bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of RFLP markers linked to the white rust resistance gene (Acr) in mustard (Brassica juncea (L.) Czern. and Coss.)
Authors: Cheung W Y , Gugel R K , Landry B S
Published: April 2011

White rust and staghead, caused by Albugo candida, is an economically important disease of Brassica juncea and Brassica rapa crops in western Canada. The identification of genes for white rust resistance in these crops and the development of molecular markers for these genes will allow the rapid identification of resistant germplasm and should accelerate the development of white rust resistant cultivars. In this study, 119 F1-derived doubled-haploid progeny lines of a cross between white rust susceptible (J90-4317) and white rust resistant (J90-2733) B. juncea lines were evaluated for resistance to A. candida race 2. A single gene (Acr) responsible for conferring resistance to this pathogen was mapped on a densely populated B. juncea RFLP map developed earlier. A cosegregating RFLP marker (X140a) and two other closely linked RFLP markers (X42 and X83) were identified; the latter two markers were 2.3 and 4 cM from the Acr locus, respectively. These markers may be useful for marker-assisted selection and map-based cloning of this gene.Key words: Brassica juncea, mustard, Albugo candida, white rust, disease resistance, RFLP.
The use of random amplified microsatellite polymorphic DNA and coefficients of parentage to determine genetic relationships in barley
Authors: Dávila J A , Sánchez de la Hoz M P , Loarce Y , Ferrer E
Published: April 2011

Seventy European barley lines (Hordeum vulgare ssp. vulgare) and 29 Hordeum vulgare ssp. spontaneum accessions were evaluated for random amplified microsatellite polymorphism (RAMP). PCR was performed with 5'-anchored primers complementary to microsatellites in combination with random primers. Of 20 primers assayed in barley, only 9 produced well-resolved fragment patterns in H. vulgare ssp. spontaneum. On the basis of 56 polymorphic fragments, genetic distances between the two subspecies were calculated. Barley samples were subdivided according to growth habit and spike morphology. The smallest genetic distance was found between winter cultivars and accessions of H. vulgare ssp. spontaneum. The 20 primers assayed in the barley lines produced 140 polymorphic fragments that were used to calculate genetic similarity between lines. Mean genetic similarity within groups of lines ranged from 0.693 for 6-rowed winter barley to 0.657 for 6-rowed spring barley. Within these groups, mean values were significantly higher than mean genetic similarity between groups. Principal-coordinate analysis clearly separated the 2-rowed spring and 6-rowed winter types. Cluster analysis of spring and winter types showed subclustering consistent with the available pedigrees. Coefficients of parentage (COPs) were calculated for 29 spring and 20 winter lines. Mean values of 0.0741 for spring barley and 0.0458 for winter barley were obtained. RAMP-based genetic similarity matrices were compared with the corresponding COP-based matrices by the Mantel test. The correlation between them was poor (r = 0.21, P < 0.05), indicating little relationship between these two estimators of genetic similarity. The relative influence of factors involved in the calculation of these two estimators is discussed.Key words: genetic diversity, microsatellites, simple sequence repeats, fingerprinting, barley.
Genome organization of Brassica napus and Lesquerella fendleri and analysis of their somatic hybrids using genomic in situ hybridization
Authors: Skarzhinskaya Marina , Fahleson Jan , Glimelius Kristina , Mouras Armand
Published: April 2011

Construction of Brassica napus (2n = 38) and Lesquerella fendleri (2n = 12) karyotypes revealed that B. napus contains 10 pairs of metacentric, 5 pairs of submetacentric, and 4 pairs of subtelocentric chromosomes, while L. fendleri contains 6 pairs of metacentric chromosomes that are, on average, 1.5 times longer than those of B. napus. By analysing the karyotypes and performing genomic in situ hybridization (GISH), the chromosome complements of somatic hybrids produced between Brassica napus (+) Lesquerella fendleri were studied. Protoplasts fused with no pretreatment, symmetric fusions, resulted in hybrids containing L. fendleri chromosomes in numbers varying from 2 chromosomes to 2 chromosome complements. In the asymmetric fusion experiments, in which L. fendleri protoplasts were irradiated before fusion, plants with from 38 to more than 76 chromosomes were obtained. In the hybrids with 38 chromosomes, the presence of L. fendleri chromosomes was not detected by GISH analysis, even though L. fendleri DNA was revealed by Southern blotting. Intra- and inter-genomic recombinations were observed in hybrids from both symmetric and asymmetric fusions. The rearrangements were more prevalent in plants resulting from asymmetric fusions. Modifications of the phenotype and reduced fertility of the hybrid plants were correlated with increased dosages of the L. fendleri genome. At least one genome complement of L. fendleri was required to express its morphological features.Key words: Agrobacterium rhizogenes transformed root cultures, Brassica napus, Lesquerella fendleri, somatic hybrids, chromosome translocation.
Flow-cytometric analyses of intraspecific genome size variations in Bacillus atticus (Insecta, Phasmatodea)
Authors: Marescalchi Ombretta , Scali Valerio , Zuccotti Maurizio
Published: April 2011

The stick insect Bacillus atticus comprises several populations with different chromosome numbers that are distributed over a large range of the Mediterranean basin. Here we have analyzed the DNA content of nine diploid and three triploid populations by flow-cytometry. The mean genome size of the diploids showed a significant decrease from east to west, ranging from 5.29 ± 0.12 pg for the population from Crete (east) to 4.28 ± 0.10 pg for the population from Sardinia (far west). This longitudinal trend of a decrease in genome size from east to west was also found for the triploid populations (from 6.80 pg for the population in Turkey to 6.08 ± 0.01 pg for the population on the Isle of Rhodes). Differences in DNA content between populations belonging to the same species have been described in animals, but the evolutionary implications of these differences are as yet unclear. What emerges from the present study is a correlation between genome-size variations and geographic distribution. The adaptive nature of genome-size variations in response to environmental changes is discussed, and the class of DNA involved hypothesized.Key words: C value, flow cytometry, genome size trends, intraspecific DNA variation, DNA classes.
A single-primer PCR-based retroviral-related DNA polymorphism shared by two distinct human populations
Authors: Deb Paromita , Klempan Timothy A , O'Reilly Richard L , Singh Shiva M
Published: April 2011

Almost 10% of the human genome consists of DNA sequences that share homology with retroviruses. These sequences, which represent a stable component of the human genome (although some may retain the ability to transpose), remain poorly understood. We used degenerate primers specific to the two conserved regions (boxes 4 and 5) of the retroviral pol gene, common to all retroviruses, and PCR-amplified related sequences from individuals representing two distinct populations: Caucasians and Dogrib Indians. The large number of sequences that are reproducibly amplified represent numerous sites of retroviral integration in the human genome. In both populations studied, one of the two primers yielded a polymorphic band, present in ~30% of the samples, that has probably been present in the human genome since before the divergence of the two populations ~10 000 years ago. It was established that this polymorphism was due to priming-site differences and not to deletions. Further, this priming site is duplicated at two genomic sites (representing 341- and 343-bp fragments) with at least two alleles each. Such novel polymorphisms should provide useful markers and permit assessment of evolutionary mechanisms associated with retroviral-related genomic evolution.Key words: Dogrib Indian, evolution, human genome, polymorphism, retrovirus.
Cytological and molecular characterization of BC1 progeny from two somatic hybrids between dihaploid Solanum acaule and tetraploid S. tuberosum
Authors: Yamada T , Hosaka K , Kaide N , Nakagawa K , Misoo S , Kamijima O
Published: April 2011

Two hexaploid somatic hybrids, DA12-3 (2n = 68) and DA28 (2n = 74), derived from cell fusion between dihaploid Solanum acaule and tetraploid Solanum tuberosum, were crossed with S. tuberosum. Two BC1 families, DA12T and DA28T, were generated, each containing 25 plants. Although the average of somatic chromosome numbers fitted hypothetical numbers assuming equal separation, considerable variation was found: 2n = 54-62 in DA12T and 2n = 58-65 in DA28T. Fifty-two of 80 RFLP single-copy probes generated 108 marker bands specific for S. acaule, by which BC1 progeny were analyzed. The segregation of marker bands from at least 44 probes was explained by two alleles per locus, which had to be heterozygous in dihaploid S. acaule and maintained in homozygous condition in homoeologous chromosomes of tetraploid S. acaule. On average, 73.7% of the chromosomes derived from S. acaule were detected as recombinants, suggesting that frequent homoeologous recombination occurred between S. acaule and S. tuberosum chromosomes. Therefore, S. acaule germplasm can be effectively transferred to the cultivated potato gene pool through backcrossing hexaploid somatic hybrids with S. tuberosum. In both BC1 families, S. acaule chromosomes 3, 4, 6, and 11 were detected as recombinants with higher frequencies (84-98%) than those of chromosomes 9 and 10 (60 and 58%, respectively), suggesting that chromosomal differentiation exists between S. acaule genomes.Key words: hexaploid somatic hybrids, Solanum acaule, homoeologous recombination, RFLP markers.
The distribution of male-transmitted and female-transmitted mitochondrial DNA types in somatic tissues of blue mussels: Implications for the operation of doubly uniparental inheritance of mitochondrial DNA
Authors: Garrido-Ramos Manuel A , Stewart Donald T , Sutherland Brent W , Zouros Eleftherios
Published: April 2011

We have examined the mitochondrial DNA (mtDNA) content of several somatic tissues from male and female individuals of the blue mussel, Mytilus edulis. As expected from the mode of doubly uniparental inheritance (DUI) of mtDNA that is characteristic of this genus, the dominant type of mtDNA in male gonads was the male-transmitted M type. In contrast, all male somatic tissues were dominated by the female-transmitted F type. The M type could occasionally be detected in one or another tissue of a few female individuals. The findings have several implications for the operation of doubly uniparental inheritance of mitochondrial DNA, among which the most important are (i) the M genome does not have an unconditional replicative advantage over the F genome, and (ii) in contrast to "masculinization" (the process by which an F molecule assumes the role of the M genome) "feminization" (the process by which an M molecule assumes the role of the F genome) might be a rare but not impossible phenomenon.Key words: mitochondrial DNA inheritance, mitochondrial DNA tissue distribution, blue mussels, gender-specific mtDNA, doubly uniparental inheritance of mtDNA, Mytilus.
The development of RAPD and microsatellite markers in lodgepole pine (Pinus contorta var. latifolia)
Authors: Hicks Mark , Adams Denise , O'Keefe Sandra , Macdonald Ellen , Hodgetts Ross
Published: April 2011

Two types of polymorphic DNA markers suitable for genome analyses, population genetic and ecological studies on lodgepole pine (Pinus contorta var. latifolia) have been developed. We detected 52 decameric oligonucleotides, within a set of 200, that could be used to amplify the pine DNA. From these, 4 that allowed unambiguous amplification of 10 random polymorphic (RAPD) loci, have been chosen for use in this species. Five polymorphic microsatellite loci were found following the screening of a genomic library and all contained the AGn motif. Such loci were present at a frequency of 1 in every 345 kb pairs of genomic DNA. Three loci were comprised of a simple dinucleotide repeat, one locus was of the form TAn - GAm and one was ATn - AGm. The number of alleles at the 5 microsatellite loci ranged from 3 to 8 in a sample of 6 trees from the eastern foothills of the Rocky Mountains in Alberta and the alleles at all loci exhibited Mendelian segregation.Key words: DNA polymorphism, RAPD, microsatellite, SSR, Pinus contorta var. latifolia.
Molecular and virulence diversity and linkage disequilibria in asexual and sexual populations of the wheat leaf rust fungus, Puccinia recondita
Authors: Liu J Q , Kolmer J A
Published: April 2011

An asexual field population and a sexually derived population of the wheat leaf rust fungus, Puccinia recondita, were examined and compared for diversity and linkage disequilibria between virulence and molecular phenotypes. Isolates in both populations were tested for virulence to 20 Thatcher wheat lines near-isogenic for leaf rust resistance genes, and for random amplified polymorphic DNA (RAPD) variation using 10 DNA primers. In the asexual field population, 36 virulence phenotypes and 14 RAPD phenotypes were identified in 43 isolates. In the sexual population, 87 virulence phenotypes and 79 RAPD phenotypes were identified in 104 isolates. Linkage disequilibria was less in the sexual population compared to the asexual field population. Virulence-RAPD phenotype pairs (110 in total) were directly compared between the two populations for association. In the asexual population, 39 virulence-RAPD phenotype pairs were associated (P < 0.05), compared with 18 pairs in the sexual population. Linkage was not evident, as some residual disequilibria remained between virulence and RAPD phenotypes. In the asexual population 18 RAPD phenotype pairs were associated, compared with 9 pairs in the sexual population. The sexual population was also tested for RAPD variation with an additional six primers. In the sexual population, amplification sites of four different primers were tightly linked which indicated a chromosomal segment in P. recondita may not readily undergo recombination. Disequilibria between virulence and RAPD phenotypes in field populations of P. recondita in Canada is maintained by asexual reproduction.Key words: Puccinia recondita, molecular diversity, virulence diversity, linkage disequilibria, wheat leaf rust.
A transient assay for evaluating promoters in wheat endosperm tissue
Authors: Clarke B C , Appels R
Published: April 2011

A transient assay was developed for the evaluation of promoter sequences in wheat endosperm tissue. A deletion series from an omega-secalin gene promoter, located on chromosome 1RS.1DL of specific wheat lines, were translationally fused to a uidA reporter gene. These promoters were evaluated for expression in wheat endosperm tissue after integration of the DNA into the cell using microprojectile bombardment. The results were compared with those obtained using other transient assay systems.Key words: particle bombardment, transient assay, omega-secalin gene, wheat endosperm.
Characterisation of genetic diversity in potential biomass willows (Salix spp.) by RAPD and AFLP analyses
Authors: Barker Jacqueline H , Matthes Michaela , Arnold Gillian M , Edwards Keith J , Åhman Inger , Larsson Stig , Karp Angela
Published: April 2011

The genus Salix (willow) contains a number of species which have great potential value as biomass crops in short rotation coppice (SRC). Efforts to improve biomass willows by breeding are currently hampered by the limited information available on genetic diversity and on genetic relationships within and among species, clones, and hybrids in the gene pool. Hybridisation occurs commonly in nature and the relatedness of many clones is unclear. Molecular markers were used to assess genetic diversity in a reference set of willows maintained within the U.K. National Collection and 16 elite clones currently being evaluated in field trials at several European sites. The two marker systems tested, RAPDs and AFLPs, were equally informative for revealing relationships within the reference set of clones. No differences were observed when alternative similarity coefficients were compared or when analysis was restricted to the use of polymorphic bands only. Good agreement with available knowledge of the clonal origins was obtained and one instance of duplicate clones was identified. AFLPs revealed more genetic diversity and discriminated between closely related clones. A difference in the relationships revealed was observed with one AFLP primer combination. RAPDs were more problematic, both in terms of reproducibility and scorability.Key words: Salix, willow, diversity, AFLP, RAPD, biomass.
Evolution of the high molecular weight glutenin loci of the A, B, D, and G genomes of wheat
Authors: Allaby Robin G , Banerjee Monica , Brown Terence A
Published: April 2011

We used PCR to obtain phylogenetically informative sequences from the high molecular weight glutenin genes of wheat. The validity of partial sequence comparisons as a means of studying glutenin phylogenetics was established by constructing neighbour-joining trees from partial alignments of 12 published glutenin allele sequences. PCR was then used to obtain 20 novel glutenin allele sequences from various Triticum and Aegilops species, including a 3000 year old preserved wheat. A neighbour-joining tree derived from all known glutenin allele sequences had eight clades, representing the eight loci from which the allele sequences were derived, and was split into two halves, one comprising alleles from the Glu-1-1 loci and the other comprising Glu-1-2 alleles. The topology was compatible with the postulated relationships between the A, B, D, and G genomes. The Glu gene duplication event was tentatively dated at 7.2-10.0 million years ago (MYA), the origin of the four genomes at 5.0-6.9 MYA, and the split between the B and G genomes at 2.5-3.5 MYA. The Glu-B1-1 alleles in cultivated wheats fell into two subgroups that diverged 1.4-2.0 MYA, suggesting that emmer was domesticated twice. The D allele sequences were relatively diverse, indicating that the hybridization event that resulted in the hexaploid bread wheats might have occurred more than once.Key words: ancient DNA, HMW glutenin genes, phylogenetic analysis, Triticum, wheat.
Use of sequence-tagged microsatellite site markers for characterizing table grape cultivars
Authors: Sánchez-Escribano E M , Martín J P , Carreño J , Cenis J L
Published: April 2011

A collection of 43 table grape cultivars, Vitis vinifera L., was studied with sequence-tagged microsatellite site (STMS) markers. The amplified loci were VVS1, VVS2, VVS3, VVS4, VVS5, VVMD5, VVMD6, and VVMD7. These loci had been previously described and used with good results by several authors. The number of alleles observed per locus ranged from 2 (VVS3) to 8 (VVS2 and VVMD7), and the number of observed genotypes from 3 (VVS3) to 19 (VVMD5). Expected heterozygosity ranged from 38% (VVS1) to 80% (VVMD5). The 43 cultivars were clearly identified with the allelic combinations of the 8 loci. In 14 cultivars, the allelic sizes were identical to the values reported in previous studies with these markers, indicating the good reproducibility of this method in different laboratories.Key words: Vitis, fingerprinting, STMS, SSR, STS.
Genetic diversity inElymus caninusas revealed by isozyme, RAPD, and microsatellite markers
Authors: Sun Gen-Lou , Díaz Oscar , Salomon Björn , von Bothmer Roland
Published: April 2011

Genetic diversity of 33 Elymus caninus accessions was investigated using isozyme, RAPD, and microsatellite markers. The three assays differed in the amount of polymorphism detected. Microsatellites detected the highest polymorphism. Six microsatellite primer pairs generated a total of 74 polymorphic bands (alleles), with an average of 15.7 bands per primer pair. Three genetic similarity matrices were estimated based on band presence or absence. Genetic diversity trees (dendrograms) were derived from each marker technique, and compared using Mantel's test. The correlation coefficients were 0.204, 0.267, and 0.164 between isozyme and RAPD distance matrices, RAPD and microsatellite distance matrices, and between isozyme and microsatellite distance matrices, respectively. The three methodologies gave differing views of the amount of variation present but all showed a high level of genetic variation in E. caninus. The following points may be drawn from this study whether based on RAPD, microsatellite, or isozyme data: (i) The Icelandic populations are consistently revealed by the three dendrograms. The congruence of the discrimination of this accession group by RAPD, microsatellite, and isozyme markers suggests that geographic isolation strongly influenced the evolution of the populations; (ii) The degree of genetic variation within accessions was notably great; and (iii) The DNA-based markers will be the more useful ones in detecting genetic diversity in closely related accessions. In addition, a dendrogram, which took into account all fragments produced by isozymes, RAPDs, and microsatellites, reflected better the relationships than did dendrograms based on only one type of marker.Key words: Elymus caninus, genetic diversity, isozymes, RAPDs, microsatellites.
Genomic origins of Thinopyrum chromosomes specifying resistance to wheat streak mosaic virus and its vector, Aceria tosichella
Authors: Chen Qin , Conner R L , Laroche A , Fedak G , Thomas J B
Published: April 2011

The genomic origin of alien chromosomes carrying resistance to wheat streak mosaic virus (WSMV) and the wheat curl mite (WCM), Aceria tosichella Keifer, was evaluated in nine wheat-alien addition, substitution, or translocation lines, derived from hybrids of wheat with Thinopyrum ponticum (Podp.) Barkworth & D.R. Dewey (2n = 10x = 70), or with Th. intermedium (Host) Barkworth & D.R. Dewey (2n = 6x = 42). One of the four wheat × Th. ponticum lines was resistant to WSMV and WCM. The other three lines were resistant to WCM, but susceptible to WSMV. Five wheat × Th. intermedium lines were susceptible to WCM, but were highly resistant to WSMV. Genomic in situ hybridization (GISH) using different genomic DNA probes demonstrated that all WSMV- and WCM-resistant lines carried an alien chromosome(s) related to the Js genome in Th. ponticum and Th. intermedium. The Js alien chromosome(s) displayed a special GISH hybridization pattern with the S genomic DNA probe, in which S genome DNA hybridized strongly in the centromeric regions and occasionally in the terminal regions with no or a weak hybridization signal in the middle of the two arms of the chromosomes. The WCM-resistant wheat × Th. ponticum lines N/5.10.10 and 63-30-2-2-2-8-1 carried the same short arm of chromosome 6Js derived from the partial amphiploid Agrotana, while the WSMV-resistant wheat × Th. intermedium lines T-Ai, CI15092, CI17766, A29-13-3-1 and KS93WGRC27 all had the same alien chromosome or chromosome arm of 4Js from Th. intermedium. The Js genome present in Th. ponticum and Th. intermedium is an important source of WSMV and WCM resistance that can be transferred into wheat.Key words: wheat-Thinopyrum lines, WSMV- and WCM-resistance, genomic in situ hybridization, Js genome.
Equal frequencies of recombination nodules in both sexes of the pigeon suggest a basic difference with eutherian mammals
Authors: Pigozzi M I , Solari A J
Published: April 2011

The total number of recombination nodules (RNs) in the autosomal synaptonemal complexes (SCs) is statistically equivalent in oocytes and spermatocytes from the domestic pigeon Columba livia. The distribution on RNs along the three longest autosomes is also equivalent in oocytes and spermatocytes. The numbers of RNs show a linear relationship when plotted against SC length both in oocytes and spermatocytes. On the other hand, the ZW pair shows a single and strictly localized RN near the synaptic termini, but the ZZ pair shows unrestricted location of RNs (average 3.8). The ZW and ZZ pairs of the pigeon are euchromatic and do not show specific chromatin packing at pachytene in either sex. The lack of sex-specific differences in the number and location of RNs in the autosomal bivalents of C. livia and previous data on the chicken, suggest that the regulation of crossing-over is basically different in birds and mammals.Key words: meiosis, genetic recombination, recombination nodules, pigeon gametogenesis.
Genetic variation within and relatedness among wood and plains bison populations
Authors: Wilson G A , Strobeck C
Published: April 2011

There are two recognized subspecies of bison, wood (Bison bison athabascae) and plains (Bison bison bison) bison. The establishment of most bison populations from a small number of individuals has raised concerns about their genetic variation. To this end, 11 bison populations were surveyed with 11 microsatellite loci in order to calculate genetic variation and genetic distances. Mean number of alleles ranged between 3.18 at Antelope Island State Park (Utah) and 6.55 at Wood Buffalo National Park (Alberta and Northwest Territories). Mean heterozygosity ranged from 0.295 at Antelope Island State Park to 0.669 at Custer State Park (South Dakota). The amount of genetic variability present in the bison populations as measured by mean number of alleles and overall probability of identity was found to correlate with the number of founders for all sampled populations. The G-test for heterogeneity revealed some evidence for the existence of subpopulations at Wood Buffalo National Park, however very small genetic distances between these subpopulations suggest that nuclear material from the plains bison introduced into Wood Buffalo National Park has diffused throughout the park. Genetic distances between the sampled populations were generally larger between than within the two bison subspecies.Key words: Bison bison bison, Bison bison athabascae, DNA microsatellites, genetic variation, genetic relatedness.
Rana/Pol III: A family of SINE-like sequences in the genomes of western Palearctic water frogs
Authors: Bucci S , Ragghianti M , Mancino G , Petroni G , Guerrini F , Giampaoli S
Published: April 2011

The highly repetitive Rana/Pol III family consists of short, tandemly arrayed sequences, scattered throughout the genomes of Palearctic green water frogs. The repeat unit is about 250 bp in length and is a composite element: it contains a SINE-like retroposon with a tRNA structure, flanked by two short direct repeats, and the occurrence of two internal repeats gives evidence that an additional transposition event may have inserted a segment within the already transposed element. Rana/Pol III family is present in the genomes of Rana lessonae, R. ridibunda, and their hybrid form R. esculenta, as well as in R. shqiperica, R. epeirotica, R. cretensis, and the Italian taxon. These sequences are also present in the Iberian R. perezi, although less abundant, but appear to be lacking in the north African speciesR. saharica. The distribution of Rana/Pol III in the genomes of Palearctic green frogs is in agreement with the phyletic history based on genetic data. The evolutionary pattern proposed for the genus Rana enables us to suppose that the hybridogenetic mechanism is one of the factors accounting for the possible horizontal transfer of Rana/Pol III elements from the central-north Europe species to R. perezi.Key words: repetitive DNA, SINE-like retroposons, hybridogenesis, Rana esculenta group.
Long tomato microsatellites are predominantly associated with centromeric regions
Authors: Areshchenkova Tatyana , Ganal Martin W
Published: April 2011

Microsatellites as genetic markers are used in many crop plants. Major criteria for their usability as molecular markers include that they are highly polymorphic and evenly spread throughout a genome. In tomato, it has been reported that long arrays of tetranucleotide microsatellites containing the motif GATA are highly clustered around the centromeres of all chromosomes. In this study, we have isolated tomato microsatellites containing long arrays (> 20 repeats) of the dinucleotide motifs GA, GT, AT, as well as GATA, assessed their variability within Lycopersicon esculentum varieties and mapped them onto a genetic map of tomato. The investigated microsatellite markers exhibited between 1 and 5 alleles in a diverse set of L. esculentum lines. Mapping of the microsatellites onto the genetic map of tomato demonstrates that, as previously shown, GATA microsatellites are highly clustered in the regions of the tomato centromeres. Interestingly, the same centromeric location was now found for long dinucleotide microsatellite markers. Because of this uneven distribution, genetic mapping of the entire tomato genome using long dinucleotide microsatellites will be very difficult to achieve and microsatellite markers with shorter arrays of microsatellites could be more suitable for mapping experiments albeit their lower level of polymorphism. Some microsatellite markers described in this study might provide a useful tool to study the molecular structure of tomato centromeric regions and for variety identification.Key words: molecular marker, Lycopersicon esculentum, genetic variability, genetic map, simple sequence repeats.
Genomic in situ hybridization (GISH) of Tripsacum dactyloides and Zea mays ssp. mays with B chromosomes
Authors: Poggio L , Confalonieri V , Comas C , Cuadrado A , Jouve N , Naranjo C A
Published: April 2011

Genomic affinities between Tripsacum dactyloides (2n = 72) and Zea mays ssp. mays (2n = 20 + 5 B) were analyzed through GISH (genomic in situ hybridization) to ascertain the degree of chromosome homology between the two genera. Mitotic cells of T. dactyloides were simultaneously probed with total genomic DNA from Z. mays ssp .mays (2n = 20) and with rDNA (pTA71). A disperse pattern of hybridization signal among all 72 chromosomes, corresponding to maize total DNA, and six strong fluorescent signals due to the rDNA probe hybridizing on 3 chromosome pairs of T. dactyloides were observed. Mitotic chromosomes from Z. mays ssp. mays (2n = 20 + 5 B) were hybridized with a maize line that lacked B chromosomes and knobs and with total DNA from T. dactyloides. The knobless line of maize hybridized intensely on all chromosomes except for some regions where the probe bound less. Tripsacum dactyloides bound intensely on one terminal region of each B chromosome and to some regions of chromosome pairs 2, 6, and 8. These regions are DAPI positive and coincide with regions that displayed lower affinity with the probe from the knobless maize line. The possible significance of these results is discussed briefly.Key words: Tripsacum dactyloides, Zea mays ssp. mays, maize B chromosomes, genomic in situ hybridization, GISH.
Orderly arrangement of the chromosomes within barley genomes of chromosome-eliminating Hordeum lechleri × barley hybrids
Authors: Linde-Laursen Ib , von Bothmer Roland
Published: April 2011

One-hundred and nineteen progeny plants of crosses between one Hordeum lechleri (2n = 6x = 42) accession and the barley varieties 'Wong' and 'Igri' comprised 54 euploids (2n = 28), 8 hyperploids (2n = 29), 46 hypoploids (2n = 22 - 27), and 11 polyhaploids (2n = 21). Giemsa C-banding showed most interplant chromosome variation to be caused by elimination or, more seldom, duplication of barley chromosomes. The chromosomes of 'Wong' were preferentially lost in the order, 1H-4H-5H-3H-7H-2H-6H (5-4-7-3-1-2-6); those of 'Igri' in the order, 1H-3H or 6H-7H or 5H or 4H-2H (5-3 or 6-1 or 7 or 4-2), indicating different patterns of elimination. Over years chromosome elimination may be continuous. Hypoploid genomes of 'Wong' had the chromosomes arranged in the order, 1H-5H-2H-6H-7H-3H-4H (5-7-2-6-1-3-4), with a discontinuity between chromosomes 1H(5) and 4H(4); whereas in 'Igri' the order was (1H)-5H-2H-4H-7H-6H-3H-(1H) ((5)-7-2-4-1-6-3-(5)) with a discontinuity at 1H(5), indicating varietal differences. The patterns of barley chromosome elimination may be derived from chromosome orders. Elimination starts with a chromosome at the discontinuity, continues with the chromosome at the other end of the order, and proceeds more or less alternately towards the middle. In hybrids including 'Wong', duplication affected the two chromosomes situated at either end of barley chromosome order. A few older hybrids with 2n = 21 had three or four H.lechleri chromosomes substituted for as many barley chromosomes suggesting homoeology. Our observations support the hypothesis of an orderly arrangement of the chromosomes within genomes (Bennett 1981), but they do not agree with the idea of one 'natural karyotype' for each species (Bennett 1984b).Key words: Hordeum, interspecific hybrids, C-banding, chromosome elimination, chromosome order.
Chromosome evolution in kangaroos (Marsupialia: Macropodidae): Cross species chromosome painting between the tammar wallaby and rock wallaby spp. with the 2n = 22 ancestral macropodid karyotype
Authors: O'Neill RJ Waugh , Eldridge MDB , Toder R , Ferguson-Smith MA , O'Brien P C , Graves JAM
Published: April 2011

Marsupial mammals show extraordinary karyotype stability, with 2n = 14 considered ancestral. However, macropodid marsupials (kangaroos and wallabies) exhibit a considerable variety of karyotypes, with a hypothesised ancestral karyotype of 2n = 22. Speciation and karyotypic diversity in rock wallabies (Petrogale) is exceptional. We used cross species chromosome painting to examine the chromosome evolution between the tammar wallaby (2n = 16) and three 2n = 22 rock wallaby species groups with the putative ancestral karyotype. Hybridization of chromosome paints prepared from flow sorted chromosomes of the tammar wallaby to Petrogale spp., showed that this ancestral karyotype is largely conserved among 2n = 22 rock wallaby species, and confirmed the identity of ancestral chromosomes which fused to produce the bi-armed chromosomes of the 2n = 16 tammar wallaby. These results illustrate the fission-fusion process of karyotype evolution characteristic of the kangaroo group.
Evaluation of genetic diversity and genome fingerprinting ofPandorea(Bignoniaceae) by RAPD and inter-SSR PCR
Authors: Jain Ajay , Apparanda Cariappa , Bhalla Prem L
Published: April 2011

Evaluation of the genetic relationship between five Pandorea jasminoides and eight Pandorea pandorana cultivars was investigated using random amplification of polymorphic DNA and inter-SSR (simple sequence repeat) PCR. Twenty-five random primers generated 375 polymorphic products with a mean number of 15 polymorphic bands per primer. The mean number of polymorphic products obtained by inter-SSR PCR was 18.7 per primer. Random amplification of polymorphic DNA and inter-SSR amplification of genomic DNA revealed higher genetic variability among the cultivars of P. pandorana than among those of P. jasminoides. Two random primers each produced species-specific amplification products in both the Pandorea species, while four random primers and two SSRs produced species-specific amplification products in only one of the species. A distinct cultivar-specific DNA fingerprint for each of the 13 cultivars was obtained by 2 random primers and 1 SSR primer. A dendrogram constructed on the basis of 513 amplification products generated by random amplification of polymorphic DNA and inter-SSR PCR showed the separation of 13 cultivars into two major groups that corresponded to P. jasminoides and P. pandorana. The data resulting from random amplification of polymorphic DNA and inter-SSR PCR were congruent. Our study showed that it should be possible to take advantage of existing genetic variability of P. pandorana to enhance the narrow genetic base of P. jasminoides by interspecific crosses. Such crosses would have the potential to generate novel commercially important elite cultivars of Pandorea.Key words: Pandorea, RAPD, inter-SSR, DNA fingerprint, genetic variability.
A fertile amphiploid between diploid wheat (Triticum tauschii) and crested wheatgrass (Agropyron cristatum)
Authors: Martín A , Cabrera A , Esteban E , Hernández P , Ramírez M C , Rubiales D
Published: April 2011

Alloploidy, one of the most efficient evolutionary mechanisms in nature, has not been extensively exploited in plant breeding programmes. Many genomic combinations remain to be created by plant breeders, to be used directly as new crops or indirectly to widen the genetic basis of crops. The Triticeae tribe, to which wheat belongs, is among the botanical groups in which this strategy has been successfully explored. However, there remain valuable genomic combinations that have not been obtained at the diploid level. The Agropyron complex (wheat-grasses) has recently been the focus of attention for interspecific hybridization, but intergeneric hybrids or amphiploids with wheat have not been reported at the diploid level. Here we report synthesis of a tetraploid amphiploid between Triticum tauschii and Agropyron cristatum by crossing two tetraploid accessions. Using total genome in situ hybridization (GISH) staining on metaphase I pollen mother cells, data on allosyndetic and autosyndetic chromosome pairing have been obtained. These data support the view that the A. cristatum tetraploid parent used in the synthesis of the amphiploid has a segmental alloploidy nature.
Homoeologous recombination in 2n-gametes producing interspecific hybrids ofLilium(Liliaceae) studied by genomic in situ hybridization (GISH)
Authors: Karlov G I , Khrustaleva L I , Lim K B , van Tuyl J M
Published: April 2011

Interspecific hybridization of Lilium longiflorum (L) with Asiatic (A) lily hybrids results in so-called LA-hybrids. Some of these hybrids produce 2n-pollen, which were used to perform crosses on Asiatic and Oriental (O) hybrids, resulting in ALA- and OLA-hybrids. Recombination between homoeologous chromosomes (introgression) and the mechanism of 2n-pollen formation in these hybrids were studied using genomic in situ hybridization (GISH). A clear differentiation between the chromosomes of L. longiflorum, Asiatic, and Oriental hybrids was observed in four ALA- and one OLA-hybrid using GISH. Two ALA-hybrids showed 3 and 5 recombinant chromosomes with a total of 5 and 10 crossover sites per hybrid, respectively. These occurred at random positions on the chromosomes. The number and the location of the rDNA-sites were determined using in situ hybridization and provided a tool, the FISH-marker, for identifying the NOR-bearing chromosomes in the lily hybrids. Evidence for the occurrence of the FDR-mechanism (first division restitution) of 2n-pollen formation in the LA-hybrids was obtained on the basis of absence of homologous chromosomes of L. longiflorum in the ALA- and OLA-hybrids.Key words: Lilium longiflorum, introgression, FDR, interspecific hybridization, FISH.
Identification and distinction among segmental duplication-deficiencies by fluorescence in situ hybridization (FISH)-adorned multivalent analysis
Authors: Ji Yuanfu , Raska Wayne A , Donato Marcos De , Islam-Faridi M Nurul , Price H James , Stelly David M
Published: April 2011

Most simple reciprocal translocation homozygotes and heterozygotes are euploid, and normal in genotype. However, translocation heterozygotes form six types of numerically balanced meiotic products. The cross of a translocation heterozygote with a normal individual can yield normal progeny, translocation heterozygotes, or any of four segmentally aneuploid duplication-deficient types (dp-dfs). Using metaphase I configuration analysis, most dp-dfs can be distinguished easily from normal and heterozygous translocations. However, identification of the four dp-df types is often impossible unless there is an appreciable karyotypic difference in arm size, relative breakpoint position, or a diagnostic cytological marker. Here we demonstrated the utility and facility of dp-df identification by means of meiotic fluorescence in situ hybridization (FISH) to adorn one chromosome arm with a molecular marker. The rationale is presented diagrammatically, and exemplified by identifying both adjacent-1 and adjacent-2 dp-dfs in Gossypium hirsutum. Polymorphism is not required among marker loci, so analysis of dp-dfs can proceed without requirement of sexual hybridization or sophisticated high-polymorphism marker systems. Besides facilitating the identification of dp-dfs, such an analysis can provide facile means to assign marker loci to chromosomes, arms, and segments. Integrative mapping of chromosomal, physical, and recombination maps will thus be facilitated. An ability to readily distinguish adjacent-1 and adjacent-2 types of dp-dfs should also enhance strategic derivation of other aneuploids, e.g., dp-df related monosomes and trisomes.Key words: Gossypium, cotton, duplication-deficiency, fluorescence in situ hybridization, repetitive DNA.
Cloning and genetic variability of aHindIII repetitive DNA inAcrossocheilus paradoxus(Cyprinidae)
Authors: Wu Wen-Luan , Wang Jiang-Ping , Tseng Mei-Chen , Chiang Tzen-Yuh
Published: April 2011

Thirty clones of a highly repetitive HindIII fragment of DNA from seven populations of Acrossocheilus paradoxus (Cyprinidae) were isolated and sequenced. The fragment represents a tandemly repeated sequence, with a monomeric unit of 270 bp, amounting to 0.08-0.10% of the fish genome. Higher units of this monomer appear as a ladder in Southern blots. The HindIII satellite DNA family is conserved in three genera of the Cyprinidae. Variation in nucleotide sequences of this repetitive fragment, which is A+T-rich, is distributed both within individuals and among populations. High overall nucleotide divergence (dij= 0.056 ± 0.001) was detected among clones of the HindIII satellite DNAs of Acrossocheilus paradoxus. Based on the molecular clock hypothesis, the maximum evolutionary rate was estimated to be 5.3 × 10-7substitutions per site per year. Lineage sorting may have contributed to the genetic heterogeneity within individuals and populations. Cladistic analyses indicated a closer phylogeographic relationship between populations of the central and south regions in Taiwan.Key words: highly repetitive DNA, HindIII restriction, nucleotide sequence, genetic variability, phylogeography.
Synapsis in a natural autotetraploid
Authors: Hauber Donald P , Reeves Aaron , Stack Stephen M
Published: April 2011

To test assumptions of the autotetraploid chromosome pairing model regarding events during synapsis, whole-mount spreads of synaptonemal complexes (SCs) of Machaeranthera pinnatifida (=Haplopappus spinulosus) (Asteraceae) (2n = 4x = 16) were analyzed by electron microscopy. On the assumption of one synaptic initiation per chromosome arm, each pachytene quadrivalent is expected to have one partner switch (PS), and the frequency of pachytene quadrivalents for each chromosome is predicted to be 2/3 (or 0.67). However, to the contrary, we observed a range of one to four PSs per pachytene quadrivalent with an overall mean of 1.56. This suggests that the number of synaptic initiations is greater than one per chromosome arm (or >two per chromosome), and the predicted frequency of pachytene quadrivalents should be >8/9 (based on a minimum of three initiations per chromosome). However, in close agreement with the model, the observed pachytene quadrivalent frequency from SCs in this study was 0.69. To explain the apparent discrepancy between the observed frequency of PSs and the observed frequency of quadrivalents, the possibility of nonindependent synaptic initiations and presynaptic alignment are discussed in the context of their potential influence on quadrivalent frequency. Recombination nodules (RNs), which were scored in about half the SC spreads, occurred at a frequency (9.6 per nucleus) comparable with the chiasma frequency at diakinesis (9.3 per nucleus). The frequency of RNs as well as their distribution is consistent with the hypothesis that RNs occur at sites of crossing over and chiasma formation.Key words: autopolyploid, Machaeranthera pinnatifida, meiosis, recombination nodules, synaptonemal complex.
Sequence analysis and gene identification in a set of mapped RFLP markers in barley (Hordeum vulgare)
Authors: Michalek Wolfgang , Künzel Gottfried , Graner Andreas
Published: April 2011

The "Igri/Franka" (I/F) map ranks among the most comprehensive genetic linkage maps of barley (Hordeum vulgare), containing a large number of markers derived from cDNA and genomic PstI clones. Fourty-three cDNA clones and 259 genomic clones were at least partially sequenced and compared with the major data bases of protein and nucleic acid sequences. Of the cDNA clones, 53% show significant similarity to known sequences in protein data bases. A comparison of sequences from genomic clones to nucleic acid sequence data bases revealed similarities for 9% of the clones. For cDNA sequences analyzed the same way, significant similarities were observed for 35% of the clones. These results show that genomic PstI clones, although containing genes at a significant frequency, represent an inappropriate source for an efficient, systematic gene identification in barley. Sequence information obtained in the context of the present study provides a resource for the conversion of these markers into sequence-tagged site (STS) markers and their use in PCR assays.Key words: data base comparison, DNA probe, gene identification, STS marker.
Approaches for breaching yield stagnation in wheat
Authors: Rajaram S
Published: April 2011

This paper outlines the breeding objectives, methodology, and genetic gains of the international wheat breeding program of the International Maize and Wheat Improvement Center (CIMMYT) based in Mexico. The historical analysis of yield gains asserts that wise use of genetic diversity has been paramount in raising the yield ceiling and expanding genetic variability. Data is provided to support a philosophical view that yield potential per se should be combined with both abiotic and biotic tolerances in the breeding of future cultivars. The erosion of high yield potential should be avoided at all costs through a protective shield of wide-spectrum disease resistance genes.Key words: yield potential, shuttle breeding, Aegilops squarrosa.
Identification of PCR-based markers flanking the recessive LMV resistance gene mo1 in an intraspecific cross in lettuce
Authors: Irwin S V , Kesseli R V , Waycott W , Ryder E J , Cho J J , Michelmore R W
Published: April 2011

Molecular markers flanking the recessive resistance gene mo1 were identified following analysis of two segregating populations. Generation of a population from a crisphead × crisphead cross of Lactuca sativa that segregated for resistance conferred by the mo12allele, but not morphological traits, was required for accurate mapping of the gene. Resistance was best assessed by symptom development after inoculating F3families with the common pathotype II isolate of lettuce mosaic virus (LMV). Bulked segregant analysis for RAPD (random amplified polymorphic DNA) markers using one population, followed by linkage analysis using another, identified markers on either side of the mo1 gene, approximately 8 cM apart. These markers will be useful for more efficient introgression of this resistance gene into additional lettuce cultivars.Key words: lettuce, lettuce mosaic virus, molecular marker, disease resistance gene, bulked segregant analysis.