bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromosome pairing in inter-racial hybrids of the house musk shrew (Suncus murinus, Insectivora, Soricidae)
Authors: Borodin Pavel M , Rogatcheva Margarita B , Zhelezova Antonina I , Oda Sen-ichi
Published: April 2011

Two chromosome races of the house shrew Suncus murinus that differ from each other for five Robertsonian translocations (8.17, 9.13, 10.12, 11.16, and 14.15), heterochromatic insertions in chromosomes 7 and X, and multiple rearrangements in the Y chromosome were crossed and then intercrossed in captivity to produce a hybrid stock. Electron-microscopic analysis of synaptonemal complexes in fertile and sterile hybrid males was carried out. Meiosis in sterile males did not progress beyond pachytene and was severely disrupted. Meiotic arrest was not determined by structural heterozygosity: heterozygotes for all variant chromosomes distinguishing two parental races were found in both sterile and fertile male hybrids. Fertile hybrids demonstrated an orderly pairing of all chromosomes. In heterozygotes for Robertsonian fusions, completely paired trivalents were formed between the Robertsonian metacentrics and homologous acrocentrics. In heterozygotes for chromosome 7, bivalents with a small buckle were observed in a small fraction of pachytene cells. No differences were found in the morphology and pairing pattern of sex bivalents, composed of the X and Y chromosomes derived from the same or different parental races. Univalents, multivalents, and associations between X and Y chromosomes and autosomal trivalents, as well as associations of autosomal trivalents with each other, were observed in a small fraction of the pachytene cells of fertile males. Our results indicate that the system controlling male sterility in interracial hybrids of S. murinus is of genic rather than of chromosomal type.
Chromocenter association in plant cell nuclei: determinants, functional significance, and evolutionary implications
Authors: Ceccarelli Marilena , Morosi Lorena , Cionini Pier Giorgio
Published: April 2011

Owing to close associations of different chromosomes at their heterochromatic regions, nuclear repatternings consisting of changes in the number and size of the chromocenters may occur with tissue differentiation in plant species. By studying these changes in the nuclear structure in a number of Magnoliopsida with chromocentric nuclei, we found: (i) that chromocenter association is affected by the degree of partitioning of the genome, since the extent of the phenomenon correlates positively with the number of chromosomes in the complement, the level of ploidy, and the number of chromocenters in meristematic nuclei, whereas the correlation with the mean DNA content per chromosome is negative; (ii) that this kind of nuclear repatterning plays a role in or is a marker of events that have a part in the control of nuclear activity, since a negative correlation was found to exist, as a rule, between the extent of chromocenter association and that of RNA synthesis in the nucleus; and (iii) that this large-scale control mechanism of gene expression is exploited in cell differentiation from its early stages. Indeed, chromocenter association takes place at the base of the meristems and remains unchanged during further tissue development. In certain species, this phenomenon has not been observed; its presence or absence may represent a character of entire families, and may be linked to the position of a species on an evolutionary scale.
Characterization of a microsatellite in the promoter region of the IGF1 gene in domestic horses and other equids
Authors: Caetano Alexandre R , Bowling Ann T
Published: April 2011

Insulin-like growth factor 1 (IGF1) regulates growth and metabolic functions in vertebrates. A dinucleotide repeat sequence located at the promoter region of the IGF1 gene has been reported in several vertebrate species and may affect the control of the transcriptional activity of this gene. The genotypes of animals from seven horse breeds were determined in order to study the potential association of allelic forms of this microsatellite with adult body size differences found in domestic horses. Among these breeds, five alleles were found. Breed-specific differences in adult body size could not be attributed to the presence or absence of any of the alleles observed. In addition, animals representing five other equid species were typed. Examples of apparent species-specific alleles were found. However, overlapping polymorphic size ranges preclude this microsatellite from being an absolute identifier for species or hybrid status in equids. The polymorphisms found at this IGF1 locus are useful for synteny and linkage mapping.
Hybridation naturelle entre deux sous-espèces de souris domestique,Mus musculus domesticusetMus musculus castaneus, près du lac Casitas (Californie)
Authors: Orth Annie , Adama Theophilus , Din Waheedud , Bonhomme François
Published: April 2011

The house mouse Mus musculus is a polytypic species, distributed worldwide, with three main subspecies: M. m. musculus in the North-East of Eurasia, M. m. castaneus in South-East Asia, and M. m. domesticus in Europe, the Near-East, and Africa. This last subspecies may also be found in Australia and the Americas, where it was brought by European colonization. Previous studies, however, have shown the presence of specific antiviral determinants of Asian origin in a mouse population at Lake Casitas, California. In this study, an analysis of the variability at 35 enzyme loci demonstrates the hybrid nature of this Californian population intermediate between M. m. castaneus and M. m. musculus. Restriction fragment length polymorphisms of two fragments of the mitochondrial DNA also confirm unambiguously the presence of two types of matrilines in comparable frequencies in our sample. Nevertheless, the study of a subspecies-specific Y chromosome microdeletion in the Zfy2 gene reveals only theM. m. domesticus haplotype at Lake Casitas, a phenomenon comparable with the one observed in other hybrid zones of the M. musculus complex. These findings testify once more that genetic exchanges between subspecies inside the broader M. musculus gene pool are still possible.
Genetic variation between several species of sections Extranervosae, Caulorrhizae, Heteranthae, and Triseminatae (genus Arachis) estimated by DNA polymorphism
Authors: Galgaro Leticia , Lopes Catalina Romero , Gimenes Marcos , Valls José FM , Kochert Gary
Published: April 2011

Genetic variation within and among accessions of the genusArachis representing sections Extranervosae, Caulorrhizae, Heteranthae, and Triseminatae was evaluated using RFLP and RAPD markers. RAPD markers revealed a higher level of genetic diversity than did RFLP markers, both within and among the species evaluated. Phenograms based on various band-matching algorithms revealed three major clusters of similarity among the sections evaluated. The first group included the species from section Extranervosae, the second group consisted of sections Triseminatae, Caulorrhizae, and Heteranthae, and the third group consisted of one accession of Arachis hypogaea, which had been included as a representative of section Arachis. The phenogramsobtained from the RAPD and RFLP data were similar but not identical. Arachis pietrarellii, assayed only by RAPD, showed a high degree of genetic similarity with Arachis villosulicarpa. This observation supported the hypothesis that these two species are closely related. It was also shown that accession V 7786, previously considered to be Arachis sp. aff.pietrarellii, and assayed using both RFLPs and RAPDs, was possibly a new species from section Extranervosae, but very distinct from A. pietrarellii.Keywords: Arachis, RFLP, RAPD, genetic similarity, genetic distance.
An X/Y DNA segment from an early stage of sex chromosome differentiation in the flyMegaselia scalaris
Authors: Traut Walther , Wollert Brigitte
Published: April 2011

The sex chromosomes of the Megaselia scalaris wild-type strain Wien are homomorphic. We studied a roughly 1.8 kb X/Y DNA segment of this strain. It includes, at one end, the first part of a coding sequence for a protein of the vespid antigen 5 family. Molecular differentiation between the X and Y chromosomes has commenced, but homology, even of short DNA stretches, is still assessable beyond doubt. The most conspicuous differences between the X and the homologous Y segment were insertions/deletions in the noncoding region: among them, deletions, a duplication, and an insertion of a mobile element. These structural changes grossly disrupted homology. In comparison, base substitutions, though more numerous, contributed little to the differentiation of the X/Y DNA segment.Key words: sex determination, molecular differentiation, mobile element, vespid antigen 5.
An evaluation of rDNA variation inLoliumspecies (ryegrass)
Authors: Warpeha KMF , Gilliland T J , Capesius I
Published: April 2011

Species of the genus Lolium are important fodder and turf grasses for agricultural and amenity use world-wide. Difficulties currently exist regarding the taxonomy of Lolium species and also in the demarcation between Lolium and the genus Festuca, with the debate focusing on the status of Festuca pratensis and its relations. The diversity in ribosomal DNA (rDNA) in Lolium was investigated. Cloned probes for rDNA, derived from the intergenic spacer (IGS-M) and transcribed regions (COD-M) of mustard (Sinapis alba) were used to investigate species relationships. Genomic DNA from seven Lolium taxa, F. pratensis, and xFestulolium braunii, were assessed for variation in rDNA by RFLP. Data support continued recognition of existing Lolium species' demarcations, and provided more taxonomic insight between allogamous Lolium taxa and F. pratensis. The COD-M and IGS-M probes grouped taxa by reproductive mode. The IGS-M probe distinguished all species as unique entities and established that hybrids, xFestulolium braunii and Lolium xboucheanum, had rDNA phenotypes that were composites of their parental species. The evolution of the ribosomal repeat unit is discussed and the potential for further rDNA taxonomic study in Lolium is considered.Key words: Lolium, variation, ribosomal, rDNA, RFLP.
FISH mapping and inter-Alu fingerprinting define the YAC contig map around the centromeric region of human chromosome 18
Authors: Greer Wenda L , Dobson Melanie J , Neumann Paul E , Girouard Gabrielle S , Sparrow Susan M , Riddell D Christie
Published: April 2011

Previous reports concerning the location of D18S44 with respect to the centromere have been ambiguous. Also, it has not been possible, based on formerly reported markers, to show that contigs WC18.0 and WC18.1 overlap. However, the data presented here definitively show, using FISH technology, that D18S44 (located on WC18.0) maps to proximal 18q. Furthermore, inter-Alu fingerprinting shows a clear overlap between WC18.0 and WC18.1, thereby establishing a complete contig between D18S44 and markers from WC18.1.Key words: FISH mapping, inter-Alu, fingerprinting, human chromosome 18.
A comparative analysis of European and American eel (Anguilla anguilla and Anguilla rostrata) genomic DNA: 5S rDNA polymorphism permits the distinction between the two populations
Authors: Nieddu M , Pichiri G , Coni P , Salvadori S , Deiana A M , Mezzanotte R
Published: April 2011

We studied possible molecular and cytological correlations between the European (Anguilla anguilla) and the American (Anguilla rostrata) eel, using either low molecular weight highly repetitive sequences isolated from genomic DNA of the two species, or highly conserved sequences, such as 45S or 5S rDNA, as probes. A clearcut difference was found only in filter hybridization experiments carried out using 5S rDNA as probe.Key words: fish, chromosomes, DNA, endonucleases, rDNA.
Cloning and molecular analysis of the human citrate synthase gene
Authors: Goldenthal Michael J , Marin-Garcia Jose , Ananthakrishnan Radha
Published: April 2011

The nucleotide sequence encoding the citrate synthase (CS) gene was determined from the sequencing of the CS cDNA isolated from a human heart cDNA library. The primary sequence of CS deduced from its nucleotide sequence reveals a highly conserved, albeit slightly larger, protein of 466 amino acids, with 95% homology to its pig homologue. The data also indicate that the human genomic CS gene contains no introns, and confirms the location of the human CS gene on chromosome 12.Key words: human, citrate synthase, Krebs' cycle.
Inheritance of male hybrid sterility in the house musk shrew (Suncus murinus, Insectivora, Soricidae)
Authors: Axenovich Tatiana I , Rogatcheva Margarita B , Oda Sen-ichi , Borodin Pavel M
Published: April 2011

Two geographic races of the house musk shrew (Suncus murinus) were crossed and intercrossed in the laboratory. Many cases of male sterility were detected among the hybrids. Segregation analysis of the pedigree data showed that the inheritance of male sterility in interracial hybrids of S. murinus can be described within the framework of monogene polyallele model with sterility of a single allele combination. This model is similar if not identical to that proposed by Dobzhansky and Muller.Key words: hybrid sterility, segregation analysis, spermatogenesis, shrew, Suncus murinus.
The development of codominant PCR/RFLP based markers for the flax rust-resistance alleles at the L locus
Authors: Hausner G , Rashid K Y , Kenaschuk E O , Procunier J D
Published: April 2011

The flax L locus exists as a single gene with at least 13 alleles with different rust-resistance specificities. With regards to resistance to North American races of flax rust the L2, L6, and L11 alleles are of major importance. Molecular markers have been developed by screening primer sets, whose sequences were based on the nucleotide sequence of L6, for their ability to amplify segments of the L gene. One primer combination was found to amplify only the L6 or L11 alleles and another primer set was found to amplify the 3' end of all important L alleles. The latter primer set yielded a 1.3 kb fragment which upon digestion with the endonuclease MboI generated RFLP patterns unique to L2, L6, L9, and L11. The application of PCR markers to a set of 22 cultivars, comprised of deregistered, recent, and yet to be released cultivars verifies genetic studies done by previous workers and demonstrates the usefulness of the markers for following segregation of L alleles in crosses amongst wide or narrow selections of cultivars. Overall, the results confirmed that L6 is present in many Canadian flax cultivars. However, in several recently-released flax cultivars that have rust resistance conditioned by genes at other loci, the L9 allele was detected. These molecular markers will be useful in marker-assisted selection and the introduction of new genes for rust resistance in the flax breeding programs.Key words: flax rust, PCR/RFLP marker, marker-assisted selection.
A molecular linkage map of tomato based on a cross between Lycopersicon esculentum andL. pimpinellifolium and its comparison with other molecular maps of tomato
Authors: Chen F Q , Foolad M R
Published: April 2011

The wild species related to the cultivated tomato, Lycopersicon esculentum Mill., are a rich source of useful genes for germplasm improvement and varietal development. Characterization and utilization of exotic germplasm can be accelerated by the use of molecular linkage maps. Recently, we have identified an accession (LA722) within L. pimpinellifolium Jusl., a closely-related, red-fruited wild species of tomato, which exhibits a number of desirable agricultural characteristics including salt tolerance, disease resistance, and high fruit quality. The limited DNA marker polymorphism between L. esculentum and L. pimpinellifolium, however, restricts the use of the high-density molecular map of tomato, which was previously constructed based on a cross between L. esculentum and L. pennellii Corr., for marker-assisted identification and utilization of useful genes in LA722. To overcome this problem, we have constructed a linkage map based on restriction fragment length polymorphisms (RFLPs) which were identified between LA722 and a fresh-market tomato breeding line (NC84173). The mapping population (consisting of 119 BC1 individuals) was genotyped for 151 RFLP markers, including 17 germination related and 2 potassium transporter cDNAs. The DNA markers spanned approximately 1192 cM of the tomato genome with an average distance of 7.9 cM between markers. The length of the map and the linear order of the markers were in good agreement with those of the previously published molecular maps of tomato, however, there were considerable differences in the distribution of recombinations along the chromosomes. Comparison of all seven published molecular maps of tomato, which were constructed based on different inter- and intraspecific crosses, indicated that some chromosomal regions were more stable than others in terms of the frequency of recombinations. Similarities and differences among tomato molecular maps are discussed in relation to phylogenetic relationships between parents of the mapping populations. In comparison, a L. esculentum ×L. pimpinellifolium map should be more useful than other interspecific maps for marker-assisted exploitation of genetic variation that exists within L. pimpinellifolium or L. esculentum; the latter is because of the extensive introgression of genes from L. pimpinellifolium into L. esculentum, which occurred over time by natural means or through plant breeding.Key words: Lycopersicon esculentum, L. pimpinellifolium, genetic marker, molecular map, recombination, restriction fragment length polymorphism (RFLP), tomato.
Directed termination of the polymerase chain reaction: Kinetics and applications in mutation detection
Authors: Chen Junjian Z , Hebert Paul DN
Published: April 2011

We describe a PCR-based method (DT-PCR) that integrates both DNA amplification and directed chain termination into a single-step process. This method exploits unbalanced nucleotide concentrations to induce the polymerase chain reaction to terminate at specific nucleotide sites, leading to the generation of two sets of nested termination fragments from genomic DNA. The kinetic mechanism underlying the termination process is outlined and the application of this method to the detection and characterization of mutations in fragments as long as 1 kb is described. The method is effective for the analysis of both haploid and diploid genomes, and not only allows the recognition of both indels (insertions and deletions) and nucleotide substitutions, but also enables the determination of their position in a single-step fashion.Key words: DT-PCR, unbalanced dNTPs, chain termination, mutation detection.
Analysis by PCR-based markers using designed primers to study relationships between species of Hordeum (Poaceae)
Authors: Bustos Alfredo De , Soler Consuelo , Jouve Nicolás
Published: April 2011

An investigation was made into the relationships between six species or subspecies of the genus Hordeum that grow in the Iberian Peninsula and Balearic Islands. Plant material included samples of 19 populations of the annual species H. marinum subsp. marinum, H. marinum subsp. gussoneanum, H. murinum subsp. murinum, and H. murinum subsp. leporinum, and the perennial species H. bulbosum and H. secalinum. Relationships were analysed using PCR-based molecular markers. Thirteen sets of primers were designed and synthesized based on sequences of mapped RFLPs from genomic libraries and conserved regions of structural genes of known function in cultivated species. Primers were used to amplify genomic DNA from all populations. The number of amplified products ranged from 1 to 18 per primer and a total of 168 markers were scored. The markers revealed different degrees of relationships. Hordeum bulbosum was clearly separated from the rest. The populations of both subspecies of H. murinum were closely related. H. marinum subsp. gussoneanum appeared to be closely related to H. secalinum, yet relatively separated from its conspecific subspecies marinum. The use of a large number of DNA markers in this kind of analysis is discussed.Key words: Hordeum, barley, DNA markers, restriction endonucleases, variability, DNA analysis.
Microsatellite retrieval in lettuce (Lactuca sativa L.)
Authors: van de Wiel Clemens , Arens Paul , Vosman Ben
Published: April 2011

By using enriched genomic libraries, microsatellite-containing sequences were isolated from lettuce (Lactuca sativa) with high efficiency. With this approach, a sizeable fraction (up to 55%) of the clones contained a microsatellite. In about half of these clones, primers could be designed for PCR amplification of the microsatellite. This yielded 28 primer sets amplifying unambiguously scorable products, of which 26 showed polymorphisms in a test set of six lettuce varieties. Practically all microsatellite-amplifying primer sets yielded products in lettuce's nearest relative, L. serriola, but only half of the primer sets yielded products in the more distant species L. saligna and L. virosa. An average polymorphism information content (PIC) value of 0.55 and an average number of 3.5 alleles per locus were in the normal range for a self-fertilizing species like lettuce. In addition, the incidental cloning of a microsatellite-containing repeat family, apparently specific for Lactuca, is reported and the implications for the efficient retrieval of single-locus microsatellite sequences are discussed. The microsatellite loci isolated will be useful for distinguishing lettuce cultivars and for screening diversity of genetic resources.Key words: STMS, SSR, repeats, genetic diversity.
Chromosome in situ hybridisation of ribosomal DNA in Erianthus sect. Ripidium species with varying chromosome numbers confirms x = 10 in Erianthus sect. Ripidium
Authors: Besse P , McIntyre C L
Published: April 2011

A wheat ribosomal DNA probe was used to determine the number of rDNA-carrying chromosomes in 2 Erianthus sect. Ripidium species using FISH (fluorescent in situ hybridisation) and non-fluorescent ISH. Two and four ribosomal DNA sites were revealed in E. elephantinus (2n = 20) and E. procerus (2n = 40), respectively. This result, together with previously published data showing 6 rDNA-carrying chromosomes in E. arundinaceus (2n = 60), confirms a possible basic chromosome number of x = 10 in Erianthus sect. Ripidium.Key words: Erianthus, FISH, ISH, ribosomal DNA, Saccharum, sugarcane.
Chromosome pairing in Solanum commersonii- S. tuberosum sexual hybrids detected by commersonii-specific RAPDs and cytological analysis
Authors: Barone Amalia , Sebastiano Angela , Carputo Domenico
Published: April 2011

BC1 pentaploid to near-pentaploid Solanum commersonii-S. tuberosum genotypes obtained from 3x × 4x crosses have been used for cytological and molecular studies on chromosome pairing and meiotic recombination. Microsporogenesis analysis at diakinesis revealed that chromosomes had a tendency to pair as bivalents, though multivalents were also observed in many cells. Meiosis resulted in a high production of tetrads and pollen stainability was high, ranging from 34.5% to 92.1%. DNA from S. commersonii and S. tuberosum was amplified with 87 decameric primers, resulting in the identification of 26 S. commersonii-specific RAPDs. The analysis of these RAPDs in BC1 genotypes showed that a number of commersonii-specific markers was present in all BC1 genotypes. On the other hand, markers which were missing in one or more of the BC1 genotypes suggested that in some cases homoeologous pairing occurred. Two linked markers were transmitted together in all of the BC1 genotypes except two. This provided evidence that a recombination event between these markers occurred during megasporogenesis of their triploid parents. The possibility of demonstrating other recombination events is discussed.Key words: triploid, pentaploid, microsporogenesis, gene flow, recombination.
Cloning and molecular characterization of three members of the NBS-LRR subfamily located in the vicinity of the Co-2 locus for anthracnose resistance in Phaseolus vulgaris
Authors: Creusot F , Macadré C , Cana E Ferrier , Riou C , Geffroy V , Sévignac M , Dron M , Langin T
Published: April 2011

Co-2 is one of the R-genes against anthracnose identified in common bean. A RAPD marker, cloned as PvH20, was previously shown to contain 6 imperfect leucine-rich-repeats and to reveal a family of related sequences in the vicinity of the Co-2 locus. Using PvH20 as probe, a genomic clone and 2 partial cDNAs were isolated. DNA sequencing revealed that the 6.1 kb genomic fragment contains sequences encoding both NBS-LRR (ORF1) and kinase-like (ORF2) products. The 2 partial cDNAs (cD7 and cD8) belong to the NBS-LRR subfamily as do most of the resistance genes cloned to date. The LRR domain of ORF1 is interrupted by 2 stop codons suggesting that it corresponds to a non-functional member of the multigene family and ORF2 appears to be a kinase pseudogene. The 3 NBS-LRR polypeptides share a high level of amino acid identity and represent different members of a related family. By genetic mapping ORF1, cD7, and cD8 were found to span a genetic distance of 3 cM: cD8 maps at 2 cM from Co-2 and 3 cM from ORF1. cD7 maps at 1 cM from ORF1 and co-segregates with Co-2, thus cD7 might be a putative candidate for the Co-2 R-gene.Key words: anthracnose (Colletotrichum lindemuthianum), common bean (Phaseolus vulgaris), disease resistance, NBS-LRR proteins, kinase.
Application of restriction fragment fingerprinting with a rice microsatellite sequence to assembling rice YAC clones
Authors: Ashikawa Ikuo , Kurata Nori , Saji Shoko , Umehara Yosuke , Sasaki Takuji
Published: April 2011

To refine the current physical map of rice, we have established a restriction fragment fingerprinting method for identifying overlap between pairs of rice yeast artificial chromosome (YAC) clones and defining the physical arrangement of YACs within contiguous fragments (contigs). In this method, Southern blots of rice YAC DNAs digested with a restriction endonuclease are probed with a rice microsatellite probe, (GGC)5. The probe produces a unique fingerprint profile characteristic of each YAC clone. The profile is then digitized, processed in a computer, and a statistic that represents the degree of overlap between two YACs is calculated. The statistics have been used to detect overlaps among YAC clones, thereby filling a gap between two neighbouring contigs and organizing overlapping rice YAC clones into contiguous fragments. We applied this method to rearranging YACs that had previously been assigned to rice chromosome 6 by anchoring with RFLP markers.Key words: fingerprinting, rice, YAC, genome, physical map.
Genetic and molecular characterization of barley chromosome telomeres
Authors: Kilian Andrzej , Kudrna David , Kleinhofs Andris
Published: April 2011

Previously, we cloned telomere-associated sequences using Vectorette-PCR and mapped the most telomeric regions of barley chromosome arms 1S (7HS), 2S (2HS), and 4S (4HS) (Kilian and Kleinhofs 1992). Here we report mapping 33 different telomere-associated markers (21 RFLPs and 12 PCR-based) identifying the most telomeric region of 10 out of the 14 barley chromosome arms. Other telomere-associated markers mapped very close, but not at the telomere, or were interstitial. Four markers mapped at centromeric regions. Two markers, generated by PCR using a single primer based on the sequence of the barley telomere repeats, mapped to the end of barley chromosome 7L (5HL) and internally on chromosome 3L (3HL). Cloning and sequencing of PCR products from the 3L (3HL) interstitial location revealed homology to the HvRT family. Several low copy number sequences physically linked to HvRTs were also cloned and used as RFLP probes. These probes often mapped close to the ends of linkage groups. A few RFLPs mapped at centromeric regions in agreement with the result of in situ hybridization of HvRT clones showing positive signal at the ends and around centromeres of barley chromosomes.Key words: Hordeum vulgare, mapping, telomeres, telomere-associated sequences.
The role of rDNA genes in X chromosome association in the aphidAcyrthosiphon pisum
Authors: Mandrioli Mauro , Bizzaro Davide , Giusti Monica , Manicardi Gian Carlo , Bianchi Umberto
Published: April 2011

Silver staining of mitotic metaphases of the aphid A. pisum reveals the presence of argentophilic bridges connecting the two X chromosomes. The presence of nucleolar material connecting sex chromosomes seems to be quite a common phenomenon in organisms belonging to very different phyla, and suggests a role of nucleolar proteins in chromosome association and disjunction. In somatic cells of A. pisum, bridges connecting X chromosomes are detectable not only after silver staining but also after CMA3staining. This finding suggests that GC rich DNA is involved in this type of association. Molecular analysis of rDNA intergenic spacers shows several 247 bp repeats containing short sequences having a high level of homology with the chi sequence of Escherichia coli and with the consensus core region of human hypervariable minisatellites. Moreover, each 247 bp repeat presents a perfect copy of a promoter sequence for polymerase I. These aphid repeats show structural homologies with a 240 bp repeat, which is considered to be responsible for sex chromosome pairing in Drosophila, not only in view of their common presence within rDNA spacers but also for their length and structure. The presence of chi sequences in the IGS of A. pisum, by promoting unequal crossing-over between rDNA genes, could thus give rise to the nucleolar organizing region (NOR) heteromorphism described in different aphid species. Although X pairing at NORs is fundamental in aphid male determination, the presence of heteromorphism of rDNA genes does not inhibit male determination in the A. pisum clone utilized for our experiments.Key words: aphid, rDNA, sex chromosome association, hotspot, NOR heteromorphism.
Molecular cytogenetic analysis ofAegilops cylindricaHost
Authors: Linc Gabriella , Friebe Bernd R , Kynast Ralf G , Molnar-Lang Marta , Köszegi Bela , Sutka Jozsef , Gill Bikram S
Published: April 2011

The genomic constitution of Aegilops cylindrica Host (2n = 4x = 28, DcDcCcCc) was analyzed by C-banding, genomic in situ hybridization (GISH), and fluorescence in situ hybridization (FISH) using the DNA clones pSc119, pAs1, pTa71, and pTA794. The C-banding patterns of the Dc- and Cc-genome chromosomes of Ae. cylindrica are similar to those of D-and C-genome chromosomes of the diploid progenitor species Ae. tauschii Coss. and Ae. caudata L., respectively. These similarities permitted the genome allocation and identification of the homoeologous relationships of the Ae. cylindrica chromosomes. FISH analysis detected one major 18S-5.8S-25S rDNA locus in the short arm of chromosome 1Cc. Minor 18S-5.8S-25S rDNA loci were mapped in the short arms of 5Dcand 5Cc. 5S rDNA loci were identified in the short arm of chromosomes 1Cc, 5Dc, 5Cc, and 1Dc. GISH analysis detected intergenomic translocation in three of the five Ae. cylindrica accessions. The breakpoints in all translocations were non-centromeric with similar-sized segment exchanges.Key words: Aegilops cylindrica, C-banding, GISH, FISH, genome evolution.
BrdU-4Na-EDTA-Giemsa band karyotypes of 3 small freshwater fish, Danio rerio, Oryzias latipes, and Rhodeus ocellatus
Authors: Ueda T , Naoi H
Published: April 2011

The 4Na-EDTA-Giemsa staining of metaphase chromosomes from embryos of three small freshwater fish, zebrafish Danio rerio, medakafish Oryzias latipes, and rosy bitterling Rhodeus ocellatus, in the presence of BrdU for one cycle gave rise to clear bands along the length of the chromosomes. These bands (B-bands) with G-band-like structures were clear and reproducible. However, as distinct B-bands were observed only in elongated chromosomes, fine chromosome preparations with a high mitotic index and elongated chromosomes were required. A technique for making preparations from embryo cells satisfied this request. The B-banding technique applied to embryo cells is useful to analyze chromosomes of fish species in which ordinary G-banding techniques have been known to bring about only unsatisfactory results.Key words: B-bands, karyotype, Danio rerio, Oryzias latipes, Rhodeus ocellatus.
Random amplified polymorphic DNA of screwworm fly populations (Diptera: Calliphoridae) from Southeastern Brazil and Northern Argentina
Authors: Infante-Malachias Maria Elena , Yotoko Karla Suemy Clemente , Lima de Azeredo Espin Ana Maria
Published: April 2011

The screwworm fly Cochliomyia hominivorax is one of the most important agents of traumatic myiasis throughout neotropical regions. In this work, we optimized the technique of RAPD-PCR for these species and used it to study the genetic variability among seven populations (six from southeastern Brazil and one from northern Argentina) of C. hominivorax. RAPD fingerprints showed high variation for 12 primers used, revealing 209 presumptive loci of which 198 were polymorphic. Marker pattern relationships for these different populations were used to determine genetic relatedness, as well as to examine potential patterns of gene flow. Our interpretation of Lynch and Milligan's analogue of Wright's F(ST) was that C. hominivorax populations are genetically subdivided (F'(ST) for pooled samples = 0.122). Our data suggested that the subdivision detected in C. hominivorax populations by RAPD can be explained by the interplay of random factors affecting allele frequency changes. These results indicate that the RAPD-PCR technique is useful for revealing genetic variation in screwworm fly populations not detected by others techniques and can represent an efficient method for understanding the genetic structure and population genetic phenomena of this important pest.Key words: Cochliomyia hominivorax, screwworm fly, population genetics, gene flow.
Isolation and characterization of simple sequence repeat loci in the gray tree frog, Hyla chrysoscelis
Authors: Krenz J D , Semlitsch R D , Gerhardt H C , Mahoney P A
Published: April 2011

A gray tree frog (Hyla chrysoscelis) genomic library was constructed and characterized with regard to the incidence and complexity of simple sequence repeat (SSR) loci. The partial genomic library, containing approximately 10 000 clones with an average-sized insert of 350 bp, was screened with six SSR repeat oligonucleotides (AC, AG, ACG, AGC, AAC, and AAG). Screening identified 31 unique positive clones containing 41 SSR loci. Sequences of tandemly arrayed dinucleotide repeats were more common (36 of 41) than trinucleotide repeats. Twenty-six loci were identified using the AC dinucleotide probe, while 7 loci were identified using the AG dinucleotide probe. An additional 3 AT dinucleotide loci were serendipitously identified. The AT repeats generally comprised the longest dinucleotide repeat loci. The SSR repeat loci reported here should provide potent markers for identity, parentage, and short-lineage determinations in large-scale experiments using gray tree frogs.Key words: Hyla chrysoscelis, simple sequence repeat, SSR, gray tree frog, microsatellite.
Clustering of the human CLCA gene family on the short arm of chromosome 1 (1p22-31)
Authors: Gruber Achim D , Pauli Bendicht U
Published: April 2011

The CLCA gene family is a novel family of calcium-activated chloride channels. Several family members have recently been cloned from different mammalian species with distinct, highly tissue-specific expression patterns. Here, we describe radiation hybrid mapping of the human CLCA2 and CLCA3 genes using the Genebridge 4 panel. Both genes were mapped to adjacent loci on the short arm of chromosome 1 (1p22-31), a region to which the human CLCA1 had been assigned earlier. The results show clustering of all human CLCA family members known so far despite their moderately low levels of sequence homology and their heterogeneous expression patterns.Key words: radiation hybrid mapping, human chromosome 1p22-31, calcium-activated chloride channels.
Differences in the synaptic pattern in two autotetraploid cultivars of rye with different quadrivalent frequencies at metaphase I
Authors: Martínez M , Cuadrado C , Sybenga J , Romero C
Published: April 2011

Synaptic behaviour of the two tetraploids rye cultivars Gigantón (G) and Tetrapico (T) displaying significant differences in their quadrivalent frequencies at metaphase I was analyzed by electron microscopy in surface-spread prophase I nuclei. A different behaviour was observed between the two cultivars; the synaptonemal complex (SC) quadrivalents frequency being significantly higher in G than in T at prophase I. Moreover, the G SC quadrivalents had more synaptic partner exchanges (SPEs) and their location was more distal than the T SC quadrivalents. However, inverse findings were found at metaphase I, the quadrivalent frequency was higher in T than in G. The role that different factors, mainly the number and location of the SPEs and the frequency and distribution of chiasmata, could play in the evolution from prophase I to metaphase I in both cultivars is discussed.Key words: autotetraploid rye, synaptonemal complex, spreading.
The localization of mitochondrial sequences to chromosomal DNA in orthopterans
Authors: Vaughan H E , Heslop-Harrison J S , Hewitt G M
Published: April 2011

There is growing evidence that the integration of mitochondrial DNA sequences into nuclear and chloroplast genomes of higher organisms may be widespread rather than exceptional. We report the localization of 18S-25S rDNA and mitochondrial DNA sequences to meiotic chromosomes of several orthopteran species using in situ hybridisation. The cytochrome oxidase I (COI) sequence localizes to the centromeric and two telomeric regions of the eight bivalents of Chorthippus parallelus, the telomeric regions in Schistocerca gregaria and is present throughout the genome of Italopodisma sp. (Orthoptera: Acrididae). The control region of the mitochondrion and COI localize to similar chromosomal regions in S. gregaria. These data explain sequencing data that are inconsistent with the COI sequence being solely mitochondrial. The different nuclear locations of mtDNA in the different genera studied suggest that grasshopper mtDNA-like sequences have been inserted into the nuclear genome more than once in Acridid history, and there may have been different mechanisms involved when these events occurred in each of these species.Key words: Schistocerca gregaria, Italopodisma spp., Chorthippus parallelus, in situ hybridisation, mitochondrial DNA, genome organization.
The 5S rRNA gene in wall barley (Hordeum murinum L. sensu lato): Sequence variation among repeat units and relationship to the Y haplome in the genus Hordeum (Poaceae: Triticeae)
Authors: Baum Bernard R , Johnson Douglas A
Published: April 2011

The molecular diversity of the 5S rDNA units in 13 accessions of wall barley, which include Hordeum murinum, H. leporinum, and H. glaucum, is reported. Our analyses, based on 54 sequenced clones, indicate the presence of two sequence classes not previously seen in other barley species; namely, the long Y1 unit class and the short Y1 unit class. In addition, the accumulation of new sequence information has allowed us to refine previous groups. Using these new results, along with previously published work, we present a summary of all the unit classes described to date and potential correspondences between 5S rDNA unit classes and haplomes identified previously. In H. murinum, we found the long H1 and long X2 unit classes, and in one of six accessions referable to H. glaucum we found the unique short Y1 unit class. Our cladistic analyses, using orthologous sequences, provide support for the current model for the relationships among several species within the Triticeae.Key words: 5S rDNA, Y haplome, genomes, wall barley, Triticeae.
RAPD analysis of seed purity in a commercial hybrid cabbage (Brassica oleracea var. capitata) cultivar
Authors: Crockett Phillip A , Bhalla Prem L , Lee C K , Singh Mohan B
Published: April 2011

The use of random amplified polymorphic DNA (RAPD) markers for evaluating seed purity in a commercial F1-hybrid cabbage (Brassica oleracea var. capitata) cultivar is demonstrated. Genomic DNA isolated from single ungerminated seed was found to be suitable for RAPD analysis. DNA from F1-hybrid and its parental lines was subjected to RAPD screening with 36 random decamer arbitrary primers. A total of 241 scorable products were observed with 54 (22%) being polymorphic. The RAPD data showed that the parental lines of this commercial cabbage cultivar were not very closely related. Two primers were chosen for purity testing of the F1-hybrid seeds. The sib (inbred seed; seed from self-pollination of parental lines) contamination results obtained by RAPD analysis were comparable to the commonly used grow-out trial and isozyme analysis, hence showing that RAPD analysis can be used for seed purity testing of commercial hybrid cabbage seeds.

Key words: Brassica, cabbage, RAPD, seed purity test, F1-hybrid seed.
QTL analysis of morphological traits in an intergeneric BC1 progeny of Citrus and Poncirus under saline and non-saline environments
Authors: Tozlu Ilhami , Guy Charles L , Moore Gloria A
Published: April 2011

The effects of salinization with 40 mM sodium chloride on Poncirus trifoliata (L.) Raf., Citrus grandis (L.) Osb., their F1, and a BC1 progeny population [C. grandis × (F1)] were investigated by measuring growth and dry mass production of different tissues and by QTL (quantitative trait locus) mapping. A total of 36 traits related to growth (six traits) and tissue or whole plant dry mass production (30 traits) in salinized and non-salinized BC1 progeny clones were evaluated. The comparison of the three parental types to the BC1 progeny under control and saline conditions showed that the BC1 progeny plants segregated transgressively for many of these traits. Mapping analyses of these quantitative traits resulted in a total of 70 potential quantitative trait loci (PQTL) with LOD scores greater than or equal to 3.0 located on a previously generated linkage map. Sixty-nine percent of the mapped PQTLs were for traits associated with salinity. The small progeny population size used made further analyses of these PQTLs necessary. By considering LOD scores, map locations, and correlation analyses of the traits, it was possible to identify 16 regions of the citrus genome of interest, six of which were involved in both growth and dry mass production. Correlation analyses and locations of PQTLs indicated that many of these regions may contain one or a few genuine QTLs of large effect. This is a first step in identifying QTLs that have a major impact on growth and dry mass production in Citrus under both optimum and stressful environments.Key words: Citrus grandis, Poncirus trifoliata, salinity stress, QTL mapping, morphological traits, transgressive segregation, NaCl, sodium, chloride, salt tolerance, citrus genetics, breeding.
Soybean genetic resources and crop improvement
Authors: Singh R J , Hymowitz T
Published: April 2011

The soybean (Glycine max (L.) Merr.) is an economically important leguminous crop for feed, oil, and soyfood products. It contains about 40% protein and 20% oil in the seed and, in the international trade markets, is ranked number one in oil production (48%) among the major oil seed crops. Despite its economic importance, the genetic base of soybean cultivars is extremely narrow. The indigenous cultivars and landraces in East Asia are on the verge of extinction, because farmers are now growing high yielding soybean cultivars. The exotic germplasm, enriched with genes for abiotic and biotic stresses, has not been fully exploited by soybean breeders. Mutation breeding has improved the fatty acids of the soybeans and has produced soybeans tolerant to herbicides. By using recombinant DNA technology, Monsanto has produced stable glyphosate tolerant soybean lines known as 'Round Up Ready' soybean. DuPont is producing transgenic soybean lines with improved fatty acids content. The feasibility of developing hybrid soybeans is still an open question.Key words: soybean, Glycine spp., exotic germplasm, mutation, interspecific hybridization, biotechnology, hybrid soybeans.
Genetic resource and the role of international collaboration in rice breeding
Authors: Singh R K
Published: April 2011

The international efforts in rice research have led to self-sufficiency and surpluses in many of the south and southeast Asian countries. The trend must continue to meet the growing demand for rice. The global partnership in plant genetic resources has played a significant role in ensuring long-term preservation of and access by researchers to the gene pool worldwide. Large numbers of high-yielding varieties with resistance to diseases and insect pests have been released by the collaborating countries and have both increased national average yields and stabilized rice production. Now, the yields must increase further, as more rice needs to be produced from less land with less labour and pesticides. The new plant type being developed at the International Rice Research Institute (IRRI) seems to have the potential to produce 20-25% more grain than the best of our modern varieties. With the growing complexity of problems, the demand for diverse genetic materials is also increasing. It is no wonder that some of the recently released varieties have genes from as many as 60 or more diverse donors. These developments owe a lot to the free exchange of germplasm among breeders. However, the ever-increasing restrictions on the flow of genetic materials due to political and plant-health requirements pose serious threats to future varietal-improvement programs. Similarly, the problem of genetic erosion continues, and shrinking research support reduces the flexibility of programs. This paper reviews and discusses some of these and other related issues and their implications for rice breeding in the future.Key words: genetic resource, new plant type, marker-aided selection, pedigree complexity, International Network for Genetic Evaluation of Rice (INGER).
Some recent issues on the conservation of crop genetic resources in developing countries
Authors: Jana S
Published: April 2011

Crop genetic resources (CGRs) are renewable resources. These resources are enriched rather than depleted by their use in research and plant breeding. Both at the time of Vavilov and, later, in the early 1970s, when concerted international efforts to collect and preserve CGRs started with the initiatives of the International Board for Plant Genetic Resources (IBPGR), CGRs were considered to be the common heritage of humankind. Now, they are widely accepted as "national heritage." Possible impacts of this nationalization on the utilization and enrichment of global crop genetic diversity and, consequently, on global food security are issues of great significance. At present, efficient management and adequate use of CGRs are more important concerns than their further exploration and collection. To increase the use of preserved CGRs in plant breeding, the formation of core collections, by selecting representative subsets from large ex situ collections of CGRs, was recommended in 1984. Since then, the core-collection strategy has been further justified as a practical approach to genetic resources management, as well as to their conservation. As a cost-saving germplasm-management strategy, the core-collection concept has considerable merit. However, the rapidly increasing popularity of core collections may undermine the genetic wealth stored in national gene banks of both developed and developing countries. Distinction is made between subsets of working collections and core collections. When a small number of CGRs is required for specific plant breeding purposes, a properly formed working collection is more useful than a representative collection. Despite the relative abundance of genetic diversity in crop plants in traditional agroecosystems, maintenance of these agroecosystems is not a realistic long-term alternative for preserving crop genetic diversity and ensuring global food security. What is needed in the "gene-rich" developing countries is the adoption of "biodiversity friendly" plant breeding and agricultural practices.Key words: crop genetic resources, core collection, germplasm conservation, in situ conservation, ex situ conservation, modern landraces.