bluuebunny/crossref_metadata_2025 huggingface dataset:
Partial deletion of the β-globin gene: a common β-thalassaemia allele in Asian Indians
Authors: Wood S. , Daya M. , Allanson J. E. , Kirby L. , Coupland R. , Gray G. R.
Published: November 2014

We have examined 11 families of Asian Indian origin, who are segregating β-thalassaemia alleles, for coupled restriction enzyme site markers. A β-thalassaemia deletion allele, which removes over 600 base pairs, is a common cause of thalassaemia in this population. This deletion can be conveniently detected in AvaII restriction enzyme digests. Consequently AvaII digests are particularly informative in this population because both the deletion and a coupled restriction site polymorphism may be simultaneously observed.Key words: β-thalassaemia, deletion, Asian Indian.
Mating system and genetic polymorphism in populations of Secale cereale and S. vavilovii
Authors: Vega M. Pérez De La , Allard R. W.
Published: November 2014

Electrophoretic banding patterns were determined for nine enzyme systems (IPO, PGM, PGI, LAP, GOT, EST, PHOS, MDH, CPX) in four populations of Secale cereale L. from widely different geographical areas, and in one population of S. vavilovii Grossh. Secale cereale was found to be extensively variable and S. vavilovii invariant for these enzyme systems. Formal genetic studies of nine polymorphic banding zones in S. cereale revealed that each zone was under single locus control. Mating system studies based on these loci indicated that 8% of self-fertilization occurred under field conditions in a population of S. cereale, a species with a highly developed self-incompatibility system. Each population was characterized by fewer heterozygotes than expected in random mating populations. Genotypic and allelic frequencies were nearly identical in four populations of S. cereale, despite their diverse origins and different cytological characteristics.Key words: mating system, Secale, rye, isozyme polymorphism.
Cytogenetics of tissue culture regenerated hybrids of Triticum tauschii × Secale cereale
Authors: Fedak George
Published: November 2014

Immature inflorescences of Triticum tauschii (Coss.) Schmal. × Secale cereale L. cv. 'Puma' hybrids were induced to callus on Kao's medium supplemented with 5 mg/L 2-4-dichlorophenoxyacetic acid (2.4-D). Plantlets with diploid and tetraploid chromosome numbers were subsequently regenerated from the callus. Chromosome pairing in the diploid regenerants and tetraploid amphiploids was incomplete and the plants were sterile.Key words: Triticum, Secale, chromosome pairing, callus, tissue culture.
Giemsa C-banding of potato chromosomes
Authors: Pijnacker L. P. , Ferwerda M. A.
Published: November 2014

An air-drying technique was developed that provided well-spread somatic metaphases of the potato Solanum tuberosum. With Giemsa C-banding, the individual chromosomes (x = 12) could be identified. Some bands are different from those in S. phureja. The technique provides a means to investigate structural differences between genomes.Key words: C-banding, chromosomes, potato.
Somatic cell cytology of the chromosome-eliminating, intergeneric hybrid Hordeum vulgare × Psathyrostachys fragilis
Authors: Linde-Laursen I. , Bothmer R. von
Published: November 2014

In the hybrid Hordeum vulgare × Psathyrostachys fragilis the two genomes were differentiated (i) by length, the P. fragilis chromosomes being 31% longer than the H. vulgare chromosomes; (ii) by a difference in staining intensity of C-banded chromosomes (of possible use for exact localization of breakpoints), the H. vulgare chromosomes being the more heavily stained; (iii) by widely different C-banding patterns; and (iv) by the difference between N-banded H. vulgare and non-N-banded P. fragilis chromosomes. Only C-banding patterns identified each chromosome. Aneuploid cells had lost between one and five P. fragilis chromosomes. Loss of H. vulgare chromosomes is ascribed to squashing. No haploid H. vulgare cell was observed. The P. fragilis chromosomes were characterized by diminished centric constrictions, suppression of nucleolar constrictions, and nucleolus activity, i.e., differential amphiplasty, and generally a peripheral location on the metaphase plate. The same characteristics are normally observed in hybrids producing haploids H. vulgare, suggesting a common mechanism of chromosome elimination. Some cells had a side-by-side arrangement of genomes. The only effect of the hybrid condition on H. vulgare chromosomes was the formation of wider nucleolar constrictions and larger nucleolus organizer regions (NORs) than in parental H. vulgare, suggesting a compensational mechanism for nucleolus activity. The passage of H. vulgare chromosomes through the hybrid to the dihaploid did not influence chromosomal characteristics.Key words: Hordeum, Psathyrostachys, hybrids, elimination of chromosomes, banding.
The genomic relationship of the diploid Bromus variegatus to Bromus inermis
Authors: Armstrong K. C.
Published: November 2014

The diploid species Bromus variegatus Bieb. was crossed to Bromus inermis Leyss (4x, 8x). Chromosome pairing in each of the six F1 hybrid plants of B. variegatus × B. inermis (4x) fit a 2:1 genomic model of chromosome pairing, which indicated that the B. variegatus genome was more closely related to the A or B genome of B. inermis than A and B were related to each other. A breakdown of microsporocytes was observed in the B. variegatus × B. inermis (8x) hybrid. However, chromosome pairing suggested that the B. variegatus genome was differentiated from the A and B genomes of octoploid B. inermis.Key words: Bromus, diploid, genome, affinity.
Quantitative variation induced by gamma rays, ethyl methane sulphonate, and hydrazine hydrate in mung bean (Phaseolus aureus Roxb.)
Authors: Khan Irfan A.
Published: November 2014

Induced variability was studied in the quantitative characters of mung bean (Phaseolus aureus Roxb.) after treatment with gamma rays, ethyl methane sulphonate (EMS), and hydrazine hydrate (HZ) in M1, M2, and M3 generations. The characters evaluated were seeds per pod, 100-seed weight, and total plant yield. The variability increased in almost all of the characters in the M1 generation. The mean number of seeds per pod and 100-seed weight decreased, whereas the plant yield did not show any particular trend. There was an increase in the mean values after gamma irradiation and EMS treatments in the M2 generation. However, HZ fails to show the same response. However, the mean values increased in the M3 generation. Estimates of heritability were higher for 100-seed weight, followed by plant yield, and then seeds per pod in the M3 generation. Coefficient of genotypic variation and genetic advance were high for the plant yield in M2 and M3 generations. In general, the genotypic coefficient of variation values, heritability, and genetic advance increased more in M3 as compared with M2, indicating that the significant gain could possibly be achieved through selection in M3 generation.Key words: quantitative, heritability, mutagenesis.
Uneven ploidy levels and a reproductive mutant required for interspecific hybridization of Medicago sativa L. × Medicago dzhawakhetica Bordz.
Authors: McCoy T. J. , Smith L. Y.
Published: November 2014

Crossing diploid (2n = 2x = 16) Medicago sativa L. (homozygous for the gene, jp, that causes failure of the postmeiotic cytokinesis) and tetraploid (2n = 4x = 32) Medicago dzhawakhetica Bordz. resulted in efficient recovery of interspecific hybrids. Interspecific hybrids were produced in large numbers (1.15 – 5.60 hybrids per pollination), comparable to intraspecific same-ploidy level crosses within M. sativa. All 237 interspecific hybrids were triploid (2n = 3x = 24) or near triploid. Morphologically, the F1 hybrids were intermediate, although they tended to be more similar to the M. dzhawakhetica parent. Medicago dzhawakhetica was resistant to spring blackstem (caused by Phoma medicaginis Malb. and Roum.), whereas the M. sativa parents were susceptible. The F1 hybrids were also resistant to P. medicaginis. Chromosome pairing in the hybrids showed plant-to-plant variation; however, trivalent frequencies in some F1 hybrids were comparable to that observed in M. sativa triploids, indicating potential for recombination between M. sativa and M. dzhawakhetica genomes. Although the triploid hybrids were male sterile, and nearly female sterile, it was possible to produce backcross progeny. The first backcross was both male and female fertile.Key words: Medicago, hybridization, breeding, tetraploid, triploid, sterility.
Chromosome pairing in triploid and tetraploid hybrids in Elytrigia (Triticeae; Poaceae)
Authors: McGuire Patrick E.
Published: November 2014

Mean chromosome pairing of 5.14I + 1.28II (rod) + 3.86II (ring) + 1.47III + 0.11IV (open) + 0.11V was observed in pollen mother cells at metaphase I in the triploid hybrid Elytrigia scirpea (K. Presl) Holub, 2n = 4x = 28 × E. bessarabica (Savul. et Rayss) Dubrovik, 2n = 4x = 14. Mean chromosome pairing of 3.71I + 2.29II (rod) + 1.82II (ring) + 2.64III + 0.29IV (open) was observed in the triploid hybrid E. curvifolia (Lange) Holub, 2n = 4x = 28 × E. bessarabica. Mean chromosome pairing of 3.00I + 0.93II (rod) + 1.57II (ring) + 1.36III + 1.79IV (open) + 1.I4IV (closed) + 0.79V was observed in the tetraploid hybrid E. junceiformis Löve et Löve, 2n = 4x = 28 × E. curvifolia. The first hybrid provides the first evidence by genome analysis that E. bessarabica possesses a genome (designated Eb) which is closely related to the genomes of E. scirpea (ES and ESC) and hence to the E genome of E. elongata (Host) Nevski, 2n = 2x = 14. The second and third hybrids provide the first evidence that the two genomes of E. curvifolia (designated EC and ECU) are related to the Eb genome of E. bessarabica and thus to the E genome of E. elongata.Key words: Elytrigia, homoeology, Triticum, phylogeny, triploid, tetraploid.
Genetically controlled desynapsis in diploid Critesion violaceum and its hybrids with autotetraploid Psathyrostachys juncea
Authors: Wang Richard R-C.
Published: November 2014

Segregation for chiasma frequency was observed in the progeny of a diploid (2n = 14) Critesion violaceum strain following self-pollination. One S1 plant had normal metaphase pairing with an average of 0.43I + 6.78II, giving a high chiasma frequency, 12.03 per cell. The other S1 plant averaged 7.89I + 3.08II and a low chiasma frequency, 3.47 per cell. Examination of pollen mother cells at early prophases revealed that chromosome pairing was not totally prevented. It was concluded that desynapsis was responsible for the meiotic irregularities observed in the variant progeny. The same phenomena were observed in F1 hybrids of the cross between diploid C. violaceum and an induced autotetraploid (2n = 28), Psathyrostachys juncea. The normal F1 hybrid had a chiasma frequency of 12.81, but the desynaptic hybrid had a chiasma frequency of 6.94. A dosage effect of the desynaptic gene, which was probably recessive, was suggested. The implications and significance of this discovery are discussed.Key words: asynapsis, chiasma, meiosis, intergeneric hybrid.
The homoeologous relationship between the chromosomes of rye and wheat. Current status
Authors: Miller T. E.
Published: November 2014

The considerable advances made in recent years to the understanding of the homocological relationships between rye and wheat chromosomes is reviewed, and descriptions of the effect of added and substituted rye chromosomes on the wheat phenotype are provided. The procedure for producing addition and substitution lines of rye chromosomes to wheat are described. The significance of the addition and substitution lines in determining homoeology with wheat chromosomes is discussed, and detailed evidence from substitution lines and homoeoallelic gene series is provided for individual chromosomes.Key words: wheat, rye, chromosomes, homoeology.
Preferential pairing in Dactylis glomerata?
Authors: Sybenga J.
Published: November 2014

Key words: Dactylis, preferential pairing, multivalents.
Morphology and metaphase chromosome pairing in three Avena hybrids
Authors: Leggett J. M.
Published: November 2014

The chromosome pairing affinities and some morphological comparisons are described between the hybrids Avena longiglumis × A. damascena, A. damascena × A. canariensis, and A. damascena × A. sativa in relation to each other and some previously reported diploid × diploid and diploid × hexaploid hybrids. Genomic affinities in the A. longiglumis × A. damascena and A. damascena × A. sativa hybrids were found to be consistent with similar hybrids reported previously, but the A. damascena × A. canariensis hybrids show a very close cytogenetic relationship.Key words: oats, hexaploid, Avena hybrids, synapsis.
Detection of cytogenetic regions influencing RNA polymerase activity in Drosophila melanogaster by segmental aneuploid mapping
Authors: Willms Jane , Phillips John
Published: November 2014

In a search for loci with RNA polymerase related function, we have screened the Drosophila melanogaster genome for regions effective in eliciting a dosage response for total RNA polymerase activity using segmental aneuploids generated by the use of Y-autosome translocations. From this screen we have identified a total of six cytogenetically defined regions which elicit significant dosage response: a single X-chromosome region, 9C-11A, within which resides a known RNA polymerase locus and five noncontiguous regions on chromosome 3 with no previously identified RNA polymerase related function.Key words: RNA polymerase, gene location, segmental aneuploids, Drosophila.
Cytoplasmic substitutions involving six Avena species
Authors: Leggett J. M.
Published: November 2014

Alloplasmic lines involving the nuclear genomes of the hexaploid oat Avena sativa, the cytoplasms of the diploid species A. canariensis, A. hirtula, A. pilosa, A. prostrata, and A. ventricosa, and the tetraploid A. barbata have been produced. The cytoplasmic effects on growth rate and flowering date are described with particular reference to the introduction of the cytoplasm from the two C-genome diploid species.Key words: Avena, quantitative inheritance, cytoplasmic effects.
Cytogenetics of a hybrid and amphiploid between Hordeum pubiflorum and Secale africanum
Authors: Fedak George
Published: November 2014

A low frequency (0.86) of rod bivalents was observed at metaphase I of meiosis in the F1 hybrid between Hordeum pubiflorum 2x and Secale africanum 2x. Seeds were obtained from colchicine-doubled sectors on the hybrid. An average of 2.49′ + 12.77″ per cell characterized meiosis in the amphiploid. The univalent and bivalent frequencies among Hordeum and Secale chromosomes were approximately equal, although there was a higher proportion of ring bivalents formed by the Hordeum chromosomes. Over 90% of the pollen was stainable, but only 40% seed set was obtained on the amphiploid. Although the seeds were badly shrivelled, some were viable.Key words: intergeneric hybrid, chiasma frequency, embryo rescue, Hordeum–Secale.
Genetic polymorphism in populations of Akodon rodents
Authors: Apfelbaum Liliana I. , Blanco Antonio
Published: November 2014

By means of starch gel electrophoresis, 16–20 loci coding for enzymes and hemoglobin have been investigated in six population samples of Akodon dolores, captured in a single site of the Córdoba province (Argentina) during a 3-year period and in three samples of an Akodon azarae population. Proportion of polymorphic loci (P) ranged from 0.278 to 0.389 in A. dolores and from 0.166 to 0.300 in A. azarae. Mean heterozygosity (H) ranged from 0.138 to 0.192 in A. dolores and from 0.099 to 0.118 in A. azarae. These values are very high compared with those reported for northern hemisphere rodent populations. The high value is remarkable since the loci sample is biased towards the less variable (group I) enzymes.Key words: polymorphism, Akodon, heterozygosity, isozymes.
The analysis of meiosis of the B genome in common wheat
Authors: Jouve N. , Gonzalez J. M. , Fominaya A. , Ferrer E.
Published: November 2014

Two intervarietal hybrids of common wheat, Triticum aestivum L., are meiotically analyzed using the C-banding staining method. The C-banding pattern of nine meiotic chromosomes (4A, 7A, and the seven of the B genome) permitted their unequivocal recognition at first metaphase plates. The pairing frequency of each B-genome chromosome arm was scored. Data on the pairing frequency of the arms, separately considered, are applied to calculate expected pairing of whole chromosomes and whole genomes. The application of mathematical models to predict the genome pairing using either equal or different frequencies per chromosome arm is discussed.Key words: meiotic analysis, Triticum aestivum L., C-banding.
Analysis of pest resistance in alfalfa with a new autotetraploid genetic model
Authors: Hill Jr. R. R. , Elgin Jr. J. H.
Published: November 2014

A genetic model for the analysis of crosses and advanced generations between autotetraploid populations had been developed and applied to an analysis of pest resistance data in an experiment on alfalfa (Medicago sativa L.). The model had the form [Formula: see text] where [Formula: see text] is the observed mean of combination ij in generation n, C is a constant, u, is a parameter for the mean of parent population i, kn and mn are constants computed from the theoretical approach to equilibrium in the population, Gij is the digenic parameter in the equilibrium population that would arise from the population cross, and Qij is the quadrigenic parameter for that population. Nonadditive genetic effects were observed for most of the traits subjected to analysis under the model. The mode of gene action varied from one population to another in many cases. Variances of estimates of Gij were small, but those of Qij were very large. The large covariance between estimates of Gij and Qij was caused by a correlation between coefficients of these parameters.Key words: pest resistance, Medicago, autotetraploid, additive effects, population genetics.
Nuclear DNA content of benomyl-induced segregants of diploid strains of the phytopathogenic fungus Armillaria mellea
Authors: Anderson J. B. , Petsche D. M. , Franklin A. L.
Published: November 2014

The relative nuclear DNA contents of haploid, diploid, and benomyl-induced segregants of diploid strains of the phytopathogenic fungus Armillaria mellea were measured by mithramycin staining and fluorescence photometry. The diploid strains, originally recovered from sexually compatible matings of haploid strains, were heterozygous at mating-type and auxotrophic marker loci. The somatic segregants examined here were derived by treatment of the diploid strains with the fungicide benomyl in previous studies. As expected, the diploid strains had approximately twice as much nuclear DNA as the haploid strains. Most segregants had near-haploid DNA contents and no detectable heterozygosity at the marker loci; these strains were most likely true haploids. Other segregants with near-haploid DNA contents were heterozygous at a marker locus indicating that they were aneuploid. A minority of segregants had near-diploid DNA contents and may have been either aneuploid or diploid.Key words: basidiomycetes, mithramycin, parasexuality.
A chromosome of Hordeum chilense homoeologous to group 7 of wheat
Authors: Miller T. E. , Reader S. M. , Ainsworth C. C.
Published: November 2014

Individual substitution lines have been produced with Hordeum chilense chromosome A substituted in turn for chromosome 7A, 7B, or 7D of Triticum aestivum. Telocentric substitutions with the α arm, substituted for chromosome 7A or 7D, or the β arm substituted for chromosome 7B have also been produced. The substitutions have been confirmed by the presence of a purple straw marker, by gel isoelectric focusing of α-amylase isozymes, and cytologically using telocentric chromosome markers. Chromosome A has consequently been designated 7Hch.Key words: Hordeum chilense, wheat, chromosome substitution, homoeology, α-amylase.
Early seed development in the annual and perennial Secale taxa
Authors: Gustafson J. P. , Lukaszewski A. J.
Published: November 2014

The early embryo and endosperm development patterns of five annual taxa and three perennial taxa of the genus Secale were analyzed. The results showed that there was considerable variation in the speed of early embryo and endosperm development within the genus Secale, and that the developmental patterns of the annual and perennial taxa overlapped. Comparisons indicated that DNA content per se did not have any influence on the speed of early embryo development or aberrant endosperm nucleus production in either the annual or perennial taxa. However, comparisons between the percent telomeric heterochromatin and the number of embryo cells produced showed a significant positive correlation in the annual taxa, and a nonsignificant correlation in the perennial taxa. There was a positive correlation between the number of aberrant endosperm nuclei and percent telomeric heterochromatin in the annual taxa, while the perennial taxa showed a nonsignificant but negative correlation. The results suggest that percent telomeric heterochromatin has a different effect on early seed development in the annual taxa than in the perennial taxa.Key words: Secale, heterochromatin, DNA content, embryo cell cycle.
Somaclonal variation in triticale (×Triticosecale Wittmack) cv. Carman
Authors: Jordan M. C. , Larter E. N.
Published: November 2014

Callus was initiated from 15-day-old embryos of 'Carman' triticale (×Triticosecale Wittmack) cultured on 2,4-dichlorophenoxyacetic acid supplemented Murashige and Skoog (MS) medium. For plant regeneration, the calli were subcultured every 4 weeks on MS media with no added hormones. The original euploid (2n = 42) regenerated plants and their progeny were examined for several traits. Considerable variation for all measured traits was observed among the regenerated plants. Variability was greatest for spike length, fertility, and plant height. Two second-generation plants were found to have a significant increase in percent kernel protein relative to 'Carman' controls. Electrophoretic studies showed that all regenerated plants of both generations had the same prolamin banding pattern as 'Carman' triticale but variation existed in the intensity of the bands. This was especially true for the bands encoded for by the rye genome. One genotype, viz. R13, exhibited extreme chromosomal instability resulting in the occurrence of both rye and wheat univalents as observed at metaphase I.Key words: somaclonal variation, triticale, tissue culture, plant regeneration.
The association of centromeres of nonhomologous chromosomes at meiotic prophase in Beta vulgaris L.
Authors: Jong J. H. De , Stam P.
Published: November 2014

Centromere association involving two or three nonhomologous bivalents at meiotic prophase of Beta vulgaris and monosomic additions of B. vulgaris × B. procumbens are described. The associations, most conspicuous at late pachytene and persisting until diakinesis, occur abundantly in a small group of genetically related plants. The presence of normal bivalents at metaphase I and the absence of irregularities at later stages show that centromere associations do not disturb meiotic recombination and transmission. A mathematical model proposed to test for randomness with respect to the number of bivalents involved in centromere associations, showed significant difference between observed and expected frequencies. On the basis of our own observations and data from the literature, it is suggested that the associations at pachytene and diplotene are delayed separations of centromere aggregates that arise at premeiotic interphase or during the formation of the synizetic knot. A possible molecular mechanism is discussed.Key words: centromere association, meiotic prophase, pachytene chromosomes, nonhomologous association, sugar beet, Beta vulgaris.
Population differentiation in lodgepole pine, Pinus contorta spp. latifolia: a discriminant analysis of allozyme variation
Authors: Yeh Francis C. , Cheliak William M. , Dancik Bruce P. , Illingworth Keith , Trust Diane C. , Pryhitka Beverly A.
Published: November 2014

Seeds from 17 populations representing most of the range of lodgepole pine in the Yukon and British Columbia were analyzed for electrophoretically demonstrable variation in 16 proteins coded by 23 genetic loci. Consistent with that reported on genetic variation in this conifer, on the average, 64% of the loci per population were polymorphic, and expected and observed heterozygosity per population were 0.165 and 0.174, respectively. Univariate F-ratio tests for homogeneity among populations indicated genetic differentiation (p < 0.05) at six loci. Two significant (p < 0.05) canonical discriminant functions accounted for 38% of the total variance in the 20 polymorphic loci. A rich structure of genetic variation associated with geography was revealed. Both latitude and altitude appeared to be important, with northern populations exhibiting a greater extent of genetic differentiation.Key words: allozymes, electromorphs, populations, Pinus, lodgepole pine.
Analyse de croisements diallèles pour les caractères agronomiques de plantes saines et virosées chez le haricot (Phaseolus vulgaris L.)
Authors: Sarrafi A. , Ecochard R.
Published: November 2014

The study of agronomic characters of healthy and virus diseased plants in a diallel cross program concerning five different varieties of bean, shows that in both cases the general combining ability for yield and its components usually has positive or negative significant values; the maximum value of the general combining ability for each yield component is characteristic of each variety; and the number of specific combining ability cases are less numerous than those of general combining ability. Usually positive specific combining ability is obtained from two negative and positive cases of general combining ability because of nonadditive genes interaction. Values for general and specific combining abilities are, in some cases, significantly modified by the bean common mosaic virus. This shows that quantitative genetic studies concerning agronomical and physiological characters are always influenced by external factors including culture conditions as well as parasites. The results obtained are valuable only for the studied varieties and conditions in which the experiment is achieved.Key words: bean, diallel crosses, virus No. 1, combining ability.
Interspecific hybridization of Medicago sativa L. and M. rupestris M. B. using ovule–embryo culture
Authors: McCoy T. J.
Published: November 2014

An ovule–embryo culture method was used to produce the first interspecific hybrids between alfalfa (Medicago sativa L.) and Medicago rupestris M. B. Culture of fertilized ovules from the cross diploid (2n = 2x = 16) M. sativa (jpjp) × diploid (2n = 2x = 16) M. rupestris began 14 days after pollination. After 5 days in culture, the interspecific hybrid embryo was removed and transferred to fresh medium, where development into a plant occurred. Forty-six M. sativa – M. rupestris F1 hybrids have been recovered using this technique. All but one of the 46 F1 hybrids were diploid (2n = 2x = 16); the only exception was tetraploid (2n = 4x = 32). The most frequent meiotic configurations observed in the F1 hybrid plants were eight bivalents or seven bivalents and two univalents, indicating significant homology between M. sativa and M. rupestris genomes. However, pollen stainability (0–12%) and pollen germination (0–6%) were extremely low. Similar to the production of the F1, no first backcross (BC1) plants were obtained from seed; however, the ovule–embryo culture method was found to be a very effective method for recovering BC1 plants and hundreds of BC1 plants have been produced. The BC1 plants from crossing the F1 with diploid M. sativa were predominantly diploid. Medicago rupestris can now be considered a potential germplasm source for alfalfa improvement. The ovule–embryo culture method represents the first successful recovery of Medicago interspecific hybrids via some form of embryo rescue. Importantly, it appears this technique can be applied to other interspecific hybrid combinations in the Medicago genus.Key words: Medicago, alfalfa, embryo culture, interspecific hybrid.
Molecular evidence for the origin and evolution of chromosome 4A in polyploidy wheats
Authors: Rayburn A. Lane , Gill B. S.
Published: November 2014

The chromosomes of polyploid Triticum species and the putative donor diploid species were analyzed by in situ hybridization with a repeated DNA sequence clone pSc 119 isolated from rye and also found in wheat. In Triticum aestivum cv. Chinese Spring, chromosome 4A showed one terminal site in the short arm and one terminal and two interstitial sites of hybridization in the long arm. Triticum turgidum contained a 4A chromosome identical to 'Chinese Spring' with respect to hybridization sites. Chromosome 4A of the timopheevi wheats differed from 4A of 'Chinese Spring' in that the site of the sequence on the short arm was subterminal rather than terminal. Of the A-, B-, and D-genome progenitor species, only potential B-genome donors Aegilops speltoides and Aegilops sharonensis each showed a chromosome with hybridization sites similar to 4A. This suggested that 4A belongs to the B genome. Moreover, with regard to this sequence, chromosome 4A has undergone only minor changes during the evolution of the polyploid wheats.Key words: wheat evolution, in situ hybridization, biotin labeling.
A simple two-step procedure for silver staining nucleolus organizer regions in plant chromosomes
Authors: Mehra Romesh C. , Brekrus Susan , Butler Merlin G.
Published: November 2014

Nucleolus organizer regions (NORs) of Allium cepa, Lens culinaris, and Vicia faba chromosomes were stained by a two-step silver staining procedure which is simple and highly reproducible. Polymorphisms are apparent with respect to the size of NORs in the taxa understudy.Key words: nucleolar organizer regions, silver staining, Allium cepa, Lens culinaris, Vicia faba.
Geographic patterns of chromosomal variation in populations of the grasshopper (Trimerotropis pallidipennis) from southern Argentina
Authors: Goñi B. , Vaio E. S. de , Beltrami M. , Leira M. S. , Crivel M. , Panzera F. , Castellanos P. , Basso A.
Published: November 2014

Geographic variation has been studied on seven south Argentina populations of Trimerotropis pallidipennis polymorphic with respect to centromere position. Univariate and multivariate statistical analysis were used to assess interpopulation relationships by considering the inversion frequency, the chiasma frequency, and the population distance from the Andes, which is considered to be the hypothetical pathway of migration of this typically North American species to southern latitudes. A cluster analysis indicated strong chromosomal differentiation between the almost monomorphic populations in the Andes' "precordillera" and the highly polymorphic populations in more eastern locations. It also showed that chromosomal similarity between populations could be predicted by geographic proximity. No attempt has been made to relate such a pattern of chromosome variation to ecological data. The lack of any clear relationship with phytogeographic regions or climatic characteristics suggests that microenvironmental factors related to aridity may be important in this case. The presence of inversions within a population has a notable effect on chiasma frequency and position. Chiasmata are suppressed within the inverted region of both inversion heterozygotes and homozygotes. The allelic sequences in the inverted region are thus preserved from recombination and exchanges are limited to terminal regions.Key words: geographic variation, chromosome polymorphism, chiasma frequency, B chromosome, pseudomultiple associations.
Studies on the Stellaria longipes complex (Caryophyllaceae): interspecific hybridization. I. Triploid meiosis
Authors: Chinnappa C. C.
Published: November 2014

Stellaria longipes was crossed with five other species to establish species relationships. Only crosses between S. longipes and S. longifolia resulted in the production of viable F1 seed and hybrid progeny. In the hybrids (2n = 39), chromosome associations at metaphase I showed complete homology between the genomes of the two species. This may suggest a close relationship between the diploid S. longifolia and the polyploid S. longipes.Key words: Stellaria, species complex, triploid, meiosis.
Genetic analysis of a population of Tribolium. VIII. The stationary stochastic dynamics of adult numbers
Authors: Desharnais R. A. , Costantino R. F.
Published: November 2014

A stochastic differential equation model for the rate of change of adult numbers was used to analyze data from two genetically differentiated groups of laboratory populations of the flour beetle, Tribolium castaneum. The first group of populations was homozygous for the corn oil sensitive allele and the other group was polymorphic at this genetic locus. Previous work has shown that mean larval viability is increased in the polymorphic populations. This suggests that the average number of potential recruits was higher in the polymorphic populations when compared to the homozygous ones. The stochastic model was used to derive predictions for the stationary distributions and the serial correlations at demographic equilibrium. These predictions were evaluated using 66 weeks of census data from both groups of populations while adult numbers were fluctuating in the region of their steady states. The data supported the following theoretical predictions: (i) the fluctuations in adult numbers can be described using a gamma probability density function; (ii) increased recruitment in the polymorphic populations results in a larger mean and variance for adult numbers; (iii) the autocorrelation of adult numbers decays exponentially with time; and (iv) increased recruitment in the polymorphic populations results in a faster rate of decay in the autocorrelations. These results suggest that genetically based fitness differences among populations can be reflected in the stationary stochastic dynamics of population size.Key words: Tribolium, population dynamics, stochastic models, stationary distributions, gamma distribution.
A direct technique for the preparation of chromosomes from early equine embryos
Authors: Romagnano April , King W. Allan , Richer Claude-Lise , Perrone Marie-Antoinette
Published: November 2014

A technique is described for the preparation of banded chromosomes from early equine embryos cultured for less than 10 h in a medium containing bromodeoxyuridine. In addition to standard Giemsa staining and C-banding, chromosomes thus prepared can also be R-banded by either the RBA or the RB-FPG methods. This technique is rapid, repeatable, and limits cell loss, making it ideal for the preparation of early embryos.Key words: embryos, chromosomes, banding, horse, cow.
Studies of haploid–diploid twins in flax (Linum usitatissimum)
Authors: Murray Beatrice E.
Published: November 2014

The present study was designed to investigate the origin of twin seedlings in flax (Linum usitatissimum L.). The twins were derived from crosses of high-twinning × nontwinning lines. The data presented were based on the following: (i) the morphology of twins in terms of variations in the position, orientation, and size of the twin embryos in the embryo sac and in the mature seed; (ii) the cytological interpretation of meiosis in the haploid and diploid member of F2 twins, and chromosomal pairing of the F3 diploid, triploid, and trisomic progeny obtained from crossing haploid × diploid F2 twins; and (iii) the genetic analysis of twinning frequencies, seed set by twins in single and double cross progenies, and the combinations of flower color phenotypes in F2 twins derived from blue flower × white flower crosses. The results, based on the survival rate of the haploid embryos, the cytological interpretation of meiosis, the fertility in the haploids, and in particular, the flower phenotype of twins in nine F2 families, support the hypothesis that the progenitors of the twin embryos are two-megaspore nuclei rather than one.Key words: flax twins.
Intergeneric hybrids of Hordeum vulgare with Agropyron caninum and A. dasystachyum
Authors: Fedak George
Published: November 2014

Hybrids were obtained by pollinating Hordeum vulgare cv. Betzes with Agropyron caninum (4x) and A. dasystachyum (4x) at frequencies of 1.4 and 6.1% of pollinated florets, respectively. The hybrids were sterile and phenotypically resembled the paternal parent, except for floret structure which was intermediate between the parental types. Chromosome pairing at meiosis was very low and thus provided no indication of homoeology between parental genomes. Abnormal meiotic chromosome behavior in meiocytes that occurred in sectors on the 'Betzes' × A. dasystachyum hybrid was attributed to abnormal spindle fibre function.Key words: intergeneric hybrids, Hordeum vulgare, Agropyron caninum, Agropyron dasystachyum.
Chromosome instability, fertility, and effect of selection in Avena abyssinica × A. sativa amphiploids
Authors: Fritz S. E. , Sorrells M. E.
Published: November 2014

Interspecific introgression of the wild species via production of amphiploids may enable breeders to utilize heterotic responses induced by new genomic interactions. Leaf guard cell and pollen size were studied in five amphiploid crosses in search of a reliable selection index for screening octoploids from large heterogeneous decaploid populations. Neither trait showed unique ploidy effects. Cytological studies indicate chromosome elimination occurred in all decaploid progenies. This somatic instability resulted in nonheritable variation. Selection for fertility, maturity, and plant vigor was ineffective because of the nonheritable variation introduced by chromosome instability.Key words: interspecific introgression, amphiploids, Avena abyssinica, somatic instability, fertility.
Heterosis and combining ability estimates in spring-planted oilseed rape (Brassica napus L.)
Authors: Grant I. , Beversdorf W. D.
Published: November 2014

A 6 × 6 diallel cross was conducted in spring-planted oilseed rape (Brassica napus L.) in 1983 at Elora and Dundalk, Ontario. The F1 hybrids exhibited positive heterosis for seed yield, of up to 72%, over the higher-yielding parent in the hybrid crosses. Heterosis for 1000 seed weight, percent oil, plant height, and lodging resistance was nonsignificant; negative heterosis for percent protein was observed with some hybrids. Generally, the hybrids were intermediate to the parents in flowering date and physiological maturity. Specific combining ability was more important than general combining ability for seed yield, percent oil, percent protein, plant height (Dundalk), and lodging resistance (Elora); specific combining ability was as important as general combining ability for 1000 seed weight, physiological maturity, plant height (Elora), and lodging resistance (Dundalk). The cultivars 'Topas' and 'Regent' were the best general combiners for seed yield. The best specific combinations for seed yield heterosis, 'Westar' × 'Hanna', 'Regent' × 'Liné', and 'Regent' × 'D-1', exhibited average high-parent heterosis values of 50, 38, and 30%, respectively. The results demonstrated that considerable potential exists for producing high-yielding single-cross hybrids of oilseed rape. Commercial exploitation of this heterosis will depend on the successful development of suitable pollination control mechanisms.Key words: Brassica napus, oilseed rape, F1 hybrid, heterosis, combining ability.
Meiotic behaviour of the holocentric chromosomes of Nezara viridula (Insecta, Heteroptera) analysed by C-banding and silver impregnation
Authors: Camacho J. P. M. , Belda J. , Cabrero J.
Published: November 2014

While silver impregnation reveals the presence of kinetochores in monocentric chromosomes, it does not do so in the holocentric system of Nezara viridula. Here, C-banding and silver impregnation techniques reveal that C-heterochromatin is present in the greater part of the Y chromosome and at the nucleolus organizer region (NOR) of the largest autosome (A 1) and in the extra NOR located in the X chromosome of a single exceptional male. Furthermore, one telomere of each autosome appeared lightly C-banded. The largest, A1, bivalent shows chiasmata almost always located at the chromosome ends. This bivalent may orient axially or equatorially in metaphase I cells depending on whether it carries a single chiasma or two chiasmata, respectively. From our cytological analysis we deduce that centromeric activity is preferentially located at the two telomeric ends and that the presence of chiasmata at an end excludes such activity.Key words: diffuse centromere, C-banding, holocentric, insect chromosomes.
The potential for diploidizing Lolium multiflorum × L. perenne tetraploids
Authors: Aung Taing , Evans G. M.
Published: November 2014

The possibility of diploidizing meiosis in tetraploid hybrids of the two closely related Lolium species, L. multiflorum and L. perenne, was investigated using specific genotypes of both parents. Both these parental genotypes had previously been shown to reduce homoeologous pairing in a separate but wider cross with the inbreeder L. temulentum. A preponderance of bivalents was recorded at first metaphase of meiosis in several of the hybrid progeny with the frequency of multivalents being reduced to 0.6/pollen mother cell in one plant. Although it is not unambiguously established that the bivalents so formed are solely between homologous chromosomes, it is highly likely that this is so. It is concluded that it is feasible to genetically modify the pattern of meiosis even in tetraploid hybrids of species of similar karyotypes.Key words: chromosome pairing, Lolium, interspecific hybrid.
Banding differences between tiger salamander and axolotl chromosomes
Authors: Cuny Robert , Malacinski George M.
Published: November 2014

The Hoechst 33258 – Giemsa banding patterns were compared on axolotl (Ambystoma mexicanum Shaw) and axolotl – tiger salamander (Ambystoma tigrinum Green) species hybrid prophase chromosomes. Approximately 369 bands per haploid chromosome set were seen in the axolotl and about 344 bands in the tiger salamander. In the haploid set of 14 chromosomes, chromosome 3 has a constant short or q-arm terminal constriction at the location of the nucleolar organizer. Chromosomes 14 Z and W carry the sex determinants, the female being the heterogametic sex (ZW). The banding patterns of chromosomes 1, 6, 11, and 14 Z of the two species are apparently indistinguishable by our banding method. In the axolotl, chromosome 9 has a small long or p-arm terminal deletion. In the tiger salamander, the remaining 10 chromosomes have terminal or internal deletions. No translocations or inversions seem to have occurred since the gene pool separation of the two closely related species.Key words: chromosome banding, species hybrids, axolotl, tiger salamander.
Heterozygosity and morphological variability of pink salmon (Oncorhynchus gorbuscha) from southern British Columbia and Puget Sound
Authors: Beacham Terry D. , Withler Ruth E.
Published: November 2014

We compared variability in gill raker number and four morphometric characters with heterozygosity at enzymatic loci within and among populations of pink salmon (Oncorhynchus gorbuscha) in southern British Columbia and Puget Sound. Among individuals, there was no relationship between levels of heterozygosity at eight electrophoretic loci and degree of meristic or morphometric variation. Decreased phenotypic variance was not associated with increased heterozygosity. Among populations of pink salmon, increased levels of average heterozygosity were not associated with decreased phenotypic variation. Our results do not support the hypothesis that more heterozygous individuals are less phenotypically variable than more homozygous ones as a result of genetic homeostasis and a canalisation of morphology during development. Genetic distances between pairs of pink populations were significantly correlated with pairwise Mahalanobis distances derived from meristic characters (gill rakers) and less strongly correlated with distances derived from morphometric characters. Pink salmon are morphometrically adapted to the natal stream environment, whereas biochemical and meristic characters in these populations may be less affected differentially by local selective forces.Key words: salmon, electromorphs, homeostasis, genetic variability, heterozygosity.
In vivo karyotypic modifications following spontaneous cell fusion in maize (Zea mays L.)
Authors: Peeters John P. , Griffiths A. J. F. , Wilkes Garrison
Published: November 2014

Spontaneous cell fusion has been detected during meiosis of pollen mother cells in a Himalayan popcorn called Sikkim Primitive. In postfusion meiotic cells one of the chromosome complements was often found to undergo modification producing a range of outcomes including aneuploidy and the formation of cells with modified supernumerary chromosomes. These abnormalities have been followed through three generations and new karyotypes containing modified supernumerary chromosomes were recovered in the F1 and F2 following the abnormal meiosis. These inherited additional chromosomes presumably arose from the cell fusions of the pollen mother cells and therefore our observations may indicate a natural mechanism for the formation of accessory chromosomes.Key words: spontaneous cell fusion, accessory chromosomes, Zea mays.
Inheritance of seed protein and seed oil content in early maturing soybean
Authors: McKendry Anne L. , McVetty Peter B. E. , Voldeng Harvey D.
Published: November 2014

The inheritance of seed protein, seed oil, and the sum of protein and oil was investigated in two early maturing soybean crosses, 'Maple Presto' × 'Sioux' and 'Maple Presto' × X446-2-1, in 2 years (1981 and 1982) at one location (Winnipeg). Analyses of variance of the parental performance over years indicated that the parents differed significantly for all three traits studied and that genotype by year interactions were effectively zero. Generation means analysis indicated that gene action for seed protein was primarily additive, with partial dominance for low protein. Seed oil was also conditioned primarily by additive gene action. Partial dominance was not consistently detected over years and therefore was of minor importance. Additive × additive epistatic effects for seed oil were also detected but were not consistent over years. The sum of seed protein and oil was conditioned solely by additive gene action. Variance analyses indicated a predominance of additive genetic variance for all three traits. Dominance variance was also detected for both seed protein and the sum of protein and oil. Broad sense heritability for the F2 generation ranged from 76 to 83% for seed protein and from 68 to 86% for the sum of protein and oil, while narrow sense heritability ranged from 34 to 72% for seed protein and from 39 to 65% for the sum of protein and oil. Narrow sense heritability values equalled broad sense values for seed oil and ranged from 58 to 68%. Heritability was also estimated from standard unit parent – progeny regression analyses and values for all three traits were found to approach the variance analyses estimated broad sense heritabilities. Comparisons with the results of late maturing soybean crosses are made and implications of the results obtained in this study on early maturing soybean breeding programs are discussed.Key words: Glycine max, heritability, 00 and 000 maturity groups, breeding strategies.
Synchronization of human lymphocyte cultures by fluorodeoxyuridine
Authors: Braekeleer M. De , Keushnig Marylinne , Lin C. C.
Published: November 2014

A simple technique for synchronization of human lymphocyte cultures with fluorodeoxyuridine (FudR) is presented. The S-phase block induced by the FudR is released by simultaneous exposure to 5-bromodeoxyuridine (BrdU) and Hoechst 33258 or by thymidine and Hoechst 33258. This method provides a high mitotic index with high percentage of prometaphase chromosomes. This simple method is highly advantageous and easy to utilize in clinical cytogenetics.Key words: fluorodeoxyuridine, high-resolution human chromosomes, cell synchronization, banding.