Genetic diversity among wild and cultivated barley as revealed by RFLP

Genetic variability of cultivated and wild barley, Hordeum vulgare ssp. vulgare and spontaneum, respectively, was assessed by RFLP analysis. The material consisted of 13 European varietes, single-plant offspring lines of eight land races from Ethiopia and Nepal, and five accessions of ssp. spontaneum from Israel, Iran and Turkey. Seventeen out of twenty-one studied cDNA and gDNA probes distributed across all seven barley chromosomes revealed polymorphism when DNA was digested with one of four restriction enzymes. A tree based on genetic distances using frequencies of RFLP banding patterns was estimated and the barley lines clustered into five groups reflecting geographical origin. The geographical groups of land-race lines showed less intragroup variation than the geographical groups of spontaneum lines. The group of European varieties, representing large variation in agronomic traits, showed an intermediate level. The proportion of gene diversity residing among geographical groups (F_ST) varied from 0.19 to 0.94 (average 0.54) per RFLP pattern, indicating large diversification between geographical groups.     

Genetic diversity in some grape varieties revealed by SCoT analyses

Start codon targeted (SCoT) polymorphic markers were used to assess genetic relationships among 64 grape varieties. Seventeen informative primers were selected from 36 SCoT primers based on their ability to produce clear and repeatable polymorphic and unambiguous bands among the varieties. A total of 131 bands were produced; 93.1% of them were polymorphic; the average polymorphism information content was 0.82. Cluster analysis of SCoT markers through the unweighted pair-group method of arithmetic averages analysis and principal coordinate analysis were largely consistent. The partition of clusters in the dendrogram and PCoA plot was similar and some degree of grouping by types of grape and taxonomic status of the varieties was revealed. Four main groups were found after cluster analysis, i.e. table grape of Vitis vinifera; table grape of Euro-America hybrid; wine grape of V. vinifera and wild Vitis species. The results showed that the wild Vitis species originated from America and China could be clearly differentiated. The results also indicated that SCoT markers are informative and could be used to detect polymorphism for grape varieties.     

Genetic diversity among European cultivated spelt revealed by microsatellites

Spelt and common wheat constitute two of the six groups of the hexaploid wheats with an AABBDD genome. Spelt culture has been progressively replaced by that of common wheat which out-yields spelt under high-input conditions. In the last decades, spelt breeders intended to introduce the yield-potential and bread-making qualities of common wheat into spelt, by frequent crossings between accessions of these two different groups. The present study aims at determining the genetic basis of modern spelt cultivars in terms of intra-group variability and inter-group (spelt vs common wheat) distances, by using microsatellite markers developed for common wheat. The allelic composition of 30 spelt and nine common wheat accessions was determined at 17 microsatellite loci. The coefficient of co-ancestry (ƒ) and the genetic distances (1 - proportion of shared alleles) based upon allelic composition were calculated for all pairs of accessions. Two dendrograms were constructed using the UPGMA method. Amplification products were found for all loci on most accessions. A total of 113 alleles was identified, of which 60.2% were specific to spelt or common wheat. The correlation between (1 –ƒ ) and the genetic distance was high (0.701***). The mean pairwise genetic distance was 0.656 ± 0.181 over the 39 accessions, 0.706 ± 0.14 among common wheat and 0.573 ± 0.172 among spelt. The mean genetic distance between spelt and wheat was 0.782 ± 0.113. The two dendrograms were in accordance with each other and clearly separated the spelt from the common wheat accessions. It is concluded that microsatellites developed for common wheat and distances based on the proportion of shared alleles are powerful tools for reconstructing phylogenies in spelt, and that the genetic basis of modern spelt cultivars is narrow despite frequent crosses made with bread wheat. Received: 26 January 2000 / Accepted: 26 May 2000     

Genetic diversity among summer and winter Beauveria bassiana populations as revealed by AFLP analysis

The genetic diversity of Beauveria bassiana was investigated by comparing 40 isolates collected from summer and overwintering populations of Sunn pest from different areas in Syria and Turkey, using amplified fragment length polymorphism (AFLP) markers. Considerable genetic variability among B. bassiana isolates was revealed. The examined isolates were divided into three distinct clusters (A, B, and C). Within these clusters, the summer isolates from Syria and Turkey were grouped together in three sub-clusters (A3, A4, and B2). Also, principal coordinate analyses (PCA) showed clear separation (62.5%) between summer and winter isolates. These differences in the genetic structure may be explained by the variety of eco-geography over the sampled areas of B. bassiana isolates. This information on genetic variation among summer and winter B. bassiana isolates is helpful in designing an effective integrated pest management program for Sunn pest.     

Phylogenetic relationships among taxa of the liverwort Conocephalum conicum (Conocephalaceae) revealed by psbA sequence

The 5' flanking and coding regions of the psbA gene were sequenced to clarify relationships among several taxa discovered recently in thalloid liverwort Conocephalum conicum. Twenty six samples included in this study represent five "cryptic species" detected in worldwide collection, five groups discovered from Japan and finally three "chemo-types" with different dominant volatile component. Pairwise differences in nucleotide sequences of coding region between samples of Conocephalum conicum varied greatly depending on the combination, ranging from 0.001 to 0.018 per site. In total, seven amino acid substitutions were found among all samples. NJ and parsimony trees among the taxa were constructed for the first time. The phylogenetic relationships among taxa were basically consistent with those inferred from isozyme and morphological studies. Conocephalum conicum -species FS and T taxon found in Japan have identical sequence of psbA gene, suggesting that they are conspecific. Similarly, YFS and KYT taxa cluster together with FS cryptic species, and "chemo-types" I and II with "cryptic species" J. A chemotype III was very different from any other taxa of C. conicum. These results suggest that morphological species, Conocephalum conicum is highly differentiated at the molecular level and some of the taxa may in fact represents different species as previous studies suggested.     

The use of DGGE analyses to explore eastern Mediterranean and Red Sea marine picophytoplankton assemblages

In vast areas of the oceans, most marine photosynthetic production is performed by cells smaller than 2-3 microm (picoplankton). Here, we report on denaturing gradient gel electrophoresis (DGGE) analyses of naturally occurring marine oxygenic picophytoplankton using the conserved photosynthetic psbA gene. The psbA gene proved to be a good indicator for picophytoplankton presence and was shown to work with DGGE. The DGGE results show the distribution of photosynthetic marine groups belonging to cyanobacteria and the eukaryotic prasinophytes (green algae) in the Red and eastern Mediterranean Seas in the seasons examined. The present study demonstrates the value of DGGE as a tool for rapid analyses of natural marine communities of picophytoplankton.     

Taxonomic relationships among Turkish water frogs as revealed by phylogenetic analyses using mtDNA gene sequences

We assessed taxonomic relationships among Turkish water frogs through estimation of phylogenetic relationships among 62 adult specimens from 44 distinct populations inhabiting seven main geographical regions of Turkey using 2897 bp sequences of the mitochondrial Cytb, 12S rRNA and 16S rRNA genes with equally-weighted parsimony, likelihood, and Bayesian methods of inference. Monophyletic clade (Clade A) of the northwesternmost (Thrace) samples is identified as Pelophylax ridibundus. The other clade (Clade B) consisted of two monophyletic subclades. One of these contains specimens from southernmost populations that are regarded as an unnamed species. The other subclade consists of two lineages, of which one corresponds to P. caralitanus and another to P. bedriagae. Taxonomic relationships of these two species are discussed and recognition of P. caralitanus as a subspecies of P. bedriagae is proposed.     

Diversity of DMSP transport in marine bacteria, revealed by genetic analyses

The enzyme product of the dddD gene, found in several different marine bacteria, acts on dimethylsulfoniopropionate (DMSP), liberating dimethyl sulfide (DMS) and generating 3-OH-propionate as the initially detected C3 product. In many bacteria, dddD is near genes whose sequence suggests that they encode a DMSP transporter. These are of two very different types, in the BCCT (betaine-carnitine-choline transporter) family or resembling members of the ABC super-family that import betaines. Even within these two families, the amino acid sequences of these putative transporters are not particularly similar to each other. Genes for the predicted DMSP transporters of Halomonas and Marinomonas (both BCCT type) and of Burkholderia ambifaria AMMD (ABC-type) were each cloned and introduced into an Escherichia coli mutant (MKH13) that is defective in betaine uptake, and so fails to catabolise DMSP even when a cloned dddD gene was present, due to the failure of the substrate to be imported. DMSP-dependent DMS production (Ddd⁺ phenotype) was restored by introducing any of these cloned transporters into MKH13 containing dddD. Other marine bacteria use a range of enzymes, called DddL, DddP, DddQ, DddW and DddY, to cleave DMSP, but the various ddd genes that encode them are usually unlinked to any that are predicted to encode betaine transporters. We identified one gene in Sulfitobacter sp. EE-36 and two in Roseovarius nubinhibens ISM, which, when cloned and introduced into E. coli MKH13, overcame its osmotic sensitivity when it was grown with DMSP or other exogenous betaines. These genes all encoded BCCT transporters, but were unlinked to any known genes involved in DMSP catabolism in these two strains of α-proteobacteria.     

Genetic diversity in marine algal virus communities as revealed by sequence analysis of DNA polymerase genes.

Algal-virus-specific PCR primers were used to amplify DNA polymerase gene (pol) fragments (683 to 689 bp) from the virus-sized fraction (0.02 to 0.2 microns) concentrated from inshore and offshore water samples collected from the Gulf of Mexico. Algal-virus-like DNA pol genes were detected in five samples collected from the surface and deep chlorophyll maximum. PCR products from an offshore station were cloned, and the genetic diversity of 33 fragments was examined by restriction fragment length polymorphism and sequence analysis. The five different genotypes or operational taxonomic units (OTUs) that were identified on the basis of restriction fragment length polymorphism banding patterns were present in different relative abundances (9 to 34%). One clone from each OTU was sequenced, and phylogenetic analysis showed that all of the OTUs fell within the family Phycodnaviridae. Four of the OTUs fell within a group of viruses (MpV) which infect the photosynthetic picoplankter Micromonas pusilla. The genetic diversity among these genotypes was as large as that previously found for MpV isolates from different oceans. The remaining genotype formed its own clade between viruses which infect M. pusilla and Chrysochromulina brevifilum. These results imply that marine virus communities contain a diverse assemblage of MpV-like viruses, as well as other unknown members of the Phycodnaviridae.     

Genotypic diversity and differentiation among populations of two benthic freshwater diatoms as revealed by microsatellites

Given their large population sizes and presumed high dispersal capacity, protists are expected to exhibit homogeneous population structure over large spatial scales. On the other hand, the fragmented and short‐lived nature of the lentic freshwater habitats that many protists inhabit promotes strong population differentiation. We used microsatellites in two benthic freshwater diatoms, Eunotia bilunaris ‘robust’ and Sellaphora capitata, sampled from within a pond and connected ponds, through isolated ponds from the same region to western Europe to determine the spatial scale at which differentiation appears. Because periods of low genotypic diversity contribute to population differentiation, we also assessed genotypic diversity. While genotypic diversity was very high to maximal in most samples of both species, some had a markedly lower diversity, with up to half (Eunotia) and over 90% (Sellaphora) of the strains having the same multilocus genotype. Population differentiation showed an isolation‐by‐distance pattern with very low standardized F_ST values between samples from the same or connected ponds but high values between isolated ponds, even when situated in the same region. Partial rbcL sequences in Eunotia were consistent with this pattern as isolated ponds in the same region could differ widely in haplotype composition. Populations identified by Structure corresponded to the source ponds, confirming that ‘pond’ is the main factor structuring these populations. We conclude that freshwater benthic diatom populations are highly fragmented on a regional scale, reflecting either less dispersal than is often assumed or reduced establishment success of immigrants, so that dispersal does not translate into gene flow.     

Bacterial diversity of the Inner Mongolian Baer Soda Lake as revealed by 16S rRNA gene sequence analyses

Bacterial diversity associated with Baer Soda Lake in Inner Mongolia of China was investigated using a culture-independent method. Bacterial 16S rRNA gene libraries were generated using bacterial oligonucleotide primers, and 16S rRNA gene sequences of 58 clones were analyzed phylogenetically. The library was dominated by 16S rDNAs of Gram-negative bacteria (24% -Proteobacteria, 31% -Proteobacteria, 33% -Proteobacteria, and 2% -Proteobacteria), with a lower percentage of clones corresponding to Gram-positive bacteria. Forty cloned sequences were similar to that of known bacterial isolates (>97% sequence similarity), represented by the species of the genera Brevundimonas, Comamonas, Alcaligenes, Stenotrophomonas, and Klebsiella. Eighteen cloned sequences showed less affiliation with known taxa (<97% sequence similarity) and may represent novel taxa.Communicated by K. Horikoshi     

Genetic relationships among Stylosanthes species revealed by RFLP and STS analyses

Genetic relationships between 6 unclassified taxa and 24 known species of the genus Stylosanthes were investigated by RFLP and STS analyses. This allowed the diploid taxa used in this study to be classified into nine basal (genome) groups. Representative species in these groups included ’S. seabrana’/S. hamata (Group A), S. viscosa (Group B), S. humilis (Group C), S. macrocephala/S. bracteata (Group D), S. pilosa (Group E), S. leiocarpa (Group F), S. guianensis (Group G), S. tomentosa (Group H) and S. calcicola (Group I). Polyploid taxa used were grouped into five classes based on their putative genomic structures. These are AABB for S. scabra, S. aff. scabra, S. sericeiceps, S. aff. hamata and S. tuberculata; AACC for S. mexicana, S. subsericea, S. sundaica and S. sp.A; DDEE for S. capitata; AAFF for S. sympodialis; and AABBXX for S. erecta, with XX representing an unknown genome. Of the 6 unclassified taxa, three were diploids and 3 tetraploids. Of the 3 diploids, the genome of S. sp. was markedly distinct from those of all other diploids analysed in this study, with that of S. leiocarpa being the closest. The genome of S. sp.B was similar to that of S. humilis, with an average dissimilarity value of 15% between them. The genome of S. aff. viscosa was very similar to that of S. viscosa. Genetic variation between these 2 taxa was not larger than that within each of the 2 taxa. Of the 3 tetraploids, the genomic structure of S. sp.A was similar to those of S. mexicana, S. sundaica and S. subsericea, and the genomic structures of S. aff. scabra and S. aff. hamata were similar to those of S. scabra and S. sericeiceps. Received: 18 September 1998 / Accepted: 23 March 1999     

Comparative microbial diversity analyses of modern marine thrombolitic mats by barcoded pyrosequencing

Thrombolites are unlaminated carbonate structures that form as a result of the metabolic interactions of complex microbial mat communities. Thrombolites have a long geological history; however, little is known regarding the microbes associated with modern structures. In this study, we use a barcoded 16S rRNA gene-pyrosequencing approach coupled with morphological analysis to assess the bacterial, cyanobacterial and archaeal diversity associated with actively forming thrombolites found in Highborne Cay, Bahamas. Analyses revealed four distinct microbial mat communities referred to as black, beige, pink and button mats on the surfaces of the thrombolites. At a coarse phylogenetic resolution, the domain bacterial sequence libraries from the four mats were similar, with Proteobacteria and Cyanobacteria being the most abundant. At the finer resolution of the rRNA gene sequences, significant differences in community structure were observed, with dramatically different cyanobacterial communities. Of the four mat types, the button mats contained the highest diversity of Cyanobacteria, and were dominated by two sequence clusters with high similarity to the genus Dichothrix, an organism associated with the deposition of carbonate. Archaeal diversity was low, but varied in all mat types, and the archaeal community was predominately composed of members of the Thaumarchaeota and Euryarchaeota. The morphological and genetic data support the hypothesis that the four mat types are distinctive thrombolitic mat communities.     

滇牡丹遗传多样性的ISSR分析

应用ISSR标记对中国西南地区特有植物滇牡丹(Paeonia delavayi)的遗传多样性进行了研究。从100个引物中筛选出10个用于正式扩增,在取自16个自然居群和1个迁地保护居群的511个个体中,检测到92个多态位点。在居群水平上,多态位点百分率（PPB）为44.61%,Nei′s基因多样性指数（H）和Shannon信息指数（I）分别为0.1657和0.2448。在物种水平上,多态位点百分率（PPB）为79.31%,Nei′s基因多样性指数（H）和Shannon信息指数（I）分别为0.2947和0.4355。居群间的遗传分化系数(G_ST)达0.4349。结果表明：滇牡丹遗传多样性水平较高,居群间遗传分化较大。结合以前的研究结果,对滇牡丹的现状进行评估的结果显示,滇牡丹并不濒危。     

Molecular diversity of dinoflagellate symbionts of Cnidaria: the psbA minicircle of Symbiodinium

Dinoflagellate algae of the genus Symbiodinium are important symbionts within corals and other benthic marine animals. The molecular diversity of Symbiodinium has been described mainly by use of ribosomal DNA sequence data. We tested whether minicircle sequences, which appear to form the chloroplast genome in many dinoflagellates, could be used as a marker for molecular diversity among symbionts found in corals and sea anemones. Partial and full-length sequences for psbA were obtained from environmental samples of coral and sea anemones of wide-ranging geographical distribution. Phylogenetic trees constructed with partial psbA sequences were consistent with the known phylotypes of the isolates. Further sequencing suggested that the psbA gene is present on a minicircle in all Symbiodinium phylotypes. The length and DNA sequence of the non-coding portion of the minicircles varied considerably among Symbiodinium phylotypes. In two Symbiodinium isolates from different phylotypes an elaborate pattern of repeat sequences of unknown function was found in the non-coding region. Phylogenetic analysis of the non-coding region of the psbA minicircle indicates that minicircle sequences could be a useful chloroplast-derived marker for differentiating both closely related and distantly related Symbiodinium isolates.     

Genetic diversity among cultivars, landraces and wild relatives of rice as revealed by microsatellite markers

Genetic diversity among 35 rice accessions, which included 19 landraces, 9 cultivars and 7 wild relatives, was investigated by using microsatellite (SSR) markers distributed across the rice genome. The mean number of alleles per locus was 4.86, showing 95.2% polymorphism and an average polymorphism information content of 0.707. Cluster analysis based on microsatellite allelic diversity clearly demarcated the landraces, cultivars and wild relatives into different groups. The allelic richness computed for the clusters indicated that genetic diversity was the highest among wild relatives (0.436), followed by landraces (0.356), and the lowest for cultivars. Allelic variability among the SSR markers was high enough to categorize cultivars, landraces and wild relatives of the rice germplasm, and to catalogue the genetic variability observed for future use. The results also suggested the necessity to introgress genes from landraces and wild relatives into cultivars, for cultivar improvement.     

Phylogenetic relationships among North Atlantic redfish (genus Sebastes) as revealed by mitochondrial DNA sequence analyses

Species structure and phylogenetic relationships among the four currently recognised North Atlantic redfish species, Sebastes mentella (‘deep‐sea’ and ‘oceanic’ phenotype), S. marinus (including ‘giant’ phenotype), S. fasciatus and S. viviparus, were investigated by sequencing the complete mitochondrial NADH dehydrogenase subunit 3 (ND3) gene for 313 individuals (333 including outliers). Low levels of sequence divergence of 0.3–2.3% between the North Atlantic Sebastes haplotypes, low resolution in phylogenetic trees and a star‐like statistical parsimony network indicate a population bottleneck and/or founder event with a subsequent population expansion and a rapid speciation in North Atlantic Sebastes. Diagnostic mutations within the ND3 gene were recognised for some of the species. The results lead to the hypothesis that the ancestral haplotype lineage is now very rare or has suffered extinction and that the most basal lineage is found in S. viviparus. The results further indicate direct descendants in the S. fasciatus and S. marinus lineages from the S. mentella lineage, whereas the S. viviparus lineage originates from an earlier division. The observation of two haplotype lineages in S. marinus with a relatively high level of intraspecific genetic divergence, points towards a possible cryptic speciation.     

Plastid 16S rRNA gene diversity among eukaryotic picophytoplankton sorted by flow cytometry from the South Pacific Ocean

The genetic diversity of photosynthetic picoeukaryotes was investigated in the South East Pacific Ocean. Genetic libraries of the plastid 16S rRNA gene were constructed on picoeukaryote populations sorted by flow cytometry, using two different primer sets, OXY107F/OXY1313R commonly used to amplify oxygenic organisms, and PLA491F/OXY1313R, biased towards plastids of marine algae. Surprisingly, the two sets revealed quite different photosynthetic picoeukaryote diversity patterns, which were moreover different from what we previously reported using the 18S rRNA nuclear gene as a marker. The first 16S primer set revealed many sequences related to Pelagophyceae and Dictyochophyceae, the second 16S primer set was heavily biased toward Prymnesiophyceae, while 18S sequences were dominated by Prasinophyceae, Chrysophyceae and Haptophyta. Primer mismatches with major algal lineages is probably one reason behind this discrepancy. However, other reasons, such as DNA accessibility or gene copy numbers, may be also critical. Based on plastid 16S rRNA gene sequences, the structure of photosynthetic picoeukaryotes varied along the BIOSOPE transect vertically and horizontally. In oligotrophic regions, Pelagophyceae, Chrysophyceae, and Prymnesiophyceae dominated. Pelagophyceae were prevalent at the DCM depth and Chrysophyceae at the surface. In mesotrophic regions Pelagophyceae were still important but Chlorophyta contribution increased. Phylogenetic analysis revealed a new clade of Prasinophyceae (clade 16S-IX), which seems to be restricted to hyper-oligotrophic stations. Our data suggest that a single gene marker, even as widely used as 18S rRNA, provides a biased view of eukaryotic communities and that the use of several markers is necessary to obtain a complete image.