bluuebunny/crossref_metadata_2025 huggingface dataset:
Two kinds of "recombination nodules" in Neurospora crassa
Authors: Bojko Maja
Published: April 2011

Two morphological types of recombination nodules, termed early and late, are recognized in Neurospora crassa. Eighty nuclei at different substages were used to determine numbers of nodules per nucleus, distribution of nodules along the nucleolus-organizing chromosome, and distribution of nodules among the two largest chromosomes. Early nodules appear at the synaptonemal complex at early zygotene and increase in number during zygotene until a dramatic reduction occurs at zygotene – pachytene transition. Thereafter early nodules are steadily eliminated until they disappear by diplotene. Late nodules are also present during zygotene. Their number doubles at the zygotene – pachytene transition and stays at this level until diplotene. The total number of nodules is rather constant through zygotene and pachytene. Distribution of bivalents with 0, 1, 2, etc. nodules follows a Poisson distribution at zygotene, but not at pachytene, where variance is less than the mean, indicating positive interference. Nodules are distributed nonrandomly along the nucleolus-organizer bivalent. The pattern differs slightly in nuclei of different origin. Nuclei with unusual synaptonemal complexes sustain normal levels of recombination by having the same amount of nodules as normal nuclei. In abnormal nuclei nodules are preferentially associated with normal segments. It is proposed that early nodules do not participate in any form of recombination but have a role in finding an appropriate site for a crossing-over event. Morphological change to the late type indicates that the site has been reached and the exchange event can be mediated by the late nodule.Key words: recombination nodules, Neurospora crassa, synaptonemal complex.
A possible origin for the sugar beet cytoplasmic male sterility source Owen
Authors: Bonavent J.-F. , Bessone L. , Geny A. , Berville A. , Denizot J.-P. , Brian C.
Published: April 2011

The cytoplasmic male sterility source of sugar beet used for hybrid seed production is distinguished from the maintainer (O type) by the HindIII chloroplast DNA (ctDNA) restriction pattern. We searched the genus Beta for a putative species carrying the same ctDNA as the Owen cytoplasmic male sterility source. Each of the three sections of this genus displays a specific HindIII profile for ctDNA. We, therefore, suggest the putative species be classified to the Vulgares section as the sugar beet. An old variety of the garden beet, "Crapaudine', in our collection carries the same ctDNA restriction profile as the Owen cytoplasmic male sterility source. This variety presumably was never crossed by breeders with either the Owen cytoplasmic male sterility line or the sugar beet. Our results, however, allow us to propose that the origin of the Owen cytoplasmic male sterility was through a cross of the 'Crapaudine' variety, as female, from the Semaphor company.Key words: cytoplasmique male sterility, sugar beet, chloroplast DNA, garden beet, wild species.
Cytological approaches to simuliid biosystematics in relation to the epidemiology and control of human onchocerciasis
Authors: Procunier W. S.
Published: April 2011

This paper presents an overview of advances in cytological research on the biosystematics of vector simuliid complexes in the areas of identification, age grading, and the evolution of resistance in relation to the epidemiology and control of human onchocerciasis. Systematic theory is discussed and relevant examples are given to show its application in predicting and resolving current problems in species identification for New World and Old World vector complexes. These complexes include Simulium damnosum s.l. and S. neavei s.l. from Africa and S. exiguum s.l., S. metallicum s.l., S. ochraceum s.l., and S. oyapockense s.l. from Latin America. The evolution of resistance in S. damnosum s.l. and the need for future molecular research as part of resistance management strategies are discussed.Key words: cytotaxonomy, systematic theory, vector simuliid complexes, resistance, onchocerciasis.
Giemsa C-banded karyotypes of Hordeum marinum and H. murinum
Authors: Linde-Laursen Ib , Bothmer Roland von , Jacobsen Niels
Published: April 2011

Giemsa C-banding patterns of the predominantly self-pollinating, annual species Hordeum marinum (2x, 4x) and H. murinum (2x, 4x, 6x) showed mostly very small to small bands at centromeric and telomeric positions, at one or both sides of the nucleolar constrictions, and at intercalary positions with no preferential disposition. A similar distribution of bands has been observed in other Hordeum species, suggesting that the pattern is the basic one in the genus Hordeum. Hordeum murinum, especially the hexaploid cytotype, was distinguished from H. marinum by having more numerous and more conspicuous bands, resulting in a significantly higher percentage of constitutive heterochromatin (9–17 vs. 4–8%). The differences in C-banding patterns supported by differences in chromosome morphology confirm that H. marinum and H. murinum are not closely related. Banding-pattern polymorphism was prevalent among populations but unobserved within populations. In spite of this polymorphism, banding patterns in combination with chromosome morphology identified homologous chromosomes of different populations of a taxon and indicated that the chromosome complements of the polyploids of both species comprised the genome of the related diploid as well as one or two "unidentified" genomes. This agrees with an alloploid origin of polyploids. The C-banding patterns of H. marinum ssp. marinum and H. marinum ssp. gussoneanum (2x) showed some divergence in spite of the close relationship. The C-banded karyotypes of H. murinum ssp. murinum and H. murinum ssp. leporinum (4x) were very similar, supporting conspecificity. Chromosome lengths and longest/shortest chromosome ratios were fairly similar to those previously published, supporting the conclusion that linear relationships of chromosomes are normally stable within genomes. The taxonomy of the two species is discussed.Key words: C-banding, karyotypes, Hordeum.
Genomic and taxonomic relationships of Agropyron vaillantianum and E. arizonicus (Poaceae: Triticeae)
Authors: Jensen K. B. , Hsiao C. , Asay K. H.
Published: April 2011

Agropyron vaillantianum (Wulf. &Schreber) Trautv. and E. arizonicus (Scribn. &Smith) Gould were studied to describe their (i) reproductive characteristics, (ii) meiotic behavior, (iii) genomic constitution, and (iv) correct taxonomic alignment based on genomic relationships. Both species were found to be self-fertile tetraploids (2n = 28) and behaved as strict allotetraploids averaging 14.00 and 13.77 bivalents per cell, respectively. The hybrids A. vaillantianum × Pseudoroegneria spicata (Pursh) A. Love, 2n = 14, SS, A. vaillantianum × E. trachycaulus (Link) Gould ex Shinners, 2n = 28, SSHH, and E. arizonicus × E. canadensis L., 2n = 28, SSHH, averaged 6.21, 12.56, and 12.60 bivalents per cell, respectively. Chromosome pairing in this series of hybrids demonstrated that A. vaillantianum and E. arizonicus contain the S and H genomes, with each taxon having a slight modification resulting from evolutionary pressures under different ecological parameters. On the basis of chromosome pairing and mode of pollination it is proposed that A. vaillantianum be treated in the genus Elymus rather than in the genus Agropyron, with the following new name combination: Elymus vaillantianus (Wulf. &Schreb.) K. B. Jensen comb.nov., based on Triticum vaillantianum Wulfen &Schreber. Elymus typically encompasses those species that are self-fertile, and contain the SH genomes. Elymus arizonicus has been correctly classified.Key words: genome, meiosis, chromosome pairing, cytology, interspecific hybridization, Elymus, Agropyron, and Triticeae.
Two-dimensional spreads of synaptonemal complexes from solanaceous plants. IV. Synaptic irregularities
Authors: Sherman Jamie D. , Stack Stephen M. , Anderson Lorinda K.
Published: April 2011

Irregularities in the structure of synaptonemal complexes have been reported in a wide variety of organisms, but so far there has been no study concentrating on synaptic irregularities per se. We have used a hypotonic bursting technique to spread synaptonemal complexes from autotetraploid Solanum tuberosum (potato) and diploid, tetraploid, and trisomic Lycopersicon esculentum (tomato). In this study we observed most of the synaptic irregularities that have been reported in other organisms as well as an irregularity that has not been illustrated previously (lateral element buckles containing additional synaptonemal complex components). These observations have been used to provide partial answers to the following questions about the formation of the synaptonemal complex. (i) In what way does homology affect synapsis? (ii) What controls multiple synapsis? (iii) What is the relationship of synaptonemal complex components to chromatin and to each other? (iv) Do lateral elements have structural or functional polarity?Key words: synaptonemal complexes, synapsis, synaptic irregularities, solanaceous plants.
Cytogenetic abnormalities of cotton somaclones from callus cultures
Authors: Stelly David M. , Altman D. W. , Kohel R. J. , Rangan T. S. , Commiskey E.
Published: April 2011

Somaclonal variation occurs among regenerants from tissue culture of many plant species. Our objective was to determine whether cytogenetic variation contributes to somaclonal variation in cotton (Gossyptum hirsutum L.,2n = 4x = 52). Of 117 somaclones of cotton regenerated from 18-month-old callus cultures of 'SJ-2' and 'SJ-5' cultivars, 35 were analyzed for meiotic abnormalities. The population of somaclones was extremely varied in phenotype, most plants being strikingly aberrant in phenotype. Fertility was generally poor: 84% failed to set bolls and only 5% set 10 or more bolls in a field environment. Only one of the somaclones (3%) formed 26 bivalents at metaphase I. Fourteen were nonsynaptic to partially synaptic at metaphase I. Synaptic abnormalities impaired fertility and precluded thorough metaphase analysis. Chromosome numbers obtained for 32 plants ranged from 49 to 53, and only 1 plant was hyperaneuploid. No plant was polyploid. Chromosomal abnormalities in plants with normal metaphase pairing included univalents, unequal bivalents, rod bivalents, trivalents, open quadrivalents, and centric fragments. Seventeen hypoaneuploid plants formed a V-shaped trivalent at metaphase I, constituting a high frequency of tertiary monosomy. The high frequencies of aneuploidy and tertiary monosomy indicate that cytogenetic anomalies are a major source of somaclonal variation in cotton. It is hypothesized that (i) primary cytogenetic events during cotton cell culture give rise to breakage – fusion – bridge (BFB) cycles, (ii) BFB cycles accrue during culture, (iii) BFB cycles cause loss of chromatin, and (iv) BFB cycles are resolved by the formation of stable tertiary chromosomes with mono-centric activity. The hypothesis accounts mechanistically for the coincidence of chromatin deficiencies and chromatin exchange involved implicitly in tertiary monosomy, as well as for the relatively high frequency of tertiary monosomy among somaclones.Key words: aneuploid, monosomic, synaptic, sterility, Gossypium.
Further observations on the nature of radiation-induced chromosomal interchanges recovered from Drosophila sperm
Authors: Eberl Daniel F. , Hilliker Arthur J. , Sharp Cecil B. , Trusis-Coulter Silvija N.
Published: April 2011

The induction and analysis of numerous translocations (identified genetically and characterized cytologically) between chromosomes 2 and 3 of Drosophila melanogaster have allowed us to reexamine three issues concerning the nature of radiation-induced interchanges in spermatozoa. First, our results support the idea that, relative to their mitotic metaphase length, all major chromosomal regions are similar in their breakability, whether euchromatic (proximal or distal) or heterochromatic. Second, analysis of all our reciprocal exchanges between the two chromosomes shows a statistically significant dependence of the position of the chromosome 2 breakpoint on that of the chromosome 3 breakpoint. Thirdly, our combined cytological and genetic approach strengthens the results of previous analyses, which suggested a strong tendency for chromosomal interchanges to be of the reciprocal type in multiple-break rearrangements. This indicates that if radiation induces chromosome breaks, then the resulting broken ends tend to rejoin in pairs rather than independently.Key words: Drosophila melanogaster, radiation mutagenesis, chromosomal rearrangements, heterochromatin, intercalary heterochromatin.
Cytogenetics of Australian scorpions. I. Interchange polymorphism in the family Buthidae
Authors: Shanahan Catherine M.
Published: April 2011

Male scorpions from Australian species of the family Buthidae exhibit a unique combination of cytogenetic features including achiasmate meiosis, holocentric chromosomes, and extensive interchange heterozygosity. Chromosome number is highly conserved, with all species having a basic diploid number of 2n = 14. There is evidence that inbreeding has contributed to the establishment of populations with interchange heterozygotes, some exhibiting rings of up to 12 chromosomes. Although most populations contain both structural homozygotes and interchange heterozygotes, one population may exhibit fixed heterozygosity. It is argued that the interchange heterozygosity observed in buthids is of adaptive significance.Key words: interchange, chromosome polymorphism, achiasmate meiosis, holocentric chromosomes.
Cytogenetics of Australian scorpions. II. Chromosome polymorphism in species of Urodacus (family Scorpionidae)
Authors: Shanahan Catherine M.
Published: April 2011

The cytogenetic features of six species of scorpion from the Australian genus Urodacus (family Scorpionidae) were examined. Australian scorpionids possess monocentric chromosomes and male meiosis is achiasmate. Chromosome numbers are generally high and in some species extremely variable. Chromosome variation in one species, U. manicatus, was found to be due to fusion – fission polymorphism and variation in the number of small telocentric chromosome pairs. Additionally two populations exhibited extensive inversion heterozygosity. Available evidence suggests that female meiosis may also be achiasmate. The extensive numerical and structural heterozygosity found in U. manicatus may be related to the achiasmate meiosis, which allows regular pairing and disjunction of the multiple chromosome associations.Key words: achiasmate meiosis, chromosome polymorphism, structural heterozygosity, Robertsonian fusions.
Relationships between environmental factors and morph polymorphism in Cepaea nemoralis, using canonical correlation analysis
Authors: Vicario A. , Mazón L. I. , Aguirre A. , Estomba A. , Lostao C.
Published: April 2011

The relationship between phenotype distribution of Cepaea nemoralis and environmental factors was investigated at 105 sites in northern Spain, using canonical correlation analysis. Two interpretable canonical correlations were identified between the phenotype and environmental variable groups at the 0.05 level of significance, and canonical loadings were determined for each set of variables. The first canonical correlation represents the association of unbanded phenotypes with rainy and cloudy sites and of the more banded phenotypes (five banded and fused bands) with high degrees of insolation and solar radiation. The second canonical correlation separates yellow from pink phenotypes, associating the former with warm places and the latter with sunny or rainy places. These results indicate that the darkening of the shell observed may be related with climatic selective forces acting in the passage from Green to Brown Iberia climatic regions.Key words: Cepaea nemoralis, polymorphism, climatic selection.
Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). II. G-banding analysis of Petrogale godmani
Authors: Eldridge M. D. B. , Johnston P. G. , Close R. L. , Lowry P. S.
Published: April 2011

Chromosomal rearrangements in the two currently recognised races of Petrogale godmani were examined using C- and G-banding. The nominate race P. godmani godmani (2n = 20) was found to possess an inverted chromosome 5 and an acrocentric 6–10 fusion, which can be derived from a 6–10 centric fusion by a centromeric transposition. The Cape York race (2n = 22) was found to retain the ancestral submetacentric chromosome 4 and the ancestral chromosome 5. Thus despite their genie similarity, the two races clearly have major chromosomal differences and should be regarded as separate species. Petrogale g. godmani shares two derived chromosomes with another Queensland taxon, the assimilis race of P. assimilis, indicating recent common ancestry. The Cape York race retains characteristics of an ancestral stock of Petrogale and its genic similarity with P. g. godmani could therefore be the result of extensive introgression.Key words: chromosomal rearrangements, G-banding, Marsupialia, Petrogale.
The frequency of fertilization in wheat × pearl millet crosses
Authors: Laurie D. A.
Published: April 2011

Wheat × pearl millet crosses were studied to determine whether fertilization occurred and whether any resulting hybrids were karyotypically stable. Crosses between the hexaploid wheat genotype 'Chinese Spring' (kr1, kr2) and the pearl millet genotype 'Tift 23BE' gave fertilization in 28.6% of the 220 florets pollinated. Chromosome counts from zygotes at metaphase confirmed the hybrid origin of the embryos. Three had the expected F1 combination of 21 wheat and 7 pearl millet chromosomes and a fourth had 21 wheat and 14 pearl millet chromosomes. The expected F1 chromosome complement was also found in a primary endosperm mitosis. The hybrid embryos were karyotypically unstable and probably lost all the pearl millet chromosomes in the first four cell division cycles. Similar results were obtained using two other wheat genotypes. Crosses between the hexaploid wheat genotype 'Highbury', which differs from 'Chinese Spring' in having alleles for reduced crossability with rye and Hordeum bulbosum at the Kr1 and Kr2 loci, and 'Tift 23BE' gave fertilization in 32% of analyzed florets. This was not significantly different from the frequency found in 'Chinese Spring', indicating that 'Tift 23BE' was insensitive to the action of the Kr genes. Crosses between the tetraploid wheat genotype 'Kubanka' and 'Tift 23BE' gave fertilization in 48% of florets. The potential of pearl millet for wheat haploid production is discussed.Key words: wheat, pearl millet, wide hybridization, chromosome elimination.
Cytogenetic analysis of interspecific hybrids and amphiploids between two diploid crested wheatgrasses, Agropyron mongolicum and A. cristatum
Authors: Hsiao Catherine , Asay Kay H. , Dewey Douglas R.
Published: April 2011

Agropyron mongolicum Keng, the narrow linear-spiked diploid species (2n = 14), was hybridized with the broad pectinate-spiked diploid (2n = 14), A. cristatum (L.) Gaertner. The F1 hybrids were all diploids and morphologically intermediate to their parents. Chromosome pairing at metaphase I in the hybrids averaged 1.40 I, 5.59 II, 0.35 III, and 0.09 IV per cell, demonstrating that the two parental genomes are very similar. The F1 hybrids were partially fertile. The F2 progeny showed a broad array of variations in spike morphology and chromosome pairing behavior. Cytological data of the F1 hybrids and the F2 progeny revealed that these two diploid species contain the same basic P genome but differ by structural rearrangements of some chromosomes. The patterns of multivalent associations were the result of a heterozygous reciprocal translocation between a long and a very short chromosome segment. The colchicine-induced C0 amphiploids were fully fertile with regular chromosome pairing behavior. These two diploid species are the likely source of morphological variation in the tetraploid crested wheatgrasses.Key words: Agropyron, cytogenetics, chromosome pairing, interspecific hybrids.
Cytogenetics and reproductive behavior of induced and natural tetraploid guayule (Parthenium argentatum Gray)
Authors: Hashemi A. , Estilai A. , Waines J. G.
Published: April 2011

Tetraploid guayule (Parthenium argentatum Gray) plants with 72 chromosomes were obtained by colchicine application to the shoot apices of the diploid (2n = 36) seedlings. Interspecific hybridization of guayule as female with Parthenium rollinsianum Rzedowski (2n = 36) was used to compare the mode of reproduction of the induced tetraploids with that of natural tetraploids. Plants produced from crosses of induced tetraploid guayule and P. rollinsianum were all hybrids. Hybrid plants showed 2n = 54 chromosomes, indicating that the artificially produced tetraploids reproduce sexually. Interspecific crosses between natural tetraploids and P. rollinsianum produced predominantly maternal type progeny. This suggests that the apomictic mode of reproduction in guayule is a consequence of mutations which accumulated in the natural polyploids. Diploid guayule plants showed regular meiosis with an average of 14.86 rod and 3.14 ring bivalents. Induced tetraploids produced 0.25 I, 29.21 II, 0.13 III, and 3.24 IV. In comparison, natural tetraploids showed 1.20 I, 30.85 II, 0.06 III, and 2.23 IV. The frequency of multivalents, which was limited in the induced tetraploids, showed further reduction in natural polyploid guayule, which may indicate diploidization in these plants. Percent pollen stainability was 98.5 ± 1.03, 83.7 ± 12.24, and 89.5 ± 3.41 for diploids, induced tetraploids, and natural tetraploids, respectively. Both induced and natural tetraploids had larger capitula, achenes, and pollen and thicker leaves than the diploids.Key words: guayule, natural rubber, reproductive behavior, meiosis, polyploid induction.
Family × photoperiod interaction on growth in juvenile Atlantic salmon, Salmo salar
Authors: Hanke A. R. , Friars G. W. , Saunders R. L. , Terhune J. M.
Published: April 2011

A factorial experiment was used to study genotype × environment interaction on growth of underyearling Atlantic salmon parr (Salmo salar). Thirty-six families, each represented by 200 randomly sampled hatchery-reared parr, the progeny of single-pair matings, were subjected to two photoperiod treatments. These were 16 h light: 8 h dark (16L: 8D) and a simulated natural photoperiod decreasing from 13L: 11D on September 8 to 9L: 15D on December 15, 1986. Families with small starting mean length or weight showed a greater difference between photoperiod treatments (16 h minus natural) for absolute gain in length and weight, resulting in family × photoperiod interaction without reranking of families between treatments. A family's length or weight distribution was generally bimodal. The expected (based on a general exponential model) and actual November and December upper mode proportions of families in the 16-h photoperiod were larger than those in the natural photoperiod treatment, for length and weight. Family × photoperiod interaction for upper mode size resulted from the reranking of families for the expected but not the actual values. In general, the 16-h photoperiod produced the biggest fish and the largest upper mode proportion. Photoperiods interacted with families. The lack of significant reranking of families in the two environments, when based on absolute gain or actual upper mode proportion, does not indicate an impediment to correlated genetic gains from selection in the alternate environment.Key words: Atlantic salmon, photoperiod, genotype × environment interaction, growth, bimodality.
Cytogenetic abnormalities in cotton (Gossypium hirsutum L.) cell cultures
Authors: Li Ruzhong , Stelly David M. , Trolinder Norma L.
Published: April 2011

High frequencies of somaclonal phenotypic and cytogenetic variation have been observed previously among regenerants from cotton (Gossypium hirsutum L., 2n = 4x = 52). In this study we endeavored to determine if cytogenetic abnormalities would be detectable in cotton cell cultures and if so, whether or not the observed abnormalities would parallel those expected on the basis of previous cytogenetic analyses of cotton somaclones. Paired samples from suspension cultures established from 21-month-old 'Coker 312' and 8-month-old 'Coker 315' calli were pretreated or not pretreated with colchicine to detect cytogenetic abnormalities at metaphase or anaphase–telophase, respectively. Cell cultures established from both calli were found to vary in chromosome number. Hypoaneuploidy was common, but hyperaneuploidy and polyploidy were rare. Modal chromosome numbers for the 'Coker 312' and 'Coker 315' cultures were 46 and 50, respectively. Bridges at anaphase and telophase were frequent in the 'Coker 312' cultures but rare in the 'Coker 315'cultures. Cytogenetic differences between the cultures could be due to effects of culture age, genotype, their interaction, or other factors. Very small chromosomes, presumably centric fragments, as well as ring chromosomes and putative bridges between metaphase chromosomes occurred at low frequencies. The prevalence of hypoaneuploidy and rarity of hyperaneuploidy and polyploidy in cultures paralleled previous results on cotton somaclones, indicating that cytogenetic abnormalities arising in vitro probably contribute significantly to cotton somaclonal variation. The occurrence of hypoaneuploidy and bridges, including multiple bridges within single cells, is concordant with the hypothesis that breakage–fusion–bridge cycles may accumulate during in vitro culture of cotton.Key words: cotton, Gossypium, tissue culture, cytogenetics.
Control of alien gene expression for aluminum tolerance in wheat
Authors: Gustafson J. P. , Ross K.
Published: April 2011

The expression of aluminum tolerance from rye (Secale cereale L.) when present in a wheat (Triticum aestivum L. em. Thell.) background has been observed to be much lower than that in rye itself. By crossing each of the ditelocentric lines of 'Chinese Spring' wheat with a tolerant rye, the effects of the presence or absence of each arm of wheat on the expression of rye aluminum tolerance could be established. Of 42 wheat chromosome arms, 18 affected the expression of rye aluminum tolerance. Tolerance was increased over that observed in the euploid wheat–rye hybrid when arms 4AL, 5AL, 6AL, 7BS, 7BL, and 3DS were absent. Tolerance was reduced when arms 2AL, 5AS, 6BS, 1DS, 1DL, 2DL, 4DL, 5DS, 5DL, 6DL, 7DS, and 7DL were absent. Thus, the control of aluminum tolerance expression from rye in a wheat background was evidently under the influence of genes located on a number of wheat chromosome arms, with a few arms tending to enhance expression and many others tending to reduce it. In fact, 5AS of 'Chinese Spring' enhances expression, while 5AL suppresses it. The D genome of bread wheat appears to have the most pronounced effect on the expression of rye aluminum tolerance.Key words: rye, activator genes, suppressor genes, alien manipulation.
Intraspecific sequence variation in the mitochondrial genome of rainbow trout (Oncorhynchus mykiss)
Authors: Beckenbach Andrew T. , Thomas W. Kelley , Sohrabi Homayoun
Published: April 2011

We examined the sequence of a 2214 base pair HindIII fragment from the mitochondrial genome of six rainbow trout. The fragment encodes four proteins and two tRNAs. Sequences for two fish from a single locality were identical. Those from separate localities differed by from 1 to 7 nucleotide substitutions. Of 13 variable sites, 12 were synonymous and 1 led to a conservative amino acid substitution. Transitions accounted for 12 of the 13 variants. In contrast to interspecific comparisons (Thomas and Beckenbach. 1989. J. Mol. Evol. 29: 233–245), the intraspecific divergence estimates based on sequence are less than those estimated from restriction fragment analysis, suggesting a complex, dynamic process for the accumulation of variation in the mitochondrial genome.Key words: rainbow trout, Oncorhynchus, mtDNA, intraspecific variation.
Characterization of expressed meiotic prophase repeat transcript clones of Lilium: meiosis-specific expression, relatedness, and affinities to small heat shock protein genes
Authors: Bouchard Robert A.
Published: April 2011

The inserts of plasmid cDNA clones for transcripts showing meiotic prophase specific expression show cross reassociation to varying degrees of intensity with one another. These clones were recovered from a cDNA library made from Lilium microsporocyte poly(A)+ RNA. RNA-dot and Northern-blot analyses indicate that these clones represent transcripts specific to the meiotic prophase interval in microsporocytes. The transcripts appear to constitute the most abundant class of meiosis-specific poly(A)+ RNAs. At least two subgroups can be distinguished by examining cloned transcripts from genes of this expressed meiotic prophase repeat (EMPR) sequence family. Members of each subgroup have similar although not identical restriction maps and show relatively high but varying fidelities of DNA cross reassociation between members. However, consensus restriction maps of the two subgroups are largely dissimilar and, except at low stringencies, cross reassociation is readily detected only at restriction fragments from a particular conserved internal segment. The DNA sequence of a representative EMPR clone has been determined, and the inferred peptide product has been found to show extensive sequence homology to that of a small heat-shock gene of Glycine max, particularly in the conserved region. Alignment of the sequences for the conserved regions of two EMPR subgroup representatives with the soybean sequence suggests that selection has acted to conserve similar blocks of amino acids in this area. These observations suggest that a major portion of the transcripts produced during the apparently unrelated processes of meiosis and heat shock in higher plants are derived from related gene sequences encoding similar products.Key words: meiosis, transcription, specific cDNA, heat-shock mRNA.
Comparative chromosome pairing in triploids and diploids of perennial Triticeae
Authors: Wang Richard R.-C.
Published: April 2011

Meiotic data were obtained for the triploid hybrids Pseudoroegneria libanotica (2n = 14; SS) × P. stipifolia (2n = 28; SSSS), P. spicata (2n = 28; SSSS) × P. spicata (2n = 14; SS), P. strigosa (2n = 28; SSSS) × P. stipifolia (2n = 14; SS) for the first time. Additional polyhaploid plants of Critesion iranicum (2n = 42; HvHvHvHvHvHv) and triploid Hordeum bulbosum (HbHbHb) were also analyzed at metaphase I. The relationships between chromosome association at metaphase I in the autotriploids and in the corresponding diploids of perennial species in the tribe Triticeae were analyzed. The results corroborated the findings in an earlier study that the trivalent frequency in triploids having one or two basic genome(s) is positively correlated with the degree of genome homology in their corresponding diploids. Therefore, chromosome association at metaphase I in diploids is a function of chromosome homology and is a legitimate tool for studying genome relationships.Key words: genome, meiosis, autoploid, alloploid, homology, homoeology.
Linkage and expression of genes for resistance to leaf rust and stem rust in triticale
Authors: Singh S. J. , McIntosh R. A.
Published: April 2011

Leaf rust resistance in five triticale cultivars was controlled by a single gene designated LrSatu. This gene was closely linked in coupling with the stem rust resistance gene SrSatu believed to be located on chromosome 3R. Approximately 50% of lines in the 17th International Triticale Screening Nursery possessed SrSatu and LrSatu. Lines carrying SrSatu and LrSatu occurred more frequently among complete than in substituted triticale lines.Key words: × Triticosecale Wittmack, P. graminis f.sp. tritici, P. recondita f.sp. tritici, leaf rust, stem rust, rust resistnace, genetic linkage.
Development and chromosomal localization of genome-specific DNA markers of Brassica and the evolution of amphidiploids and n = 9 diploid species
Authors: Hosaka K. , Kianian S. F. , McGrath J. M. , Quiros C. F.
Published: April 2011

Ten genome-specific probes were developed from Brassica napus and B. oleracea genomic DNA libraries. Selection was based on polymorphism between and limited variation within genomes, permitting their localization on six individual C-genome chromosomes. Chromosome assignment was accomplished by using two sets of B. campestris – oleracea alien addition lines derived from (i) B. napus and (ii) the artificially synthesized B. napus 'Hakuran'. The presence of shared fragments between A, B, and C genomes indicates partial homology of the three genomes. However, several genome-specific markers could separate these three genomes. Genome-specific clones developed in this study served to confirm the parental diploid species originating the three amphidiploids, B. napus, B. carinata, and B. juncea. At least one clone suggests that B. napus has a polyphyletic origin. These clones were also useful to confirm the close evolutionary proximity among wild species in the B. oleracea cytodeme; however, no clear trends were found to suggest specific wild ancestors for the different B. oleracea horticultural types. Brassica oxyrrhina was distinct from other n = 9 species with most clones tested.Key words: restriction fragment length polymorphism, DNA marker, chromosome addition lines, Brassica oleracea cytodeme, amphidiploids, genome-specific markers.
Differential action of restriction endonucleases on chromosomes prepared for light and electron microscopy
Authors: Gosálvez J. , López-Fernández C. , Campos A. , Rodriguez M. , Rodriguez E. , Goyanes V.
Published: April 2011

Whole mounted chromosomes from the L929 mouse cell line were digested on grids with HinfI and AluI restriction endonucleases and studied by electron microscopy. Results show differences in the pattern of bands obtained in a marker chromosome when compared with those previously reported by light microscopy with the same restriction endonucleases. These differences suggest that the accessibility of restriction sites on chromosomes may be modulated by preparatory methods for chromosome analysis.Key words: restriction endonucleases, cytogenetics, mammalian chromosomes, chromosome structure, electron microscopy.
The inheritance of gynoecy in muskmelon
Authors: Kenigsbuch David , Cohen Yigal
Published: April 2011

The gynoecious Cucumis melo (muskmelon) GY-4 (derived from WI-998 after four generations of selfing and selection) was crossed with the monoecious PI124111F or the andromonoecious '36'. The F1 progeny plants from both crosses were all monoecious. The F2 progeny plants of the cross GY-4 × PI12411 IF (gynoecious × monoecious) segregated 12 monoecious: 3 gynomonoecious or trimonoecious: 1 gynoecious, indicating a two recessive gene difference between gynoecy and monoecy. The backcross to the monoecious parent gave rise to monoecious plants, whereas the backcross to the gynoecious parent segregated 2 monoecious: 1 gynomonoecious: 1 gynoecious. The F2 progeny plants of the cross GY-4 × '36' (gynoecious × andromonoecious) segregated 36 monoecious: 12 andromonoecious: 9 gynomonoecious or trimonoecious: 4 hermaphrodite: 3 gynoecious, indicating a three recessive gene difference between the parents. The backcross to the andromonoecious parent segregated 1 monoecious: 1 andromonoecious, whereas that to the gynoecious parent segregated 2 monoecious: 1 gynomonoecious or trimonoecious: 1 gynoecious. The F2 gynoecious plants from the cross GY-4 × '36' segregated in F3 into 4 all progeny gynoecious: 10 mixed progeny of gynoecious (¾) and hermaphrodite (¼) plants. The results suggest that the monoecious, andromonoecious, and gynoecious parents carried the genes AAGGMM, aaGGMM, and AAggmm, respectively, for sex expression. The following phenotype–genotype relationships are proposed for sex expression in muskmelon: monoecious, A-G---; andromonoecious, aaG---; trimonoecious or gynomonoecious, AA-ggM-; hemaphrodite, aagg--; and gynoecious, A-ggmm.Key words: Cucumis melo, femaleness, germ plasm, F1 hybrids, cantaloupe, Cucurbitaceae, sex expression.
Preparing plant chromosomes for scanning electron microscopy
Authors: Dillé John E. , Bittel Douglas C. , Ross Kathleen , Gustafson J. Perry
Published: April 2011

The scanning electron microscope may be useful in the analysis of plant chromosomes treated with in situ hybridization, especially when the probes and (or) chromosomes are near or beyond the resolution of the light microscope. Usual methods of plant chromosome preparation are unsuitable for scanning electron microscope observation as a result of cellular debris, which also interferes with probe hybridization. A method is described whereby protoplasts are obtained from fixed root tips by enzymatic digestion and applied to slides in a manner that produces little or no cellular debris overlying the chromosomes. The slides were examined by scanning electron microscopy and light microscopy after C-banding and in situ hybridization with a rye nucleolus organizer region spacer probe. This technique, which allows for scanning electron microscope visualization of bands and probes not easily identified with light microscopy, should prove useful in the physical mapping of low copy number or unique DNA sequences.Key words: protoplasts, rice, wheat, rye, physical maps, in situ hybridization.
Male germ line polysomy in the grasshopper Chorthippus binotatus: extra chromosomes are not transmitted
Authors: Talavera M. , López-Leon M. D. , Cabrero J. , Camacho J. P. M.
Published: April 2011

Some males of the grasshopper Chorthippus binotatus from a natural population in Sierra Nevada (Granada, Spain) were found to be polysomic mosaics for the presence of extra chromosomes (E) in a high proportion of testicular follicles. Transmission analysis of these chromosomes was performed in 21 controlled crosses, 2 of which involved a polysomic parent. While most spermatozoa produced by polysomic males carried E chromosomes, these chromosomes were not transmitted to the progeny, since all 22 embryos descended from a polysomic male parent lacked them.Key words: transmission, polysomy, grasshopper, Chorthippus binotatus.
The genetics and gliadin protein characteristics of a wheat–alien translocation that confers resistance to colonization by the wheat curl mite
Authors: Whelan E. D. P. , Lukow O. M.
Published: April 2011

The wheat curl mite (Eriophyes tulipae Keifer) is the vector of both wheat streak mosaic virus and the wheat spot mosaic agent, which cause damaging diseases of wheat (Triticum aestivum). A spontaneous translocation between chromosome 6A of the hard spring wheat cultivar 'Cadet' and a group 6 chromosome (6Ag) from decaploid Agropyron elongatum (Host) Beauv. resulted in a transfer of resistance to colonization by the wheat curl mite from 6Ag to a wheat chromosome. Transmission of resistance was 50.2% through the egg and 28.2% through the pollen. In segregating progenies, 64.1% of the plants were resistant, and 25.5% of the resistant plants were homozygous resistant. Meiotic pairing of hybrids from crosses between the translocation line and ditelocentrics for chromosome 6A suggested that the translocated chromosome consisted of the short arm of 'Cadet' 6A and the p or short arm of chromosome 6Ag of A. elongatum that confers mite resistance. This postulation was confirmed by electrophoretic patterns of seed endosperm proteins; the translocation line produced α-gliadins coded by genes on the short arm of 'Cadet' 6A as well as β-gliadins coded by genes on the short arm of A. elongatum chromosome 6.Key words: electrophoresis, gliadins, wheat streak mosaic virus, Agropyron elongatum, Robertsonian translocation.
Genetics of isozyme loci in Brassica campestris L. and in the progeny of a trigenomic hybrid between B. napus L. and B. campestris L.
Authors: Chen B. Y. , Heneen W. K. , Slmonsen V.
Published: April 2011

F2 progeny of Brassica campestris crosses were analyzed for single-locus inheritance of glucosephosphate isomerase, leucine aminopeptidase, 6-phosphogluconate dehydrogenase, phosphoglucomutase, and shikimate dehydrogenase enzymes. In most of the F2 families, the observed inheritance data for six polymorphic isozyme loci coincided well with the ratios expected under Mendelian segregation of either codominant alleles or dominant-recessive alleles when a null allele was involved. Complete linkage was observed for one locus pair (Lap-2A/6Pgd-2Ac), with the recombination frequency estimated to be r ≈ 0.000. From isozyme analyses made on resynthesized Brassica napus (AACC) and the actual parents B. campestris (AA) and B. alboglabra (CC) and on a trigenomic hybrid (AAC) between B. napus and B. campestris, it was possible to recognize A and C genome specific isozyme loci through the nonoverlapping electrophoretic mobilities of alleles characteristic of each genome. The trigenomic hybrid was selfed and genetic analyses of the offspring indicated that the A genome specific isozyme loci displayed a normal disomic inheritance. The C genome specific isozyme loci, on the other hand, showed nonrandom loss in the aneuploid offspring, thereby indicating the nonrandom loss of C genome chromosomes. At least 4 of the 8 C genome specific isozyme loci studied were located on separate chromosomes. The apparent occurrence of multiplicates of certain isozyme loci supports the concept that duplication of structural nuclear genes prevails in the diploid Brassica genomes.Key words: isozymes, Brassica, inheritance, trigenomic hybrid (2n = 29, AAC), genome-specific isozyme loci.
Genomic organization, evolution, and structural peculiarities of highly repetitive DNA of Hordeum vulgare
Authors: Vershinin A. V. , Salina E. A. , Solovyov V. V. , Timofeyeva L. L.
Published: April 2011

A fraction of highly repeated DNA sequences of Hordeum vulgare has been investigated by cloning 19 separate highly repetitive sequences in the plasmid pBR327. Characteristics studied included genus specificity of isolated sequences, their prevalence, and genome organization. Sequences (pHv7161, pHv7191, pHv7179) have been identified that are the most widespread in the H. vulgare genome and have a complicated arrangement. A tandemly arranged sequence, pHv7141, was also identified. The primary structure of a 999 bp long, BamHI fragment of one of the most widespread sequences, pHv7161, as well as the adjacent pHv7302 and pHv7245 sequences was determined. The fragment abounds in inverted repeats, of which two are flanked by direct repeats, and contains short subrepeats, A, B, and C, and a great variety of potential protein-binding sites. A comparison is drawn between the content and genome organization of highly repeated DNA sequences of H. vulgare and those of the wild barley species Hordeum bulbosum, Hordeum jubatum, Hordeum geniculatum, Hordeum brevisubulatum, Hordeum turkestanicum, and Hordeum murinum. According to the above characters (close copy number and genome organization similarity of highly repetitive sequences) the species under discussion have been classified into four groups. This division is in good agreement with other data on interspecific crossing in Hordeum and on chromosome pairing in hybrid meiosis.Key words: Hordeum, highly repeated DNA sequences, copy number.
Analysis of synaptonemal complexes and chromosome pairing at metaphase I in the diploid intergeneric hybrid Lolium multiflorum × Festuca drymeja
Authors: Thomas Hum M. , Morgan W. G.
Published: April 2011

The synaptonemal complexes in the diploid hybrid Lolium multiflorum × Festuca drymeja were examined by the surface spreading technique, and chromosome pairing at metaphase I was analysed. Synaptonemal complex analysis revealed "illegitimate" pairing, including multivalents and foldback pairing. At metaphase I, most chiasmata were between chromosomes of the same genome, and again multivalents were found. It was concluded that most synaptonemal complexes resulted in chiasma formation. The effects of the large differences in DNA values of the two species and the possible genotypic effect of F. drymeja on chromosome pairing are discussed.Key words: Lolium-Festuca, synaptonemal complexes, nonhomologous pairing, DNA values.
Amylase gene expression in intraspecific and interspecific somatic transformants of Drosophila
Authors: Hawley Sylvia A. , Norman R. A. , Brown Celeste J. , Doane Winifred W. , Anderson Wyatt W. , Hickey Donal A.
Published: April 2011

The Amylase locus in Drosophila melanogaster normally contains two copies of the structural gene for α-amylase, a centromere-proximal copy, Amy-p, and a distal copy, Amy-d. Products of the two genes may display discrete electrophoretic mobilities, but many strains known to carry the Amy duplication are characterized by a single amylase electromorph, e.g., Oregon-R, which produces the mobility variant AMY-1. A transient expression assay was used in somatic transformation experiments to test the functional status of the Amy genes from an Oregon-R strain. Plasmid constructs containing either the proximal or distal copy were tested in amylase-null hosts. Both genes produced a functional AMY-1 isozyme. Constructs were tested against an AMY-3 reference activity produced by a coinjected plasmid that contains the Amy-d3 allele from a Canton-S strain. With reference to the internal control, the Amy-p and Amy-d genes from Oregon-R expressed different relative activity levels for AMY-1 in transient assays. The transient expression assay was successfully used to test the functional status of, Amy-homologous sequences from strains of other species of Drosophila characterized by a single amylase electromorph, namely, Drosophila pseudoobscura ST and Drosophila miranda S 204. The amylase-null strain of D. melanogaster provided the hosts for these interspecific somatic transformation experiments.Key words: α-amylase, Amy, transient assay, gene duplication, intergenic transformation.
Cytology, fertility, and morphology of Elymus kengii (Keng) Tzvelev and E. grandiglumis (Keng) A. Löve (Triticeae: Poaceae)
Authors: Jensen Kevin B.
Published: April 2011

This study reports on the cytogenetics, fertility, mode of reproduction, and morphological variation of two perennial Triticeae grasses, Elymus kengii (Keng) Tzvelev and Elymus grandiglumis (Keng) A. Löve, from west central China. Both species are allohexaploids (2n = 42), self-fertile, and morphologically distinct on the basis of their plant color, glume length, and lemma and rachis vestiture. F1 hybrids between these two species are partially fertile and morphologically intermediate to their parents. Analysis of chromosome pairing in hybrids between E. grandiglumis or E. kengii and the following "analyzer" species, Psathyrostachys juncea (Fisch.) Nevski (NN), Psathyrostachys huashanica Keng (NN), Elymus lanceolatus (Scribn. &Smith) Gould (SSHH), Elymus dentatus (Hook. f.) Tzvelev ssp. ugamicus (Drob.) Tzvelev (SSYY), Elymus ciliaris (Trin.) Nevski (SSYY), Pseudoroegneria spicata (Pursh) A Löve (SS), and Pseudoroegneria tauri (Boiss. &Bal.) A. Löve (SSPP), suggested that both taxa contain the S, Y, and P genomes. This represents a new genome combination not previously reported and shows that the P genome from the crested wheatgrasses (Agropyron) has been involved in polyploid evolution within the. Triticeae.Key words: genome, meiosis, chromosome pairing, interspecific hybrids, Elymus, Triticeae.