bluuebunny/crossref_metadata_2025 huggingface dataset:
Segregation at enzyme loci in megagametophytes of white spruce, Picea glauca
Authors: Stewart Steven Craig , Schoen Daniel J.
Published: November 2014

Segregation patterns of six enzyme loci expressed in megagametophytes of white spruce (Picea glauca) were studied as part of an investigation of the mating pattern in a clonal seed orchard. More than 3000 megagametophytes from 79 trees representing 18 clones were assayed. The single locus patterns of segregation for each enzyme locus are consistent with simple Mendelian inheritance. The two locus patterns of segregation reveal that Idh and Gdh are tightly linked with an estimated recombination rate of 0.027 ± 0.004. No other pair of loci deviates significantly from the ratios expected for unlinked loci. Little heterogeneity in the pattern of gametic segregation was detected among ramets within clones or among clones for any of the loci. The results contribute to knowledge of genetic variation in this species and provide a basis for assumptions about segregation made in mating system estimation models.Key words: segregation, linkage, allozymes, Picea glauca, white spruce.
Sex chromosome aneuploidy in a male-linked translocation in Ceratitis capitata
Authors: Zapater M. , Robinson A. S.
Published: November 2014

A translocation line in Ceratitis capitata (2n = 12) linking the male-determining Y chromosome with the autosome carrying the alcohol dehydrogenase (Adh) locus was examined to assign the locus to its chromosome. Adh was assigned to chromosome 2, the largest autosome, representing the first correlation between genetic and cytological data in this species. During the study, male adults with 11 and 12 chromosomes were identified in the population and a model was proposed to account for the appearance of these individuals. Predictions made from the model were in general verified by the subsequent experiments. It was shown that 11-chromosome males were more fertile and produced more males than 12-chromosome males. Eleven-chromosome males produced 11- and 12-chromosome progeny, whereas 12-chromosome males produced only 12-chromosome male progeny. The results are discussed with relation to sex determination in this species and to the use of male-linked translocations for the development of genetic sexing techniques.Key words: Ceratitis, male determination, translocation, aneuploidy.
Chromosome numerical mosaicism in pearl millet (Pennisetum americanum (L.) Leeke)
Authors: Rao Panuganti N. , Nirmala A.
Published: November 2014

In pearl millet (Pennisetum americanum (L.) Leeke, 2n = 14), a wide range of intraplant chromosome numerical variation occurring in pollen mother cells at meiosis within the same anther, floret, or spike was found in eight plants. The types of mosaicism encountered were haploid–diploid, diploid–tetraploid, haploid–diploid–aneuploid, and diploid–tetraploid–aneuploid–teloaneuploid. Their probable mode of origin is discussed.Key words: Pennisetum, chromosomal numerical mosaicism.
The effect of double-strength standard saline citrate on silver staining. I. Nucleoli and micronucleoli in the somatic and germ line of the grasshopper Arcyptera fusca (Orthoptera)
Authors: Gosàlvez J. , Torre J. de la , Vega C. Garcia de la , López-Fernández C.
Published: November 2014

The nucleolar activity in cells from both somatic and germ line of the grasshopper Arcyptera fusca has been analyzed by means of silver staining using a standard technique with and without a previous treatment of the slides with double-strength standard saline citrate (2 × SSC). Results show that the treatment with 2 × SSC improves the silver staining of the main nucleoli and in some tissues reliably uncovers other sites along the chromosomes with attached silver precipitates (micronucleoli). The parallel origin of the main nucleoli and the micronucleoli, the possible enlargement of rDNA activity in some tissues, and the ability of the silver nitrate to stain certain nucleolar proteins are discussed.Key words: Arcyptera, Orthoptera, nucleolus, micronucleus, silver staining.
Nucleolar organizer activity at meiosis in wheat–rye hybrid plants
Authors: Cuñado N. , Cermeño M. C. , Orellana J.
Published: November 2014

Nucleoli and nucleolar organizer regions (NORs) have been studied by a silver staining method in all meiotic stages of wheat–rye hybrid plants. The maximum number of nucleoli per cell scored at meiotic prophase and tapetum binucleate cells indicates that only the NORs of 1B, 6B, and 5D wheat chromosomes are active, whereas that of chromosome IR (SAT) of rye is inactive. However, at diakinesis, metaphase and anaphase meiotic stages only chromosomes 1B and 6B show Ag-NOR as was reported previously in somatic metaphase. The absence of Ag-NOR on chromosome 5D has been imputed to its low nucleolar organizer activity, not detectable by silver staining, because of the small number of rDNA clusters it carries. On the other hand, the meiotic behaviour of chromosomes 1B and 6B has been studied at metaphase I and anaphase I, using the Ag-NORs as cytological markers.Key words: nucleolar organizer, Ag-NOR, meiosis, wheat–rye hybrids.
DNA variation in flax tissue culture
Authors: Cullis C. A. , Cleary W.
Published: November 2014

The DNAs from leaves and callus from a series of flax genotrophs have been compared. The probes used for this comparison represent all of the highly repeated DNA sequence families in the flax genome. The abundance of most of the families could vary in culture, but the extent of variation was dependent on the genotroph. The extent of the variation observed between leaf DNA and callus DNA from a single genotroph was greater than that observed between the genotrophs in vivo. The DNAs from the progeny of a number of regenerated plants were also compared. They sometimes differed both from the callus from which the plants were regenerated and the original line from which the callus was derived. Individual progeny from a single inbred regenerated plant also differed.Key words: flax, DNA variation, somaclonal variation.
Rapidly varying DNA sequences in flax
Authors: Cullis C. A. , Cleary W.
Published: November 2014

The highly repetitive sequences of the flax genome have been characterized. This has been done using a series of cloned probes that represent most, if not all, of the highly repetitive families in the flax genome. All of them are arranged as tandem arrays. The organization and copy number of these sequences has been compared in a number of lines including those lines (termed genotrophs) derived from the flax variety 'Stormont Cirrus' by the environmental induction of heritable changes, two other flax and linseed cultivars, and some of the supposed wild progenitors of flax. It was found that all except the light satellite differed in copy number between some of the lines. A particular subset of the 5S genes was shown to be preferentially affected when changes occurred. The extent of the variation between genotrophs was similar to that between different varieties or between flax and its supposed progenitor.Key words: flax, DNA variation, repeated sequences.
Location of chromosomal regions controlling fatty acid composition of embryo oil in Zea mays L.
Authors: Shadley Jeff , Weber David
Published: November 2014

B–A translocations were utilized in Zea mays L. to assign regions affecting the fatty acid composition of embryo oil to chromosome arms. A region affecting all four measured fatty acids (palmitic, stearic, oleic, and linoleic acids) was assigned to the long arm of chromosome 4 by results of tests with TB-4Lb, whereas another affecting palmitic and stearic acids was assigned to the long arm of chromosome 10 by tests with TB-10L19. These effects were in agreement with previous results from analysis of trisomy for chromosome 4 and monosomy for chromosome 10. The fatty acid composition of euploid embryos containing a B chromosome was not significantly different from that of embryos not containing a B chromosome. Thus, the B chromosome is not responsible for the differences observed using B–A translocations. TB-5La was backcrossed into two inbred lines having a relatively high percentage of linoleic acid. Hyperploidy for the long arm of chromosome 5 significantly increased the percentage of linoleic acid in both inbreds. Aneuploidy for the long arm of chromosome 5 also had a dosage effect on fatty acid composition of the endosperm.Key words: Zea, corn oil, fatty acids, B chromosome, translocation.
Genotype- and age-associated in vivo cytogenetic alterations following mutagenic exposures in mice
Authors: Singh S. M. , Toles J. F. , Reaume J.
Published: November 2014

We studied mice from eight genetic strains at two ages (young, 10 weeks; and old, more than 80 weeks) for cytogenetic alterations (sister chromatid exchange (SCE), micronulei, and metaphase indices) following challenges by two known mutagens: N-nitrosoethyl urea (ENU, 17 mg/kg) and cyclophosphamide (CP, 4.5 mg/kg) on bone marrow cells in vivo. The data were used to evaluate the effect of age, genotype, and differential aging patterns of genotypes in relative susceptibility to chromosomal breakage and instability in otherwise normal individuals. The older animals had a higher frequency of micronuclei, reduced metaphase indices, and lower SCE/cell as compared with their younger counterparts. Treatment with both mutagens significantly increased micronuclei and SCEs/cell in almost all strains at both ages but had little effect on the frequency of cells in metaphase. Among individual differences for SCEs/cell at most treatment combinations were not significant. In general, the induced SCEs (treatment–control) are significantly higher in older animals, variable among strains, and relatively higher as a result of CP than the ENU treatment. When the age effect was evaluated as the difference of SCE/cell in old and SCE/cell in young animals of each genotype–treatment combination, an age-dependent pattern was evident. In the presence of a mutagen the pattern in aging response was highly variable and strain (genotype) dependent. This variability may be viewed as subtle inherent genetic predisposition of sensitivity to mutagens that could be evaluated only using sensitive measures (e.g., SCE and not micronuclei) following more than one mutagenic challenges. These subtle differences coud become pronounced when these parameters are evaluated at different ages on the same genotype. Although these observations suggest that even normal individuals differ in their relative sensitivity to genetic instability, it may not be easy to recognize these differences in simple experimental protocols.Key words: age effect, sister chromatid exchange, mutagenesis, micronuclei.
Transmission of a wheat alien chromosome translocation with resistance to the wheat curl mite in common wheat, Triticum aestivum L.
Authors: Whelan E. D. P. , Conner R. L. , Thomas J. B. , Kuzyk A. D.
Published: November 2014

A translocation between a common wheat (Triticum aestivum L.) chromosome and chromosome 6 of Elytrigia pontica (Podp.) Holub conferred resistance to feeding by Eriophyes (= Aceria) tulipae Keifer, the mite vector of wheat streak mosaic virus and the wheat spot mosaic agent. Resistance was dominant, but differential transmission occurred between the pollen and the egg. Transmission of resistance through the pollen was low, about 3% in 'Cadet', 'Rescue', and 'Winalta', but significantly higher in 'Norstar' (9.1%). Significant differences also were detected in transmission through the egg. 'Cadet' had the highest transmission (50.9%) and 'Rescue' the lowest (40.5%). However, there were no significant differences among varieties in the frequencies of resistance (50.3–54.5%) in the F2. Less than 10% of the F2 plants were homozygous resistant. Selfed progeny from monosomic or disomic F1 plants from crosses between the homozygous translocation and group-6 monosomics all segregated for susceptibility. Meiotic studies of 25 susceptible F2 plants from these F1 monosomics showed that 21 were either monosomic or disomic and only 4 were nullisomic, indicating that the translocation did not involve any of the group-6 homoeologues. The translocation is considered to be a noncompensating translocation involving a whole arm of chromosome 6 of E. pontica.Key words: wheat, mite (wheat curl), translocation, Triticum.
Cytogenetic relationship within cultivated Brassica analyzed in amphihaploids from the three diploid ancestors
Authors: Attia T. , Röbbelen G.
Published: November 2014

To investigate the factors controlling evolutionary differentiation within the genus Brassica, chromosome pairing in amphihaploids from crosses between the three elementary diploid species B. campestris (AA), B. oleracea (CC), and B. nigra (BB) was analyzed. The amphihaploid AC showed a high amount of pairing, while the two amphihaploids AB and BC, both including the genome of B. nigra, exhibited only low degrees of chromosome association. By the occurrence of tetra- and penta-valents, auto- as well as allo-syndetic pairing was demonstrated to exist in the AC amphihaploid. True homologous pairing between the genomes A and C was deduced from the occurrence of chromosomal interchange configurations. Although the genomes of B. oleracea and B. campestris are evolutionarily distinct, as shown by the different number and structure of their chromosomes, their close relationship is readily evident from the high level of pairing observed in the AC amphihaploids. On the other hand, the much lower pairing within the amphihaploids including the B genome is unexpected in view of the hypothesis of a common ancestor for all three of the cultivated Brassica diploids from an ancestral genome with x = 6 chromosomes. It is discussed whether B. nigra is indeed more distantly related to the two other species or whether this genome carries a suppressor of chromosome pairing.Key words: chromosome pairing, amphihaploids, evolutionary relations.
The differentiation between chromosome 7D of Triticum aestivum cv. Canthatch and Triticum tauschii as measured by chromosome pairing
Authors: Penner G. A. , Kerber E. R. , Larter E. N.
Published: November 2014

Disomic substitution stocks in which chromosome 7D of Triticum aestivum cv. Canthatch was replaced by the corresponding homologous chromosome of each of four varieties of Triticum tauschii were crossed with 'Canthatch' to investigate the degree of differentiation for this chromosome between these two species. These disomic substitutions were also crossed with a 'Canthatch' plant double monotelosomic for chromosome 7D. Three double telotrisomics were produced, one of which had the complete 7D chromosome derived from 'Canthatch', one had 7D derived from the T. tauschii var. typica, and one had 7D from T. tauschii var. strangulata. Analysis of chromosome pairing demonstrated that chromosome 7D from var. typica formed fewer bound arms with 'Canthatch' 7D than did the corresponding chromosome from the other three tauschii varieties. The reduction in pairing between chromosomes 7D of var. typica and 'Canthatch' is greater than that previously reported from intraspecific D-genome chromosome pairing studies within T. aestivum. It is suggested that intraspecific divergence for at least chromosome 7D occurred between var. typica and these other three tauschii varieties before the synthesis of common hexaploid wheat.Key words: Triticum, aneuploidy, chromosome pairing, chromosome substitution.
Meiotic pairing in new hybrids of Hordeum procerum (6x) with H. parodii (6x) and Elymus virginicus (4x)
Authors: Gupta P. K. , Fedak George
Published: November 2014

Hybrids of Hordeum procerum were readily produced with H. parodii (7.9%) and Elymus virginicus (14.3%). The average meiotic pairing per cell in the interspecific hybrid between H. procerum and H. parodii was 14.56 I + 12.19 II + 1.04 III, which indicated that the species have two genomes in common. In the hybrid between H. procerum and E. virginicus the average metaphase I configuration was 20.35 I + 6.86 II + 0.31 III indicating one common genome. Keywords: interspecific, intergeneric hybrids, chromosome pairing, Hordeum, Elymus.
Variation in induction of homoeologous pairing among chromosomes of 6x Hordeum parodii as a result of three triticale (×Triticosecale Wittmack) cultivars
Authors: Gupta P. K. , Fedak George
Published: November 2014

Intergeneric hybrids were obtained between Hordeum parodii Covas s.1. (6x) and three cultivars of triticale (×Triticosecale) at frequencies of 0.47 to 1.21% of pollinated florets. The triticale cultivars varied in their chromosome constitutions of the rye genome as well as the telomeric heterochromatin content of some of the rye chromosomes. The average chiasmata frequency per cell varied from 0.58 to 13.14 in different hybrid combinations. The differences in the chiasmata frequencies in the different hybrid combinations were attributed to a meiotic pairing control mechanism in H. parodii whose function was affected primarily by the rye chromosome constitutions of the triticale cultivars and to a lesser extent by the heterochromatin content of the rye chromosomes.Key words: hybrids (intergeneric), Hordeum, meiotic pairing control, chiasma.
Meiosis in Triticum aestivum × Elytrigia repens hybrids
Authors: Fedak G. , Comeau A. , St-Pierre C. A.
Published: November 2014

The average meiotic configuration in Triticum aestivum × Elytrigia repens hybrids was 31.951 + 4.97 II + 0.03 IV per cell. Chromosome synapsis was likely due to autosyndesis between chromosomes of the S genomes and not due to intergenomic homology.Key words: hybrids, intergeneric, Elytrigia repens, Triticum aestivum, chromosome synapsis.
Generation by a polymorphic supernumerary segment of recombination in a normally achiasmate proximal region in Acrotylus insubricus (Scopoli) (Orthoptera, Acrididae)
Authors: Rufas J. S. , Suja J. A. , Vega C. García de la
Published: November 2014

Four of 20 males collected from a Spanish natural population of Acrotylus insubricus (Scopoli) present a supernumerary segment that is distally located in one of the chromosomes of the M9 bivalent. In meiosis this segment is positively heteropyenotic during the first prophase and reverses its pycnosis at first metaphase. The extra material shows "grey" staining after C-banding and fluoresces brightly with acridine orange. The nucleolar expression in this species is not affected by the presence of the supernumerary segment. However, it provokes a considerable alteration in the pattern of chiasma distribution in the M9 bivalent if compared with standard individuals. Certain aspects related to the possible structural influence of the segment in the displacement of the chiasmata are discussed.Key words: Acrotylus, supernumerary segment, chiasma distribution.
Origin of aneuploid plants obtained by anther culture in triticale
Authors: Charmet Gilles , Bernard Sylvie , Bernard Michel
Published: November 2014

A very large proportion of plants regenerated from anther culture of triticale F1 hybrids do not show the euploid number of chromosomes. Of 408 androgenetic plants checked for their chromosome numbers, 228 were aneuploid, of which 39 had one or several telosomes. Two observations suggest that most of the chromosome variations observed probably preexist in microspores of the F1 hybrids and would be caused by meiotic irregularities: on the one hand, the majority of these phenomena involve R-genome chromosomes, which also give rise to meiotic univalents; on the other hand, the chromosome number frequency distribution of the microspores from a fairly asyndetic hybrid fits well with that of the androgenetic plants. Thus aneuploidy and chromosome rearrangement do not implicate the in vitro technique itself but rather the choice of the material in triticale.Key words: × triticosecale, in vitro culture, chromosome variation, aneuploidy, C-banding.
Evidence for local DNA influences on patterns of substitutions in the human α-interferon gene family
Authors: Golding G. Brian , Glickman Barry W.
Published: November 2014

The evolutionary history of genes can be used to examine patterns of spontaneous mutation if the sequences are sufficiently extensive to provide reliable data. Many human α-interferon genes have been sequenced and they form a large multigene family including several pseudogenes. A phylogenetic history for 15 human interferon sequences was reconstructed and their ancestral sequences inferred using a maximum parsimony method. This evolutionary history provided a record of more than 738 spontaneous mutations that have occurred in man's recent evolution. Of these mutations, more than 267 base substitution and deletion–insertion events were analyzed to determine the possible effects of nearby DNA sequences. Many substitutions occur at the end of long runs of identical bases and some dinucleotide pairs may mutate more often than others. Because templating by local DNA sequences has been implicated in prokaryotic mutation, the sequences were also examined for nearby repeats that include the substituted nucleotide and hence are potentially capable of templating the substitution. The majority of sequence alterations examined have either a similar direct repeat or palindrome nearby. Often such templates can account for simultaneous multiple mutations. These results suggest that sequence-directed events may occur occasionally in eukaryotes and that neighbouring DNA sequences can influence both the occurrence and types of mutations in several different ways.Key words: spontaneous mutation, template-directed mutations, phylogenetic history, evolution.
Meiosis in interspecific Hordeum hybrids. I. Diploid combinations
Authors: Bothmer Roland Von , Flink Jan , Landström Thomas
Published: November 2014

The meiotic pairing behaviour of 39 new interspecific combinations between diploid Hordeum species are reported. On the basis of this data, four "basic genomes" are probably present in the genus. Hordeum bulbosum and H. vulgare have the same genome (I); H. marinum ("X") and H. murinum ("Y") each have one distinct genome. All other diploid taxa have either the same or a somewhat modified form of genome H. In this latter group of diploids, the South American taxa together with H. pusillum and H. intercedens in North America constitue a homogeneous group with respect to genomic structure, which differs somewhat from that found in the other Asiatic and North American species. Hordeum roshevitzii from Central Asia is unique, showing high affinity to both the Asiatic and to the American taxa. Evidence suggesting genetic regulation of chromosome pairing (both pairing promoting and pairing reducing) was obtained from a number of the diploid hybrids.Key words: Hordeum, interspecific hybrids, meiosis, diploids.
Genetic mapping of the 5S rRNA gene cluster of the nematode Caenorhabditis elegans
Authors: Nelson D. W. , Honda B. M.
Published: November 2014

We have identified a restriction fragment length difference (RFLD) affecting the genomic sequences immediately flanking the 5S rRNA gene cluster in the Bristol and Bergerac strains of the nematode Caenorhabditis elegans. We have used this RFLD as a molecular marker to follow the segregation of the 5S rRNA gene cluster through a series of two- and three-factor interstrain crosses. Our results show that the 5S rRNA gene cluster maps between unc-76 and dpy-21 on the right arm of linkage group V. This genetic localization provides a linkage group V "landmark" with which to localize other cloned sequences by in situ hybridization.Key words: Caenorhabditis elegans, 5S rRNA gene cluster, restriction fragment length difference, genetic mapping.
Inheritance of siliqua strength in Brassica campestris L. II. Quantitative genetic analysis
Authors: Kadkol G. P. , Halloran G. M. , Macmillan R. H.
Published: November 2014

Quantitative genetic analysis of siliqua strength in Brassica campestris L. was conducted in the cross cv. Torch × DS-17-D using the North Carolina experiment II design. This revealed the presence of a high degree of nonadditive genetic variance and a high heritability (broad sense) for all measures of siliqua strength. These results are in accordance with earlier findings of the likelihood of a small number of genes controlling siliqua strength which interact epistatically.Key words: siliqua strength, shatter resistance, genetic variances (additive and nonadditive), heritability.
Cytogenetic analysis of translocation heterozygosity in the common bean (Phaseolus vulgaris L.)
Authors: Ashraf M. , Bassett M. J.
Published: November 2014

Twelve semisterile lines of Phaseolus vulgaris L. (2n = 22) were reported previously by this laboratory. Here we verify through cytological investigations that 5 of the 12 stocks are indeed chromosome translocations. Cytological analysis of a half diallel set of crosses indicates that these five stocks involve eight different chromosomes in reciprocal translocations. Pollen and ovule abortion rates increase with the increasing number of interchanges in a stock. Cytological behavior and morphological abnormalities with respect to pollen and ovule abortion produced by translocation heterozygosity in the common bean, as observed in this study, are similar to those reported in other crops.Key words: Phaseolus, chromosome translocation, translocation heterozygosity.
Inheritance and linkage of allozymes in seed tissue of whitebark pine
Authors: Furnier Glenn R. , Knowles Peggy , Aleksiuk Mary A. , Dancik Bruce P.
Published: November 2014

Allozyme variants were examined for 12 enzyme systems in haploid megagametophyte tissue of whitebark pine (Pinus albicaulis Engelm.). Inheritance and linkage information is reported for 11 loci (Aat-3, Aco, Adh, Fle-2, Idh, Mdh-2, Mdh-3, Mdh-4, Mdr, Pgi-2, and Pgm-2). Deviations from a 1:1 segregation ratio were observed at Fle-2, Pgi-2, and between two of the three alleles at Mdh-4. Significant linkage was observed for two pairs of loci (Aco–Fle-2 and Adh–Pgi-2), but estimates of recombination frequencies were relatively high.Key words: Pinus albicaulis, isozymes.
Chromosome instability in somaclones of a Triticum crassum × Hordeum vulgare hybrid
Authors: Fedak George , Grainger John
Published: November 2014

Immature inflorescence culture and subsequent plant regeneration was practiced for four successive cycles using a Triticum crassum × Hordeum vulgare hybrid cultured on Kao's medium supplemented with 2,4-dichlorophenoxyacetic acid (5 mg/mL). In one line, chromosomal mixoploidy was observed among both mitotic and meiotic cells. Variation in chromosome number of 20 to 98 was observed in mitotic and 14 to 68 among meiocytes in the first cycle regenerants. The range in chromosome number decreased in subsequent regeneration cycles. Fragmented chromosomes were observed at low frequencies in both groups of cells. The high frequency of univalents at meiosis was attributed to possible elimination of chromosomes carrying meiotic pairing control genes.Key words: somaclonal variation, hybrids (intergeneric), tissue culture, chromosomal mixoploidy.
Heterochromatin organization in the nucleus of Indian muntjac (Muntiacus muntjak)
Authors: Verma Ram S. , Jacob Jessey P. , Babu Arvind
Published: November 2014

The heterochromatin in Indian muntjac (Muntiacus muntjak) is located at the periphery of primary constrictions of all the chromosomes. The X chromosome contains significantly larger amounts of heterochromatin than the rest of the complement by C-banding technique. However, the small portion of C-band region was found to be resistant by restriction endonuclease HaeIII (5′… GG ↓ CC … 3′) and was clearly visible on the nucleus. Therefore, the position of this large heterochromatic segment is examined at somatic metaphases. The distribution of the heterochromatin of the X chromosome observed in Indian muntjac is contrary to the general pattern observed in other species, i.e., the chromosomes consisting greater amount of heterochromatin are located more peripherally than those with lesser amount. However, the smaller Y chromosome (Y1) is frequently found at the periphery. The present findings suggest that the role of heterochromatin organization in the nucleus vary between different heterochromatic segments of the same species and vary from species to species.Key words: heterochromatin, chromosome, nucleus, metaphase, Muntiacus muntjak.
The structure of DNA from the rye (Secale cereale) NOR R1 locus and its behaviour in wheat backgrounds
Authors: Appels R. , Moran L. B. , Gustafson J. P.
Published: November 2014

The nucleotide sequence of a 4.5-kilobase (kb) segment of rye DNA (in the clone pScR4) containing the major spacer region of ribosomal DNA, 0.25 kb of the 5′ end of the 18S gene and approximately 1.2 kb of the 3′ end of the 26S gene is presented. The 5′ end of the 18S gene, and most of the 3′ end of the 26S gene, could be readily defined by comparisons with previously published sequences. The major spacer region was dominated by the presence of 10 repeating units, with a basic length of 134 base pairs (bp), which showed sequence variability in that deletions of sections of the sequence as well as base-pair changes were common. A portion of the sequence which was common to almost all the spacer repeats and is also found in the corresponding wheat spacer repeats (in pTa250), with only two mismatches (using a consensus sequence of the rye spacer repeats as a comparison), is GCGACATGGAAAACCGGGCAAAACCACGTAC. The occurrence of this conserved sequence between more divergent sequences in both wheat and rye suggests that it may be important in forming the pretranscription complex involving RNA polymerase I and other protein cofactors. Probes were isolated from the spacer region to preferentially assay the rye rDNA in wheat backgrounds. In situ hybridization studies revealed that when 1R was the only NOR-containing chromosome present the rDNA was in a dispersed state. This dispersed state correlates with nucleolus formation and presumably with rDNA transcription. In the presence of chromosomes 1B and (or) 6B of wheat (these chromosomes carry NOR loci) the dispersed state of rye rDNA was generally suppressed, but not completely, suggesting that 1R retains some potential for activity.Key words: rye, NOR R1 locus, nucleotide sequence, transcription.
Modification of barley powdery mildew resistance gene Ml-a12 by induced mutation
Authors: Torp J. , Jørgensen J. Helms
Published: November 2014

Kernels from a barley line, 'Sultan-5', with powdery mildew resistance gene Ml-a12 were treated with mutagens. Among 10 381 M1 spikes progeny tested with Ml-a12 avirulent powdery mildew, 25 segregated mutants with infection types between 0–1 n and 3–4cn. The resistance of the mutants is race specific in the sense that it is expressed only with powdery mildew cultures that are Ml-a12 avirulent but not with an Ml-a12 virulent culture. Genetic analysis of 10 mutants revealed that 9 had mutant genes that were allelic to gene Ml-a12, and one had a recessive mutant gene inherited independently of Ml-a12 on which it acted as a suppressor. The high mutation frequency in gene Ml-a12 and the gradual inhibition of the expression of gene Ml-a12, by mutation or suppression, strongly supports the suggestion that the gene function is associated with incompatibility rather than with compatibility.Key words: barley, Hordeum vulgare, powdery mildew, Erysiphe graminis hordei, mutation, resistance, suppressor.
Heterochromatin composition and nucleolus organizer activity in four canid species
Authors: Mayr B. , Geber G. , Auer H. , Kalat M. , Schleger W.
Published: November 2014

Sequential staining with a counterstain-contrasted fluorescent banding technique (chromomycin A3 – distamycin A – DAPI) revealed the occurrence of distamycin A – 4,6-diamidino-2-phenylindole (DA–DAPI) staining heterochromatin in the centromeric regions of chromosomes 33, 36, 37, and 38 in the wolf (Canis lupus pallipes) and of chromosomes 13, 16, and 23 in the blue fox (Alopex lagopus). The red fox (Vulpes vulpes) lacked such regions. Staining with DAPI – actinomycin D produced a QFH-type banding pattern with clearcut differences in the staining behaviour of DA–DAPI positive regions between these three canid species. Staining with the fluorochrome D 287/170 did not preferentially highlight any of the DA–DAPI positive regions in any of them. Counterstain-enhanced chromomycin A3 R-banding and studies of nucleolus organizer region location and activity confirmed a close relationship between the karyotype of the wolf and the domestic dog. Few heterochromatic marker bands were encountered in these two species, but heterochromatin polymorphism was evident in the blue fox.Key words: Canidae, heterochromatin, nucleolus organizers.
Chromosomal evolution in finches and their allies (families: Ploceidae, Fringillidae, and Emberizidae)
Authors: Christidis L.
Published: November 2014

Five species of sparrows, weavers, and finches belonging to the Ploceidae, Fringillidae, and Emberizidae were examined cytogenetically by G- and C-banding. There was significant G-band homology between the families, with pericentric inversions being the principal form of chromosome change both at the intra- and inter-specific levels. In some instances there was more homology between species from different families than there was between species within a family. Possible explanations for this phenomenon are discussed.Key words: chromosome banding, inversion polymorphism, Passeriformes, Aves.
Variability in the effect of alcohol on alcohol metabolizing enzymes may determine relative sensitivity to alcohols: a new hypothesis
Authors: Singh Shiva M.
Published: November 2014

Individual and racial differences in response to alcohol and with respect to alcoholism have strong genetic predispositions. Most studies on the actual genetic determinants have concentrated on the isozymes of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH), the two enzymes of the primary pathway of alcohol metabolism. Although few "activity" variants (associated with mutations in the structural genes) of the two enzymes are known to exist in susceptible groups, these observations do not offer an adequate explanation for the observed variability in response to alcohols in the population. Some recent studies have reported alterations in the specific activity of the two enzymes following exposure to alcohol for different lengths of time in man, rat, and mice. The induction–repression so observed is hypothesized to be regulated by one or more inducibility genetic elements (IGE) associated with the structural loci of the two enzymes. Variability in IGE will permit a genotype (individual) specific response in ADH and ALDH specific activity when challenged with a given level of alcohol. Considering the relative toxicity of acetaldehyde, the primary metabolite of this pathway, the resistant individuals would be expected to show ALDH induction. Conversely, the susceptible individuals should respond to alcohol by ALDH repression. The ability of an individual to show induction or repression following alcohol ingestion will depend on his or her IGE genotype(s) associated with specific enzyme loci. Also, the degree of polymorphism at these loci would be expected to be extensive and yet population and race specific. Once experimentally established, this approach could have important implications in screening, counselling, prevention, and in novel approaches to treatment.Key words: alcohol metabolism, acetaldehyde, alcohol dehydrogenase, aldehyde dehydrogenase, alcohol sensitivity, induction–repression of enzymes.
Interactions of Agrobacterium tumefaciens with soybean (Glycine max (L.) Merr.) leaf explants in tissue culture
Authors: Kudirka D. T. , Colburn S. M. , Hinchee M. A. , Wright M. S.
Published: November 2014

Wounded petiole surfaces of excised soybean (Glycine max (L.) Merr.) leaves of 'Peking' formed neoplastic growths testing positive for opines after inoculation with a tumorigenic strain of Agrobacterium tumefaciens. During the 48-h inoculation period, uninoculated explants and explants inoculated with A136 (avirulent), A208 (tumorigenic), and ASE1-200 (nontumorigenic) strains of A. tumefaciens showed initiation of mitotic activity at the wound surface conforming with classical descriptions of the wound response; however, shortly after explant transfer to tissue culture medium, morphogenetic patterns in explants inoculated with tumorigenic A. tumefaciens deviated from the uninoculated and A136 inoculated controls. This developmental deviation was correlated to the presence of the Ti plasmid in the bacterium. Explants inoculated with nontumorigenic A. tumefaciens showed a morphogenetic pattern intermediate between the controls and explants inoculated with tumorigenic bacteria. This suggests that the latter plant response might be due to a plant regulator gene found in the vir region of the Ti plasmid. Explants inoculated with tumorigenic bacteria showed decreasing efficiency of transformation if inoculations were delayed 4 h after excision and explants showed greatest thermosensitivity to transformation during the 48-h inoculation period. Reduced thermosensitivity was evident after transfer to tissue culture medium supplemented with carbenicillin. In this in vitro inoculation procedure, 'Peking' was shown to be twice as transformable as 'Corsoy 79'. This offers an opportunity to determine if there is a heritable component associated with transformation in this soybean explant system.Key words: Agrobacterium tumefaciens, Glycine, transformation, wound response, tissue culture.
Selection on phenotypic variation of pupa weight in Tribolium castaneum
Authors: Cardin Sylvie , Minvielle Francis
Published: November 2014

Responses to selection for high and low intrafamily coefficients of variation of pupa weight in Tribolium castaneum were observed for 10 generations. A significant decrease of the coefficient of variation has been observed in the replicated lines selected downwards while no response occurred in the other lines. Mean pupa weights did not change significantly throughout the experiment while mean fertility decreased in all lines, probably as a consequence of inbreeding depression. Realized heritability of the coefficient of variation of pupa weight was 0.15 ± 0.04 and 0.03 ± 0.01% for the downwards and upwards lines, respectively. These results show that the manipulation of the phenotypic variability by direct selection is possible.Key words: Tribolium, phenotypic variance, coefficient of variation of pupa weight.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. III. Cytology, breeding behavior, fertility, and morphology of autotriploids
Authors: Kuspira J. , Bhambhani R. N. , Sadasivaiah R. S. , Hayden D.
Published: November 2014

Mature triploid seed from reciprocal (2n = 4x × 2n = 2x) crosses in Triticum monococcum was minute and shrivelled because of endosperm collapse and therefore failed to germinate. This necessitated the excision of embryos from successful pollinations and their growth in vitro to ensure subsequent germination so as to obtain viable and vigorous autotriploids. A comparison of these triploids with their diploid and tetraploid progenitors revealed that cell size, kernel weight, and pistil size increased with an increase in ploidy level. However, unlike other species, optimum expression was observed in these triploids for plant height, tillering, size of spikes, number of spikelets/spike, and leaf size. Earliness, althoughenhanced in tetraploids relative to diploids, was delayed in the triploids. Mean numbers of univalents, bivalents, and trivalents per microsporocyte were 2.65, 2.60, and 4.38, respectively. Only chains (93.5%), which formed V-shaped metaphase I (MI) configurations, frying pan (5.0%), and Y-shaped (1.5%) trivalent associations occurred. On the average, two reciprocal exchanges occurred per bivalent and trivalent. Trivalents corriented randomly at MI. At anaphase I, all sets of three homologues segreated randomly to the two poles, lagging univalents always divided equationally, and only meiocytes with such chromosomes formed micronuclei. The reasons for similarities and differences in meiotic behaviour of T. monococcum triploids with those of other species are discussed. Confirmation of the conclusions drawn with respect to the cytology of the triploids was obtained from similar cytological observations with primary single trisomics. These triploids produced euploids, primary single trisomics as well as some double and triple trisomics all of which differed phenotypically from diploids. Triticum monococcum, like most diploid species, is highly intolerant of aneuploidy. Possible reasons for the differences in levels of tolerance of aneuploidy in species like T. monococcum and those like Petunia hybrida, which are highly tolerant of aneuploidy, are discussed. Pollen fertility was high and seed fertility was very low. Reasons for the latter as well as the high fertility in species that are highly tolerant of aneuploidy and allotriploids are discussed.Key words: Triticum monococcum, autotriploid, trisomic, cytology, breeding behavior, fertility, morphology.
Chromosomal structure of homozygous common wheat lines obtained from (wheat × Agropyron) × Aegilops speltoides derivatives. II. A screening of paracentric inversions
Authors: Ortiz L. T. , Gonzalez Agueda , Chueca Maria Cristina , Cauderon Yvonne
Published: November 2014

The presence of inversions is important in the evolution and cultivar differentiation of wheats, Even though we can't have conclusive cytological proof of the presence of inversions in wheat, we can use the indirect way of screening paracentric inversions through chromosome configuration at anaphase I and II. This work presents the comparison of 'Chinese Spring' structure (with respect to the presence of inverted segments) to (i) 52 homozygous wheat lines obtained in the progenies of the cross between a wheat × Agropyron intermedium substitution line and Aegilops speltoides homoeologous pairing promotor and (ii) three wheat cultivars ('Vilmorin 27', 'Ducat', and 'Tormes') that were used in developing the above mentioned lines. The three cultivars present inverted segments relative to 'Chinese Spring' structure. Some of these inverted segments are possibly maintained in some of the lines studied. Four of them show the primitive structure of 'Chinese Spring' even though none of the wheat parents had it. Finally, other lines show new structure that could have been due to the Aegilops speltoides effect, but the method used did not allow us to reach a definite conclusion on this point. It is interesting to emphasize that the use of this homoeologous pairing promotor led to a chromosomal structure that was not so different from that existing in wheats.Key words: pairing (homoeologous), hybridization (interspecific), gene transfer, Triticum, Agropyron, Aegilops.
Chiasma distribution and centromere orientation in a spontaneous interchange in the grasshopper Chorthippus vagans
Authors: Cabrero Josefa , Camacho Juan Pedro M.
Published: November 2014

One of 18 Chorthippus vagans males from a natural population was heterozygous for an interchange between the L1 and M4 chromosomes when examined cytologically. Chiasma distribution within multiple chromosome configurations and the relation between chiasma formation in the interstitial segments and centromere orientation were investigated. Our results confirm previous observations that adjacent-2 is the most common orientation in absence of chiasmata on the interstitial segments.Key words: Chorthippus, interchange, interstitial segments, chiasma distribution, orientation.
Genetic analysis of blood pressure in the Milan hypertensive strain of rat (Rattus norvegicus)
Authors: Schlager G. , Barber B. R. , Bianchi G.
Published: November 2014

Estimates of heritability (h2) of blood pressure level and the number of loci controlling the trait were derived from two genetic crosses involving the Milan hypertensive strain of rat and its control with normal blood pressure. In the genetic cross involving backcrosses, the estimates were h2 = 64% and the number of loci was two or three; there was some evidence of dominance of the alleles for normal blood pressures. In the other cross with only F2's, the degree of genetic determination (heritability in the broad sense) was 45%, involving at least three loci.Key words: rat, blood pressure, models, quantitative inheritance.
Ascus development in two temperature-sensitive Four-spore mutants of Neurospora crassa
Authors: Raju Namboori B.
Published: November 2014

Two nonallelic Four-spore mutants are known in which ascospore walls enclose the four immediate products of meiosis rather than the normal eight products of a postmeiotic mitosis. Expression depends on temperature. The Four-spore phenotype is expressed when the developing asci are subjected either to high temperatures (25–30 °C) for Fsp-1 or to low temperatures (15–20 °C) for Fsp-2. Heterozygous Fsp-1 × Fsp-1+ crosses make eight-spored asci at 15–20 °C but produce many four-spored asci at 25 °C and mostly four-spored asci at 30 °C. Homozygous Fsp-1 × Fsp-1 crosses respond similarly to increasing temperature but make 40–50% four-spored asci even at 20 °C. Heterozygous Fsp-2 × Fsp-2+ crosses produce almost exclusively four-spored asci at 15 °C but a mixture of four- and eight-spored asci at 20, 25, and 30 °C. Homozygous Fsp-2 × Fsp-2 crosses make all four-spored asci at 15 and 20 °C and a mixture of four- and eight-spored asci at 25 and 30 °C. When both Fsp-1 and Fsp-2 are present in a cross, either homozygous or heterozygous, no asci contain more than four ascospores at any temperature. Limited temperature-shift experiments with Fsp-1 and Fsp-2 show that the sensitive period for Four-spore expression is sometime after meiotic prophase, possibly at interphase II.Key words: Neurospora, temperature sensitive, Four-spore mutants, large ascospores.
Chromosomes in 'Cadet' and 'Rescue' wheats carrying loci for cold hardiness and vernalization response
Authors: Roberts D. W. A.
Published: November 2014

'Rescue', 'Cadet', and the 42 reciprocal chromosome substitution lines derived from these two spring wheat cultivars were tested for vernalization response and cold hardiness. Cold hardiness was tested after hardening under a 16-h day for 8 weeks with 6 °C day and 4 °C night temperatures or in the dark for 7 weeks at 0.8 °C followed by 8 weeks at −5 °C. Chromosomes 5A, 5B, 7B, and possibly 2A carried loci for vernalization response. Chromosomes 2A, 5A, and 5B carried loci affecting cold hardiness measured after 8 weeks in the light at 6 °C during the day and 4 °C at night, whereas chromosomes 6A, 3B, 5B, and 5D were involved in cold hardiness after hardening in the dark at 0.8 °C followed by −5 °C. The results suggest that the rank order of cultivars for cold hardiness depends on the hardening technique used since the two different techniques tested had different genetic and presumably somewhat different biochemical bases.Key words: Triticum aestivum L., cold hardiness, vernalization.
Nuclear DNA variation in Piper (Piperaceae)
Authors: Samuel Rosabelle , Smith J. B. , Bennett M. D.
Published: November 2014

Significant interspecific variation in DNA amount was observed among nine species of Piper. The DNA amount of a wild octoploid accession of Piper nigrum was approximately double that of the cultivated tetraploid variety of the same species. However, three New World diploid species had higher nuclear DNA amounts than several New or Old World tetraploid species. The DNA content per basic genome was, on the whole, lower in cultivated than in wild species.Key words: Piperaceae, Piper, Piper nigrum (black pepper), polyploids, DNA amounts.