutariifolia were assessed by inter-simple sequence repeats (ISSR) and simple sequence repeat (SSR) markers. Both markers revealed that there was remarkably low genetic variation within populations (e.g., H_e = 0.19 and 0.18, for ISSR and SSR respectively) and high differentiation among populations (G_ST = 0.714 and 0.611; Φ_ST = 0.698 and 0.599, for ISSR and SSR respectively). The level of population genetic diversity was correlated to population size only detected by ISSR markers. The genetic structure of P. cicutariifolia may be explained by limited gene flow that was caused by habitat fragmentation and limited seeds and pollen dispersal ability, self breeding system and biennial life form. To protect and avoid disappearance of P. cicutariifolia, much more attentions should be paid to protect all the remnant populations and their habitats, and three management units, i.e. Tianmushan, Damodao, and Panan units, were proposed.     

Population structure and genetic diversity of the only extant Baroninae swallowtail butterfly,Baronia brevicornis,revealed by ISSR markers

Due to its relict nature, the unique Baroninae swallowtail, Baronia brevicornis, is considered a “living fossil”. It is also one of the most enigmatic butterfly species with contentious origins and peculiar ecological characteristics. The aim of this study is to evaluate the genetic diversity and population structure of this endemic species of butterfly in Mexico. We sampled populations in two areas within its restricted geographical range in central Mexico and the isolated subspecies population in the state of Chiapas. Three ISSR primers produced 66 loci, indicating a high genetic diversity (P = 100 %, H _e  = 0.22) and variation range in these populations (62 % < P < 85 %, 0.18 < H _e  < 0.25). The Chiapas population presented the lowest values. The observed high values can be explained by the population dynamic of this species characterized by a very high density of individuals over very limited areas. Variation between populations appears to reflect both the age of colonization and locality perturbation level. Two methods of genetic structure analysis (Self-Organizing Map and Structure analysis) match to define three clusters. Natural and anthropogenic barriers may explain the separation between two clusters (cluster 1 and 2) of central Mexico but an unexpected result revealed that the Chiapas population is not genetically distinguishable from the central Mexico populations (cluster 3) leading us to hypothesize a possible “recent” separation or anthropogenic introduction. Habitat and host plant specificity probably limits the exchange of individuals between populations thus increasing fragmentation and leading to a complex genetic structure. We should put in place population monitoring schemes at different spatial scales, combining field occurrences and genetic tools, in order to reduce extinction susceptibility and keep track of recolonization events for this enigmatic species.     

Clonal diversity and genetic differentiation revealed by SSR markers in wild Vaccinium macrocarpon and Vaccinium oxycoccos

American cranberry (Vaccinium macrocarpon) is a perennial, woody plant species, native to North American bogs and wetlands. Cranberries represent one of the few agriculturally important native plants in which wild gene pools are still readily available within the undeveloped wetlands of the northern US and Canada. Earlier studies have reported low genetic variation in V. macrocarpon at the species and population level. However, in this study, we characterised 229 individuals of wild V. macrocarpon and V. oxycoccos (small cranberry) from Wisconsin and 22 accessions using microsatellite markers and observed substantial genetic variation and differentiation within and among populations and species. While V. macrocarpon was analysed using 108 alleles from 11 microsatellite loci revealing 42 unique genotypes, V. oxycoccos was analysed using 156 alleles from eight loci revealing 28 unique genotypes. There were a total of 182 alleles found in both species combined with 156 of those alleles present in V. oxycoccos and 84 alleles found in V. macrocarpon. All eight loci possessed species‐specific alleles with V. oxycoccos possessing 98 private alleles versus 26 private alleles found V. macrocarpon, and 58 alleles were found in common between both species. Our data will be valuable not only for future wild cranberry diversity and population genetics research, but for other cranberry breeding and genetics studies.     

Genetic diversity and structure among natural populations of Sindora glabra in Hainan Island,China as revealed by ISSR markers

Sindora glabra, one of the second-class national protective plants in China, has important ecological and commercial values. To understand the genetic diversity and structure of S. glabra, eleven natural populations from four areas of Hainan Island in China were analyzed by inter-simple sequence repeat (ISSR) markers. Thirteen primers were screened out and used to amplify 157 DNA samples. A total of 122 bands were obtained, among which 114 (93.4%) bands were polymorphic. Genetic parameters including average number of effective alleles (1.547), Nei's gene diversity (0.321), Shannon's information index (0.482), and gene differentiation coefficient (0.1944) revealed a high level of genetic diversity maintained in S. glabra populations. The variation within populations accounted for 85.6% of total variation based on analysis of molecular variance. Genetic distance analysis showed that 11 populations could be divided into three groups and populations from the same areas were classified as one group, suggesting that high genetic diversity of S. glabra was attributable to geographic isolation. Together, introduction of germplasm from distant natural distribution areas would be a sound strategy for germplasm resource conservation of S. glabra and selection of elite individuals from populations of far relationship for hybridization is of great importance for breeding improvement programs in future.