bluuebunny/crossref_metadata_2025 huggingface dataset:
A genetic map for Brassica oleracea based on RFLP markers detected with expressed DNA sequences and mapping of resistance genes to race 2 of Plasmodiophora brassicae (Woronin)
Authors: Landry Benoit S. , Hubert Nathalie , Crete René , Chang Morgan S. , Lincoln Steven E. , Etoh Takeomi
Published: April 2011

F2 segregation analyses of DNA restriction fragment length polymorphisms (RFLPs) detected between a cabbage line (No. 86-16-5) resistant to race 2 of Plasmodiophora brassicae (Woronin), the fungus responsible for clubroot disease, and a rapid cycling line (CrGC No. 85) was used to construct a detailed genetic map of Brassica oleracea. RFLP markers were random and seedling-specific cDNA clones. The 201 loci so far mapped in B. oleracea covered 1112 cM. They are assembled into nine major linkage groups and four small linkage groups. Twelve loci were found unlinked to any other markers. Twenty-one loci were detected with the 18 seedling-specific cDNAs. Two dominant QTLs for resistance to race 2 of the clubroot disease causal agent were also identified. Leaf morphology and biennial flowering appeared to segregate as single Mendelian traits, but only leaf morphology could be linked to other markers. This RFLP study in B. oleracea is providing additional information on genome organization and complements current RFLP mapping effort in B. napus.Key words: genetic mapping, Brassica oleracea, Plasmodiophora brassicae, breeding, clubroot resistance, DNA markers, RFLP.
Identification of Hordeum bulbosum chromosomes in H. vulgare – H. bulbosum substitutions using isozyme markers
Authors: Thiele V. , Pickering R. A. , Melz G. , Pohler W.
Published: April 2011

Hordeum bulbosum chromosomes 1Hb, 4Hb, 6Hb, and 7Hb were identified in five monosomic and one double monosomic H. vulgare – H. bulbosum substitution using 11 isozyme systems. In all substitutions analyzed, diagnostic isozyme bands for H. bulbosum chromosomes were found in the same isozyme systems and zones having diagnostic value for the homoeologous H. vulgare chromosomes. However, bands that are normally diagnostic for the 3Hv region appeared in one 6Hv substitution and in one selfed progeny from another 6Hv substitution.Key words: Hordeum vulgare, Hordeum bulbosum, alien chromosome substitutions, isozymes, chromosome identification, homoeologous relationships.
Genetic variation between strains of the Mediterranean fruit fly, Ceratitis capitata, detected by DNA fingerprinting
Authors: Haymer David S. , Mcinnis Donald O. , Arcangeli Loretta
Published: April 2011

DNA fingerprinting has been used to detect genetic variation in the Mediterranean fruit fly, Ceratitis capitata. Three different probes have been identified that can be used to detect DNA restriction fragment length polymorphisms between strains of this species. The strains used in this study differ only in terms of their geographic origin or genetic background. One of the probes used is the bacteriophage vector M13, and the other two are repetitive sequences derived from the medfly genome based on a weak homology to M13. Within a strain, each probe produces a consistent restriction fragment profile that is not affected by the method or timing of DNA extraction. Between strains, when M13 is used as a probe, an average of 10% of the observable bands are polymorphic. Use of the medfly genomic sequences as a probe increases the proportion of polymorphic bands between strains up to 30%. The fact that genetic differences between even such closely related strains can be reliably detected by this method holds great promise for studies of insect pests including the ability to monitor the movements of pest species, determining the extent of genetic variation in pest populations, and in making identifications from otherwise unidentifiable material.Key words: genetic variation, Ceratitis capitata, DNA fingerprinting.
Chromosome segregation from cell hybrids. VII. Reverse segregation from karyoplast hybrids suggests control by cytoplasmic factors
Authors: Marshall Graves Jennifer A. , Barbieri Iole
Published: April 2011

Using human and Chinese hamster established lines as cell parents, we constructed hamster–human cell hybrids and human cell – hamster karyoplast hybrids. The cell hybrids retained one or two sets of hamster chromosomes and lost most of the human chromosomes. The karyoplast hybrids, however, retained a full set of human chromosomes and lost most of the Chinese hamster chromosomes. This reverse segregation pattern implies that cytoplasmic factors are major determinants of the direction of chromosome segregation.Key words: cell hybrids, chromosome loss, cytoplasmic factors, reverse segregation.
New intergeneric diploid hybrids among Agropyron, Thinopyrum, Pseudoroegneria, Psathyrostachys, Hordeum, and Secale
Authors: Wang Richard R.-C.
Published: April 2011

Eight diploid intergeneric hybrids representing six genomic combinations were synthesized and meiotically analyzed. The SN hybrids of Pseudoroegneria spicata and P. spicata spp. inermis with Psathyrostachys juncea resembled the Pseudoroegneria species in that the spikes had a single spikelet per node. The spikes of all other hybrids were intermediate to those of their respective parents. The mean meiotic pairing pattern for two SN hybrids was 9.90 I + 1.74 rod II + 0.16 ring II + 0.07 III + 0.02 IV, which was equivalent to a mean arm-pairing frequency (c) of 0.16. When the results were averaged with a previously reported hybrid, the mean pairing in two hybrid plants of P. spicata × Thinopyrum bessarabicum (SJ genome combination) was 4.79 I + 3.24 rod II + 0.91 ring II + 0.18 III + 0.09 IV and c = 0.41. Of the JeS hybrids, mean pairing was 8.40 I + 2.30 rod II + 0.25 ring II + 0.13 III + 0.03 IV (c = 0.28) for T. elongatum × P. spicata and 6.98 I + 2.90 rod II + 0.39 ring II + 0.12 III + 0.02 IV (c = 0.28) for T. elongatum × P. spicata ssp. inermis. The JP hybrid of T. bessarabicum × Agropyron cristatum had 8.99 I + 2.11 rod II + 0.14 ring II + 0.13 III + 0.03 IV and c = 0.20. Pairing was lower in the new PH hybrids A. mongolicum × Hordeum californicum and HR hybrids H. californicum × Secale montanum: 12.20 I + 0.82 rod II + 0.05 III (c = 0.06) and 13.04 I + 0.44 rod II + 0.01 III (c = 0.03), respectively. These data contribute to the elucidation of the genomic relationships among diploid species of the perennial Triticeae.Key words: hybrid, genome, chromosome pairing, Triticeae.
Linkage of stem rust resistance gene Sr33 and the gliadin (Gli-D1) locus on chromosome 1DS in wheat
Authors: Czarnecki E. M. , Lukow O. M.
Published: April 2011

A gene for stem rust resistance, Sr33, backcrossed into 'Columbus' wheat was linked with the gliadin locus on chromosome 1DS with a recombination value of 9.0 ± 3.2%. No major quality differences were apparent in the comparison of the two gliadin alleles associated with Sr33.Key words: linkage, Sr33, gliadin alleles, quality.
Polymerase chain reaction based mapping of rye involving repeated DNA sequences
Authors: Rogowsky Peter M. , Shepherd Ken W. , Langridge Peter
Published: April 2011

A novel type of polymerase chain reaction (PCR) marker was developed for the mapping of cereal rye (Secale cereale). Primer pairs were synthesized targeting the insertion sites of three individual copies of the R173 family of rye specific repeated DNA sequences. While one primer was derived from a sequence within the respective R173 element, the second primer corresponded to a flanking region. The complex banding patterns obtained in rye allowed not only the mapping of the three R173 elements to certain chromosome regions of 1RS (the short arm of rye chromosome 1) but also the mapping of an additional 3–10 easily identifiable bands per primer pair to other rye chromosomes. Linkage mapping of a polymorphic 1R band derived from three rye cultivars demonstrated the presence of nonallelic, dominant markers in two independent crosses. Because of the high copy number of the R173 family (15 000 copies per diploid rye genome), its dispersion over the entire length of all chromosomes and the high number of markers obtained per primer pair, PCR markers based on the R173 family provide an almost unlimited source for well-spaced markers in rye mapping.Key words: polymerase chain reaction, mapping, repetitive DNA sequences, wheat, rye.
Influence of DNA methylation on rye B-chromosome nondisjunction
Authors: Neves N. , Barāo A. , Castilho A. , Silva M. , Morais L. , Carvalho V. , Viegas W. , Jones R. N.
Published: April 2011

Regulation of nondisjunction of the rye B chromosome was investigated using the cytidine analog 5-azacytidine, which affects DNA methylation. The B chromosome of rye normally undergoes nondisjunction at first pollen grain mitosis and is stable at all other mitotic nuclear divisions. Observations on mitosis in the control root cells showed normal chromosome behaviour, whereas the treated roots were characterized by a high frequency of anaphases with lagging chromosomes showing evidence of failure of chromatid separation. The occurrence of nondisjunction was confirmed by the presence of variable numbers of B chromosomes between cells within roots, whereas the A-chromosome number remained constant. These results suggest that the epigenetic process by which somatic cells maintain the inactivity of the gene(s) responsible for B chromosome nondisjunction, between fertilization and meiosis, is mediated through DNA methylation.Key words: B chromosome, DNA methylation, meiotic reprogramming, 5-azacytidine, rye.
Ribosomal DNA studies in poplars: Populus deltoides, P. nigra, P. trichocarpa, P. maximowiczii, and P. alba
Authors: Faivre-Rampant P. , Jeandroz S. , Lefevre F. , Lemoine M. , Villar M. , Berville A.
Published: April 2011

The nuclear rDNA physical maps of Populus nigra, P. deltoides, P. trichocarpa, P. maximowiczii, and P. alba have been built up for the restriction enzymes EcoRI, EcoRV, BamHI, PstI, and SacI. There is no HindIII site. A large variability appeared between the species in the intergenic spacer mainly for EcoRI and PstI. For several clones of each species two to three major unit types coexist in the genome, while several minor units as well as length variant units or new unit types have been found. The variability between the species is due to different major unit types, while the variability between clones in one species is due to the minor unit types. Every species carries several rDNA unit types either different in size (variable length unit) or variable in restriction sites (variable unit types). Four thousands copies of rDNA units were found in P. nigra, P. deltoides, and P. maximowiczii. The clones belonging to the same species carry the same major unit types but are different in their minor variable length units or minor unit types. The hybrid clones carry the sum of the major unit types of the two parental species. These facts suggested the existence of three rDNA loci. The combination of one enzyme EcoRI and one probe (flax entire rDNA unit) allowed to easily recognize each of the five species. Conversely, we detected the presence of rDNA fragments characteristic to P. deltoides in some clones belonging to P. nigra. We conclude that these clones are likely to have a hybridization in their stands but without observable phenotypic consequences. This technique will be used to verify the purity of each P. nigra candidate clone before exploiting it in a breeding or propagation program.Key words: Populus, nuclear rDNA, intergenic spacer variation, introgression.
Transfer of a gene for stem rust resistance from Triticum araraticum to hexaploid wheat
Authors: Dyck P. L.
Published: April 2011

A partially dominant gene for seedling resistance to Puccinia graminis f.sp. tritici was transferred from two accessions of Triticum araraticum (PGR 6126 and PGR 6195) to hexaploid wheat by a series of backcrosses. This gene confers an intermediate level (infection type 1+ to 2) of resistance to a large number of P. graminis isolates. Because of linkage with the genes Lr13 (1.0%), Lr23 (4.7%), Lr16 (34.4%), Sr36 (21.9%) and the Sr9 (28.0%) locus, this gene is probably on the short arm of chromosome 2B. It has been assigned the symbol Sr40. No apparent deleterious quality characteristics were associated with the transfer of Sr40. This gene is being combined with the closely linked gene Lr13. This recombinant line should be useful in wheat breeding. The concurrent attempt to transfer resistance to P. recondita from T. araraticum to hexaploid wheat was not successful.Key words: Triticum aestivum, stem rust resistance, Triticum araraticum.
Distribution of telomeric repeats and their role in the healing of broken chromosome ends in wheat
Authors: Werner Joanna E. , Kota Rama S. , Gill Bikram S. , Endo T. R.
Published: April 2011

The distribution of the telomeric repeats in common wheat and their role in the healing of broken ends of deleted chromosomes was studied. In situ hybridization to mitotic chromosomes was carried out using a synthetic probe that was derived from the sequence of the telomeric repeats of Arabidopsis thaliana. Sites of hybridization were visualized as double dots at both ends of each wheat chromosome. Variation in the strength of the signal that was detected among chromosome arms might be due to the variable number of telomeric repeats of each chromosome end. While signals were absent on normal chromosomes at the pericentric and intercalary regions, hybridization sites were detected at the broken chromosome ends of all deleted chromosomes included in the study. All telocentric chromosomes of multitelocentric lines of 'Chinese Spring' showed a strong signal at the centromeric region. The results suggest that a de novo chromosome healing mechanism exists in wheat involving the addition of the telomeric sequences to the ends of broken chromosome. Further evidence indicated that the healing of broken ends is probably intrinsic to replication during gametogenesis.Key words: in situ hybridization, telomeric sequences, deleted chromosomes, chromosome healing, telosome.
Introgression of genes from Canada wildrye to slender wheatgrass: cytology and fertility of backcross progeny
Authors: Kumar P. S. , Walton P. D.
Published: April 2011

Partially fertile synthetic amphiploids (2n = 8x = 56) of Canada wildrye × slender wheatgrass F1 hybrid were crossed to slender wheatgrass and tetraploid lines resembling slender wheatgrass were recovered after four backcrosses. The BC1 progeny was hexaploid, while the BC2 and BC3 progenies were aneuploids with chromosome numbers ranging from 31 to 38. Tetraploid lines were recovered in the BC4 generation along with 29- and 30-chromosome types. Multivalents (mostly trivalents) resulting from intergenomic pairing were fequently encountered in BC1 and BC2 plants. The multivalent frequencies declined with each succeeding backcross. Pairing in the 28-chromosome BC4 plants was completely regular with 14 bivalents. Intergenomic pairing in the backcross progeny promoted introgression from Canada wildrye to slender wheatgrass.Key words: Elymus, intergenomic pairing, trivalents, recombination.
Two molecular probes characterizing the A and C genomes in the genus Avena (oats)
Authors: Gupta Pushpendra K. , Giband Marc , Altosaar Illimar
Published: April 2011

Two clones were isolated from oat (Avena sativa cv. Hinoat) genomic DNA. Restriction analysis and cross-hybridization studies revealed that these clones represent two different families of repeated DNA. Single accessions of 10 Avena species, representing three ploidy levels (2x, 4x, and 6x; x = 7) and comprising all available genomic constitutions (AA, CC, AABB, AACC, and AACCDD), were analyzed with these probes. Differences were observed among single representatives of the 10 species in the relative abundance of each probe and between the probes in relative abundance in each species. In slot-blot experiments, for each of the two probes, hybridization intensities were independent of genome composition. Southern blots of HindIII DNA digests from the 10 species, using each of the two probes, allowed classification of these species into two groups: the three diploid species with a CC genomic constitution had one specific pattern and the remaining seven species having different genomic constitutions (AA, AABB, AACC, AACCDD, the A genome being in common) had a different pattern. Therefore, these probes will distinguish the C-genome diploid species from the diploid and polyploid species carrying the A genome.Key words: Avena genomes, repeated DNA, molecular probes, speciation, A and C genomes.
A distribution model for heritability
Authors: Magnussen Steen
Published: April 2011

A regression model to predict quantiles of narrow sense individual and family mean heritabilities is developed and used to predict confidence intervals either directly or via a generalized beta distribution model. Extensive simulations of balanced sib analysis trials in randomized complete block designs and normal distributed environmental and additive genetic effects confirmed that heritabilities follow a beta distribution even in cases with up to 10% of the data missing at random. The new model is both more accurate and more precise than commonly used alternatives based on "exact" χ2 distributions and Satterthwaites approximations to the degrees of freedom. Estimates of the expected heritability and a Taylor approximation of the standard error of the heritability are needed as input to the quantile model. Applications of the presented models for estimating confidence intervals and as an aid in the design of experiments are provided.Key words: heritability, confidence intervals, beta distribution, quantiles, experimental design.
Genetic control of green plant regeneration from anther culture of wheat
Authors: Zhou Huaping , Konzak Calvin F.
Published: April 2011

The low percentage of green plants from anther cultures has limited the applications of haploid techniques in cereal breeding programs. The objective of this study was to estimate the genetic control of green plant percentage in wheat anther culture. Reciprocal crosses were made between a spring wheat 'Chris', which produces a high percentage of green plants, and an experimental line WA7176, which produces a low percentage of green plants. The reciprocal crosses were backcrossed with the respective male parents. A second group of reciprocal crosses and backcrosses was made between 'Yecora Rojo' (high green plant producing parent) and 'Edwall' (low green plant producing parent). Anthers from the parents, reciprocal cross, and backcross progeny were cultured to estimate the relative importance of nuclear genes in the control of green plant production. The percentages of green plants derived from the reciprocal crosses were intermediate between the parents and no significant reciprocal differences were detected. Backcrosses of the reciprocal crosses shifted the percentage of green plants towards the male parents. These results indicate that the percentages of green plants from anther culture of the tested genotypes are under the control of nuclear genes and that the genes are predominantly additive. Significant differences (p ≤ 0.05) for green plant percentage as well as for callus induction and plant regeneration were also detected within the parental genotypes. The within-genotype variation for green plant percentage accounted for 24.5 and 34.1% of total variation for the two groups of crosses, indicating the potential for in vitro prescreening to identify specific parental plants to improve anther culture responses.Key words: Triticum aestivum, wheat, anther culture, albinism, inheritance.
Genetic analysis of chlorophyll-deficient somaclonal variants in rye
Authors: Linacero R. , Vazquez A. M.
Published: April 2011

Albino plants have been observed among regenerated plants from immature embryo calluses in four cultivars of rye. The frequency of albino plants was very similar between the plants regenerated from embryogenic (8.78%) or organogenic (12.06%) cultures. However, these frequencies varied widely between cultivars (from 0 to 23.46%). On the other hand, 12% of the green regenerated plants segregated in their progeny plants with chlorophyll deficiencies, and most of these mutations segregated as we can expect a Mendelian trait to do. The behaviour of the regenerated plants from cv. Ailes was particularly interesting, because the appearance of a particular phenotype could be related to the in vitro activation of a transposable element.Key words: Secale cereale, regeneration, somaclonal variation, albino plants, transposable elements.
Purification and characterization of histone H1 from meiotic cells of a monocotyledonous plant, Lilium longiflorum
Authors: Riggs C. Daniel
Published: April 2011

To identify molecules involved in regulating meiotic chromatin structure, nuclear proteins from meiocytes of Lilium longiflorum were chromatographed on hydroxylapatite and the bound and unbound proteins were examined. An abundant nuclear protein was purified from the unbound fraction and by the following criteria was identified as a histone H1 molecule. The protein is soluble in acidic (perchloric and sulfuric acid) solutions, and its amino acid composition and the sequence of its amino terminus are similar to that of known histone H1s. An antiserum was produced against the protein to facilitate subsequent studies. Immunoblotting experiments demonstrated that histone H1 immunostaining declines in the developmental interval spanning the diplotene to tetrads stages. Concommitant with this decline is the appearance of several lower molecular mass, cross-reacting proteins. Neither the identity nor roles of these proteins is known. Immunoblotting experiments also demonstrate that, while the level of the protein is relatively constant in nuclei prepared from meiotic and vegetative cells, histone H1 is apparently enriched in total cellular extracts of meiotic cells compared with vegetative cells. This difference was found to be at least 16-fold. I conclude that in meiotic cells, histone H1 accounts for more of the total cellular protein than it does in vegetative cells. The difference in its relative abundance as a percent of the total cellular protein is probably in part due to differences in the ratio of nuclear to cytoplasmic volume in the different cell types, or the purging of sporophytic proteins from the cytoplasm of the meiocytes, or both.Key words: meiosis, histone H1, immunoblotting, meiotic purging.
Gene-for-gene interactions between the rye mildew fungus and wheat cultivars
Authors: Tosa Y.
Published: April 2011

Genetic mechanisms of the incompatibility between Erysiphe graminis f.sp. secalis and wheat cultivars were analyzed using F1 hybrids between E. graminis f.sp. secalis, Sk-1, and f.sp. tritici, Tk-1. The avirulence of Sk-1 on Triticum aestivum 'Norin 4', 'Chinese Spring', and 'Kokeshi-komugi' was controlled by a single gene. The resistance of the three cultivars to Sk-1 was also controlled by a single gene, Pm15, a gene for resistance to E. graminis f.sp. agropyri. Implications of these results were discussed in terms of host–parasite coevolution.Key words: powdery mildew, Erysiphe graminis, resistance, wheat.
Genetic mapping and variability of seven soybean simple sequence repeat loci
Authors: Morgante M. , Rafalski A. , Biddle P. , Tingey S. , Olivieri A. M.
Published: April 2011

Microsatellites or simple sequence repeats are stretches of short tandemly repeated DNA sequence motifs, dispersed throughout the genomes of most eukaryotes. Simple sequence repeat polymorphisms (SSRPs) have recently been reported in plants. Here we present the genetic map position of seven different soybean (Glycine max (L.) Merr. and Glycine soja Sieb. and Zucc.) SSRPs contained in sequenced genes, four of which represent newly mapped positions for these genes. The other three SSRPs coincided with independently established RFLP map positions for the corresponding genes. When a set of 61 soybean accessions was screened at four of these loci by using agarose gels, the average number of alleles per locus was 7.75, the effective number of alleles (ne) was 2.57, and the level of allele differentiation (δT) was 0.62. Allelic variation decreased sharply with increasing levels of domestication, with the level of differentiation going from 84% in the wild soybean to 43% in the elite germplasm. Variation levels observed on a subset made of 19 of the 61 lines were always higher for SSRPs than for RFLP markers, with the average number of alleles per locus going from 4.25 to 2.15. In comparison with RFLP markers, SSRPs are more informative and are easier to analyse but require more effort to develop.Key words: simple sequence repeats, soybean, variability, mapping, domestication, microsatellites.
Comparison of the neuralized genes of Drosophila virilis and D. melanogaster
Authors: Zhou Lily , Boulianne Gabrielle L.
Published: April 2011

The neurogenic gene neuralized of Drosophila melanogaster is thought to play a role in the determination of cell fate in the embryonic nervous system as well as other tissues during development. To determine which sequences within the neuralized gene encode functionally important domains, we have initiated an interspecific comparison of the neuralized gene of D. virilis and D. melanogaster. In this study we show that several motifs that we have previously identified in the neuralized protein of D. melanogaster are conserved in D. virilis. These include a putative nuclear localization signal, a homeodomain similarity region, and a zinc finger motif. In contrast, a helix-turn-helix motif with structural similarity to those identified as DNA-binding regions of bacterial repressors is deleted. These results demonstrate that it is possible to identify key functional regions of the neuralized protein by an interspecific comparison.Key words: Drosophila melanogaster, Drosophila virilis, neuralized, nucleotide sequence, evolutionary comparison.
Rust resistance in Triticum cylindricum Ces. (4x, CCDD) and its transfer into durum and hexaploid wheats
Authors: Bai D. , Scoles G. J. , Knott D. R.
Published: April 2011

In order to counteract the effects of the mutant genes in races of leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm.) and stem rust (P. graminis f.sp. tritici Eriks. &Henn.) in wheat, exploration of new resistance genes in wheat relatives is necessary. Three accessions of Triticum cylindricum Ces. (4x, CCDD), Acy1, Acy9, and Acy11, were tested with 10 races each of leaf rust and stem rust. They were resistant to all races tested. Viable F1 plants were produced from the crosses of the T. cylindricum accessions as males with susceptible MP and Chinese Spring ph1b hexaploid wheats (T. aestivum, 6x, AABBDD), but not with susceptible Kubanka durum wheat (T. turgidum var. durum, 4x, AABB), even with embryo rescue. In these crosses the D genome of hexaploid wheat may play a critical role in eliminating the barriers for species isolation during hybrid seed development. The T. cylindricum rust resistance was expressed in the F1 hybrids with hexaploid wheat. However, only the cross MP/Acy1 was successfully backcrossed to another susceptible hexaploid wheat, LMPG-6. In the BC2F2 of the cross MP/Acy1//LMPG-6/3/MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 (infection types (IT) 1=, 1, or 1+; addition line 1) or stem rust race 15B-1 (IT 1 or 1+; addition line 2) were selected. Rust tests and examination of chromosome pairing of the F1 hybrids and the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the added T. cylindricum C-genome chromosomes rather than on the D-genome chromosomes. The T. cylindricum chromosome in addition line 2 was determined to be chromosome 4C through the detection of RFLPs among the genomes using a set of homoeologous group-specific wheat cDNA probes. Addition line 1 was resistant to the 10 races of leaf rust and addition line 2 was resistant to the 10 races of stem rust, as was the T. cylindricum parent. The added C-genome chromosomes occasionally paired with hexaploid wheat chromosomes. Translocation lines with rust resistance (2n = 21 II) may be obtained in the self-pollinated progeny of the addition lines through spontaneous recombination of the C-genome chromosomes and wheat chromosomes. Such translocation lines with resistance against a wide spectrum of rust races should be potentially valuable in breeding wheat for rust resistance.Key words: wheat, Triticum cylindricum, rust resistance, gene transfer, addition line, molecular cytogenetics.
Changes in NOR activity pattern in the presence of supernumerary heterochromatin in the grasshopper Eyprepocnemis plorans
Authors: López-León M. D. , Cabrero J. , Camacho J. P. M.
Published: April 2011

Nucleolus organizer region (NOR) activity was analysed in four types of males of the grasshopper Eyprepocnemis plorans, possessing two kinds of supernumerary heterochromatin: a B chromosome and a supernumerary chromosome segment proximally located on the smallest autosome (S11). In males lacking extra heterochromatin, the four active NORs located on the S9, S10, S11, and X chromosomes showed independent activity patterns, but several kinds of dependence appeared in the presence of supernumerary heterochromatin. Furthermore, temporal changes in NOR activity were observed during the first 2 weeks of adult life in standard males but not in males carrying supernumerary heterochromatin. It is suggested that all these effects are related to the DNA content of both types of extra heterochromatin.Key words: NOR, supernumerary heterochromatin, grasshopper, Eyprepocnemis plorans.
On the mechanism of homologous synapsis in lycosid spiders
Authors: Wise Dwayne A. , Taylor Jeanne L.
Published: April 2011

Lycosid spiders have 13 pairs of telocentric chromosomes and 2 nonhomologous sex chromosomes in males. At leptotene, the kinetochore ends are attached to the nuclear envelope via thickened attachment plaques. Homologous synapsis begins at the attachment plaques and proceeds zipper-like through the length of the synaptonemal complex. We have tested whether or not this simple form of homologous synapsis is obligatory by inducing reciprocal translocations. Since we find many irradiated cells with quadrivalents at diakinesis–prometaphase and metaphase I, clearly a backup system exists that can bring together homologous segments disparate from each other in the nucleus. This mechanism apparently does not depend on end-initiated synapsis. Furthermore, we have found in previous studies that wolf spider bivalents are always unichiasmate, with either proximally or distally placed chiasmata. Since many chain quadrivalents, but no ring quadrivalents, were seen in this study, crossing over and chiasma placement obey a different set of rules when homologous segments are switched between chromosomes.Key words: chromosome pairing, zygotene, homology search, spiders.
Localization of a new ferritin heavy chain sequence present in human brain mRNA to chromosome 11
Authors: Percy Maire E. , Bauer Sharon J. , Rainey Susan , McLachlan Donald R. C. , Dhar Madhu S. , Joshi Jayant G.
Published: April 2011

Two types of ferritin heavy (H) chain clones have been isolated from cDNA libraries of human fetal and adult brain: one corresponds to the ferritin H chain mRNA that is abundant in liver and is called "liver-like" brain cDNA; the other contains an additional 279 nucleotide (nt) sequence in the 3′untranslated region and is called brain ferritin H chain cDNA. To map the 279-nt sequence, polymerase chain reaction (PCR) amplification was carried out using DNA from rodent × human hybrid cell lines containing single human chromosomes as templates, and oligomeric primers homologous to the 3′end of the 279-nt sequence (primer A) and to a coding sequence just 5′ to the 279-nt sequence. Significant PCR product of the size expected from analysis of the brain ferritin H chain cDNA clones and a genomic ferritin H chain clone (487 bp) was generated only from hybrid-cell DNA containing human chromosome 11. This PCR product and the "liver-like" brain cDNA (lacking the 279-nt sequence) both hybridized to chromosome 11 fragments that are known to define the well-characterized functional liver ferritin H chain gene and a putative pseudogene. Preliminary data indicate that primer A (and thus the 279-nt sequence) maps to the functional ferritin H chain gene fragments, but binding to the pseudogene has not been ruled out.Key words: gene mapping, human brain ferritin, chromosome 11.
A stably transmitted pair of translocated supernumerary chromosomes in maize
Authors: Maguire Marjorie P.
Published: April 2011

A pair of stably transmitted supernumerary chromosomes of unknown source has been found in a maize stock carrying a desynaptic mutant. The presence of the supernumerary chromosome appears to be unrelated to the meiotic mutant, but is believed to have been derived from a translocated B chromosome contaminant. The supernumerary chromosomes carry a segment of a A chromosome in this stock where there appear to be two normal copies of each of the 10 A chromosomes. Thus, this A chromosome segment is present in quadruplicate. Surprisingly, a quadrivalent configuration is formed in most microsporocytes, which involves not only synapsis but also chiasma formation in the A chromosome segments involved in the quadrivalent. This represents a strong preferential pairing of supernumeraries with the normal A chromosome segments. Such nonrandom association and crossing over might provide information on the nature of early homologue alignment at meiosis.Key words: supernumerary chromosomes, modified B chromosome, BAtranslocation, preferential pairing and crossing over.
Association of morphological and RFLP markers in rice (Oryza sativaL.)
Authors: Yu Z. H. , McCouch S. R. , Tanksley S. D. , Kinoshita T. , Sato S.
Published: April 2011

Seventeen morphological marker genes were associated with restriction fragment length polymorphism markers in rice by using four F2populations, each segregating for a few observable traits, and 14 near isogenic lines (NILs), each containing one morphological mutant gene. The location of five genes was confirmed on the basis of F2analysis: Purple hull (Pr) (16.8 ± 7.9 cM away from RG163 on chromosome 4); Phenol staining (Ph) (20.8 ± 8.4 cM away from RG163 on chromosome 4); glabrous leaf and hull (gl-1) (14.3 ± 7.4 cM away from RG182, and 20.9 ± 8.3 cM from RG403 on chromosome 5); Brown pericarp (Rc) (12.5 ± 7.2 cM away from RG30 on chromosome 7); and lazy growth habit (la) (28.8 ± 9.4 cM away from RG118 on chromosome 11). In addition, 12 other morphological markers, including the agronomically important genes semi-dwarf (sd-1) and Pollen restoring factor (Rf-1) were tentatively associated with mapped DNA clones based on screening pairs of NILs.Key words: linkage mapping, morphological marker, rice, Oryza sativa L., restriction fragment length polymorphism.
Synapsis in grasshopper bivalents heterozygous for centric shifts
Authors: Cerro A. L. del , Santos J. L.
Published: April 2011

Analysis of surface-spread synaptonemal complexes of zygotene and pachytene spermatocytes was carried out on centric-shift heterozygotes of grasshoppers. These rearrangements affected the M7 chromosome in Chorthippus vagans and the M6 and S8 chromosomes in Chorthippus apricarius. The shifts in the latter two chromosomes were also associated with C-heterochromatin variations between homologous chromosomes. Rearranged chromosomes proceeded directly to heterosynapsis without an apparent intervening homosynaptic phase in M7 bivalents of Ch. vagans and M6 bivalents of Ch. apricarius. In the latter case, axial equalization of the heterochromatin polymorphism was also achieved. On the other hand, asynapsis of the intercentromeric regions throughout pachytene was the rule in the centric shift involving the S8 chromosome of Ch. apricarius. In the three cases analysed, the production of unbalanced gametes in the heterozygotes is precluded either by the lack of chiasma formation in heterosynapsed rearranged segments or by the lack of pairing between such segments. Chiasmata were limited to the homologous regions of the heteromorphic bivalents.Key words: synapsis, surface spreading, centric shift, chiasma distribution, meiosis.
Clonal variation in the parthenogenetic rock lizardLacerta armeniaca
Authors: MacCulloch Ross D. , Murphy Robert W. , Kupriyanova Larissa A. , Darevsky Ilya S. , Danielyan F. D.
Published: April 2011

Genetic diversity at 35 allozyme loci was surveyed in seven populations of Lacerta armeniaca. Fixed heterozygotes were present at 16 loci, with homozygotes at 17 loci. Variation occurred at two loci, one in each of two populations, indicating one widespread clone, one restricted clone, and one apparently restricted clone. The low level of variation in this species suggests a recent restricted origin, involving few parental individuals.Key words: Lacerta, allozymes, parthenogenesis.
Frequent nonreciprocal translocations in the amphidiploid genome of oilseed rape (Brassica napus)
Authors: Sharpe A. G. , Parkin I. A. P. , Keith D. J. , Lydiate D. J.
Published: April 2011

A RFLP map of Brassica napus, consisting of 277 loci arranged in 19 linkage groups, was produced from genetic segregation in a combined population of 174 doubled-haploid microspore-derived lines. The integration of this map with a B. napus map derived from a resynthesized B. napus × oilseed rape cross allowed the 10 linkage groups of the B. napus A genome and the 9 linkage groups of the C genome to be identified. Collinear patterns of marker loci on different linkage groups suggested potential partial homoeologues. RFLP patterns consistent with aberrant chromosomes were observed in 9 of the 174 doubled-haploid lines. At least 4 of these lines carried nonreciprocal, homoeologous translocations. These translocations were probably the result of homoeologous recombination in the amphidiploid genome of oilseed rape, suggesting that domesticated B. napus is unable to control chromosome pairing completely. Evidence for genome homogenization in oilseed rape is presented and its implications on genetic mapping in amphidiploid species is discussed. The level of polymorphism in the A genome was higher than that in the C genome and this might be a general property of oilseed rape crosses.Key words: restriction fragment length polymorphism, genetic linkage map, homoeologous recombination, microspore culture, doubled haploid.
Genome- and species-specific markers and genome relationships of diploid perennial species in Triticeae based on RAPD analyses
Authors: Wei Jun-Zhi , Wang Richard R.-C.
Published: April 2011

Eight different genomes (E, H, I, P, R, St, W, and Ns) represented by 22 diploid species of the tribe Triticeae were analyzed using the random amplified polymorphic DNA (RAPD) technique. The genome relationships were obtained based on 371 RAPD fragments produced with 30 primers. The four species of the genus Psathyrostachys (having various Ns genomes) were closely related. The genomes Ee and Eb had a similarly close relationship and were distinct from all other genomes analyzed. Genomes P, R, and St were grouped in one cluster and genomes H and I in another. Genome W had a distant relationship with all other genomes. These results agree with the conclusions from studies of chromosome pairing and isozyme and DNA sequence analyses. Twenty-nine and 11 RAPD fragments are considered to be genome- and species-specific markers, respectively. One to six genome-specific markers were identified for each genome. These RAPD markers are useful in studies of genome evolution, analysis of genome composition, and genome identification.Key words: Triticeae, perennial, diploid, genome, RAPD, genome-specific markers.
Molecular and cytological characterization of a highly repeated DNA sequence in Raphanus sativus
Authors: Hirai K. , Irifune K. , Tanaka R. , Morikawa H.
Published: April 2011

A highly repeated DNA sequence with a repeat unit of ca. 180 bp was found in genomic DNA HindIII-digests of Raphanus sativus. The repeating units of six isolated, independent clones were sequenced. These units have 177 or 178 bp, are 36% G+C in their DNA base composition, and show 90% sequence homology. The copy number of this 180-bp repeat unit is about 0.5 × 106 per diploid genome. In situ hybridization analysis with the repeating unit as the probe and C-banding analysis indicated that the repeated DNA sequence of R. sativus is closely associated with the major C-heterochromatins in the proximal regions of all 18 chromosomes at mitotic metaphase.Key words: Raphanus sativus, repeated DNA sequence, nucleotide sequence, in situ hybridization, C-banding.
Standard Giemsa C-banded karyotype of Russian wildrye (Psathyrostachys juncea) and its use in identification of a deletion–translocation heterozygote
Authors: Wei Jun-Zhi , Campbell William F. , Wang Richard R.-C.
Published: April 2011

Ten accessions of Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski (2n = 2x = 14; NsNs), collected from different geographical regions were analyzed using the C-banding technique. C-banding pattern polymorphisms were observed at all levels, i.e., within homologous chromosome pairs of the same plant, among different individuals within accessions, between different accessions of the same geographic area, and among accessions of different origins. The seven homologous groups varied in the level of C-banding pattern polymorphism; chromosomes A, B, E, and F were more variable than chromosomes C, D, and G. The polymorphisms did not hamper chromosome identification in Ps. juncea, because each chromosome pair of the Ns genome had a different basic C-banding pattern and karyotypic character. A standard C-banded karyotype of Ps. juncea is proposed based on the overall karyotypes and C-bands in the 10 accessions. The C-bands on the Ns-genome chromosomes were designated according to the rules of nomenclature used in wheat. A deletion–translocation heterozygote of Russian wildrye was identified based on the karyotype and C-banding patterns established. The chromosome F pair consisted of a chromosome having the distal segment in the long arm deleted and a translocated chromosome having the distal segment of long arm replaced by the distal segment of the long arm of chromosome E. The chromosome E pair had a normal chromosome E and a translocated chromosome having the short arm and the proximal segment of the long arm of chromosome E and the distal segment of the long arm of chromosome F.Key words: Psathyrostachys juncea, karyotype, Giemsa C-banding, polymorphism, B chromosome.
Cytological identification of some trisomics of Russian wildrye (Psathyrostachys juncea)
Authors: Wei Jun-Zhi , Campbell W. F. , Scoles G. J. , Slinkard A. E. , Wang R. Ruey-Chyi
Published: April 2011

Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski (2n = 2x = 14; NsNs), is an important forage grass and a potential source of germplasm for cereal crop improvement. Because of genetic heterogeneity as a result of its self-incompatibility, it is difficult to identify trisomics of this diploid species based on morphological characters alone. Putative trisomies (2n = 2x + 1 = 15), derived from open pollination of a triploid plant by pollen grains of diploid plants, were characterized by Giemsa C-banding. Based on both karyotypic criteria and C-banding patterns, four of the seven possible primary trisomics, a double-deletion trisomic, and two tertiary trisomics were identified.Key words: Russian wildrye, Psathyrostachys juncea, trisomic, C-banding, karyotype.
Alteration of basic chromosome number by fusion–fission cycles
Authors: Schubert Ingo , Rieger Rigomar , Fuchs Jörg
Published: April 2011

A complete chromosomal fusion–fission cycle is described for the first time. In the field bean, Vicia faba, this cycle probably started with a reversible fusion of two telocentrics giving rise to the standard metacentric chromosome I. The next step was a recent fission of this chromosome into two stable telocentrics eventually followed by a new fusion reconstituting the metacentric chromosome.Key words: karyotype evolution, chromosome number, chromosomal fusion–fission cycle, Vicia faba.
B-chromosome origin in the endemic New Zealand frogLeiopelmahochstetterithrough sex chromosome devolution
Authors: Sharbel Timothy F , Green David M , Houben Andreas
Published: April 2011

The endemic New Zealand frog Leiopelma hochstetteri has variable numbers of mitotically stable B chromosomes. To assess whether the B chromosomes were derived from the autosome complement, they were isolated by micromanipulation and their DNA amplified by degenerate oligonucleotide primed PCR. Southern hybridizations of B chromosome DNA probes to genomic DNA from males and females characterized by differing numbers of B chromosomes demonstrated that the B chromosomes were derived from the univalent W sex chromosome characteristic of North Island populations. The presence of homologous B chromosome specific sequences from geographically distinct populations indicates a single origin of the B chromosomes. Furthermore, a primitive homology shared by B chromosomes and the W sex chromosome from an ancestral WZ/ZZ karyotype, which is still present in frogs from Great Barrier Island, shows that the B chromosomes originated soon after the univalent W sex chromosome had originated. Sequence analysis revealed that B chromosome DNA is composed of repeat sequences and has the potential to form stable hairpin structures. The molecular dynamics of these structures may reflect an inherent propensity to undergo rapid change in nucleotide sequence and chromosome structure.
Mapping a gene conferring resistance toPseudocercosporella herpotrichoideson chromosome 4V ofDasypyrum villosumin a wheat background
Authors: Yildirim Ahmet , Jones Stephen S , Murray Timothy D
Published: April 2011

The objectives of this study were to map and tag the previously undescribed eyespot resistance gene PchDv on chromosome 4V of Dasypyrum villosum in a wheat background. The 82 F2plants used for mapping were produced from a cross between a susceptible\i wheat 'Yangmai-5' (4V(4D)) substitution line and a resistant wheat 'Chinese Spring' disomic addition line of chromosome 4V of D. villosum. Segregation for resistance and susceptibility among F2plants was 3:1, indicating that resistance was controlled by a single dominant gene. PchDv mapped to the distal part of chromosome 4V and was bracketed by two RFLP markers, Xcdo949 and Xbcd588, in a 33-cM interval. This distance could not be reduced, owing to a lack of polymorphic loci in this region. Theoretically, double recombination in this region occurs in 3.3% of the individuals; therefore, 96.7% of the selected genotypes would have PchDv, with simultaneous selection for both flanking markers. Double recombination between the flanking markers was observed in 2 out of 82 (2.4%) F2individuals.