bluuebunny/crossref_metadata_2025 huggingface dataset:
Restriction fragment length polymorphisms linked to genes for resistance to crown rust (Puccinia coronata) in near-isogenic lines of hexaploid oat (Avena sativa)
Authors: Bush A. L. , Wise R. P. , Rayapati P. J. , Lee M.
Published: April 2011

Crown rust, perhaps the most important fungal disease of oat, is caused by Puccinia coronata. An examination of near-isogenic lines (NILs) of hexaploid oat (Avena sativa) was conducted to identify markers linked to genes for resistance to crown rust. These lines were created such that a unique resistance gene is present in each of the two recurrent parent backgrounds. The six NILs of the current study, X434-II, X466-I, and Y345 (recurrent parent C237-89) and D486, D494, and D526 (recurrent parent Lang), thus provide a pair of lines to study each of three resistance genes. Restriction fragment length polymorphisms and resistance loci were mapped using BC1F2 populations. Three markers were found linked to a locus for resistance to crown rust race 203, the closest at 1.9 cM in line D494 and 3.8 cM in line X466-I. In lines D526 and Y345 a marker was placed 1.0 and 1.9 cM, respectively, from the locus conferring resistance to crown rust race 345, and in D486 and X434-II a marker mapped at 8.0 and 10.2 cM from the locus for resistance to rust race 264B.Key words: genetics, disease resistance, monocots, near-isogenic lines.
Unstable transmission and frequent rearrangement of two closely linked transposed Ac elements in transgenic tomato
Authors: Belzile François , Yoder John I.
Published: April 2011

We are examining the behavior of the maize transposable element Ac in transgenic tomato with the goal of developing an efficient insertional mutagenesis system. Among the self progeny of a transgenic tomato plant containing an active Ac element, we identified six plants that contained the same germinally transposed Ac. In one of these plants, we found a second Ac element inserted in the same orientation and approximately 2 kb to the 5′ side of the original Ac insertion. Transmission of this composite structure was significantly reduced with less than one-quarter of the self progeny inheriting Ac either in the form of the intact parental allele (two neighboring Ac's) or derivatives of it. The derivative alleles that arose were complex in structure and could not be explained solely on the basis of the excision of one or the other Ac element. These results illustrate the potential of transposable elements to cause genetic instabilities and complex chromosomal rearrangements.Key words: Ac element, rearrangements, tomato, transposable element, transposon tagging.
Using disomic 4x(2EBN) potato species' germplasm via bridge species Solanum commersonii
Authors: Bamberg J. B. , Hanneman Jr. R. E. , Palta J. P. , Harbage J. F.
Published: April 2011

The cultivated potato Solanum tuberosum Dunal has many wild related species with desirable traits. Some of these wild tetraploids have disomic chromosome pairing, ready selfing with little inbreeding depression, but have strong crossing barriers with cultivars. They hybridize most easily with 2EBN forms (which include most diploid species). Chromosome doubling to the 8x level, use of 2n gametes, use of 2n gametes of 4x–2x triploid hybrids, and embryo rescue have been proposed to overcome the crossability barrier of these species with S. tuberosum. In this study, 2x S. commersonii (cmm) was used as a bridge species with S. acaule and series Longipedicellata species. Synthetic tetraploid 4x-cmm crossed readily to disomic 4x species, resulting in fertile F1 and F2 hybrids. Some of these had 2n gametes, which enabled direct crossing to tuberosum, resulting in 6x hybrids. The benefits of this scheme are (i) hybrids are relatively fertile, so many progeny may be produced for selection at each step, (ii) hybridization with cmm results in 2n gametes needed for crossing to tuberosum, and breaks up restricted recombination within disomic genomes, and (iii) simple techniques and tools are employed.Key words: Solanum, potato, germplasm, crossability.
RFLP markers linked to powdery mildew resistance genes Pm1, Pm2, Pm3, and Pm4 in wheat
Authors: Ma Z. Q. , Sorrells M. E. , Tanksley S. D.
Published: April 2011

Near-isogenic lines (NILs) and their recurrent parent Chancellor (Cc) were used to identify restriction fragment length polymorphic markers linked to powdery mildew (Blumeria graminis (DC.) E.O. Speer f.sp. tritici) resistance genes Pm1, Pm2, Pm3, and Pm4 in wheat (Triticum aestivum L. em. Thell). By mapping these polymorphic markers in F2 progenies from crosses of the NILs with Cc, it was found that Pm1 cosegregated with a polymorphic locus detected by DNA probe CDO347; Pm2 was linked to a locus detected by probe BCD1871 with a distance of 3.5 cM; Pm3b was linked to a locus detected by probe BCD1434 with a distance of 1.3 cM; Pm4a cosegregated with Xbcd1231-2A(2) and Xcdo678-2A, and was closely flanked by Xbcd1231-2A(1) and Xbcd292-2A both with a distance of 1.5 cM. Aneuploid mapping of these markers indicated that locus Xcdo347-7A is on 7AL, Xbcd1871-5D on 5DS, Xbcd1434-1A on 1AS, and loci Xbcd292-2A and Xcdo678-2A are on 2AL. The same polymorphic fragments detected in the Pm3b NIL by Xbcd1434-1A were found in Pm3a NIL using several enzyme digestions.Key words: RFLP markers, Pm1, Pm2, Pm3, Pm4, Blumeria graminis (DC.) E.O. Speer f.sp. tritici (Erysiphe graminis f.sp. tritici), wheat (Triticum aestivum L. em. Thell), gene tagging.
Cytological and molecular characterization of a Triticum aestivum × Lophopyrum ponticum backcross derivative resistant to barley yellow dwarf
Authors: Zhong Gan-Yuan , Mcguire Patrick E. , Qualset Calvin O. , Dvořák Jan
Published: April 2011

Barley yellow dwarf is the most damaging virus-caused disease in bread wheat (Triticum aestivum L.). A resistant line, SW335.1.2-13-11-1-5 (2n = 47), derived from a cross of T. aestivum × Lophopyrum ponticum was characterized by meiotic chromosome pairing, by in situ DNA hybridization and by expression of molecular markers to determine its chromosome constitution. All progeny of this line had three pairs of L. ponticum chromosomes from homoeologous chromosome groups 3, 5, and 6 and the 2n = 47 progeny had an additional L. ponticum monosome. The pairs from groups 3 and 6 were in the added state, while the group 5 pair was substituted for wheat chromosome 5D. Several wheat–wheat translocations with respect to the parental wheat genotype occurred in this line, presumably owing to the promotion of homoeologous chromosome pairing by L. ponticum chromosomes. It was hypothesized that homoeologous recombination results in homoeologous duplication–deletions in wheat chromosomes. An aberrant 3:1 disjunction creates the potential at each meiosis for replacement of these wheat chromosomes by homoeologous L. ponticum chromosomes. Wheat chromosomes 3A and 6A appeared to be in intermediate stages of this substitution process.Key words: wheat, wheatgrass, Lophopyrum, barley yellow dwarf virus, disease resistance, homoeologous chromosome recombination, homoeologous pairing, alien chromosome substitution.
Detection of interchromosomal translocations within the Triticeae by RFLP analysis
Authors: King I. P. , Purdie K. A. , Liu C. J. , Reader S. M. , Pittaway T. S. , Orford S. E. , Miller T. E.
Published: April 2011

Twenty-three wheat/alien addition or substitution lines were screened using restriction fragment length polymorphisms for the presence or absence of 4/5 and 4/7 reciprocal translocations in the alien chromosomes. Such translocations have previously been identified in wheat and rye. Group 4 and group 5 Aegilops umbellulata, Triticum urartu, and Thinopyrum bessarabicum chromosomes were found to carry 4/5 translocations. Evidence for a 4/7 translocation was also found in Secale montanum. The presence of the 4/5 translocations in T. urartu indicates that the translocation predates the polyploidization of wheat. The implications of these results are discussed.Key words: wheat/alien addition and substitution lines, RFLPs, translocations, wheat/alien introgression, Triticeae, evolution.
Chromosomal nucleolar organizer regions in four sturgeon species as markers of karyotype evolution in Acipenseriformes (Pisces)
Authors: Fontana F.
Published: April 2011

Nucleolar organizer regions in Acipenser ruthenus (2n = 118 ± 4) are localized on the telomeric regions of two morphologically different pairs of chromosomes. In A. baeri (2n = 250 ± 8), A. transmontanus (2n = 248 ± 8), and A. naccarii (2n = 246 ± 8) they are localized on eight chromosomes arranged in two quadruplets. Contrary to what is commonly accepted, such distribution suggests that species with 120 chromosomes should be considered diploids and species with 240–250 chromosomes should be considered tetraploid.Key words: Acipenseridae, karyotype, nucleolus organizers, polyploidy.
Meiotic behaviour of 11 primary trisomics in diploid potato and its consequences for the transmission of the extra chromosome
Authors: Wagenvoort M.
Published: April 2011

Meiosis was studied in 11 primary trisomics (2n = 2x + 1 = 25) from diploid Solanum tuberosum L. ssp. tuberosum Hawkes (2n = 2x = 24) and from interspecific Solanum hybrids. The three homologous chromosomes were associated in a trivalent in 90% of more than 175 pollen mother cells analysed at pachytene. Trivalents showing a two by two pairing and partner exchanges at pachytene along with incomplete triple synapsis were frequently observed. Foldback pairing, predominantly observed in the heterochromatic parts of the chromosomes, occurred in 28.3% of the trivalents. Nonhomologous association of chromosome segments was observed in 29.1% of the trivalents. Up to six telomeres were associated homologously in 46.2% of the trivalents. Genotypic differences with respect to trivalent formation at metaphase I occurred in almost all the trisomic types and was significant for the trisomics for chromosomes 4, 7, and 9. The coefficient of realization of a trivalent (CRT) at metaphase I in the 11 primary trisomics varied from 0.20 to 0.80, and was positively correlated with the absolute length of the extra chromosome (r = 0.61, p ≤ 0.05) and with the absolute, as well as the relative, length of the euchromatic segments of the extra chromosome (r = 0.70, p ≤ 0.05). There was no apparent relationship between the CRT and the distribution pattern at anaphase I or anaphase II. The rate of female transmission of the extra chromosome varied from 10.0 to 44.6% among different trisomics. For chromosomes 4, 7, and 9, this rate differed significantly among genotypes of the same trisomic.Key words: primary trisomics, meiosis, nonhomologous chromosome association, telomere pairing, triple synapsis, female transmission, Solanum.
Overcoming crossing barriers between nontuber-bearing and tuber-bearingSolanumspecies: towards potato germplasm enhancement with a broad spectrum of solanaceous genetic resources
Authors: Watanabe K. N. , Orrillo M. , Vega S. , Valkonen J. P. T. , Pehu E. , Hurtado A. , Tanksley S. D.
Published: April 2011

The first direct sexual hybrids between diploid nontuber-bearing species and diploid potato breeding lines are reported here. Three nontuberous species of Solanum, S. brevidens, S. etuberosum, and S. fernandezianum, were used for sexual crosses, achieved by a combination of rescue pollinations and embryo rescue. Initial hybrid selection was made using an embryo spot marker, followed by the evaluation of morphological and reproductive traits. Putative hybrids were first tested for resistance to potato leaf roll virus derived from the wild species, and then were tested with molecular markers using species-specific DNA probes. Finally, the tuberization of several 2x hybrids was tested for actual potato germplasm enhancement. These hybrids are unique in terms of their potential to enhance recombination between chromosomes of wild species and those of cultivated potatoes in germplasm utilization, and to exploit the genetic nature of tuber formation. The finding that nontuber-bearing Solanum spp. can be directly crossed with tuber-bearing species also has important implications for the regulatory aspects of the use of genetically modified organisms.Key words: nontuber-bearing Solanum, potato germplasm enhancement, interspecific crosses, chromosome manipulation, inter-EBN crosses, diploid.
Molecular markers for four leaf rust resistance genes introgressed into wheat from wild relatives
Authors: Autrique Enrique , Tanksley Steven D. , Sorrells Mark E. , Singh Ravi P.
Published: April 2011

Near-isolines carrying four different genes for resistance to leaf rust were used to find linked molecular markers for these genes. Clones used to detect polymorphism were selected on the basis of the reported chromosomal location of the resistance genes. Both Lophopyron-derived resistance genes, Lr19 and Lr24, cosegregated with eight molecular markers assigned to chromosomes 7DL and 3DL, respectively. One clone cosegregated with Lr9 and two closely linked RFLP markers were found for Lr32, mapping at 3.3 ± 2.6 and 6.9 ± 3.6 cM from the resistance gene. The Lophopyron-chromatin segment in isolines carrying chromosomes 7E (Lr19) and 3E (Lr24) replaced a large portion of chromosome 7D and the distal portion of chromosome 3D, respectively. Clones assigned to these chromosomes on the basis of aneuploid analysis hybridized to 7E and 3E segments, thus confirming cytological results that these introgressed segments represent homoeologous chromosomes. The linked RFLP markers could be used to identify the resistance genes and generate new combinations in breeding populations, especially in the absence of disease in the environment or when virulence is lacking.Key words: leaf rust, RFLP, Lophopyron, gene tagging, wheat, Aegilops umbellulata, Triticum tauschii.
GATA- and GACA-repeats are not evenly distributed throughout the tomato genome
Authors: Arens P. , Odinot P. , Heusden A. W. van , Lindhout P. , Vosman B.
Published: April 2011

This paper describes the distribution of highly polymorphic GATA- and GACA-containing DNA regions in tomato. To study the distribution of these polymorphic regions, a mapping experiment was done. The segregation of 32 GATA- and GACA-containing loci was analyzed in a F2population from a cross between Lycopersicon esculentum and L. pennellii. From these loci, 28 could be mapped to 8 of the 12 tomato chromosomes. Both the GATA- and GACA-containing loci seem to cluster in the same chromosomal regions. To our knowledge, this is the first report on mapping of GATA- and GACA-containing loci in plants.Key words: mapping, microsatellites, Lycopersicon esculentum, RFLP, DNA-fingerprinting.
Unusually high numbers of ribosomal RNA genes in copepods (Arthropoda: Crustacea) and their relationship to genome size
Authors: Wyngaard G. A. , McLaren I. A. , White M. M. , Sévigny J.-M.
Published: April 2011

We report on copy numbers of 18S ribosomal RNA genes in three species of copepods (Crustacea: Copepoda), two of which possess an unusual arrangement in which 5S genes are included within the 18S–5.8S–28S repeat unit. Slot blots of genomic and standard DNA were hybridized with an 18S rRNA gene probe constructed from one of the marine species and hybridization was quantified using chemiluminescence. Diploid 18S rRNA gene copy numbers are estimated as ca. 15 300 and 33 500 in the marine species Calanus finmarchicus (13.0 pg DNA in 2C adult nuclei) and C. glacialis (24.2 pg DNA), respectively, and ca. 840 and 730 in two freshwater populations of Mesocyclops edax (both ca. 3 pg DNA) from Virginia and Nova Scotia, respectively. The roughly proportional relationship between 2C somatic nuclear DNA contents and rRNA gene copy number in the sibling species C. finmarchicus and C. glacialis may reflect polytenic replication of entire genomes during abrupt speciation events. Copy numbers may also reflect differential losses during embryonic chromatin diminution.Key words: rRNA genes, copy number, genome size, Calanus, Mesocyclops.
Meiotic variation in an intergenomic autopolyploid series. I. Chiasma frequency
Authors: Wallace A. J. , Callow R. S.
Published: April 2011

Variation in chiasma frequency has been studied in PMCs of diploids and C0 autotetraploids of seven Lathyrus species exhibiting a range of genome size (10.8–19.9 pg DNA/2C). Variation in chiasma frequency showed no relation to changes in genome size, either between species or between disomic sets within nuclei. Mean chiasma frequency of the tetraploids showed a 75% increase over that in the diploids. Half of this increase represents an additive effect of chromosome doubling. Total variance in chiasma frequency of autotetraploids increases by 80% over that in diploids, in line with the square of the multiplicative effect of chromosome doubling. At the diploid level, interspecific differences account for the major component of variance (63.1%). Phenotypic variation in chiasma frequency was apparent in all seven species but represented the smallest component of variance (2.8%). Chromosome doubling results in an eightfold increase in the absolute size of the phenotypic component of variance in chiasma frequency and a threefold increase in that of the cellular component. It has no effect on the absolute size of the interspecific component.Key words: meiosis, chiasma frequency, autopolyploid, Lathyrus.
The hyperactive X chromosome is not early replicating in mitotically active somatic cells ofDrosophila nasutamales
Authors: Lakhotia S. C. , Roy J. K.
Published: April 2011

The temporal order of replication of the X chromosome(s) in mitotically dividing male and female cells in early embryos and in brain ganglia of Drosophila nasuta larvae was examined using [3H]thymidine pulse labelling and autoradiography. Both the X chromosomes in female cells and the single X chromosome in male cells replicated in complete synchrony with the autosome set in the nucleus. Thus, unlike the well-known early completion of replication by the hemizygous X chromosome in polytene nuclei in the salivary glands of male Drosophila larvae, the single X chromosome in mitotically dividing cells does not replicate earlier than the autosomes. We conclude that transcriptional hyperactivity of the single X chromosome required for dosage compensation in somatic cells of male Drosophila is not dependent upon its early replication.Key words: dosage compensation, hyperactive X chromosome, early replication.
Pulsed-field gel analysis of 5S and satellite DNA in barley
Authors: Röder Marion S. , Sorrells Mark E. , Tanksley Steven D.
Published: April 2011

Pulsed-field gel electrophoresis was used to study the variability of clustered tandemly repeated sequences in barley. Twelve spring barley cultivars were investigated with a heterologous 5S DNA probe and the 118 base pair barley satellite DNA probe HVT01. On a per fragment basis, the 5S probe was 5 times and the barley satellite probe 6.7 times more variable than single-or low-copy RFLP markers, demonstrating their usefulness for cultivar distinction.Key words: pulsed-field gel electrophoresis, tandemly repeated satellite HVT01, 5S rRNA genes, barley, genetic fingerprinting.
Reciprocal substitutions analysis of embryo induction and plant regeneration from anther culture in wheat (Triticum aestivum L.)
Authors: Ghaemi M. , Sarrafi A. , Morris R.
Published: April 2011

Reciprocal substitutions for all chromosomes between the hard red winter wheat cultivars Wichita and Cheyenne were used to investigate the effects of individual chromosomes, as well as their interactions with the genetic background, on androgenesis. Duplicate lines for each chromosome were included to check background homogeneity. Six experiments, two for each genome, were performed. In each experiment, 14 substitution lines, their 14 duplicate lines, and the two parental genotypes ('Cheyenne' and 'Wichita') were studied. The experimental design was a randomized block with three replications. 'Wichita' and 'Cheyenne' differed significantly in embryo yield and green plant regeneration (except green plant regeneration for the B-genome tests) and were equal for albino and total plant regeneration. Embryogenesis was influenced by some chromosomes of the A, B, and D genomes; green plant production was influenced by all chromosomes of the A and D genomes except 5D; albino and total plant regeneration were affected by some chromosomes of the B and D genomes. Reciprocal effects were obtained with chromosomes 1A, 7A, 1B, 5B, 1D, and 2D for embryogenesis, chromosomes 2D and 7D for green plant regeneration, and chromosome 2D for total plant regeneration. Reciprocal substitution lines revealed reciprocal effects of homologous chromosomes, as well as interactions between substituted chromosomes and their specific genetic background.Key words: anther culture, reciprocal effect, substitution lines, Triticum aestivum, embryogenesis.
Characterization ofHordeum chilensechromosomes by C-banding and in situ hybridization using highly repeated DNA probes
Authors: Cabrera A. , Friebe B. , Jiang J. , Gill B. S.
Published: April 2011

C-banding patterns of Hordeum chilense and of Triticum aestivum 'Chinese Spring' – H. chilense disomic addition lines were analyzed and compared with in situ hybridization patterns using a biotin-labeled highly repetitive Triticum tauschii DNA sequence, pAs1, and a wheat 18S–26S rDNA probe. All seven H. chilense chromosomes pairs and the added H. chilense chromosomes present in the addition lines were identified by their characteristic C-banding pattern. Chromosome morphology and banding patterns were similar to those of the corresponding chromosomes present in the parent H. chilense accession. A C-banded karyotype of the added H. chilense chromosomes was constructed and chromosome lengths, arm ratios, and relative length, as compared with chromosome 3B, were determined. The probe pAs1 was found to hybridize to specific areas on telomeres and interstitial sites along the chromosomes, allowing the identification of all seven pairs of the H. chilense chromosomes. Comparison of the patterns of distribution of the hybridization sites of clone pAs1 in the T. tauschii and H. chilense chromosomes was carried out by in situ hybridization on somatic metaphase chromosomes of the HchHchDD amphiploid. In situ hybridization using the 18S–26S rDNA probe confirmed that the H. chilense chromosomes 5Hchand 6Hchwere carrying nucleolus organizer regions. The results are discussed on the basis of phylogenetic relationships between D and Hchgenomes.Key words: Hordeum, Triticum, C-banding, in situ hybridization, phylogeny.
The role of B chromosomes in the population dynamics of yellow-necked wood miceApodemus flavicollis(Rodentia, Mammalia)
Authors: Blagojević J. , Vujošević M.
Published: April 2011

Seasonal changes in the frequency of animals with B chromosomes were studied during 1989 in the population of yellow-necked wood mice, Apodemus flavicollis, on the mountain Jastrebac in Yugoslavia. During the study the estimated density of animals reached a very large value (378.8 individuals/ha for the April sample), which produced stress conditions leading to population decline. Six samples with a total of 247 specimens were karyotypically analyzed. Animals with Bs were present in all samples in frequencies that differed significantly at the 5% level. This difference was produced by the reduction in frequencies of specimens with Bs between the April and May samples (0.53 versus 0.29; [Formula: see text]; p < 0.002) and appeared mostly as a result of increased elimination of B-carrying animals from the prereproductive group. Young animals with Bs were inferior in stress conditions produced by overabundance of animals. From the first to the last sample, the frequency of animals with one B among B-containing animals constantly decreased, while the frequency of animals with more than one B increased. The possible role of Bs in regulating population dynamics is discussed.Key words: B chromosomes, Apodemus flavicollis, population dynamics, stress conditions.
Molecular characterization of a tandem repeat, Afa family, and its distribution among Triticeae
Authors: Nagaki Kiyotaka , Tsujimoto Hisashi , Isono Kazuhiro , Sasakuma Tetsuo
Published: April 2011

We have characterized a so-called D genome specific repetitive DNA sequence (pAs1) of Aegilops squarrosa L. (2n = 14, genome DD) with respect to its DNA sequence and its distribution among Triticeae species. The clone consisted of three units of a repetitive DNA sequence of 336 or 337 base pairs, and was AT rich (65.2%). DNA analyses revealed the presence of the pAs1-like sequences in other genomes of Triticeae species, although the repetition was greatly (as much as 100-fold) variable among the genomes. The repetitive sequences from 10 diploid species were amplified using PCR with specific primers, and the sequential variability was analyzed by the digestion pattern obtained with five restriction enzymes. Since the AfaI site was the most conservatively present in the unit of the repetitive sequences, we named them "Afa family." The analysis clearly displayed the variation of the repetitive sequences regardless of the uniformity of the size of the amplified product. These results indicated that plural amplification events of these repetitive sequences happened independently in the genome evolution of Triticeae.Key words: Triticeae, Aegilops squarrosa, repetitive DNA sequence, CAPS analysis, Afa family.
Variation in highly repetitive DNA composition of heterochromatin in rye studied by fluorescence in situ hybridization
Authors: Cuadrado A. , Jouve N. , Ceoloni C.
Published: April 2011

The molecular characterization of heterochromatin in six lines of rye has been performed using fluorescence in situ hybridization (FISH). The highly repetitive rye DNA sequences pSc 119.2, pSc74, and pSc34, and the probes pTa71 and pSc794 containing the 25S–5.8S–18S rDNA (NOR) and the 5S rDNA multigene families, respectively, were used. This allowed the individual identification of all seven rye chromosomes and most chromosome arms in all lines. All varieties showed similar but not identical patterns. A standard in situ hybridization map was constructed following the nomenclature system recommended for C-bands. All FISH sites observed appeared to correspond well with C-band locations, but not all C-banding sites coincided with hybridization sites of the repetitive DNA probes used. Quantitative and qualitative differences between different varieties were found for in situ hybridization response at corresponding sites. Variation between plants and even between homologous chromosomes of the same plant was found in open-pollinated lines. In inbred lines, the in situ pattern of the homologues was practically identical and no variation between plants was detected. The observed quantitative and qualitative differences are consistent with a corresponding variation for C-bands detected both within and between cultivars.Key words: fluorescence in situ hybridization, repetitive DNA, rye, Secale cereale, polymorphism.
Quantitative trait loci for heading date and straw characters in barley
Authors: Kjær B. , Jensen J. , Giese H.
Published: April 2011

Quantitative trait loci (QTLs) for heading date and straw characters were examined in 79 chromosome-doubled haploid lines derived from the F1generation of a cross between a six-rowed winter barley and a two-rowed spring barley. A genetic map covering 1100 cM containing 85 markers, including isozyme, morphological, RFLP, and RAPD markers, was constructed. All traits examined had two QTLs with large effects on chromosome 2. In addition, a QTL for length of the top internode was found on chromosome 6. The QTL in the chromosome segment around locus v (two row/six row) on chromosome 2 may be caused by pleiotropic effects of this locus. The same QTLs for heading date and straw length were found in both 1989 and 1991. The results indicate that two QTLs on chromosome 2 affect a group of correlated traits.Key words: Hordeum vulgare, earliness, RFLP, two rowed, six rowed, linkage map.
Cytogenetics off interpopulationCuphea lanceolatahybrids
Authors: Ali M. Shajahan , Knapp Steven J.
Published: April 2011

Cuphea lanceolata Ait. (Lythraceae) is an annual diploid (x = 6) with medium-chain fatty acid rich seed oils. Wild C. lanceolata populations are classified as C. lanceolata f. silenoides or C. lanceolata f. lanceolata on the basis of flower pigment differences. Although these taxa are taxonomically close, their interfertility has not been demonstrated. We describe meiotic phenomena underlying the sterility of hybrids between C. lanceolata f. silenoides (LNS-43) and C. lanceolata f. lanceolata (LNC-78) populations. We assayed metaphase and anaphase I microsporocytes of the parent and hybrid populations. The hybrids were female and male sterile. The mean percentage of stainable pollen was 94.9% for the parents and 1.1% for the hybrids. Chromosomes paired and disjoined normally in the parents (LNS-43 and LNC-78) and abnormally in the hybrids (LNS-43 × LNC-78 and LNC-78 × LNS-43). Univalents, unequal chromosome distributions, and laggards were observed in the hybrids. The mean number of univalents per cell was 0.00 for the parents and 5.95 for the hybrids, the mean number of bivalents per cell was 6.00 for the parents and 1.51 for the hybrids, and the mean number of chiasmata per cell was 9.19 for the parents and 4.04 for the hybrids. The most frequently observed (75%) anaphase I chromosome distribution for the hybrids was 7:5:0 (pole–pole–laggards). The genome affinities of the hybrids were half those of the parents (a mean of 0.5 for the hybrids as opposed to 1.0 for the parents). Although C. lanceolata f. silenoides and C. lanceolata f. lanceolata freely hybridize, their progeny are sterile, and the genetic diversity of LNC-78, and perhaps of C. lanceolata f. lanceolata as a whole, cannot be accessed through hybrids with C. lanceolata f. silenoides or C. viscosissima.Key words: Lythraceae, Cuphea, medium-chain fatty acids, interspecific hybrids, meiosis.
Cloning and characterization of the majority of repetitive DNA in cotton (GossypiumL.)
Authors: Zhao Xinping , Wing Rod A. , Paterson Andrew H.
Published: April 2011

Repetitive DNA elements representing 60–70% of the total repetitive DNA in tetraploid cotton (Gossypium barbadense L.) and comprising 30–36% of the tetraploid cotton genome were isolated from a genomic library of DNA digested with a mixture of four blunt-end cutting restriction enzymes. A total of 313 clones putatively containing nuclear repetitive sequences were classified into 103 families, based on cross hybridization and Southern blot analysis. The 103 families were characterized in terms of genome organization, methylation pattern, abundance, and DNA variation. As in many other eukaryotic genomes, interspersed repetitive elements are the most abundant class of repetitive DNA in the cotton genome. Paucity of tandem repeat families with high copy numbers (>104) may be a unique feature of the cotton genome as compared with other higher plant genomes. Interspersed repeats tend to be methylated, while tandem repeats seem to be largely unmethylated in the cotton genome. Minimal variation in repertoire and overall copy number of repetitive DNA elements among different tetraploid cotton species is consistent with the hypothesis of a relatively recent origin of tetraploid cottons.Key words: genome analysis, genome evolution, tandemly repetitive DNA sequences, interspersed repetitive DNA sequences, polyploid.
Variations of two repetitive DNA sequences in several Triticeae genomes revealed by polymerase chain reaction and sequencing
Authors: Wang Richard R.-C. , Wei Jun-Zhi
Published: April 2011

Genomes of Triticeae were analyzed using PCR with synthesized primers that were based on two published repetitive DNA sequences, pLeUCD2 (pLe2) and l-E6hcII-l (L02368), which were originally isolated from Thinopyrum elongatum. The various genomes produced a 240 bp PCR product having high homology with the repetitive DNA pLe2. The PCR fragments produced from different genomes differed mainly in amplification quantity and in base composition at 89 variable sites. On the other hand, amplification products from the primer set for L02368 were of different sizes and nucleotide sequences. These results show that the two repetitive DNA sequences have different evolutionary significance. pLe2 is present in all genomes tested, although differences in copy number and nucleotide sequence are notable. L02368 is more genome specific, i.e., fewer genomes possess this family of repetitive sequences. It was concluded that the repetitive sequence pLe2 family is an ancient one that existed in the progenitor genome prior to divergence of annual and perennial genomes. In contrast, sequences similar to L02368 have only evolved following genome divergence.Key words: repetitive sequence, PCR, genome, evolution, Thinopyrum, Triticeae.
Centromere structure and chromosome number in mitosis of the colourless phytoflagellate Polytoma papillatum (Chlorophyceae, Volvocales, Chlamydomonadaceae)
Authors: Wolf Klaus Werner
Published: April 2011

Centromere structure is described in mitosis of the unicellular biflagellate alga Polytoma papillatum using transmission electron microscopy. The kinetochores are five-layered elements at the poleward surface of the chromosomes. The five layers consist of three dense plates interspersed by two transparent zones. The polemost dense layer serves as the attachment site for kinetochore microtubules and the innermost dense layer is intimately associated with the chromatin. The five-layered organization of the kinetochore in the alga is unusual. In animals, three-layered kinetochores are the rule. This type has also been found in some algae, while higher plants do not possess striated kinetochores. An attempt was made to determine the chromosome number of P. papillatum. Individual chromosomes could not be recognized with confidence, since there were numerous lateral contacts between the chromosomes throughout mitosis. An alternative approach, however, was successful. Counting the kinetochores in serial sections through mitotic metaphase and anaphase plates revealed a number of 15 chromosomes.Key words: anaphase, kinetochore, metaphase, microtubule.
Y chromosome specific markers and the evolution of dioecy in the genusSilene
Authors: Zhang Y Hi , Stilio Veronica S , Rehman Farah , Avery Amy , Mulcahy David , Kesseli Rick
Published: April 2011

Sex determination in plants has been most thoroughly investigated in Silene latifolia, a dioecious species possessing heteromorphic sex chromosomes. We have identified several new Y chromosome linked RAPD markers and converted these to more reliable sequence characterized amplified region (SCAR) markers by cloning the RAPD fragments and developing longer primers. Of the primer pairs for seven SCARs, five amplify a single, unique fragment from the DNA of male S. latifolia. Two sets of primers also amplify additional fragments common to males and females. Homology between the X and Y chromosomes is sufficient to allow the amplification of fragments from females under less stringent PCR conditions. Five of the SCARs also distinguish between the sexes of closely related dioecious taxa of the section Elisanthe, but not between the sexes of distantly related dioecious species. These markers will be useful for continued investigations into the evolution of sex, phylogenetic relationships among taxa, and population dynamics of sex ratios in the genus Silene.Key words: Melandrium, RAPDs, sex chromosomes, SCARs.
Lethal P-lacZinsertion lines expressed during pattern respecification in the imaginal discs ofDrosophila
Authors: Russell M A , Ostafichuk L , Scanga S
Published: April 2011

The imaginal discs of Drosophila are a useful experimental system in which we can study the origin and genetic determination of spatial patterns in development. This involves the separation of the disc-cell population into distinct lineage compartments, based on clonally transmitted expression states of a number of known selector genes. However, these commitments can be abrogated and the compartment boundaries redeployed, when repatterning occurs in cultured disc fragments. This has so far only been explained using the idea of positional information. The genetic basis of this property of the imaginal disc system and its relationship to compartments have not been identified. Here we have screened over 470 recessive lethal P-lacZ enhancer-trap insertions from the Berkeley Drosophila Genome Project for expression after cell death, which initiates pattern respecification in the imaginal discs. The positive lines obtained identify essential genes that may be important for pattern formation. Most show patterned imaginal disc expression, and many have maternal or zygotic effects on embryonic development. One is an allele of schnurri, a gene that encodes a component of the decapentaplegic (dpp) signal transduction pathway used for positional signalling in the embryo and in imaginal discs.
Linkage group alignment from four independent Brassica oleracea RFLP maps
Authors: Hu J , Sadowski J , Osborn T C , Landry B S , Quiros C F
Published: April 2011

A Brassica oleracea linkage map was constructed from an F2 population of 69 individuals with sequences previously mapped independently in three linkage maps of this species. These were the maps published by Kianian and Quiros (1992), Landry et al. (1992), and Camargo et al. (1997). The base map developed in this study consisted of 167 RFLP loci in nine linkage groups, plus eight markers in four linkage pairs, covering 1738 cM. Linkage group alignment was also possible with a fourth map published by Ramsay et al. (1996), that contained loci in common with the map of Camargo et al. (1997). Common sequences across the mapping populations served to align most of the linkage groups of the independently developed maps. In general, consistent linear order among markers was maintained, although often the distances between markers varied from map to map. A linkage group in the map of Landry et al. carrying a clubroot resistance QTL and consisting of markers from two other linkage groups, was found to be rearranged. This was not surprising, considering that the resistance gene was introgressed from Brassica napus. The extensively duplicated nature of the C genome was revealed by 19 sequences detecting duplicated loci within chromosomes and 17 sequences detecting duplicated loci between chromosomes. The variation in mapping distances between linked loci pairs on different chromosomes demonstrated that sequence rearrangement is a distinct feature of this genome. Although the consolidation of all linkage groups in the four B. oleracea maps compared was not possible, the present work served to add a considerable number of markers to corresponding linkage groups. Some of the chromosome segments in particular, were enriched with many markers that may be useful for future gene tagging or cloning. It will be possible in the future to complete the consolidation of all four maps as new loci are added to each map.Key words: cole crops, Cruciferae, molecular markers, linkage maps.
Development of a DNA marker for Vm, a gene conferring resistance to apple scab
Authors: Cheng Frank S , Weeden Norman F , Brown Susan K , Aldwinckle Herb S , Gardiner Susan E , Bus Vincent G
Published: April 2011

Primers of arbitrary sequence were screened by bulked segregant analysis to identify DNA fragments linked to Vm, a gene conferring resistance to apple scab (Venturia inaequalis). A 687-bp fragment generated by 10-base primer OPB12 gave tight linkage (no recombinants) in a population of 59 individuals from the cross 'Empire' x NY74828-12. The DNA fragment was sequenced, and two specific primers were generated to produce a STS marker for Vm. These primers were used in New Zealand to screen a second population of 180 individuals from a different cross. In this population, the marker displayed 8% recombination with Vm. A survey of Malus germplasm indicated that the marker was present in relatively few accessions, but was present in all known sources of Vm, including the cultivar Murray. However, none of the other sources of scab resistance, nor any other commercial cultivar, displayed the OPB12 fragment. These results suggest that this marker should be useful for the pyramiding of scab resistance genes in cultivated apple and, perhaps, for identifying other accessions in the Malus germplasm collection that possess Vm.Key words: sequence tagged site, gene pyramiding, Malus, Vm.
TheDrosophilageneasteroidencodes a novel protein and displays dosage-sensitive interactions withStarandEgfr
Authors: Kotarski Michael A , Leonard Deborah A , Bennett Sean A , Bishop Clifton P , Wahn Stephen D , Sedore Stacey A , Shrader Marissa
Published: April 2011

The asteroid gene of Drosophila was found to lie within 189 bp of Star. Asteroid cDNA clones were isolated and sequenced and a single putative open reading frame was identified that encodes a novel protein of 815 amino acids with a calculated molecular mass of 93 kilodaltons. Using cDNA probes, asteroid transcripts were localized to the proliferative tissues of embryos and to the mitotically active tissue anterior to the morphogenetic furrow in eye imaginal discs. Ribonuclease protection assays identified a mutation of asteroid that acts as a dominant enhancer of Star mutations and also enhances the Ellipse mutation, EgfrE1. Based on these data, a model for asteroid gene function in EGF receptor signaling is presented.Key words: Drosophila, asteroid, Star, EGF receptor, eye development.
Three novel Nicotiana debneyi specific repetitive DNA elements derived from a RAPD marker
Authors: Bai D
Published: April 2011

The RAPD marker UBC4181050, tightly linked in coupling with the Nicotiana debneyi gene for resistance to black root rot (Chalara elegans Nag Raj and Kendrick; Syn. Thielaviopsis basicola [Berk. and Broome] Ferraris), has been cloned and sequenced. The terminal 10 bases of this RAPD marker exactly match the sequence of the primer UBC418. UBC4181050 was restricted into 6 subfragments of 75, 91, 110, 174, 274, and 336 bp (the accession numbers for these 6 subfragments in the GenBank Data Base are U84217, U84218, U84219, U84220, U84221, and U84222, respectively) by combined restriction with HindIII and RsaI. The entire UBC4181050 marker and its 6 subfragments were used as probes in RFLP analyses. The RFLP analyses were performed on 'Delgold' tobacco (Nicotiana tabacum L.), the tobacco plants (2n = 48) recovered from the somatic hybrids between 'Delgold' and N. debneyi, the 'Delgold' tobacco translocation line carrying the N. debneyi gene for resistance to black root rot, the 'Delgold' tobacco addition lines carrying various N. debneyi chromosomes, and an additional 27 species in the genus Nicotiana. The analyses indicated that UBC4181050 is composed of at least 6 different repetitive DNA elements that are independently interspersed in N. debneyi genomes. Three of them (subfragments of 91, 274, and 336 bp) are N. debneyi specific. The N. debneyi specific repetitive DNA elements are distributed primarily within the taxonomic section (Suaveolentes) to which N. debneyi belongs.Key words: RAPD, repetitive DNA, Nicotiana debneyi, species-specific.
Two well-known mutants of chiasma maintenance function in maize are allelic
Authors: Maguire Marjorie P , Jackson Janet Day
Published: April 2011

By a series of traditional crosses, allelism has been tested for two maize recessive mutants of independent origin, dy1 and dsy1, both called desynaptic. These mutants both display loss of chiasmate association during diakinesis (late prophase I) but at differing frequencies. This chiasma loss happens before nucleolar loss and nuclear membrane system breakdown. That crossovers have occurred to establish the chiasmata in the first place has been documented by diakinesis-stage separation of heterozygous heterochromatic regions in univalents formed by bivalent-association breakdown. In the present work, the two mutants have been found to be allelic by the outcome of traditional crosses that produced variant plants which were heterozygous for the two alleles. These plants express a unique phenotype at diakinesis, but are essentially normal at pachytene, metaphase I, anaphase I, and later stages of meiosis.Key words: chiasma, crossover, complementation.
A study of variation in rDNA ITS regions shows that two haplotypes coexist within a single aphid genome
Authors: Fenton Brian , Malloch Gaynor , Germa Florence
Published: April 2011

We report variation in the rDNA internal transcribed spacers (ITSs) of aphid species, the first for these insects. Variation at 6 sites within ITS1 sequences of the green peach aphid, Myzus persicae, identified two haplotypes coexisting within the same individuals, indicating that molecular drive has not homogenised different copies of rDNA. During this study, we found that PCR can cause a precise 58-bp loss in the amplified copies of an ITS haplotype (type 1). This occurs in all detectable copies under routine PCR conditions, at different annealing temperatures and with Pfu and Taq polymerases. In addition, "hot-start" PCR exclusively copied a different, rare haplotype (type 2). These observations have important considerations for using PCR, as large deletions in PCR products may not reflect real deletions in the genome, and changes in PCR conditions may be needed to copy cryptic haplotypes.Key words: PCR, aphid, ITS, variation, selection.
Mitochondrial DNA analysis of the neotropical malaria vectorAnopheles nuneztovari
Authors: Conn J E , Mitchell S E , Cockburn A F
Published: April 2011

Restriction endonucleases were used to test an hypothesis, based on cytological data, proposing the existence of two races in Anopheles nuneztovari, one Venezuelan-Colombian and the other Amazonian, and to examine variation in the mitochondrial DNA (mtDNA) of 263 individual A. nuneztovari mosquitoes from 12 sites in Bolivia, Brazil, Colombia, Suriname, and Venezuela. Cladistic analysis of the mtDNA data using three outgroups suggests that A. nuneztovari is monophyletic. However, this analysis is poorly resolved by parsimony, probably caused by extensive homoplasy. Analysis of the relationships among haplotypes, based on genetic distances, results in five haplotype lineages, three of which are in the Amazon Basin. Relationships among the 12 populations reveal distinctive lineages, one in Venezuela-Colombia and two within the Amazon Basin. Molecular variance components and F statistics (phi) among neotropical biomes, among populations/biomes, among cytotypes, among populations/cytotypes, and within populations all demonstrate significant subdivision and strongly support multiple lineages, which could be interpreted as recently evolved species, within A. nuneztovari. The Mantel analysis showed no significant correlation between genetic and geographic distances, suggesting that it is biomes and cytotypes that contribute most strongly to subdivision.Key words: mtDNA lineages, anopheline mosquito, gene flow, genetic diversity, neotropical.
Drosophila melanogasterhistone H2B retropseudogene is inserted into a region rich in transposable elements
Authors: Akhmanova Anna , Hennig Wolfgang
Published: April 2011

We have isolated and characterized the genomic sequence of a Drosophila melanogaster histone H2B pseudogene that is localized outside of the cluster of the replication-dependent histone genes and has all the properties of a retropseudogene. It is highly homologous to the transcribed region of the D. melanogaster histone H2B gene, but not to its flanking regions, and is surrounded by short direct repeats. The pseudogene contains several point mutations that preclude its translation. The sequence of the 3' region of this pseudogene is compatible with the hypothesis that the 3' terminal stem-loop structure of the histone H2B mRNA has served as a primer for the reverse transcription event from which this pseudogene originated. Analysis of the regions flanking the histone H2B pseudogene revealed the presence of three different types of transposable elements, suggesting that this chromosomal locus represents a hotspot for transposition.Key words: retropseudogene, histone H2B, Drosophila.