bluuebunny/crossref_metadata_2025 huggingface dataset:
An RFLP species-specific DNA sequence for the A genome of rice
Authors: Dallas John F. , McIntyre C. Lynne , Gustafson J. Perry
Published: May 2008

A DNA sequence, pOs6.20, was cloned from the nuclear genome of cultivated rice (Oryza sativa L.) by hybridization with a human minisatellite sequence. At high hybridization stringency, a subfragment of the rice sequence, pOs6.20.3, detected low-copy restriction fragment length polymorphisms (RFLPs), which behaved as Mendelian genetic markers. This subfragment detected multicopy RFLPs between an indica and a javanica cultivar at medium hybridization stringency. The sequences detected by pOs6.20.3 at high hybridization stringency did not occur in rice species possessing the B, C, D, E, and F genomes. These results suggest that the RFLPs detected by this sequence can be placed on a genetic map of rice and that this sequence can be used as a species-specific probe for the A genome of rice.Key words: restriction fragment length polymorphisms, Oryza sativa.
Conservative genome size and rapid chromosomal evolution in the South American tuco-tucos (Rodentia: Ctenomyidae)
Authors: Ruedas Luis A. , Cook Joseph A. , Yates Terry L. , Bickham John W.
Published: May 2008

Genome size (the amount of DNA per cell) was measured by flow-cytometric analysis in seven species of a chromosomally variable rodent genus: Ctenomys boliviensis, C. conoveri, C. frater, C. leucodon, C. lewisi, C. opimus, and C. steinbachi. The mean genome size of these species was 7.19 pg DNA and little inter- and intra-specific variation was observed. Genome size was not correlated with diploid number, suggesting that chromosomal evolution at this level is independent of total DNA content. A hypothetical taxonomic unit optimization procedure was carried out using genome size change on a Wagner tree derived from allozyme data. Allozyme evolution and genome size change are linked by a weak, but significant, negative correlation suggestive of preferential genie evolution in the absence of genome size evolution.Key words: genome size, Ctenomyidae, chromosomal evolution.
Molecular cloning and expression of a cDNA encoding the proliferating cell nuclear antigen from Brassica napus (oilseed rape)
Authors: Markley Nancy-Ann , Bonham-Smith Peta C. , Moloney Maurice M.
Published: May 2008

A cDNA clone encoding the proliferating cell nuclear antigen (PCNA) has been isolated from a Brassica napus apical meristem cDNA library. The putative full-length cDNA contains an open reading frame of 1004 nucleotides, which predicts a protein of 263 amino acids (Mr = 29 231). Sequence analysis has revealed that the plant PCNA exhibits 81.6% amino acid similarity with the human PCNA. Genomic Southern blot analysis indicates the presence of at least two copies of PCNA per genome. The B. napus PCNA mRNA (1.0 kb) was expressed in rapidly dividing tissues such as flower buds, apical meristems, and young leaves, while mature stem and fully expanded leaves showed significantly lower levels of PCNA transcript. The B. napus PCNA cDNA was expressed in Escherichia coli as a fusion protein with glutathione-5-transferase (GST) in the bacterial expression vector pGEX-2T. A broad specificity monoclonal antibody raised against rabbit PCNA cross-reacted with the GST–PCNA fusion peptide but not with the GST moiety alone. This antibody also recognized the human PCNA (36 kDa) polypeptide, confirming the structural similarities between the human and plant PCNA. The high degree of structural conservation of PCNA from such diverse organisms as humans and higher plants suggests that the plant PCNA may function in a manner analogous to that found in mammals with respect to plant cell DNA replication. Such conservation suggests that PCNA is also a critical component of the plant cell DNA replication complex.Key words: proliferating cell nuclear antigen, DNA replication, DNA polymerase-δ, cell cycle regulation, Brassica napus (oilseed rape).
Geographical distribution of isozyme alleles for phosphogluconate dehydrogenase in barley
Authors: Konishi T. , Yoshimi R.
Published: May 2008

The Ak and Tj alleles at the Pgd1 locus and the Ps and Tn alleles at the Pgd2 locus were detected for phosphogluconate dehydrogenase in barley. The Ak allele at the Pgd1 locus was widely distributed around the world, while the Tj allele was found only in two accessions from Nepal and one from India. At the Pgd2 locus, the Ps allele was abundant everywhere, whereas the Tn allele was occasionally found in Caucasus, Turkey, and Europe, and scarcely or none in Korea, China, Nepal, India, and Ethiopia. The Tn allele was also detected in Japanese accessions. Among them, six-rowed varieties carrying the Tn allele were principally grown in northern parts of Japan and characterized by covered kernel, the Occidental type for nonbrittleness of rachis, and resistance to Japanese races of powdery mildew. However, the loci responsible for these characteristics were independent of the Pgd1 locus.Key words: barley, isozymes, phosphogluconate dehydrogenase, geographical distribution.
Heterochromatin heterogeneity and rapid divergence of the sex chromosomes in Chorthippus parallelus parallelus and C. p. erythropus (Orthoptera)
Authors: Bella J. L. , Serrano L. , Hewitt G. M. , Gosálvez J.
Published: May 2008

Mitotic chromosomes from individuals of a Pyrenean hybrid zone between two subspecies of the grasshopper Chorthippus parallelus have been pretreated as for C-banding and subsequently stained with 4,6-diamidino-2-phenylindole (DAPI) and (or) Chromomycin A3 (CMA). The results, which are different from those obtained with Giemsa C-banding or standard DAPI – CMA treatments show (i) hidden heterochromatic heterogeneity that may be correlated with the existence of distinct families of repetitive DNAs, (ii) information about the possible independent origin of the three detected types of heterochromatin, and (iii) a further marker difference between the sex chromosomes of these two subspecies. This last result leads us to discuss the possible differential rates of evolution of sex chromosomes and autosomes in these subspecies and provides us with a new tool for the study of the structure and dynamics of this hybrid zone.Key words: hybrid zones, Orthoptera, cytogenetics, heterochromatin, fluorescence.
A cytogenetically based physical map of chromosome 1B in common wheat
Authors: Kota R. S. , Gill K. S. , Gill B. S. , Endo T. R.
Published: May 2008

We have constructed a cytogenetically based physical map of chromosome 1B in common wheat by utilizing a total of 18 homozygous deletion stocks. It was possible to divide chromosome 1B into 17 subregions. Nineteen genetic markers are physically mapped to nine subregions of chromosome 1B. Comparison of the cytological map of chromosome 1B with an RFLP-based genetic linkage map of Triticum tauschii revealed that the linear order of the genetic markers was maintained between chromosome 1B of hexaploid wheat and 1D of T. tauschii. Striking differences were observed between the physical and genetic maps in relation to the relative distances between the genetic markers. The genetic markers clustered in the middle of the genetic map were physically located in the distal regions of both arms of chromosome 1B. It is unclear whether the increased recombination in the distal regions of chromosome 1B is due to specific regions of increased recombination or a more broadly distributed increase in recombination in the distal regions of Triticeae chromosomes.Key words: common wheat, chromosome 1B, homozygous deletion lines, physical map, RFLP markers.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. IX. Cytological behaviour, phenotypic characteristics, breeding behaviour, and fertility of primary, double, and triple trisomics
Authors: Kim N.-S. , Kuspira J.
Published: May 2008

Cytogenetic studies in Triticum monococcum (2n = 2x = 14, AA) were initiated by generating a series of primary as well as double and triple trisomics from autotriploids derived from crosses between induced autotetraploids and a diploid progenitor. Analysis of meiotic chromosome behaviour revealed that, with the exception of primary trisomics for chromosome 7A, the chromosome present in triple dose in all other trisomics formed either a bivalent plus a univalent or a trivalent (always V shaped) at diakinesis – metaphase I in approximately equal proportions. Trisomics for chromosome 7A formed a bivalent plus a univalent or a trivalent in approximately a 1:2 ratio. About 99% of the anaphase I segregations in all the trisomics were seven to one pole and eight to the other, suggesting that primary trisomics in T. monococcum form n and n + 1 meiotic products in equal proportions. The double trisomics and triple trisomics formed 5 II + 2 III and 4 II + 3 III during metaphase I, respectively. A majority of the secondary meiocytes from the double and triple trisomics possessed unbalanced chromosome numbers. All the trisomics differed phenotypically from their diploid progenitors. Single primary trisomics for chromosomes 3A and 7A produced distinct morphological features on the basis of which they could be distinguished. The phenotypes of the double and triple trisomics deviated to a greater extent from that of diploids than those of the single trisomics. Less than 50% of the progeny of all primary trisomics were trisomics themselves. Trisomic progeny were not produced in diploid female × trisomic male crosses, indicating that functional n + 1 male gametes were not generated. Diploid as well as trisomic progeny were produced in the reciprocal crosses and upon self-fertilization of the trisomics. The average frequency of trisomic progeny was 9.9%. The fertility of primary trisomics ranged from 3.8% in trisomics for chromosome 1A to 40.6% in trisomics for chromosome 2A and was significantly less than that of diploids (99.6%). The breeding behaviour and low fertility of these trisomics make their maintenance and use in cytogenetic analyses difficult.Key words: Triticum monococcum, primary trisomics, double trisomics, triple trisomics, meiotic chromosome behaviour, phenotypes, breeding behaviour, fertility.
Molecular characterization of a mouse Y chromosomal repetitive sequence amplified in distantly related species in the genus Mus
Authors: Nishioka Yutaka , Dolan Becky M. , Zahed Laila
Published: May 2008

This report describes a 1.1 kb long mouse Y chromosomal sequence designated 142-4. It has a 42% GC content and is rich in short direct and inverted repeats. 142-4 related sequences are repeated about 200 times in the Mus musculus Y chromosome and their distribution was visualized by in situ hybridization. 142-4 detected a restriction fragment length polymorphism that differentiated between the M. m. musculus type and the M. m. domesticus type Y chromosome. Southern blot analysis of DNAs isolated from a panel of mouse species showed that 142-4 related sequences were amplified in the Y chromosomes of M. minutoides, M. musculus, M. saxicola, M. spicilegus, and M. spretus but not in those of M. caroli, M. cookii, and M. pahari. These results suggest that 142-4 related sequences are evolutionary unstable and their accumulation patterns do not correlate with the known phylogenetic relationships of mouse species in the genus Mus.Key words: mouse Y chromosome, repetitive sequence, Mus, sequence amplification, Y chromosome evolution.
Phenetic relationships and levels of variability detected by restriction fragment length polymorphism and random amplified polymorphic DNA analysis of cultivated and wild accessions of Lycopersicon esculentum
Authors: Williams Christie E. , Clair Dina A. St.
Published: May 2008

Random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers were used to assess the variability in tomato germplasm (Lycopersicon esculentum Mill.), which included 46 accessions from the following groups: vintage cultivars, modern cultivars, South American regional cultivars, and wild L. esculentum van cerasiforme. Two L. cheesmanii accessions served as an outgroup. The 48 accessions were monomorphic at 135 of the 215 RAPDs loci and 31 of the 48 RFLP loci that were assayed. Alleles were identified that distinguished the five groups and many of the cultivars. The frequency of polymorphic loci was low in vintage cultivars, with less than 2.8% of the loci being variable within the group. In contrast, introgression of wild germplasm into modern cultivars has increased the polymorphic loci to 11.6%, whereas within the group of regional cultivars linkage drag and outcrossing may be responsible for the further increase to 20.3%. These levels of genetic variability were lower in comparison to the 24.5% polymorphic loci of cerasiforme, a group that may contain unutilized desirable traits. The small genetic distance from the vintage cultivars to several of the widely distributed regionals and cerasiformes indicated that proximity of vintage cultivars in Latin America may have resulted in intercrossing of these materials with the wilder germplasm. RAPDs appear promising for both germplasm fingerprinting and as a predictor of genetic diversity for plant breeding applications.Key words: tomato, restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), genetic distance.
Genome size and karyotype length in some interstitial polychaete species of the genus Ophryotrocha (Dorvilleidae)
Authors: Sella G. , Redi C. A. , Ramella L. , Soldi R. , Premoli M. C.
Published: May 2008

Interstitial polychaetes of the genus Ophryotrocha are very small, progenetic, and morphologically very similar. These worms have been widely used in evolutionary biology and sexuality studies. To have a better insight into the karyological evolution of this genus, we measured the total karyotypic length and the 2C nuclear DNA content of the nine best-known species of this genus. No interspecific differences were observed in karyotypic lengths, apart from that of O. gracilis, which was significantly greater than the karyotypic length of five of the nine species. The genome size (i.e., 1C DNA content calculated from 2C DNA content) in eight of the nine species is about 0.4 pg, irrespective of the chromosome number. A group of four gonochoric and morphologically indistinguishable species, with 2n = 6 metacentric chromosomes, appears to be heterogeneous with regard to its DNA content, because one of the species, O. macrovifera, has a genome twice the size of that of the other three species. A hermaphroditic species, O. hartmanni, has a genome three times that size. No correlation has been observed between genome size and body size, egg cell diameter, or time interval from egg fertilization to sexual maturity. The basic genome size of 0.4 pg is among the lowest recorded in invertebrates. Hypotheses about selective pressures that maintain such a low amount of nuclear DNA in this genus are discussed.Key words: genome size, meiofauna, Ophryotrocha, Polychaeta.
Occurrence of G-banding in metaphase chromosomes of Encarsia berlesei (Hymenoptera: Aphelinidae)
Authors: Odierna Gaetano , Baldanza Fulvio , Aprea Gennaro , Olmo Ettore
Published: May 2008

Well-defined G-bands were obtained on somatic metaphase chromosomes of Encarsia berlesei using trypsin and warm 2× SCC in sequence. The G-banded pattern allowed rapid identification of all five metacentric chromosomes, which appeared uniformly lighted when stained with DAPI fluorochrome dye. It is stressed that ageing affects G-banding in this insect species; in fact, good banded chromosomes were obtained on 1-month air-stored chromosomes. Evidence for asynchronous condensation on the chromosomes of this species is also provided.Key words: G-banding, chromosomes, insect, Encarsia.
The rbcL gene sequence from chestnut indicates a slow rate of evolution in the Fagaceae
Authors: Frascaria Nathalie , Maggia Laurent , Michaud Martin , Bousquet Jean
Published: May 2008

The nucleotide sequence was obtained for the chloroplast gene coding for the large subunit of the ribulose 1,5-bisphosphate carboxylase (rbcL) of chestnut (Castanea sativa Mill.), a member of the woody family Fagaceae. Amplification primers downstream and upstream the rbcL open reading frame are also described. By comparing with other angiosperm sequences, we show that the rate of evolution of rbcL in the family Fagaceae is much slower than that observed for the families of annuals analyzed.Key words: angiosperms, Castanea sativa, Fagaceae, phylogeny, rbcL.
A developmental and molecular analysis of Cdc2 mutations in Drosophila melanogaster
Authors: Clegg N. J. , Whitehead I. P. , Williams J. A. , Spiegelman G. B. , Grigliatti T. A.
Published: May 2008

In fission yeast, the product of the cdc2 gene is required both for entry into S phase and mitosis. Homologs of cdc2 have been isolated from a number of metazoans, but in general they have not been amenable to genetic analysis. Here we describe P element transposon tagging of Cdc2 in Drosophila melanogaster and the analysis of 10 Cdc2 mutants. The recessive lethality of Cdc2P is associated with a P element located in the 5′ untranslated region of the gene. Seven other alleles have unique single base pair substitutions in the coding region of Cdc2. One allele, Cdc2B47, is mutated in the splice donor site of exon 1. Most mutations in Cdc2, including the presumptive null allele Cdc2B47, die at the pupal stage, suggesting that the maternally supplied Cdc2 gene product drives earlier cell divisions. The phenotypes of our mutants are consistent with a role for Cdc2 in cell proliferation; however, we did not observe any perturbation of the endoreduplication cycle associated with the acquisition of polyteny.Key words: Cdc2, Drosophila, mutations, sequence.
Genetic diversity and phylogeny analysis of Azolla based on DNA amplification by arbitrary primers
Authors: Coppenolle Benoit Van , Watanabe Iwao , Hove Charles Van , Second Gerard , Huang Ning , McCouch Susan R.
Published: May 2008

The polymerase chain reaction was used to amplify random sequences of DNA from 25 accessions of Azolla to evaluate the usefulness of this technique for identification and phylogenetic analysis of this aquatic fern. Accessions were selected to represent all known species within the genus Azolla and to encompass the worldwide distribution of the fern. Primers of 10 nucleotides with 70% G + C content were used to generate randomly amplified polymorphic DNA from the symbiotic Azolla–Anabaena complex. Twenty-two primers were used and each primer gave 4–10 bands of different molecular weights for each accession. Bands were scored as present or absent for each accession and variation among accessions was quantified using Nei's genetic distances. A dendrogram summarizing phenetic relationships among the 25 accessions was generated using the unweighted pair-group method with arithmetic mean. Principal component analysis was also used to evaluate genetic similarities. Three distinct groups were identified: group 1 contains five species, group 2 contains the pinnata species, and group 3 contains the nilotica species. The analysis demonstrates that the major groups of Azolla species can be easily distinguished from one an other and, in addition, that closely related accessions within species can be identified. We further found that using 10 primers, a phylogeny that is essentially the same as that derived from 22 primers can be constructed. Our results suggest that total DNA extracted from the Azolla–Anabaena symbionts is useful for classification and phylogenetic studies of Azolla.Key words: Azolla–Anabaena symbiosis, genetic distances, polymerase chain reaction, principal component analysis.
An optimized fluorescence in situ hybridization procedure for detecting rye chromosomes in wheat
Authors: Nkongolo K. K. , Lapitan N. L. V. , Quick J. S. , Muhlmann M. D.
Published: May 2008

In situ hybridization with an interspersed repeat clone from rye, pSc119, was shown to be useful for detecting rye chromosomes introduced into wheat. However, since pSc119 also shows strong hybridization to a few sites in certain wheat chromosomes, small rye chromosome segments added to wheat may be difficult to detect. In this study, detection of rye chromosomes present in triticale and triticale × wheat hybrids was accomplished with the use of a subfragment from pSc119 (pSc119.1) whose sequence is dispersed throughout the rye chromosomes and only weakly cross-hybridizes to a few telomeric and centromeric regions of wheat. The in situ hybridization conditions were optimized to readily distinguish rye chromosomes from wheat chromosomes without the need for intensive analysis of hybridization patterns. Rye chromosomes were readily detected using fluorescence in situ hybridization. Fluorescence detection provided increased sensitivity over enzymatic detection and allowed signals to be amplified with repeated use of biotinylated anti-avidin antibody and avidin-FITC. Detection of rye chromatin was further optimized by doubling the probe concentration. Finally, double exposure photography of the same cell with two different filters provided another means to further increase the contrast between rye and wheat chromosomes.Key words: fluorescence in situ hybridization, rye, wheat.
Identification of the E3900 family, a second family of rye B chromosome specific repeated sequences
Authors: Blunden Richard , Wilkes Timothy J. , Forster John W. , Jimenez Mar M. , Sandery Michael J. , Karp Angela , Jones R. Neil
Published: May 2008

A second family of highly repeated sequences has been identified on the B chromosome of rye (Secale cereale). The E3900 family was detected as a variant band in EcoRI digests of +B DNA. A clone of the basic repeat of the family was obtained, and the organization of the family was investigated by genomic hybridization. The E3900 family has no apparent homology to the A chromosome sequences of rye or other members of the Gramineae. The family has been localized by in situ hybridization to the end of the long arm of the rye B chromosome. The previously characterized E1100 sequence shows in situ hybridization to the same location as the E3900 family. These results are discussed in light of current theories of the origin of B chromosomes.Key words: B chromosome, Secale cereale, repeated sequence, cloning, in situ hybridization.
The genetic and RFLP characterization of the left end of linkage group III in Caenorhabditis elegans
Authors: Pilgrim Dave
Published: May 2008

A genetic approach was taken to identify new transposable element Tc1 -dependent polymorphisms on the left end of linkage group III in the nematode Caenorhabditis elegans. The cloning of the genomic DNA surrounding the Tc1 allowed the selection of overlapping clones (from the collection being used to assemble the physical map of the C. elegans genome). A contig of approximately 600–800 kbp in the region has been identified, the genetic map of the region has been refined, and 10 new RFLPs as well as at least four previously characterized genetic loci have been positioned onto the physical map, to the resolution of a few cosmids. This analysis demonstrated the ability to combine physical and genetic mapping for the rapid analysis of large genomic regions (0.5–1 Mbp) in genetically amenable eukaryotes.Key words: Caenorhabditis elegans, genome analysis, RFLP, physical map, genetic map.
Characterization of new variants of a satellite DNA from Oryza officinalis, specific for the CC genome of wild rice
Authors: Reddy A. S. , Kiefer-Meyer M. C. , Delseny M.
Published: May 2008

Two groups of tandemly repeated DNA fragments have been isolated and cloned from the Oryza officinalis genome (W 1278). These fragments have been sequenced and are 374 and 367 bp long. They were compared with an element previously isolated from another O. officinalis accession. They are 76 and 92% homologous to the latter and show 78% homology between themselves. The two types of elements are interspersed within large blocks of tandemly organized units. Their copy number is in the range of 200 000 units. This sequence was present only in wild rice accessions with a CC genome. However, this apparent specificity is even more restricted, since it was absent from some O. officinalis accessions and from the allotetraploid species of the CCDD type. Use of digestions with 4-bp restriction enzyme cutters and analysis on denaturing polyacrylamide gels revealed polymorphism that might be used to map the repeats in the genome as well as to establish the relationship between accessions. Finally, hybridization of the repeated sequence to DNA prepared from the eight available O. sativa – O. officinalis monosomic addition lines revealed that the elements are located on two alien chromosomes. This suggests that these elements have at least some restricted chromosome specificity.Key words: satellite DNA, rice, monosomic addition lines, RFLP, evolution.
Identification of an RAPD marker for the crown rust resistance gene Pc68 in oats
Authors: Penner G. A. , Chong J. , Wight C. P. , Molnar S. J. , Fedak G.
Published: May 2008

The feasibility of using bulk segregant analysis to identify molecular markers for disease resistance genes in oats was investigated, utilizing random primers in conjunction with polymerase chain reaction technology. Random primers were screened for the amplification of polymorphic DNA fragments on two pools of genomic DNA isolated from plants that were homozygous for the presence and absence of the crown rust resistance gene Pc68. Ten primers were identified that amplified polymorphic DNA fragments. Of these, one was tightly linked, in repulsion, to the target gene, while the other nine were not linked to this trait. The relatively low cost of polymerase chain reaction technology, coupled with rapid leaf disc genomic DNA extraction techniques should result in the effective use of this linked marker in oat breeding selection programs.Key words: RAPD, molecular marker, oats Puccinia coronata, bulk segregant analysis, Pc68.
Genetic variation for waterlogging tolerance in the Triticeae and the chromosomal location of genes conferring waterlogging tolerance in Thinopyrum elongatum
Authors: Taeb M. , Koebner R. M. D. , Forster B. P.
Published: May 2008

A number of Triticeae species were tested for tiller production, shoot dry matter production, and root penetration in waterlogged soil, and Thinopyrum elongatum and Elytrigia repens were shown to have better tolerance than wheat using these criteria. Tests of a number of wheat–alien amphiploids showed that there was at least partial expression of this exotic genetic variation in a wheat genetic background. The presence of chromosomes 2E and 4E of Th. elongatum was associated with a positive effect on root growth in waterlogged conditions. The positive effect of the 4E chromosome addition was mimicked by tetrasomic lines carrying extra doses of wheat homoeologues 4B and 4D, and it was concluded that the beneficial effect contributed by the presence of 4E was probably due to an increased dosage of group 4 chromosomes. However, the positive effect of adding chromosome 2E to wheat could not be reproduced by added doses of chromosomes 2A, 2B, or 2D, suggesting that this alien chromosome carries gene(s) for tolerance not present on its wheat homoeologues. This gene(s) was further located to the long arm of chromosome 2E by testing ditelosomic addition lines.Key words: wheat, Thinopyrum elongatum, waterlogging tolerance.
Genomic constitutions of four Chinese endemic Elymus species: E. brevipes, E. yangii, E. anthosachnoides, and E. altissimus (Triticeae, Poaceae)
Authors: Lu Bao-Rong , Bothmer Roland von
Published: May 2008

The objectives of this study were to determine the genomic constitution and to explore the genomic variation within four Chinese endemic Elymus species, i.e., E. brevipes (Keng) Löve (2n = 4x = 28) and E. yangii B.R. Lu (2n = 4x = 28), E. anthosachnoides (Keng) Löve (2n = 4x = 28), and E. altissimus (Keng) Löve (2n = 4x = 28). Intraspecific crosses between different populations of the four Elymus species, as well as interspecific hybridizations among the four target species, and with six analyzer species containing well-known genomes, i.e., E. caninus (L.) L. (2n = 4x = 28, SH), E. sibiricus L. (2n = 4x = 28, SH), E. semicostatus (Lees ex Steud.) Melderis (2n = 4x = 28, SY), E. parviglumis (Keng) Löve (2n = 4x = 28, SY), E. tsukushiensis Honda (2n = 6x = 42, SHY), and E. himalayanus (Nevski) Tzvelev (2n = 6x = 42, SHY), were achieved through the aid of embryo rescue. Chromosome pairing behaviors were studied in the parental species and their hybrids. Numerical analysis on chromosome pairing was made on the interspecific hybrids. With one exception, each meiotic configuration at metaphase I in the hybrids involving the target taxa and the analyzer species containing the "SH" genomes fit a 2:1:1 model with x-values ranging between 0.91 and 1.00; chromosome pairing in the hybrids involving analyzer parents with the "SY" genomes match a 2:2 model, with x-values between 0.97 and 0.99. All pentaploid hybrids with a genomic formula "SSYYH," except for two crosses having unexpected low c-values, had pairing patterns fitting the 2:2:1 model with x-values varying between 0.96 and 1.00. It is concluded based on hybridization, fertility, and chromosome pairing data that (i) the four target Elymus species are strictly allotetraploid taxa, (ii) they are closely related species, all comprised of the "SY" genomes, (iii) minor genomic structural rearrangements have occurred within the four Elymus species, and (iv) meiotic pairing regulator(s) exists in some of the Elymus taxa studied.Key words: Triticeae, Elymus, interspecific hybrid, meiosis, numerical analysis, genome.
The mechanism and inheritance of adult plant leaf rust resistance in 12 wheat lines
Authors: Knott D. R. , Yadav B.
Published: May 2008

Twelve lines of wheat (Triticum aestivum L.) were developed that had susceptible infection types to leaf rust (Puccinia recondita Rob. ex Desm. f.sp. tritici) race UN 15 in the seedling stage but were resistant in the adult plant stage in the field. The lines were developed from four crosses, each involving four parents (eight in total) that had originally been selected for adult plant or field resistance to stem rust (Puccinia graminis Pers. f.sp. tritici Eriks, and Henn.). The objectives of the present study were to determine the mechanism of resistance to leaf rust and its inheritance in the 12 lines. The 12 lines were grown in an artificially inoculated field nursery in Saskatoon, coefficients of infection (CI) were determined at four dates, and the areas under the disease progress curve (AUDPC) were calculated. Four representative lines were grown in a growth chamber to measure the latent period and pustule size at the two-leaf and flag-leaf stages. Eight lines were crossed and backcrossed to a susceptible check and the parents, F1, F2, F3, and BC1F2 generations were grown in a field nursery. The 12 lines showed wide ranges in CI and AUDPC but all were significantly more resistant than the susceptible check. The four lines studied in the growth chamber had longer latent periods and smaller pustules than the susceptible check at both stages. The differences tended to be greater at the flag-leaf stage. The inheritance studied showed that resistance was recessive or partially recessive and was controlled by two or more genes in each line of the eight lines. In three of the eight lines, Lr34 may be one of the genes and in the other five both Lr13 and Lr34 could be present. However, additional genes are clearly involved. A single gene by itself had only a small effect, but in two and three gene combinations the effects appeared to be greater. This type of resistance appears to occur frequently and may be durable because its complex inheritance may make it more difficult for the rust fungus to overcome. It should be used in breeding wheat for areas where leaf rust is a major problem.Key words: wheat, adult plant rust resistance.
Molecular characterization and cytonuclear disequilibria of two Drosophila subobscura mitochondrial haplotypes
Authors: Moya Andrés , Barrio Eladio , Martínez David , Latorre Amparo , González-Candelas Fernando , Ramón Misericordia , Castro José A.
Published: May 2008

According to restriction site analyses of mitochondrial DNA, Drosophila subobscura shows a polymorphism that consists of two frequent haplotypes that are evenly distributed all over the Old World and several rare haplotypes never present in more than one locality. To ascertain the causes responsible for such distribution, three different mtDNA fragments from haplotypes I and II sampled in a population from Zürich have been partially sequenced. Only three silent nucleotide changes have been detected in the ND5 gene. One of them implies the loss of the HaeIII restriction site, which differentiates haplotype I from haplotype II. On the basis of these results as well as on others involving the geographic distribution of haplotypes I and II, they can be considered phenotypically equivalent. The sequencing study has been complemented with the analysis of cytonuclear disequilibria between mitochondrial haplotypes and different nuclear loci in four D. subobscura populations. As expected, no significant cytonuclear disequilibria have been found between haplotypes I and II. Moreover, when haplotypes I and II were pooled and compared with the rare, endemic haplotypes similar results were obtained.Key words: mitochondrial DNA, allozymes, selection, neutrality, cytonuclear disequilibria.
Interspecific hybridizations in the Elymus semicostatus group (Poaceae)
Authors: Salomon Björn
Published: May 2008

Meiotic pairing in 16 interspecific hybrids in the genus Elymus is reported. The hybrids were made among seven species in the Elymus semicostatus group, viz., E. semicostatus, E. validus (subgroup I), E. abolinii (subgroup II), E. fedtschenkoi, E. nevskii, E. praeruptus (subgroup III), and E. panormitanus (subgroup IV). All species are tetraploid (2n = 4x = 28) and possess the SY genomes. Meiotic pairing was distinctly higher in hybrids made within subgroups than between subgroups, but the genomes in E. panormitanus have differentiated from those in the other species. These results generally support the subdivision of the E. semicostatus group based on morphological data but also indicate that the subgroups are more distantly related than previously believed, and that the group may be nonmonophyletic.Key words: meiotic pairing, interspecific hybridization, relationships, Triticeae, Poaceae.
Variation among alfalfa somaclones in copy number of repeated DNA sequences
Authors: Kidwell K. K. , Osborn T. C.
Published: May 2008

Repeated DNA sequences of alfalfa (Medicago sativa L.) somaclonal variants were analyzed to determine if changes in copy number had occurred during tissue culture. DNA clones containing highly repeated nuclear sequences from the diploid line HG2 (2x = 16) were slot blotted and probed with labeled DNAs from HG2 and several somaclones of HG2. Two DNA clones that differed visually in hybridization intensity among the plant DNAs and one clone that had constant hybridization intensity were selected and used as probes on Southern blots and slot blots containing equal quantities of DNAs from HG2 and 15 régénérants. Statistically significant differences were detected in the copy number of two anonymous DNA sequences initially selected as variable and in the copy number of sequences homologous to pea ribosomal DNA. Based on Southern blot analysis, these sequences appeared to be arranged as tandem repeats. The cloned sequence initially selected as stable did not vary significantly in copy number and it appeared to be arranged as a dispersed repeat. Both increases and decreases in copy number of repeated sequences were observed in plants from successive regeneration cycles. Results from this study indicate that specific repeated nuclear DNA sequences have changed copy number in plants regenerated from tissue culture.Key words: somaclonal variation, repeated DNA, slot blot, quantitative variation.
Chromosomal localization of intergenomic RFLP loci in hexaploid wheat
Authors: Devey Michael E. , Hart Gary E.
Published: May 2008

Hybridization of radiolabeled wheat DNA probes to genomic DNA digests of compensating nullisomic-tetrasomic lines and ditelosomic lines of hexaploid wheat (Triticum aestivum L. cv. Chinese Spring) can be used to identify intergenomic RFLPs. Sixty-three PstI/BamHI genomic DNA probes and eight cDNA probes were used to determine the chromosomal locations of 223 DNA fragments that define a minimum of 189 RFLP loci. Eighty-four percent of the genomic DNA clones hybridize to fragments located in homoeologous chromosomes and 16% hybridize to fragments located in one chromosome only or to fragments located in nonhomoeologous chromosomes. All of the cDNA probes hybridize to fragments located in homoeologous chromosomes.Key words: aneuploids, genetic mapping.
The adenosine2 gene of Drosophila melanogaster encodes a formylglycineamide ribotide amidotransferase
Authors: Tiong S. Y. K. , Nash D.
Published: May 2008

Drosophila melanogaster genomic DNA spanning an adenosine2 gene rearrangement breakpoint (in cytological map region 26B1-2) was cloned and a composite ade2 base sequence was derived from this DNA and from a corresponding cDNA. Based on genetic evidence, the ade2 gene is thought to encode the purine biosynthetic enzyme formylglycineamide ribotide amidotransferase (FGARAT). The cDNA hybridizes to a 4.8-kb message that encodes a 1354 amino acid polypeptide with extensive similarity to Escherichia coli FGARAT. The D. melanogaster FGARAT amino acid sequence is considerably more like that of the E. coli enzyme than is the FGARAT of B. subtilis, which has two polypeptides with, collectively, 969 amino acids. It is suggested that the taxonomically anomalous similarity between the eukaryotic FGARAT and that from E. coli may indicate horizontal exchange of genetic material. On the basis of substantially greater conservation of sequences snared by all three species compared with those present only in E. coli and D. melanogaster, we suggest that no radical alteration of enzymatic function accompanied the transition between the single-gene and the two-gene state.Key words: Drosophila melanogaster, purine biosynthesis genes, formylglycineamide ribotide amidotransferase, formylglycineamidine ribotide synthase, adenosine2 locus, horizontal gene transfer.
Expression of an amylase - alcohol dehydrogenase chimeric gene in transgenic strains of Drosophila melanogaster
Authors: Grunder Allan A. , Loverre-Chyurlia Ada , Hickey Donal A.
Published: May 2008

A chimeric gene, consisting of 428 bp of the promoter sequences of the α-amylase gene of Drosophila melanogaster, fused to the transcribed region of the alcohol dehydrogenase (Adh) gene, was introduced into the genome of an Adhnull stock of Drosophila via P element mediated transformation. DNA analysis (Southern blotting) of three transformant strains confirmed the insertion of either one or two copies of the chimeric gene per strain. A histochemical study of ADH enzyme activity in dissected tissues of the transgenic larvae revealed that the chimeric Amy–Adh gene was expressed only in the posterior larval midgut and that this expression was repressed by dietary glucose, thus representing an expression pattern characteristic of the Amy gene. This indicates that the Amy upstream promoter sequences contain signals mediating both tissue specificity and glucose repression of the Adh structural gene in the transgenic larvae. The level of ADH activity expressed in transgenic flies was relatively low. This was paralleled by a low level of Adh mRNA, indicating a reduction in the transcriptional rate of the chimeric gene.Key words: Drosophila, germline transformation, chimeric gene, cis-regulatory sequences, α-amylase, alcohol dehydrogenase, tissue-specific expression, glucose repression, mRNA levels.
Characterization of the hexaploid oat Avena byzantina cv. Kanota monosomic series using C-banding and RFLPs
Authors: Jellen E. N. , Rooney W. L. , Phillips R. L. , Rines H. W.
Published: May 2008

The establishment of a C-banded karyotype of hexaploid oat (Avena spp., 2n = 6x = 42) has facilitated the cytological characterization of a monosomic series in 'Kanota', an A. byzantina (C. Koch) cultivar. The 'Kanota' series of monosomics analyzed in this study consists of only 12 of the 21 different chromosome-deficient lines possible plus potential translocated segments of two or three additional chromosomes. These findings were confirmed by RFLP mapping data from studies in which oat probes were assigned to syntenic groups using the 'Kanota' set of monosomic lines. Among the remaining nine monosomic lines analyzed, eight are missing chromosomes represented in the set of 12 unique lines and one line, monosomic K13, is missing a chromosome from the unique set of 12 that possesses a cytologically detectable translocation. This same translocation, involving chromosomes 7C and 14, is found in 5 of the 21 'Kanota' monosomics. The incompleteness of the set of 'Kanota' monosomics might be due to (i) difficulty in identifying individual oat chromosomes without C-banding, (ii) plant genotypic and phenotypic variability in the original source population of the 'Kanota' monosomics, and (or) (iii) a high frequency of monosomic shifts in progency of the original 'Kanota' monosomic lines.Key words: oats, C-banding, RFLPs, image analysis, aneuploids.
Genetic relatedness among rabbiteye blueberry (Vaccinium ashei) cultivars determined by DNA amplification using single primers of arbitrary sequence
Authors: Aruna Myneni , Ozias-Akins Peggy , Austin Max E. , Kochert Gary
Published: May 2008

Most improved cultivars of commercially important hexaploid rabbiteye blueberry were developed from only four native selections collected from the wild; thus, many cultivars are closely related by lineage. The consanguinity among major cultivars is a potential problem, as the rabbiteye blueberries are highly self-incompatible natural outcrossers with potential inbreeding depression. We investigated the extent of genetic relatedness among 15 improved cultivars and four wild selections by the technique of random amplified polymorphic DNA, also referred to as arbitrarily primed polymerase chain reaction. Single decanucleotides of arbitrary sequence revealed polymorphism among cultivars and wild selections. Genetic distances were estimated based on the amount of band sharing. Cluster analysis of genetic distance estimates tended to group siblings with each other and with one or both parents. The average genetic distance between improved cultivars decreased relative to the four wild parental selections, which might indicate progression towards inbreeding. The significance of increased genetic relatedness among the improved cultivars of rabbiteye blueberry and the application of molecular methods in breeding and commercial cultivation is discussed.Key words: genetic distance, polymerase chain reaction, inbreeding.
Characterization of minisatellite sequences from Oryza sativa
Authors: Winberg B. C. , Zhou Z. , Dallas J. F. , McIntyre C. L. , Gustafson J. P.
Published: May 2008

Two DNA sequences were cloned from the genome of cultivated rice (Oryza sativa L.) by cross-hybridization with the human minisatellite sequence 33.6. The rice sequences consisted of tandem direct repeats, which showed significant similarity to the 33.6 concensus sequence. Profiles capable of distinguishing different rice cultivars were detected by cross-hybridization with a DNA probe amplified by the polymerase chain reaction from one of the rice minisatellite sequences.Key words: Oryza sativa, minisatellite, hypervariable, DNA fingerprint.
Aberrant microspore development in hybrids of maize × Tripsacum dactyloides
Authors: Kindiger Bryan
Published: May 2008

Cytogenetic investigations of meiosis in hybrids between maize and Tripsacum have been well documented; however, the inherent problem of male and female sterility has not been addressed either on a genetic or cytogenetic level. The purpose of this cytological study was to identify some of the probable causes of male sterility in maize × Tripsacum dactyloides hybrids. Disturbances in pollen development of maize × T. dactyloides hybrids, derived from both diploid (2n) and tetraploid (4n) Tripsacum sources, were commonly observed. Anomalies in the development of the microspore apparently occurred because of a failure of the chromosomes to congregate at the metaphase plate, development of a tripolar spindle, and failure of cytokinesis at the first and second meiotic divisions. Phenotypic features of abnormal microspore development were the maturation of large pollen grains, "Siamese" pollen grains, the occurrence of variable invaginations, and a nuclear budding-type behavior. These abnormalities were not observed in the 56-chromosome amphidiploid or the 38-chromosome backcross generations.Key words: maize, Tripsacum, microspore, sterility.
Banding of rye (Secale cereale) chromosomes using the restriction enzymes AluI, DraI, HpaII, and MspI
Authors: Stößer T. , Günther T. , Hesemann C. U.
Published: May 2008

Mitotic metaphase chromosomes of the rye inbred line L 301, which belongs to the Sortiment of the University of Hohenheim, were treated in situ with the restriction enzymes AluI (recognition sequence: 5′-AC/GT-3′), DraI (recognition sequence: 5′-TTT/AAA-3′), and the isoschizomeres HpaII and MspI (recognition sequence: 5′-C/CGG-3′) and stained with Giemsa. The chromosomes indicated similar banding patterns in comparison with the conventional Giemsa-C-banding. However, we have found in rye chromosomes after restrictase treatment that the telomeric bands were reduced in extension. In a lower degree the centromeric bands of individual chromosomes could be absent in dependence of the used restriction enzymes. The number of the intercalary bands were also reduced. Nevertheless, the tested restriction enzymes produced characteristic banding patterns of the rye genome. This uncomplicated banding technique is suited for a very quick banding method of karyotype analysis especially to obtain a first survey of the band patterns on the rye chromosomes.Key words: Secale cereale L., chromosome band pattern, in situ digestion, restriction endonuclease, restriction banding.
Identification of a homeologous chromosome pair by in situ DNA hybridization to ribosomal RNA loci in meiotic chromosomes of cotton (Gossypium hirsutum)
Authors: Crane Charles F. , Price H. James , Stelly David M. , Czeschin Jr. Don G. , McKnight Thomas D.
Published: May 2008

In situ DNA hybridization with 18S–28S and 5S ribosomal DNA probes was used to map 18S–28S nucleolar organizers and tandem 5S repeats to meiotic chromosomes of cotton (Gossypium hirsutum L.). Mapping was performed by correlating hybridization sites to particular positions in translocation quadrivalents. Arm assignment required translocation quadrivalents with at least one interstitial chiasma and sufficient distance between the hybridization site and the centromere. We had previously localized a major 18S–28S site to the short arm of chromosome 9; here we mapped two additional major 18S–28S sites to the short arm of chromosome 16 and the left arm of chromosome 23. We also identified and mapped a minor 18S–28S site to the short arm of chromosome 7. Two 5S sites of unequal size were identified, the larger one near the centromere of chromosome 9 and the smaller one near the centromere of chromosome 23. Synteny of 5S and 18S–28S sites indicated homeology of chromosomes 9 and 23, while positions of the other two 18S–28S sites supplement genetic evidence that chromosomes 7 and 16 are homeologous.Key words: in situ hybridization, physical mapping, ribosomal DNA loci, Gossypium hirsutum.