bluuebunny/crossref_metadata_2025 huggingface dataset:
The molecular diversity of the 5S rRNA gene inKengyilia alatavica(Drobov) J.L. Yang, Yen &Baum (Poaceae: Triticeae): potential genomic assignment of different rDNA units
Authors: Baum Bernard R. , Bailey L. Grant
Published: May 2008

5S rRNA sequences from several accessions of Kengyilia alatavica, a member of a tribe that includes wheat and wheat relatives, have been amplified by the polymerase chain reaction, cloned, and sequenced. From an evaluation of the aligned sequences, five 5S unit classes have been discerned. One class consists of short units, while the other four contain longer units. BLAST searches of the GenBank®database have allowed us to tentatively assign these to classes found in genomes of other species. For example, the short 5S unit class and one long 5S unit class were designated, respectively, "short P1" and "long P1" because of their match with the comparable sequenced 5S rDNA accessions of Agropyron cristatum, a carrier of the P genome. Another unit class, is coined as "long R1", because of its similarity to the units sequenced from Secale cereale and Secale vavilovii, carriers of the R genome. The third unit class was designated "long S1" and is found also in Elytrigia spicata, a carrier of the S genome. Implications of these findings on the possible association of some unit classes with cytological haplome and on concerted evolution are discussed.Key words: 5S RNA gene, genomes, concerted evolution, Triticeae.
Detection of quantitative trait loci associated with leaf rust resistance in bread wheat
Authors: William H. M. , Hoisington D. , Singh R. P. , González-de-León D.
Published: May 2008

Leaf rust, caused by Puccinia recondita Rob. ex Desm., is a common disease in wheat. The objective of this study was to develop molecular markers associated with the quantitative trait loci (QTLs) putatively conferring durable leaf rust resistance in Triticum aestivum L. em. Thell. A population of 77 recombinant inbred lines (RILs) developed from 'Parula' (resistant) and 'Siete Cerros' (moderately susceptible) was used. Bulked segregant analysis was done using random amplified polymorphic DNAs (RAPDs) with DNA enriched for low-copy sequences using hydroxyapatite chromatography. Out of 400 decamer primers screened, 3 RAPD markers were identified between the bulk of the most resistant and the bulk of the most susceptible lines. These were cloned and used as probes on the RILs in Southern hybridizations. Two probes revealed two tightly linked loci. One-way analysis of variance showed that these two loci, and another revealed by the third probe, were linked to QTLs controlling leaf rust resistance based on data taken from 2 years of replicated field trials. Cytogenetic analysis placed the two tightly linked loci on the long arm of chromosome 7B. The third probe detected loci located on the short arms of chromosomes 1B and 1D. It is suggested that the QTL detected on 7BL may well be homoeoallelic to Lr34.Key words: bulked segregant analysis, RAPDs, RFLPs, DNA enrichment, leaf rust, QTL.
Genetic and cytological analyses of three lethal ovule mutants in soybean (Glycine max; Leguminosae)
Authors: Pereira T. N. S. , Ilarslan H. , Palmer R. G.
Published: May 2008

Soybean partially sterile mutants 2, 3, and 4 (PS-2, PS-3, and PS-4), recovered from a gene-tagging experiment, were studied to clarify their inheritance, linkage, allelism, and reproductive biology. The PS-2, PS-3, and PS-4 mutants were maintained as heterozygotes and upon self-pollination segregated l fertile: l partially-sterile. For inheritance and linkage tests, all three PS mutants were crossed to flower color mutant Harosoy-w4 and to chlorophyll-deficient (CD) mutants CD-1 and CD-5, also recovered from the tagging study. For allelism tests, reciprocal crosses were made among the three partially sterile mutants. Linkage results indicated that the gene for partial sterility in the PS-2, PS-3, and PS-4 mutants was not linked either to the w4 locus or to the genes for chlorophyll deficiency. Studies of pollen development, pollen viability, and pollen-tube germination indicated no difference between normal and partially sterile genotypes. Linkage and allelism tests indicated that the gene in the three partially sterile mutants was not transmitted through the female when they were used as a female parent. A study of megagametogenesis indicated that the ovules from partially sterile plants had normal embryo sac development. Ovule abortion was due to failure of fertilization.Key words: partially sterile, gene tagging, ovule abortion, soybean.
Identification of sex in hop (Humulus lupulus) using molecular markers
Authors: Polley Andreas , Ganal Martin W. , Seigner Elisabeth
Published: May 2008

The rapid identification of sex in the dioecious hop (Humulus lupulus) is important for the breeding of this cultivated plant because only unfertilized flowers of the female plants are used as an ingredient in the production of beer. It is thought that a sex-chromosome mechanism controls the development of male or female plants. We have compared pools of male and female plants derived from a hop cross to identify molecular markers associated with the Y or male-specific chromosome. Of 900 functional RAPD primers, 32 revealed fragments specific for male plants that were absent in female plants of this cross. Subsequently, the 32 positive primers were tested on unrelated male and female plants. Three of these 32 primers were specific for the Y chromosome in all lines. The Y-specific product derived from one of these primers (OPJ9) was of low copy in hybridization experiments and predominantly present in male plants. Primers developed from the DNA sequence of this product provide a marker for rapid sex identification in crosses of hop by means of PCR.Key words: chromosomes, RAPD, sex-specific DNA sequences, plant breeding, Y chromosome.
Fine structure of the kinetochores in six species of the Coleoptera
Authors: Wolf Klaus Werner
Published: May 2008

Kinetochore structure was examined in a total of 6 species from 5 different families of the Coleoptera using transmission electron microscopy of ultrathin serial sections. Metaphase spermatogonia and primary and secondary spermatocytes were studied in Tenebrio molitor (Tenebrionidae) to determine whether kinetochore structure varies depending on the cell type. In all three cell types, the kinetochore microtubules (MTs) were in direct contact with the chromosomal surface, and kinetochore plates were not detectable. In the other species, only metaphase I spermatocytes were examined. As in T. molitor, distinct kinetochore plates were also absent in Adelocera murina (Elateridae), Agapanthia villosoviridescens (Cerambycidae), and Coccinella septempunctata (Coccinellidae). However, bivalents in male meiosis of two representatives of the Chrysomelidae, Agelastica alni and Chrysolina graminis, showed roughly spherical kinetochores at their poleward surfaces. Microtubules were in contact with this material. Thus, although the present survey covers only a small number of species, it is clear that at least two kinetochore types occur in the Coleoptera. The cytological findings are discussed in the context of chromosome number and genome size variability in the Coleopteran families studied. It is suggested that properties of the kinetochores could play a role in karyotype evolution in the Coleoptera.Key words: bivalent, microtubule, meiosis, metaphase, spermatocyte.
Aneuploid marker assignment in hexaploid oat with the C genome as a reference for determining remnant homoeology
Authors: Kianian Shahryar F. , Wu Bai-Chai , Fox Stephen L. , Rines Howard W. , Phillips Ronald L.
Published: May 2008

Nullisomic lines of hexaploid oat Avena sativa L. (2n = 6x − 2 = 40, AACCDD) cultivar Sun II were used to assign 134 DNA sequences to 10 chromosome-associated syntenic groups. A limited set of ditelosomic lines allowed localization of subsets of these sequences to six chromosome arms. Advantages of using such aneuploids in mapping are in the assignment of gene families, monomorphic RFLP sequences, and oat linkage groups to chromosomes. The published hexaploid oat RFLP linkage map has 38 linkage groups, 17 more than expected on the basis of the haploid chromosome number. Using nullisomics, eight linkage groups were assigned to five physical chromosomes; using ditelosomics, three of these linkage groups were assigned to their respective chromosome arms. The A- and D-genome chromosome sets of oat are indistinguishable from each other based on different staining and genomic in situ hybridization techniques, while C-genome chromosomes are distinct. Because chromosomal rearrangements such as translocations and inversions have played an important role in the evolution of hexaploid oat, the distinction of C-genome chromosomes can be used to determine remnant homoeologous segments that exist in the other two genomes. Among the 10 syntenic groups identified, six chromosomes showed sequence homoeology believed to represent segmental homoeologous regions. Owing to various evolutionary forces, segmental homoeology instead of whole chromosome homoeology appears to best describe the genome organization in hexaploid oat.Key words: oat, aneuploids, syntenic associations, homoeology, C genome.
Using genomic slot blot hybridization to assess intergeneric Saccharum x Erianthus hybrids (Andropogoneae – Saccharinae)
Authors: Besse P. , McIntyre C. L. , Burner D. M. , Almeida C. G. de
Published: May 2008

The use of genomic slot blot hybridization enabled the differentiation of hybrids from selfs in Saccharum × Erianthus intergeneric crosses in which Saccharum was used as the female parent. Based on the genomic in situ hybridization technique, slot blots of DNA from the parents and the progeny were blocked with the Saccharum parent DNA and hybridized with the labelled male Erianthus genomic DNA. This technique allowed a rapid screening for hybrids and was sensitive enough to detect a 1/20 dilution of Erianthus in Saccharum DNA, which should enable the detection of most partial hybrids. The genomic slot blot hybridization technique was shown to be potentially useful for assessing crosses involving Saccharum species with either Old World Erianthus section Ripidium or North American Erianthus (= Saccharum) species. The effectiveness of the technique was assessed on 144 progeny of a Saccharum officinarum × Erianthus arundinaceus cross, revealing that 43% of the progeny were selfs. The importance of this test as a tool to support intergeneric breeding programs is discussed.Key words: slot blot, Erianthus, genomic DNA, Saccharum, sugarcane.
AFLP fingerprinting reveals pattern differences between template DNA extracted from different plant organs
Authors: Donini P. , Koebner R. M. D. , Elias M. L. , Bougourd S. M.
Published: May 2008

AFLP (amplified fragment length polymorphism) fingerprinting of cultivars of bread wheat (Triticum aestivum) and some of its wild relatives has allowed the efficient detection of large numbers of polymorphic amplified fragments. While the reproducibility of fingerprints in repeated experiments is high, pattern differences were observed between fingerprints obtained from seed and leaf DNA template from the same wheat accession. These distinct organ specific amplified DNA fragments were shown to be due neither to genotypic mixtures nor to pathogen contamination. They are likely a result of differences in DNA methylation between organs. Even greater numbers of organ specific amplified fragments were observed when fingerprints obtained from the root and shoot of individual seedlings of the wheat relatives Aegilops mutica and Aegilops speltoides were compared. This phenomenon underlines the importance of ensuring that DNA is extracted from physiologically uniform tissue in phylogenetic studies based on AFLP fingerprints. For this purpose, mature seed is a convenient source.Key words: AFLPs, fingerprinting, genome mapping, organ specificity.
Identification of RAPD markers linked to common bacterial blight resistance genes inPhaseolus vulgarisL.
Authors: Bai Yonghe , Michaels T. E. , Pauls K. P.
Published: May 2008

Seven hundred and fifty-six random primers were screened with bulks of genomic DNA from common bacterial blight (CBB) resistant and susceptible bean plants. The plants were from a breeding population derived from an interspecific cross between Phaseolus acutifolius and Phaseolus vulgaris. Four RAPD markers, named R7313, RE416, RE49, and R4865, were found to be significantly associated with CBB resistance in this population. Forty-nine molecular markers segregating in the population were clustered into 8 linkage groups by a MAPMAKER linkage analysis. The largest linkage group was 140 cM long and contained 25 marker loci, including marker R4865. Markers R7313, RE416, and RE49 were clustered on another linkage group. A regression analysis indicated that the markers in these two groups together accounted for 81% of the variation in CBB resistance in the population. The addition of another marker, M56810, which was not individually associated with CBB resistance, increased the total contribution to the trait to 87%.Key words: Phaseolus vulgaris L., common bacterial blight (CBB), polymerase chain reaction (PCR), RAPD markers, linkage groups.
Chromosome doubling of haploids of common wheat with caffeine
Authors: Thomas Julian , Chen Qin , Howes Neil
Published: May 2008

Treatment of dividing plant cells with caffeine inhibits their cytokinesis, thereby inducing the formation of binucleate cells that contain polyploid nuclei. This study was undertaken to determine whether caffeine treatments would induce chromosome doubling and seed set in haploids of common wheat (Triticum aestivum L. em. Thell.) through the further development of diploid nuclei. Ten sterile wheat haploid plants, obtained through the agency of corn (Zea mays L.) pollination, were multiplied by vegetative propagation (subdivision of well-tillered plants) to produce about 50 crowns per haploid. Washed and trimmed crowns were treated with 0.3, 1.0, 3.0, and 10.0 g∙L−1 caffeine for 3, 6, 12, and 24 h. While treatment with 0.3 g∙L−1 caffeine did not restore fertility, higher concentrations of caffeine resulted in pollen shedding and substantial seed set compared with untreated controls. Many combinations of caffeine concentration and duration produced comparable results; however, treatment with 3 g∙L−1 for 24 h was the most effective caffeine treatment on the basis of the number of seeds recovered, as well as the size and incidence of fertile sectors. Compared with a standard colchicine treatment (3-h immersion in 2 g∙L−1 colchicine dissolved in 0.5% dimethyl sulfoxide), all caffeine treatments produced fewer seeds, principally because colchicine-doubled sectors were often large, while caffeine-doubled sectors were numerous but generally small. In conclusion, caffeine produced useful numbers of seeds for all clones; gliadin banding patterns and chromosome counts indicated that genetic and cytogenetic stability of the doubling process were equal or superior for caffeine compared with colchicine.Key words: chromosome doubling, haploid, caffeine, colchicine, Triticum aestivum.
Construction of midget chromosomes in wheat
Authors: Lukaszewski Adam J.
Published: May 2008

To test the usefulness of breakage–fusion–bridge (BFB) cycles in generating new chromosome aberrations in bread wheat (Triticum aestivum L.) and to extend the range of aberrations available, a series of midget chromosomes was produced from the long arm of chromosome 1B. Using a reverse tandem duplication initiated chromatid type BFB cycle, the 1BL arm was broken and fused with centromeres of either chromosome 5BL or 1RS to form dicentric chromosomes. The 1R and 5B centromeres were broken by centric misdivision. Among the progenies of plants with dicentric chromosomes, two classes of monocentric chromosomes were selected: deficient chromosomes 1B and chromosomes that had 1RS or 5BL for one arm and various fragments of 1BL for the other arm. Following centric misdivision of these monocentrics, midget chromosomes 1BL were isolated: deficient and deletion telocentrics and telocentrics derived from interstitial regions of 1BL. By chance, one deficient chromosome 1BS and one deletion chromosome 1BS were identified in unrelated lines of the same wheat. Following centric misdivision of these chromosomes, two midget chromosomes covering the whole of 1BS were added to the set.Key words: breakage–fusion–bridge cycle, centric misdivision, chromosome aberrations.
Chromosomal localization and characterization of rDNA loci in theBrassicaA and C genomes
Authors: Snowdon R. J. , Köhler W. , Köhler A.
Published: May 2008

Using fluorescence in situ hybridization, we located ribosomal DNA loci on prometaphase chromosomes of the diploid species Brassica rapa and Brassica oleracea and their amphidiploid Brassica napus. Based on comparisons of chromosome morphology and hybridization patterns, we characterized the individual B. napus rDNA loci according to their presumed origins in the Brassica A and C genomes. As reported in other studies, the sum of rDNA loci observed on B. rapa (AA genome) and B. oleracea (CC genome) chromosomes was one greater than the total number of loci seen in their amphidiploid B. napus (AACC). Evidence is presented that this reduction in B. napus rDNA locus number results from the loss of the smallest A genome rDNA site in the amphidiploid.Key words: Brassica, fluorescence in situ hybridization, ribosomal DNA, rDNA.
RAPD analysis off genetic variation in the Australian fan flower, Scaevola
Authors: Swoboda Ines , Bhalla Prem L.
Published: May 2008

The use of randomly amplified polymorphic DNA (RAPD) to study genetic variability in Scaevola (family Goodeniaceae), a native Australian species used in ornamental horticulture, is demonstrated. Plants of the genus Scaevola are commonly known as "fan flowers," due to the fan-like shape of the flowers. Nineteen accessions of Scaevola (12 cultivated and 7 wild) were studied using 20 random decamer arbitrary primers. Eight primers gave a distinct reproducible amplification profile of 90 scorable polymorphic fragments, enabling the differentiation of the Scaevola accessions. RAPD amplification of genomic DNA revealed a high genetic variability among the different species of Scaevola studied. Molecular markers were used to calculate the similarity coefficients, which were then used for determining genetic distances between each of the accessions. Based on genetic distances, a dendrogram was constructed. Though the dendrogram is in general agreement with the taxonomy, it also highlights discrepancies in the classification. The RAPD data showed that Scaevola aemula (series Pogogynae) is closer to Scaevola glandulifera of series Globuliferae than to the rest of members of series Pogogynae. In addition, the RAPD banding pattern of white flower S. aemula, one of the commercial cultivars, was identical to that of Scaevola albida, indicating their genetic similarity. Our study showed that there is a large genetic distance between commercial cultivars of Scaevola (Purple Fanfare, Pink Perfection, and Mauve Cluster), indicating considerable genetic variation among them. The use of RAPDs in intra- and inter-specific breeding of Scaevola is also explored.Key words: Scaevola, Australian native, RAPD, genetic distance, genetic variability.
Potential off biolistic transformation of barley microspores based on viability and transient β-glucuronidase activity
Authors: Yao Qing A. , Kasha Ken J.
Published: May 2008

Microspores could be an excellent target for plant transformation, owing to their haploid nature, the availability of a large population of fairly synchronous single cells, and their potential to regenerate into plants through embryogenesis. Therefore, the potential for microspore transformation by biolistic procedures was examined cytologically, based on the viability and β-glucuronidase (GUS) activity of bombarded microspores. The microspores were bombarded with gold particles coated with the plasmid pAHC25. On average, 10.7% of the total number of microspores bombarded contained particles. Of these, 4.7, 1.2, and 4.7% received one, two, and three or more particles, respectively. Of the microspores receiving particles, ca. 7% had one or more particles in the nucleus. Viability of bombarded microspores was followed for 7 days in culture. Over this period, the frequency of viable microspores with particles was significantly reduced from 1.56% at day 1, to 0.72% at day 3, and finally to 0.05% at day 7, with this last group having only a single particle. While microspores that received multiple particles did not survive after 1 week in culture, initially they could be scored as positive for transient GUS activity. Microspores with particles delivered directly into the nucleus (vs. other cell compartments) showed enhanced uidA transient expression and these microspores were most likely the source of integration of the introduced DNA into the recipient genome. The potential for the recovery of transgenic barley plants following biolistic bombardment is discussed.Key words: barley, microspore, microprojectile bombardment, GUS activity.
Identification of alien chromosomes through GISH and RFLP analysis and the potential for establishing potato lines with monosomic additions of tomato chromosomes
Authors: Garriga-Calderé F. , Huigen D. J. , Filotico F. , Jacobsen E. , Ramanna M. S.
Published: May 2008

To increase the potential for establishing a complete series of tomato chromosome addition–sbstitution lines in a potato background, six new BC1progeny were produced. All of them originated from crosses between three different hexaploid potato (+) tomato fusion hybrids. Three different somatic hybrids, viz., C31-17-5, C31-17-24, and C31-17-51, were used as female parents, and four different tetraploids, viz., Katahdin, Frieslander, 6704-1, and AM66.42 were used as male parents. A characterisation of the genomes of the three fusion hybrids and the six BC1progenies (6739, 2001, 2002, 2003, 2004, and 2005) through genomic in situ hybridization and restriction fragment length polymorphism (RFLP) analysis indicated that there was preferential tomato chromosome elimination in the fusion hybrids. Similar analyses of the six BC1progeny indicated that a variable number of the alien tomato chromosomes (6–11) were present in individual plants. RFLP analysis using chromosome specific DNA probes indicated that BC1progenies had retained all 12 tomato chromosomes, albeit in different individual plants. This means that the available BC1progenies have the potential for establishing a complete series of tomato chromosome addition–substitution lines in a potato background.Key words: protoplast fusion hybrids, Solanum tuberosum, Lycopersicon esculentum, BC1progeny, in situ hybridization, RFLP analysis.
Ribosomal RNA genes specific to the B chromosomes in Brachycome dichromosomatica are not transcribed in leaf tissue
Authors: Donald Tamzin M. , Houben Andreas , Leach Carolyn R. , Timmis Jeremy N.
Published: May 2008

Ribosomal RNA genes are present near the end of the short arm and, to a lesser extent, near the centromere of the B chromosomes of some populations of Brachycome dichromosomatica. The internal transcribed spacer (ITS2) was amplified by PCR from total leaf DNA using primers within the conserved regions encoding the 5.8S and 25S stable rRNA species. Comparison of PCR amplified ITS2 sequences from several individual plants without B chromosomes with corresponding sequences derived from microdissected B chromosomes revealed two consistent differences between the rDNA of A and B chromosomes. One of these differences produced an SfcI restriction site that was present only in the ITS2 of the B-chromosome rDNA. Amplification by PCR of ITS2 from total genomic DNA from plants with and without B chromosomes showed an additive relationship between the amount of PCR product containing the SfcI site and the number of B chromosomes present. Quantitative analysis indicated that the proportion of total nuclear rDNA present on a single B chromosome varied between 2 and 4% in different A chromosome backgrounds. Similar experiments, with appropriate positive and negative controls, using reverse transcriptase PCR of the equivalent region within the 40S precursor rRNA, suggested that the B-chromosome rDNA was not transcribed. Similarly, PCR of reverse transcribed total RNA from plants containing B chromosomes using primers specific for the B chromosome ITS2 was unable to detect a transcript from the B chromosome. Keywords: B chromosome, ribosomal RNA genes, transcription.
Simple sequence repeat DNA markers in alfalfa and perennial and annualMedicagospecies
Authors: Diwan Noa , Bhagwat Arvind A. , Bauchan Gary B. , Cregan Perry B.
Published: May 2008

Simple sequence repeat (SSR) or microsatellite DNA markers have been shown to function well in plant and mammalian species for genetic map construction and genotype identification. The objectives of the work reported here were to search GenBank for the presence of SSR-containing sequences from the genus Medicago, to assess the presence and frequency of SSR DNA in the alfalfa (Medicago sativa (L.) L. &L.) genome, and to examine the function of selected markers in a spectrum of perennial and annual Medicago species. The screening of an alfalfa genomic DNA library and sequencing of clones putatively containing SSRs indicated approximately 19 000 (AT)n + (CT)n + (CA)n + (ATT)nSSRs in the tetraploid genome. Inheritance was consistent with Mendelian expectations at four selected SSR loci with different core motifs. Additionally, genotypes of a range of Medicago species, including 10 perennial subspecies of the M. sativa complex and other perennial and annual Medicago species, were analyzed at each of the loci to ascertain the presence, number, and size of SSR alleles at each locus in each genotype. These studies indicate that SSR markers can function in alfalfa for the construction of genetic maps and will also be useful in a range of Medicago species for purposes of assessing genetic relatedness and taxonomic relationships, and for genotype identification.Key words: microsatellites, SSR markers, simple sequence repeats, alfalfa, annual medics.
Construction of a MluI-YAC library from barley (Hordeum vulgare L.) and analysis of YAC insert terminal regions
Authors: Kleine Michael , Jung Christian , Michalek Wolfgang , Diefenthal Thomas , Dargatz Harald
Published: May 2008

We describe the construction of a specific yeast artificial chromosome (YAC) library from barley (Hordeum vulgare L.) using the vector pYAC-RC. The library was generated by total digestion of high molecular weight DNA with the infrequently cutting restriction enzyme MluI. Only 10–30% of the colonies were recombinant, as visualized by red–white selection and subsequent pulsed-field gel electrophoresis analysis. About 17 000 individual recombinant YAC clones with insert sizes ranging from 50 to 700 kb, with a mean of 170 kb, were selected. No chloroplast sequences were detected and the proportion of YAC clones containing BARE–1 copia–like retroelements is about 5%. Screening of the library with a single-copy RFLP marker closely linked to the Mla locus yielded three identical clones of the same size. Insert termini of randomly chosen YAC clones were investigated with respect to their redundancy in the barley genome and compared with termini of YAC clones from an EcoRI-based YAC library, resulting in a fourfold enrichment of single-copy sequences at the MluI vector–insert junctions.Key words: yeast artificial chromosomes, YAC, Hordeum vulgare, pulsed-field gel electrophoresis.
Characterization of Thinopyrum distichum chromosomes using double fluorescence in situ hybridization, RFLP analysis of 5S and 26S rRNA, and C-banding of parents and addition lines
Authors: Fominaya A , Molnar S. , Fedak G. , Armstrong K. C. , Kim N.-S. , Chen Q.
Published: May 2008

Diagnostic markers for eight Thinopyrum distichum addition chromosomes in Triticum turgidum were established using C-banding, in situ hybridization, and restriction fragment length polymorphism analysis. The C-band karyotype conclusively identified individual Th. distichum chromosomes and distinguished them from chromosomes of T. turgidum. Also, TaqI and BamHI restriction fragments containing 5S and 18S–5.8S–26S rRNA sequences were identified as positive markers specific to Th. distichum chromosomes. Simultaneous fluorescence in situ hybridization showed both 5S and 18S–5.8S–26S ribosomal RNA genes to be located on chromosome IV. Thinopyrum distichum chromosome VII carried only a 18S–5.8S–26S rRNA locus and chromosome pair II carried only a 5S rRNA locus. The arrangement of these loci on Th. distichum chromosome IV was different from that on wheat chromosome pair 1B. Two other unidentified Th. distichum chromosome pairs also carried 5S rRNA loci. The homoeologous relationship between Th. distichum chromosomes IV and VII and chromosomes of other members of the Triticeae was discussed by comparing results obtained using these physical and molecular markers.Key words: Triticum turgidum, homoeologous relationship, Triticeae, addition lines, NOR.
The relationship between genetic and cytogenetic maps of pea. I. Standard and translocation karyotypes
Authors: Hall K. J. , Parker J. S. , Ellis T. H. N.
Published: May 2008

A detailed cytogenetical study of inbred lines of pea and their F1hybrids has been undertaken to study the relationship between the cytogenetic map and the molecular linkage map. The mitotic karyotypes of a standard pea line, JI15, a translocation line, JI61, and line JI281, a line used in the production of a mapping population, are given. A chromosome rearrangement detected by cytogenetic analysis of mitotic chromosomes has been further defined by synaptonemal complex (SC) analysis and the study of metaphase I chromosome behaviour. This meiotic analysis has allowed a comparison of SC physical lengths, observed chiasma frequencies, and recombination frequencies, as estimated from the genetic map, as a means of comparing physical and genetic distances.Key words: Pisum, linkage map, cytogenetics, chromosome rearrangement, synaptonemal complex.
Pattern of X–Y chromosome pairing in the Japanese field vole, Microtus montebelli
Authors: Borodin P. M. , Rogatcheva M. B. , Koyasu K. , Fukuta K. , Mekada K. , Oda S. I.
Published: May 2008

Pairing of X and Y chromosomes at meiotic prophase in males of Microtus montebelli was analyzed. The sex chromosomes form a synaptonemal complex at pachytene and end-to-end association at diakinesis – metaphase I in two species of the genus Microtus (M. montebelli and M. oeconomus) only, while they do not pair at all in the other species of this genus that have been studied so far. These data confirm that M. montebelli and M. oeconomus are very closely related in their origin. It is suggested that the sex chromosomes of M. montebelli and M. oeconomus display the ancestral type of X–Y pairing. The lack of X–Y pairing in most species of Microtus appeared after the split in lineage that led to M. oeconomus and M. montebelli on the one hand and the remaining species on the other.Key words: Microtus montebelli, arvicoline phylogeny, synaptic sex chromosome, synaptonemal complex, chromosomal evolution.
Effects of thetolmutation on allelic interactions athetloci inNeurospora crassa
Authors: Leslie John F. , Yamashiro Carl T.
Published: May 2008

A mutant at the tol locus of Neurospora crassa can suppress heterokaryon (vegetative) incompatibility associated with differences at the mating-type locus. We tested the ability of this allele to suppress the vegetative incompatibility reactions that can occur when strains differ at one of nine het loci (het-C, -D, -E, -5, -6, -7, -8, -9, and -10). We found no cases in which the tol mutant suppresses a heteroallelic het locus interaction. Thus, the interaction(s) that leads to vegetative incompatibility because of differences at the mating-type locus is distinct from the interaction(s) that leads to vegetative incompatibility because of differences at any of these nine het loci.Key words: heterokaryon, mating type, vegetative compatibility.
Identification of RAPD markers for percent hull in oat
Authors: Ronald P. S. , Penner G. A. , Brown P. D. , Brûlé-Babel A.
Published: May 2008

Percent hull is an important physical parameter of oat grain quality, but it is affected by environment. Multiple time-consuming evaluations are required to obtain a correct determination of phenotype. The application of marker-assisted selection for the genes involved would greatly simplify the identification of desirable oat genotypes. Bulked segregant analysis, with selected progeny lines derived from a cross between Cascade and AC Marie (30 and 23% hull, respectively), was used to identify randomly amplified polymorphic DNA markers linked to genetic factors controlling primary kernel hull percentage in oat. Twelve polymorphisms, identified between bulks, were tested for linkage to genetic factors controlling hull percentage by genotyping 80 randomly selected F2-derived F8 lines from the progeny population. Three markers showed significant test statistics for quantitative trait locus effects, when tested with primary kernel percent hull data from two environments. Together, the unlinked marker loci OPC13800, OPD20600, and OPK71300 explained approximately 41% of the genetic variance in primary kernel percent hull, after accounting for the main effect of environment.Key words: Avena sativa, hull percentage, bulked segregant analysis, quantitative trait locus.
Mode of shear effects on yield and liquefied strength ratios
Authors: Olson Scott M. , Mattson Benjamin B.
Published: May 2008

A database of 386 laboratory triaxial compression, direct simple shear, rotational shear, and triaxial extension test results was collected to examine yield and liquefied strength ratio concepts used in liquefaction analysis of sloping ground. These data envelope the yield and liquefied strength ratios obtained from back-analyses of liquefaction flow failure case histories. Generally, triaxial compression exhibits the highest yield and liquefied strength ratios, triaxial extension yields the lowest ratios, and direct simple shear – rotational shear shows intermediate responses. However, mode of shear appears to have a considerably smaller effect on laboratory-measured liquefied strength ratios for specimens with a positive state parameter (i.e., difference in consolidation void ratio and steady state void ratio at the same effective stress).
Equations for the entire soil-water characteristic curve of a volume change soil
Authors: Pham Hung Q. , Fredlund Delwyn G.
Published: May 2008

Numerous curve-fitting equations have been proposed for soil-water characteristic curves. While these equations have been of considerable value in geotechnical and geoenvironmental engineering, the equations are not able to adequately fit gravimetric soil-water characteristic curve data over the entire range of soil suction for a soil that changes volume when suction is changed. Two new equations for the soil-water characteristic curve are presented in this paper. One equation has curve-fitting parameters that bear a meaningful relationship to conventional physical soil properties (e.g., air-entry value and residual soil suction), but the equation is somewhat complex. The equation is particularly useful for sensitivity type studies when undertaking computer modeling. The other equation is relatively simple to use and is developed as a conventional curve-fitting equation. The two equations are used to best-fit several soil datasets. Both equations perform well and can be used in research and engineering practice to define the gravimetric water content versus soil suction relationship for a soil exhibiting volume change.
Sand–rubber mixtures: Experiments and numerical simulations
Authors: Valdes Julio R. , Evans T. Matthew
Published: May 2008

This paper documents the results of laboratory experiments and numerical simulations conducted to examine the behavior of mixtures composed of rubber and sand particles of similar size. Emphasis was placed on assessing the role of loading type on the load-deformation behavior and selecting appropriate parameters for the discrete element modeling of sand–rubber, with relevance to the use of compressible particulate systems for filtration control. Experimental results show that sand–rubber exhibits load–unload hysteresis and residual strains post-unloading due to particle–particle and particle–wall locking effects that arise from sidewall friction. It is shown that the discrete element modeling of sand–rubber requires unconventional schemes because of the stiffness contrast between sand grains and rubber grains. The results have implications in the design of compressible particulate systems for seepage and filtration control and in the development of prediction tools for the field performance soil–rubber, which is finding increased usage in geotechnical and civil engineering infrastructures.
Deformation Characteristics of Granular Materials Under Hydrostatic Compression
Authors: El-Sohby M. A. , Andrawes K. Z.
Published: May 2008

The deformation characteristics of sand and other granular materials under hydrostatic compression are studied in the conventional triaxial apparatus using 4 × 4 in. (10 × 10 cm) specimens. Modifications have been made for measuring small axial strains and free end platens were used. The errors in testing have been estimated and their effect was evaluated. Different kinds of granular materials were tested to study the effect of the physical properties of the material on its deformational behavior.The results showed that the total deformation of a mass of sand subjected to a hydrostatic compression is generally not recoverable, and can be divided into elastic (recoverable) and sliding (irrecoverable) components. It has also been found out that for a dense specimen of sand most of the total deformation is recoverable, since the sliding component of deformation represents only a small fraction of the total deformation. The results also showed that for the very dense specimen axial and radial strains were nearly equal which implies that the material behaves isotropically. On the other hand for a loose specimen the sliding component of deformation becomes large and thus the total deformation of the specimen cannot be considered completely elastic. Furthermore axial and radial strains of the loose specimen were not equal.
Duisburg Harbour Lowered by Controlled Coal Mining
Authors: Legget R. F.
Published: May 2008

Duisburg on the Rhine, at the heart of the Ruhr, one of Europe's greatest industrial areas, is the world's largest inland port. Located at the junction of the Rhine and Ruhr Rivers, its harbour includes twenty major docks with a total of 45 km of wharves over which more than 45 million tons of cargo are handled each year.Starting in the middle of the nineteenth century, the course of the Rhine has been improved by straightening, cleaning, and dredging. A serious drop in upstream water levels has been the inevitable result, 2 m at Duisburg since 1900, with the prospect of a similar drop by the end of this century.Geological strata beneath the harbour area include three valuable coal seams, mining of which had been prohibited for centuries. After careful study it was decided to extract most of this coal by controlled mining, in this way securing settlement of the whole harbour area to counterbalance the drop in river level. Mining was started in 1956; by 1968, when work had to stop, most of the harbour had been lowered as much as 1.5 m, with no interference with its normal operation.
Device for Cutting Varved Soil Samples
Authors: Chan H. T.
Published: May 2008

A device was designed and manufactured for cutting a 4.5-in. (11.4-cm) diameter varved soil sample into a 2.5-in. (6.4-cm) cubical sample for directional permeability measurements. The chief requirement was to produce cut surfaces in a layered soil which were unsmeared and untorn. The design was based on three requirements: (1) confinements of the soil during the cutting process, (2) movement of the cutting wire in the direction parallel to the soil layers and (3) small longitudinal vibratory movements of the cutting wire.
Bearing Capacity of Strip Footings in Two Layered Cohesive-friction Soils
Authors: Purushothamaraj P. , Ramiah B. K. , Rao K. N. Venkatakrishna
Published: May 2008

A method has been formulated for bearing capacity of footings on two layered soils with varying cohesion, friction, and unit weight based on the second theorem of Drucker and Prager (kinematical consideration). The failure mechanism considered was fundamentally similar to that of Prandtl–Terzaghi but with different wedge angles. The critical wedge angles were found in each case. Bearing capacity charts for footings are presented by varying cohesion in layers, with the same friction angle and unit weight. The charts are readily usable for any combination of c2/c1, d/b, φ, and γ.
The Analysis of Two Slope Failures in Cemented Champlain Clays
Authors: Lefebvre G. , Rochelle P. La
Published: May 2008

Detailed investigations have been made on the sites of two landslides which occurred in the sensitive Champlain clay deposits of the Saint-Laurent Lowlands. Laboratory tests made on specimens cut from block samples have led to a better understanding and evaluation of the brittle behavior of these cemented clays. The results have shown that very little strain is required for the strength to decrease from a well defined peak value to a residual value; this brittle behavior is evident only when tests are made at sufficiently low stress level such that the cementation bonds are preserved during consolidation.The analyses of the slides have shown that the use of the peak strength parameters led to a gross overestimate of the factors of safety; the residual strength parameters, however, give a fairly accurate assessment of the stability, the calculated factors of safety being close to unity. That behavior may be explained by the fact that the cemented clay is extremely brittle and, like any other strain softening material, is subjected to the mechanism of progressive failure. This study leads to a very efficient practical approach to the analysis of the stability of natural slopes.
Failure of a Test Embankment On a Sensitive Champlain Clay Deposit
Authors: Rochelle P. La , Trak B. , Tavenas F. , Roy M.
Published: May 2008

The present paper reports on the failure of a test embankment built on a soft, sensitive, and cemented clay in Saint-Alban, Quebec. The embankment was built as a first stage of a research program aimed at studying the short and long term behavior of embankments on soft clay foundations.A complete description of the embankment, of the instrumentation, and of the failure is given, followed by the analysis of the failure performed on the basis of different assumptions of fill behavior and of vane strength values mobilized in the clay crust. The analyses show that the assumptions of full mobilization of friction in the fill seems to be the most representative of the fill behavior in the present case and that a suitable factor of safety is obtained only when a reduction of vane strength is assumed to act in the crust.A new approach based on the residual undrained strength is suggested and seems to offer some potential as a valuable means of analyzing the stability of embankments on clay foundations.
Numerical studies of soil–structure interaction using a simple interface model
Authors: Griffiths D. V.
Published: May 2008

The effect of interface roughness in problems of soil–structure interaction is demonstrated using a simple finite element interface model. Three examples of geotechnical interest are presented to demonstrate the approach, and comparisons are made with closed-form solutions where available. Both rough and smooth extremes of interface behaviour are analysed. The smooth interface modelling is performed without the use of specialized elements, and involves uncoupling and rotation of freedoms parallel to the proposed interface direction. It is suggested that, in view of the uncertainties often associated with interface properties, a rational approach for engineering purposes is to obtain solutions for the perfectly rough and perfectly smooth cases leading to upper and lower bounds on the full range of interface behaviour. Key words: finite elements, interfaces, soil–structure interaction, foundations, lateral loads, culverts, piles.
Numerical analysis of temperature field in a thawing embankment in permafrost
Authors: Shen Mu
Published: May 2008

The objective of this paper is to present a numerical analysis by finite elements of a two-dimensional nonlinear mathematical model for heat conduction with phase change in a thawing embankment in permafrost. The calculated results are compared with actual measured data, and good agreement is obtained. All calculations were carried out on a personal computer. Key words: permafrost, thawing, embankment, temperature field, numerical analysis.
Till behavior and its relationship to active-layer hydrology, District of Keewatin, Northwest Territories
Authors: Dyke Larry , Egginton Paul
Published: May 2008

Well-graded tills are a common surficial material over much of the Canadian Arctic from northern Manitoba to Somerset Island. The compactibility and bearing strength of these tills when thawed appear to be controlled by groundwater flow in the active layer. Water seeping from bedrock outcrops flanked by till enters the till active layer and flows via macropores formed as ice lenses thaw. This flow appears to retard consolidation of the till. Slopes having no seepage source consolidate more rapidly. This seepage maintains the till in a state highly susceptible to liquefaction and would yield material with a moisture–density condition unsuitable for construction use. Key words: till, surficial, compactibility, bearing capacity, groundwater, seepage, freeze–thaw, liquefaction.