bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. I. Cytology, breeding behaviour, fertility, and morphology of induced autotetraploids
Authors: Kuspira J. , Bhambmani R. N. , Shimada T.
Published: November 2014

Autotetraploids were colchicine-induced in Triticum monococcum and, upon comparison to their diploid progenitor, possessed the following characteristics: (i) their cells were on the average 20.8% larger; (ii) plant height was reduced by 15% and tillering by 37.5%; (iii) spikes, 1000-kernel weight, pistil size (length (L)/weight (W), and leaf size (L/W) were 53.9, 51.2, 80/57.1, and 60/26.4% larger, respectively; and (iv) they were 12.4% earlier in heading. Observed mean numbers of univalents, bivalents, trivalents (linear, convergent, and indifferent coorientations), and quadrivalents (convergent and parallel alignments only) per microsporocyte at metaphase I were 0.62, 9.86, 0.23, and 1.74, respectively; 65.4% of all meiocytes possessed bivalents and (or) quadrivalents and produced balanced meiotic products; 34.6% also possessed univalents and (or) trivalents and, therefore, produced balanced and unbalanced meiotic products. The actual 70.9% balanced meiotic products falls within the calculated range of 65.4–81.3%. Our tetraploids breed true. Evidence and reasons for this are discussed. The fertility of our tetraploids was high (79.8%). Irregular chromosome behaviour during meiosis may play a decisive role in determining the fertility level. Genic factors may also be involved. Methods of improving fertility and whether chromosomal factors alone are responsible for tetraploid fertility levels are discussed. Mature seed from reciprocal 2n = 4x × 2n = 2x crosses was shrivelled because of endosperm collapse and did not germinate. Thus, embryo excision and culturing on artificial medium was required to obtain viable autotriploids.Key words: Triticum monococcum, autotetraploid, cytology, breeding behavior, fertility, morphology.
Bilateral sexual tetraploidization in red clover
Authors: Parrott W. A. , Smith R. R. , Smith M. M.
Published: November 2014

Twenty-four diploid red clover (Trifolium pratense L.) plants, from the cultivars 'Arlington', 'Florex', and 'Redman', and C760, a Wisconsin synthetic, were tested for 2n egg production by crossing them with tetraploid plants. Four plants were identified and selected as 2n egg producers. These plants were then crossed with a known producer of 2n pollen in an attempt to obtain tetraploid plants through bilateral sexual polyploidization. Thirteen percent of the seed obtained in one of the 2x–2x crosses were tetraploid. The female plant produced an estimated 0.14 2n eggs per 1000 flowers in the cross. In a second experiment, bilateral sexual polyploidization was attempted, using 14 plants which had not been previously tested for 2n egg production. Two of these plants produced one and two tetraploids each, representing 2n egg frequencies of 3.33 and 5.00 2n eggs per 1000 flowers, respectively. It seems likely that it will be possible to use bilateral sexual polyploidization to tetraploidize red clover germplasm in the future.Key words: tetraploid red clover, Trifolium pratense. 2n gametes.
Studies of the X chromosome of Anopheles albimanus
Authors: Seawright J. A. , Benedict M. Q. , Narang S.
Published: November 2014

Snow (sn) is a recessive, eye color mutant that is phenotypically indistinguishable from the previously described mutant, white eye (we). The loci for these mutants are over 30 map units apart on the X chromosome. Analysis of salivary gland chromosomes of radiation-induced X-autosome translocations were used to define the positions of sn and we on the distal euchromatic portion of the long arm of the X chromosome. A recessive lethal trait (bubble head) was also mapped relative to we and sn, and the gene order on the long arm of the X chromosome is as follows: centromere – ? – snow – bubble head – white eye. Translocation breakpoints in the euchromatic portion of the X chromosome caused sterility or lethality in males hemizygous for the translocations, but breaks in the heterochromatin had no effect. Crossing-over was greatly reduced when translocation breakpoints were located in the euchromatic part of the X chromosome. The translocations were used to determine that the nucleolar organizer region is probably on the short arm of the X chromosome.Key words: Anopheles albimanus, eye colour mutant, X chromosome.
Analysis of high-resolution R-bands, obtained by heat-denaturation and Giemsa staining, on human prophase chromosomes
Authors: Drouin R. , Richer C. L.
Published: November 2014

RHG-bands (heat-denatured Giemsa R-bands) of human prophase chromosomes were analyzed at high resolution, and the banding patterns at prophase and metaphase are presented. The bands were compared with those of the International Standard Cytogenetic Nomenclature idiograms and of the G-band idiograms proposed by J. J. Yunis. The number, size, and position of the RHG-bands correspond rather well with their equivalent G-negative bands, but some differences were noted in the zones of preferential stretching, the juxtacentromeric regions, and the telomeres. Variations in the centromere index and the banding pattern in heterochromatin were also discussed.Key words: human prophase chromosomes, RHG-bands, high-resolution chromosomes.
Chromosomal locations of phosphoglucomutase, phosphoglucose isomerase, and glutamate oxaloacetate transaminase structural genes in different rye cultivars
Authors: Salinas J. , Benito C.
Published: November 2014

Phosphoglucomutase, phosphoglucose isomerase, and glutamate oxaloacetate transaminase isozymes have been studied in 'Chinese Spring' – 'Imperial', 'Holdfast' – 'King II', and 'Kharkov'–'Dakold' wheat–rye addition lines using starch and polyacrylamide gel electrophoresis. The analyses were conducted with different parts of dry kernels (embryo plus scutellum, and endosperm), leaves, and roots. In all cases the zymogram phenotypes obtained were the same, independent of the tissue analysed. Germination and maturation processes were also studied. One locus involved in the production of phosphoglucomutase isozymes was located on chromosome 4R of 'Dakold' and on 4RS of 'Imperial' and 'King II' cultivars. Evidence was obtained that one locus controlling the phosphoglucose isomerase isozymes is located on chromosome 1R of these three rye cultivars analysed, specifically on the short arm of chromosome 1R in 'King II'. Also, three loci controlling the glutamate oxaloacetate transaminase isozymes have been placed on chromosomes 7R, 6R, and 3R of the rye cultivars analysed, and more exactly, on 7RL of 'Imperial' and 'King II' and on 6RL of 'King II'. Biochemical evidence of homology between chromosome arms of the different cultivars of rye analysed, and homoeology between chromosome arms of wheat and rye is reported. Germination and maturation processes support the hypothesis that the expression of rye isozymes studied in dry kernel, leaf, and root, and during germination and maturation, is controlled by the same chromosome arms.Key words: wheat–rye addition lines, isozyme structural genes, phosphoglucomutase, phosphoglucose isomerase, glutamate oxaloacetate transaminase.
Simultaneous estimation of additive and dominance genetic variance in heterozygous and homozygous populations
Authors: Patel J. D. , Bains K. S. , Chahal G. S.
Published: November 2014

A new mating procedure for estimating additive and dominance genetic variances in a random mating population is presented. With this procedure, m number of plants from a random mating population are selfed to produce S1 families and are also crossed to n inbreds. Subsequently, all the m × n hybrids are selfed. while keeping remnant crossed seeds for the final experiment. The final experiment comprises m × n hybrids, their m × n selfs, m S1, and m S2 families as well as n inbreds. The analysis of the data, recorded on the quantitative traits provides information for both the random mating as well as the inbred populations. Epistasis can be detected by two different tests. The analysis can be applied to F2 instead of random mating populations with less effort.Key words: random mating, genetic variance, epistasis, inbred.
Mutagenicity of drinking water detected by the Tradescantia micronucleus test
Authors: Ma Te-Hsiu , Anderson Van A. , Harris Mary M. , Neas Robert E. , Lee Tze-San
Published: November 2014

Spring Lake reservoir of Macomb, Illinois, is a typical model of the drinking water supply of some midwestern towns of the United States. Water samples collected periodically in 1980 and 1981 from this lake were tested for mutagenicity using the Tradescantia micronucleus (Trad-MCN) test, a highly sensitive mutagen-detecting bioassay. Water samples from 1981 were also analyzed chemically. The micronucleus (MCN) frequency peaked (12–14 MCN/100 tetrads) in mid-July in both years, as compared with the average frequency (5 MCN/100 tetrads) of the base-line control that was maintained in nutrient solution (prepared with distilled water and pure chemicals). Drinking water from the tap was tested in parallel with lake water, and its mutagenicity tended to fluctuate with the mutagenicity of the lake water.Key words: mutagenicity, drinking water, Tradescantia, micronucleus.
Recurrent selection in doubled-haploid populations of barley (Hordeurn vulgare L.)
Authors: Patel J. D. , Reinbergs E. , Fejer S. O.
Published: November 2014

Cycle zero (C0) of recurrent selection in barley (Hordeum vulgare L.) was initiated by diallel mating of seven highly selected parents. A total of 398 doubled-haploid (C0DH) lines were derived from 21 crosses and were evaluated along with their parents in C0 experiment. Seven doubled-haploid lines (DH) were selected from the cycle zero (C0) experiment and intercrossed to form cycle 1 (C1). From the 21 crosses of the diallel, 260 doubled-haploid lines (C1DH) were derived and were evaluated along with the C0 and C1 parents. The frequency distribution of the standardized means of the DH lines from C0 and C1 indicated a slight response to selection for seed yield. Genetic analysis of the C1DH population showed high additive genetic variance for yield per hill, plant height, and yield per spike, and a high proportion of additive × additive epistasis for spikes per hill, days to heading, and 100-seed weight. Seven doubled-haploid lines were selected from different high-yielding crosses represented by C1DH lines. High selection pressure was applied for yield per hill, yield per spike, and spikes per hill. Further response to selection is expected in later cycles. The seven selected doubled-haploid lines will be used as the parents of the next recurrent selection cycle.Key words: recurrent selection, doubled haploids, additive, epistasis, heritability, Hordeum.
Gametocidal genes in wheat and its relatives. II. Suppressor of the chromosome 3C gametocidal gene of Aegilops triuncialis
Authors: Tsujimoto H. , Tsunewaki K.
Published: November 2014

Chromosome 3C of Aegilops triuncialis, in the monosomic state, causes semisterility in common wheat cultivars (Triticum aestivum). The Japanese cultivar 'Norin 26' carries a gene that acts as dominant suppressor of the gametocidal gene on chromosome 3C. However, this suppressor gene does not alter the functions of the gametocidal gene on chromosome 4S1 of Ae. longissima or Ae. sharonensis. By means of monosomic analyses, the suppressor has been located on chromosome 3B and is designated Igc1. This gene is distributed widely among wheat cultivars bred in central and southwest Japan. In the presence of Igc1 chromosome 3C shows no preferential transmission, but is transmitted to offspring at a frequency similar to those of other alien chromosomes. The progeny of plants that carry a single chromosome 3C exhibit chromosome aberrations, and possibly mutations, at high frequencies. Thus, the gametocidal gene on chromosome 3C causes a syndrome similar to hybrid dysgenesis in common wheat.Key words: common wheat, Aegilops triuncialis, gametocidal gene, suppressor, hybrid dysgenesis.
Seasonal variation and clonal selection in cyclically parthenogenetic rose aphids (Macrosiphum rosae)
Authors: Rhomberg L. R. , Joseph S. , Singh R. S.
Published: November 2014

Patterns of geographic and seasonal genetic variation were assessed in natural populations of cyclically parthenogenetic rose aphids Macrosiphum rosae (L.). Nine populations were studied for a red–green colour morph and 30 allozyme loci (20 coding for enzymes and 10 for abundant proteins). Genetic variation was found at 5 of 20 enzyme loci (20%); all 10 abundant proteins proved monomorphic. The average heterozygosity was 4.3%. At some polymorphic loci genotypic frequencies showed significant deviations from Hardy–Weinberg proportions. Six local populations from Hamilton, Ontario, were studied for seasonal variation at the colour locus and at two polymorphic esterase loci (Est-2 and Est-4). All three loci showed large changes in genotypic frequencies over the season during the asexual cycle, but only for Est-4 were changes consistent among populations. This locus undergoes a regular seasonal cycle, the directional changes during the asexual phase presumably being balanced by changes during the sexual phase. The frequencies of three-locus genotypes within each locality fluctuated dramatically over the course of a season, reflecting the domination of local infestations by a few particularly successful clones. We speculate that because of such clonal competition followed by extensive migration, much of the selectively neutral variation is purged from aphid populations. The remaining polymorphic loci, which are mostly di- or tri-allelic, are subject to balancing natural selection at the gene or at closely linked loci. The Est-4 in rose aphids is an example of such a selectively maintained polymorphism.Key words: aphids, allozyme variation, seasonal variation, parthenogenesis, clonal selection, population structure.
The effects of alternated cycles of full-sib and random mating on selection for pupa weight in Tribolium castaneum
Authors: Dion Nicole , Minvielle Francis
Published: November 2014

Individual responses to selection for high pupal weight in Tribolium castaneum under two types of mating, cyclic full-sib random-mating system and random mating, were observed for 15 generations. No significant differences have been observed between the two types of mating for the selection response, differential selection, realized heritability, and the number of larvae per generation. Realized heritability of the pupal weight was 0.33 ± 0.02 and 0.42 ± 0.02 for the inbred lines and for the random-mated lines, respectively.Key words: inbreeding, pupa weight, Tribolium.
Genetic factors determining plasticity in flax genotrophs
Authors: Al-Saheal Y. A. , Larik A. S.
Published: November 2014

Changes in the amount of nuclear DNA can be induced in 'Stormont Cirrus', a plastic variety (PL) of flax, by different environments, but not in the linseed variety 'Royal' (R) which is not plastic. PL is thought to contain nuclear and cytoplasmic factors, not possessed by R, which are necessary for the plastic characters to appear. Further crosses have shown that the PL nuclear factor plays a direct part in the determination of plasticity and that the cytoplasmic factor is maintained in the presence of both PL and R nuclei. Insofar as the genetic analysis has been taken, the distribution of genetic factors determining plasticity (+) or nonplasticity (−) in PL and R are as follows: nuclear factor (PL, +; R, −); cytoplasmic factor (PL, +; R, −); nuclear factor for synthesizing de nouveau cytoplasmic factor (PL, −; R, −); nuclear factor for maintaining the cytoplasmic factor (PL, +; R, +); site at which DNA changes occur (PL, +; R, +). It is suggested that the nuclear factor is activated by the cytoplasmic factor, and must come directly from a cytoplasm containing the cytoplasmic factor to be operative.Key words: flax, genotype plasticity, plasticity, genotrophs.
Linkage of the reindeer and alate prothorax loci and sex differences in recombination frequency in linkage group IX of Tribolium castaneum
Authors: Dawson Peter S. , Berends Kelly L.
Published: November 2014

Reindeer (Rd), an autosomal dominant mutant in the flour beetle, Tribolium castaneum, is located in linkage group IX. Recombination between Rd and alate prothorax occurs more frequently in males than in females. Linkage group IX appears to be the third linkage group for which recombination frequency is greater in males for one region and in females for another region of the chromosome.Key words: Tribolium, linkage.
Metaphase karyotype identity in four homosequential Drosophila species from Hawaii
Authors: Chang Linda S. , Carson Hampton L.
Published: November 2014

Four recently evolved species of Hawaiian Drosophila (silvestris, heteroneura, dijferens, and planitibia) have previously been shown to be homosequential in all five polytene chromosome arms. This suggests that the changes involved in speciation are at the genic level and hence are not evident in the polytene banding sequences. Because this does not rule out the occurrence of heterochromatic differences between these homosequential species, the present study was carried out to examine this possibility. These species are now shown to have identical heterochromatin distributions in mitotic metaphase chromosomes. This proves that neither gross chromosomal rearrangements nor novel heterochromatic blocks have been involved in the divergence of these four species. A fifth, and evolutionarily more distant, species (hemipeza) belonging to the same subgroup has a significantly different heterochromatin distribution from the other four species.Key words: heterochromatin, metaphase karyotypes, Hawaiian Drosophila.
Cytogenetic localization of a putative regulatory gene affecting an NADP+-dependent enzyme in Drosophila melanogaster
Authors: Bentley Michael M. , Williamson John H.
Published: November 2014

The cytogenetic localization of a putative regulatory locus affecting an NADP+-dependent enzyme is described. This locus, Mex, is in region 8D10-12 to 9A1-2 on the X chromosome of Drosophila melanogaster. Hyperploidy for this region is associated with significant increases in NADP+-dependent malic enzyme specific activity and specific immunologically cross-reacting material. This is the first report of a specific locus, unlinked to the locus coding for the major polypeptide of the enzyme, which affects an NADP+-dependent enzyme in Drosophila melanogaster.Key words: Drosophila melanogaster, NADP malic enzyme, gene regulation.
Relative rate of development of aneuploid and euploid microspores in a tertiary trisomic of rye, Secale cereale L.
Authors: Janse J.
Published: November 2014

Meiotic configurations were studied in pollen mother cells of a tertiary trisomic of rye. Chains of five and chains of three, in alternate orientation, were the most frequent configurations. Assuming loss of univalents in anaphase I or single chromatids in anaphase II, a total of 58.1% of the viable gametes resulting after meiosis were expected to contain the normal haploid complement, whereas 41.9% were expected to have the translocated chromosome in addition. The percentages of uninucleate and binucleate microspores in anthers containing dividing microspores provided a time scale for the development of euploid and aneuploid spores during first pollen mitosis. Microspores containing the extra translocated chromosome tended to divide at a later stage than euploid microspores. The slower development was also illustrated by the course of the mitotic index of both types. It was found that 58.1% of all microspores passing through pollen mitosis contained seven chromosomes and 41.9% contained eight chromosomes, which means that up to the end of first pollen mitosis aneuploid spores were not lost significantly more than euploid spores. It is likely that the delay in development already starts immediately after meiosis.Key words: rye, tertiary trisomic, euploid microspores, aneuploid microspores, rate of development.
The cytology of Brachycome lineariloba. 9. Chromosomal heterogeneity in natural populations of cytodeme C (2n = 16)
Authors: Watanabe K. , Carter C. R. , Smith-White S.
Published: November 2014

Ten natural populations of B. lineariloba cytodeme C (2n = 16) were analysed cytologically. The plant is annual, ephemeral, and self-compatible. Two subdemes, C1 and C2, which are geographically separate, include about 40 kinds of karyological variants. These are of three principal kinds; namely, translocation products, hybrids, and monosomic or polysomic products of such hybrids. Cytodeme C is found to overlap extensively with cytodeme B (2n = 12) and with B. dichromosomatica (2n = 4). A considerable number of hybrids or hybrid derivatives were found between cytodemes B and C. They are fertile and able to produce viable progenies. In contrast, cytodeme C is well isolated from B. dichromosomatica reproductively, although the two are sympatric in many localities. Interchanges are maintained almost entirely in the homozygous condition in variants with a relatively high frequency of occurrence.Key words: Brachycome, karyotype, polymorphism, annual, inbreeding.
Cloning within the unc-43 to unc-31 interval (linkage group IV) of the Caenorhabditis elegans genome using Tc1 linkage selection
Authors: Baillie D. L. , Beckenbach K. A. , Rose A. M.
Published: November 2014

The region around the twitcher gene, unc-22, flanked by unc-43 on the left and by unc-31 on the right, has been intensively studied in our laboratory over the period of the last 8 years. In this paper we describe the identification and isolation of probes specific for several restriction fragment length differences (RFLDs) which lie within this region. Many RFLDs in Caenorhabditis elegans are caused by the insertion of a transposable element, Tc1. The method we used involved the isolation of Tc1-containing genomic fragments. These were recovered from a λgt 10 library of DNA from a specially constructed genetic strain containing the unc-43 to unc-31 interval from the BO strain and the rest of the genome from N2. Because the BO strain is rich in Tc1 insertion sites and the N2 strain has few, the majority of Tc1-bearing genomic fragments in the constructed strain were derived from the unc-22 region. Of nine such Tc1-bearing genomic fragments isolated, six were found which mapped within the region of interest. The 350 kilobases of genomic sequences isolated as a result of these studies are being used to study the molecular organization of this region. The method described here for Tc1 linkage selection is one that is rapid, general, and may be targeted to any genetically characterized region of the C. elegans genome.Key words: Tc1, unc-22, restriction fragment length differences, Caenorhabditis elegans, linkage selection.
Nucleolar organizer competition in Aegilops–rye hybrids
Authors: Cermeño M. C. , Lacadena J. R.
Published: November 2014

The nucleolar organizer activity in several Aegilops × rye hybrids (A. triuncialis × Secale cereale, A. variabilis × S. cereale, A. biunicialis × S. cereale, A. biuncialis × S. vavilovii, A. juvenalis × S. cereale) is analyzed by using a highly reproducible silver-staining procedure. The 1U and 5U chromosomes show a strong nucleolar activity, suppressing the NOR activity of chromosome 1R from rye in all the hybrid combinations (UCR, USvR, UMbR, UMbRv, and UMjDR). The nucleolus organizer chromosomes from the genomes C, Sv, Mb, and Mj show small activities. Our results confirm previous data of the nucleolar organizer activity predominant status of the 1U and 5U chromosomes from the U genome (A. umbellulata) and the weakest condition of the 1R chromosome from rye. A diagram showing the relationships between the nucleolar organizer activities of chromosomes from different genomes of Triticeae is presented.Key words: nucleolar competition, amphiplasty, Ag-NORs, Triticeae, Aegilops, Secale.
Cytogenetic analysis of 34 early stage bovine embryos from superovulated Hereford donors
Authors: Murray J. D. , Moran C. , Boland M. P. , Doff A. M. , Nancarrow C. D.
Published: November 2014

One hundred and thirty-four bovine embryos were collected from 17 superovulated Hereford cows and processed for metaphase chromosome spreads. Mitotic figures were obtained from 54 embryos (40%), but only 34 embryos (25%) provided analyzable chromosome spreads. Thirty embryos were 2n = 60, one was a possible 2n/4n mosaic and three were hypodiploid. The hypodiploid cases and the 2n/4n mosaic could be due to technical artifacts.Key words: embryo, cattle, chromosomes, superovulated.
Identification of a diploidizing genotype of Lolium multiflorum
Authors: Evans G. M. , Aung Taing
Published: November 2014

Thirty diploid populations of Lolium multiflorum were screened for genes that were capable of modifying meiosis in species hybrids. A standard genotype of L. temulentum was used as the tester species. Modified pairing at first metaphase of meiosis was identified in some of the hybrid progeny of a single plant from a population from Uruguay and also in one from Portugal. Evidence is presented to show that the high incidence of univalents in diploid hybrids of L. temulentum × L. multiflorum from Uruguay was due to the suppression of homoeologous chromosome association only. A proportion of equivalent triploid and tetraploid hybrids had an excess of bivalents at first metaphase of meiosis. This was confirmed by comparison of the observed meiotic data with that expected from three separate mathematical models. It is concluded that this single plant from the Uruguayan population was heterozygous for genes that suppress chiasmate association of homoeologous chromosomes.Key words: interspecific hybrid, Lolium, chromosome pairing.
Genetic control of meiotic chromosome pairing in polyploids in the genus Hordeum
Authors: Gupta P. K. , Fedak George
Published: November 2014

Existing data on meiosis in hexaploid and tetraploid species of Hordeum, their respective polyhaploids, and intergeneric – interspecific hybrids indicate that a meiotic pairing control system exists in this genus. The system is probably polygenic and it is therefore unlikely that a major locus such as Ph in Triticum controls chromosome pairing. It is more efficient in the tetraploids than hexaploids, permitting some intergenomic pairing in the latter. In the polyhaploids the pairing control is somewhat hemizygous ineffective. The pairing of homoeologous chromosomes in the wild polyploid Hordeum species is generally inhibited by H. vulgare and variably enhanced by genomes of Secale species.Key words: Hordeum, synapsis regulation, intergeneric hybrid, polyhaploids, hemizygous.
Variation in induction of homoeologous chromosome pairing in 6x Aegilops crassa by genomes of six different species of Secale
Authors: Gupta P. K. , Fedak George
Published: November 2014

Meiosis was studied in hybrids between Aegilops crassa (Boiss.) Hitch and Hensl. (2n = 6x = 42) having the genomes DD2MCr and six species of Secale. The chiasmata frequency per cell ranged from 6.86 in hybrids with S. cereale to 9.93 in hybrids with S. montanum ssp. dalmaticum. These results provide further evidence that a meiotic pairing control system is operating in Ae. crassa. The Secale genotypes suppress the function of this system in a manner which was inversely related to their heterochromatin content and total DNA content.Key words: Secale, Aegilops, chiasmata, meiotic pairing control, hybrids.
Early seed development in Triticum-Secale amphiploids
Authors: Gustafson J. P. , Lukaszewski A. J.
Published: November 2014

Considerable variation was observed in the early embryo and endosperm developmental patterns of several Triticum durum × Secale species (africanum, cereale, dighoricum, kuprijanovii, montanum, segetale, vavilovii) amphiploids. However, the Triticum – S. africanum hybrid was the only one which developed at a faster rate than either of its parents. Its endosperm became cellular and began depositing starch at least 24 h before any previously analyzed cereal. The influence of Secale DNA and heterochromatin on the developmental patterns of the amphiploids was exactly the opposite of that in the genus Secale itself (i.e., as the amount of telomeric heterochromatin increases developmental speed decreases). The results, in general, suggest that the control of Secale developmental characteristics, whether they are genotypic or nucleotypic, are suppressed when placed in a wheat background.Key words: triticale, heterochromatin, interspecific hybrid, wheat embryo.
A rapid technique for substituting alien chromosomes into Triticum aestivum and determining their homoeology
Authors: Kota Rama S. , Dvořák Jan
Published: November 2014

A rapid technique is described for the production of a disomic substitution of an alien chromosome for a selected wheat chromosome directly from the amphiploid. Determination of homoeology between the chromosomes involved is a by-product of this technique. The technique involves the production of a nullisomic amphiploid from a cross between a wheat mono-telosomic and a diploid species and recurrently backcrossing it as a male twice to the monotelosomic. Disomic and ditelosomic substitutions are then selected upon self-pollination. The utility of this technique is shown by producing a large number of disomic and ditelosomic substitutions of an Aegilops longissima chromosome homoeologous to wheat chromosome 6B from two populations of Ae. longissima. The incorporated Ae. longissima chromosome was characterized by C-banding and in situ hybridization of an 18S–26S rRNA gene probe. The chromosome differs in C-band pattern from chromosome 6B of 'Chinese Spring' and does not pair with the 6Bp telosome at metaphase I. It also differs from 'Chinese Spring' chromosome 6B by having the 18S–26S rRNA compound locus in the long arm.Key words: disomic substitution, homoeology, C-banding, in-situ hybridization, rRNA genes, gene synteny, Triticum, Aegilops longissima.
β-carotene as an inhibitor of benzo(a)pyrene and mitomycin C induced chromosomal breaks in the bone marrow of mice
Authors: Raj A. S. , Katz Morris
Published: November 2014

Female mice of hybrid strain B6C3F1, 8–10 weeks old, were fed on powdered food with or without β-carotene (100 mg/kg food). After 1 week of these diets, some of each group of mice were injected i.p. with either benzo(a)pyrene (150 mg/kg) in dimethyl sulfoxide, or mitomycin C (1 mg/kg) in distilled water. In the course of separate experiments, bone marrow samples were collected at various intervals after injection for analysis in the in vivo bone marrow micronucleus assay. At the time at which the maximum induction was observed, which coincided between experiments, the frequency of micronuclei induced by benzo(a)pyrene was reduced by 41–61% and that induced by mitomycin C was reduced by 44–71% in the presence of β-carotene. β-carotene is widely distributed in plant material such as carrots and green leafy vegetables and, as such, is a component of the human diet. Our results suggest that β-carotene provides significant protection against the genotoxicity of benzo(a)pyrene and mitomycin C.Key words: β-carotene, inhibitor, chromosomal breaks, micronucleated polychromatic erythrocytes.
Centric fusion between nonhomologous rye chromosomes in wheat
Authors: Davies P. A. , Pallotta M. A. , Driscoll C. J.
Published: November 2014

The frequency of centric fusion has been compared in three wheat–rye double monosomic addition lines. In one plant, designated plant A, both monosomes were bibrachial. In the second plant, B, one monosome was bibrachial and one telocentric. In the remaining plant, C, both monosomes were telocentric. Rye centric fusion chromosomes were identified in the progeny by C-banding mitotic root-tip chromosomes and electrophoresis of endosperm storage protein. Four of 97 analyzed progeny of plant A and 4 of 96 analyzed progeny of plant B possessed centric fusion chromosomes. In contrast, none of the 492 progeny of plant C possessed centric fusion chromosomes. The data indicate that at least one bibrachial monosome is necessary for the efficient production of centric fusion chromosomes.Key words: centric fusion, centromeric misdivision, monosomes.
Genetic basis of extremely slow development in a population of Tribolium confusum
Authors: Riddle Russel A. , Sykes Reneé , Leffel Linda J. , Dawson Peter S.
Published: November 2014

An extremely slow developing form of Tribolium confusum is described. The slow phenotype is caused by an autosomal recessive mutation, sl (slow). Expression of this allele on growth rate was not significantly altered by diet, although a pleiotropic effect on survival was diet dependent. The allele has become fixed in a laboratory population, producing a phenotypic shift in developmental time of 7.1 standard deviations. Pupal weight is reduced in homozygotes by about 15%. Allele frequency data suggest that fixation of the sl allele may have been the result of selection and not genetic drift. The mutation is discussed in relation to models of phenotypic evolution.Key words: Tribolium, phenotypic evolution, slow development.
A further modification in the triple testcross analysis when testers share common loci
Authors: Virk Parminder S. , Virk D. S.
Published: November 2014

For investigating the genetical structure of a population of homozygous lines, modifications in the triple testcross analysis that allow for the effect of common loci shared by the pure-breeding testers, L1 and L2, have been previously proposed. The unbiased estimates of the additive genetic and dominance components are, however, correlated as they are obtained from statistics that are nonorthogonal. Further modifications are suggested where full triple testcross families L1i (= Pi × L1), L2i (= Pi × L2) and L3i (= Pi × L3; L3 = L1 × L2) along with selfed progenies of L1i (= L1si) and L2i (= L2si) and pure-breeding lines (Pi) themselves are raised. Alternatively, full triple testcross progenies (L1i, L2i, and L3i) can be raised along with the selfs of L3i (= L3si) families and parental (Pi) lines. These combinations of normal and selfed progenies allow one to test and estimate unbiased additive and dominance components, free from the effect of common loci in the testers and from statistics that are statistically orthogonal. The components of variation are, therefore, estimated independently.Key words: triple testcross, inadequate testers, components of variation.
Levels of conservation and variation of heterochromatin and nucleolus organizers in the Bovidae
Authors: Mayr B. , Schweizer D. , Mendelak M. , Krutzler J. , Schleger W. , Kalat M. , Auer H.
Published: November 2014

Chromomycin A3 banding of the mitotic sets of 10 species of Bovidac (cattle, wisent, yak, banteng, gaur, red buffalo, swamp buffalo, sheep, mufflon, and goat) serves to demarcate both centromeric constitutive heterochromatin and R-banding patterns capable of identifying all the chromosomes within a given complement. In all species significant amounts of chromomycin-bright heterochromatin are present at the centromeres of all autosomes, though there was a high degree of intra- and inter-individual variation in the size of the heterochromatic blocks. Marked interspecies differences in the centromeric patterns were evident. The X chromosomes contained appreciable amounts of centromeric heterochromatin only in the two buffaloes. All the animals studied lacked distamycin A – diamidinophenylindole type heterochromatin. AgNO3 staining was applied sequentially to detect the location of active nucleolus organizer regions (NORs). The distribution of NORs was reasonably conservative in most of the species. An exceptional situation was found in the two buffaloes, where only one NOR pair matched with the standard karyotype of the Bovidae.Key words: heterochromatin, chromomycin A3 fluorescence, nucleolus organizers, Bovidae.
A cytogenetic study of monosomics in Brassica napus L.
Authors: Fan Zhegong , Tap William
Published: November 2014

Two types of monosomic plants of Brassica napus L. were discovered among the backcross progenies of crosses between Diplotaxis muralis L. and B. napus and between Brassica juncea L. and B. napus. These monosomics were designated mono-1 and mono-2, respectively. Morphologically the monosomic plants were virtually indistinguishable from their sib disomic plants. Seed production on both mono-1 and mono-2 plants was normal. Cytological examination revealed that most pollen mother cells (85%) of mono-1 plants formed 18 bivalents plus one univalent at diakinesis, while the remainder (15%) formed 17 bivalents plus a trivalent. The univaltn in mono-1 was submetacentric and its two arms were always stained more lightly than the centromeric region. Later meiotic stages in mono-1 plants appeared normal. The plants of mono-1 produced two types of pollen grains which were different in size. Both the large and small pollen grains of mono-1 were deeply stained with an I2–KI solution. Meiotic behavior of mono-2 plants was similar to that of mono-1 plants, but the frequency of trivalent formation was higher (62%). The univalent in mono-2 was longer than the two chromosomes it paired with to form a trivalent. Pollen produced on mono-2 plants was uniform in size and comparable to that of the normal disomics.Key words: Brassica napus, Brassica juncea, Diplotaxis muralis, aneuploidy, monosomics.
C-banding at meiosis as a means of analyzing cytogenetic structure in wheat
Authors: Fominaya A. , Jouve N.
Published: November 2014

The characterization of reciprocal interchanges between chromosomes of wheat in the progeny of the backcross ((T. aestivum H-53 × S. cereale) × T. aestivum H-53) using Feulgen and C-banding staining techniques has been attempted. The translocated chromosomes were studied in detail in three lines using monosomic analysis. In the F1 of the crosses between these lines and the 21 monosomic lines of 'Chinese Spring' a total of five interchanges were identified. Using a Giemsa C-banding procedure it was possible to confirm the identity of the interchange chromosome pairs that were previously identified by monosomic analysis. Moreover, a total of 12 new interchanges were characterized or identified. C-banding also facilitated the identification of the arms involved in translocations and permitted the quantitative analysis of each multivalent in multiple interchange heterozygotes. The comparative availability of Feulgen and C-banding in studies of cytogenetic structure in wheat is discussed.Key words: C-banding, meiosis, heterochromatin, translocations, wheat, Triticum.
Genetic analyses of electrophoretic enzyme variants, mating type, and hermaphroditism in Pyricularia oryzae Cavara
Authors: Leung Hei , Williams Paul H.
Published: November 2014

Pyricularia oryzae (teleomorph: Magnaporthe grisea) parasitizes a variety of gramineous hosts and causes the rice blast disease worldwide. Through matings among P. oryzae isolates from rice, finger millet, and weeping lovegrass the inheritance of electrophoretic variants of six enzymes, phosphoglucomutase (PGM), phosphoglucose isomerase (PGI), glycerate-2-dehydrogenase (G2DH), malate dehydrogenase-3 (MDH-3), lactate dehydrogenase-1 (LDH-1), and lactate dehydrogenase-3 (LDH-3) was determined. All six variants were under single gene control as determined by tetrad and random spore analysis. However, at Ldh-3 and Mdh-3, there were consistent excesses of variant alleles among ascospore segregants. Preliminary data on the genetic control of hermaphroditism suggested that maleness in two Japanese rice isolates might be due to a single gene mutation. Linkage analyses among the six electrophoretic markers, mating type, and hermaphroditism suggested loose linkage between Pgm and G2dh with a recombination frequencies of 43.0%.Key words: linkage, Magnaporthe grisea, rice blast fungus.
Genetic control of sex-chromosomal univalency in the spermatocytes of C57BL/6J and DBA/2J mice
Authors: Biddle F. G. , MacDonald B. G. , Eales B. A.
Published: November 2014

The genetic control of sex-chromosomal univalency was examined in the primary spermatocytes of the mouse. The C57BL/6J strain expresses 3% X–Y univalency and DBA/2J expresses 37% univalency. The reciprocal F1 and the eight types of reciprocal backcross males were examined. In the C57BL/6J–DBA/2J strain pair, X–Y univalency is controlled by three genetic systems. Autosomal factors of unknown number that are dominant in DBA/2J increase the probability of univalency from 3% in C57BL/6J to 12%. The DBA/2J-Y chromosome, in place of the C57BL/6J-Y chromosome, has an additive effect to increase the probability of univalency from 12 to 37% in the DBA/2J strain. Two X-chromosome factors that differ between C57BL/6J and DBA/2J regulate the probability of univalency. The X-chromosome factors appear to be separated by sufficient distance so that, with the DBA/2J-Y chromosome and dominant DBA/2J autosomal factors, there are two recombinant classes of X–Y univalency at 20 and 60%. The genetic factors in the univalency trait may be involved in the regulation or structure of the terminal attachment sites between the X and Y chromosomes.Key words: meiosis, mouse, sex-chromosomal univalency.
High bivalent frequencies in artificial autopolyploids of Hyoscyamus muticus L.
Authors: Lavania U. C.
Published: November 2014

High pollen and seed fertility of induced autotetraploids of the medicinal solanaceous plant Hyoscyamus muticus (4x = 56) could, at least in part, be attributed to low quadrivalent and high bivalent frequencies at metaphase I (MI). Mean configuration frequencies per cell were 3.45 ring quadrivalents, 0.49 chain quadrivalents, 0.55 trivalents, 5.98 ring bivalents, 12.67 open (rod) bivalents, and 1.34 univalents. In the diploid, ring bivalents were most common with chiasmata predominantly distal at diakinesis–MI. Different causes can explain the low quadrivalent frequencies in the tetraploids. Using a simple algebraic model, calculations show that the most probable explanation is reduced chiasma formation in one arm per chromosome, resulting from nonmedian partner exchange and special interference patterns. This agrees best quantitatively with high open (rod) bivalent frequencies compared with the diploid, accompanied by high ring quadrivalent frequencies.Key words: Hyoscyamus, autotetraploid, seed fertility, meiotic mechanism, pairing.
The field reaction to stem rust of 'Chinese Spring' substitution lines carrying chromosomes from 'Hope' and 'Thatcher' wheats
Authors: Knott D. R.
Published: November 2014

Studies were done in an attempt to determine the inheritance of adult plant resistance to stem rust (Puccinia graminis f. sp. tritici Eriks. and E. Henn.) in the wheat (Triticum aestivum L.) cultivars 'Hope' and 'Thatcher'. 'Chinese Spring' substitution lines carrying individual chromosomes from 'Hope' and 'Thatcher' were tested in field rust nurseries, three times each with races 15B-1 and 56, and twice with multirace mixtures. In 1976 it was found that the date of heading often had a significant effect on rust severity, with early lines showing less rust. In 1977 and 1984 the lines were divided into three groups based on maturity and were planted on three dates about 10 days apart to make heading dates more uniform. The data indicate that 'Hope' has genes for resistance to race 56 on chromosomes 3B (Sr2) and 4D, and to a multirace mixture on 1B, 3B, and 7B. 'Thatcher' possibly has genes for resistance to race 56 on chromosomes 6A and 3B (Sr12). The results show that the resistance of both cultivars is complex and most genes have only small effects.Key words: Triticum, Puccinia, rust resistance, substitution lines.
Polyploid speciation in hybrid morning glories of Ipomoea L. sect. Quamoclit Griseb.
Authors: Eckenwalder James E. , Brown Brett P.
Published: November 2014

Diploid artificial hybrids between Ipomoea coccinea L. and I. quamoclit L. produced eight seeds in a sample of 280 000 ovules. The resulting F2 plants were tetraploid and fertile. Polyploidy probably occurred through the union of two unreduced gametes. The F2 plants appear reproductively isolated from their F1 parents and from the progenitor species. This cross recreates the cardinal climber, I. sloteri (House) van Ooststr., a culivated species thought to have arisen originally from a single seed.Key words: hybridization, Ipomoea, tetraploidy, unreduced gametes.
Giemsa C-banded karyotypes of Hordeum taxa from North America
Authors: Linde-Laursen I. , Bothmer Roland von , Jacobsen Niels
Published: November 2014

Giemsa C-banding patterns of Hordeum pusillum, H. intercedens, H. brachyantherum (2x, 4x, 6x), H. jubatum, H. arizonicum, and H. depressum (2x and 4x) were rather similar, with mostly small to very small bands with no preferential disposition. The use of C-banding patterns did not improve the level of identification of taxa beyond that reached by the use of chromosome morphology. Widespread banding-pattern polymorphism prevented a reliable identification of homologues among populations based on this character alone. Chromosome length did not differentiate taxa. The ratio longest/shortest chromosome was remarkably constant over taxa, only differentiating the race of H. brachyantherum (4x) from Newfoundland, H. arizonicum, and H. depressum (4x). Marker chromosome morphology suggested the presence of one genome common to all taxa. A further but different genome was common to the perennial polyploids, indicating an alloploid origin and a close relationship calling into question the biological relevance of some sectional divisions in Hordeum. A number of intraspecific chromosome polymorphisms were observed rendering the number of marker chromosomes, a poor diagnostic marker. A pair of relatively shorter submetacentrics than previously reported in Hordeum distinguished the genomes of H. arizonicum and H. brachyantherum (4x) from Newfoundland. A partial inactivation of the nucleolus organizers of one parental genome in interspecific hybrids is considered more common than generally appreciated.Key words: C-banding, karyotype, Hordeum.
Epistatic relationships and linkage among colour markers of the imperfect entomopathogenic fungus Metarhizium anisopliae
Authors: Magoon Joanne , Messing-Al-Aidroos Karen
Published: November 2014

Diploid strains of the imperfect entomopathogen Metarhizium anisopliae were obtained by forced matings of complementary auxotrophic and spore-colour marked mutants. Genetic analysis of diploid and haploid mitotic recombinants suggests the existence of two metabolic pathways for spore pigmentation biosynthesis in Metarhizium anisopliae. Ten markers (two new and eight previously identified) were assigned to five linkage groups.Key words: Metarhizium, linkage, epistasis, biosynthesis.
A nucleolar-organizing B chromosome showing segregation–distortion in the grasshopper Dichroplus pratensis (Melanoplinae, Acrididae)
Authors: Bidau Claudio J.
Published: November 2014

A nucleolar-organizing B chromosome occurs at low frequency in some populations of the grasshopper Dichroplus pratensis. This B chromosome is telocentric, mitotically stable, and has a proximal secondary constriction. Haematoxylin and silver staining both demonstrate that the constriction organizes a nucleolus in addition to the standard nucleolar organizing region present in the S8 bivalent. In the single 2B male carrier studied, both B's organized nucleoli. The analysis of the meiotic behaviour of 1B males revealed that the B and the X chromosome associate preferentially during early prophase I. At leptotene the B and the X are associated in approximately 50% of the nuclei, but by zygotene – early pachytene the mean frequency of association is 86 reaching 100% in one male. This difference in association frequency between the two stages is highly significant. Persistent X–B associations lead to both chromosomes moving to the same pole in approximately 60% of the first anaphases. In the 2B male, both B's are paired in all early pachytene nuclei, while X–B associations seem to be random and much less frequent than in 1B males. Both B's remain associated in 60% of the metaphase I meiocytes, although true chiasmata do not seem to be involved. Nevertheless the B bivalent disjoins regularly. In 2B cells where both B's are univalents their segregation is random with respect to the X.Key words: B chromosome, nucleolus, nucleolar-organizing region, segregation–distortion, grasshopper.