bluuebunny/crossref_metadata_2025 huggingface dataset:
Combining conventional plant breeding procedures with molecular based approaches
Authors: Bartels D. , Gebhardt C. , Knapp S. , Rohde W. , Thompson R. , Uhrig H. , Salamini F.
Published: April 2011

This presentation covers the professional experience of the authors in the plant breeding research section of the Max-Planck-Institut für Züchtungforschung, Köln. Results available from current projects are discussed in the framework of breeding strategies aimed at the improvement of plant traits based on few or many genes. The following aspects are considered: use of genes for virus, insect, and herbicide resistance; tolerance to abiotic stresses (resistance to desiccation is studied in several model tissues and plants); identification and isolation of genes governing seed quality in cereals; possibility of tagging relevant genes in potato by the use of the exogenous transposon Ac; use of anther culture in potato breeding by changing the ploidy level from tetraploidy to diploidy and the reverse; marker-assisted selection in potato (a restriction fragment length polymorphism is under development and already molecular probes can be used to identify diploid and tetraploid potato strains).Key words: plant breeding, potato, molecular biology, disease and pest resistance, tolerance to stress.
Biotechnological approaches for the control of plant morphogenesis and their applications in agriculture
Authors: Crocomo Otto J.
Published: April 2011

As plant biotechnology is an application of cell engineering by which the plant cell genome is manipulated to improve agricultural productivity, leading to increases in production, many fundamental questions related to crop improvement arise, such as (i) how to propagate a great number of plants in a small space and within a shorter period of time; (ii) how to control the reversion to juvenility in forest species; (iii) how to decrease the time required to release new varieties to plant producers; (iv) how to control pests without causing environmental pollution; (v) how to regenerate intact transgenic plants after DNA insertion into protoplasts; (vi) how to transfer genetic characters between incompatible plant species; (vii) how to obtain somaclones resistant to adverse conditions; (viii) identification of the molecular mechanisms governing the processes of plant cell morphogenesis and how to control them to obtain better agricultural performance. Many of these questions are being studied in our laboratory and the results are discussed here.Key words: plant biotechnology, micropropagation, transgenic plants, somaclonal variation, hybrid embryo rescue, plant tissue culture.
Linkage maps of human chromosomes
Authors: White Ray , Lalouel Jean-Marc , Leppert Mark , Lathrop Mark , Nakamura Yusuke , O'Connell Peter
Published: April 2011

Finding the chromosomal location of human genes that heretofore have been defined solely by phenotypes, in particular clinical phenotypes that are transmitted in Mendelian fashion in families, is an early and often crucial step in the process of identifying the molecular basis of a disease. Recent progress in construction of chromosomal maps of genetically linked DNA markers has made almost the entire human genome accessible to linkage studies in families that are segregating genetic defects. Construction of linkage maps requires a panel of three-generation families for genotyping, a large number of polymorphic markers, and sophisticated computer programs for analysis of genotypic data. After a locus harboring a deleterious mutation has been identified by linkage to a mapped marker, a high-resolution map of the region can be constructed with new markers derived from cosmid libraries, to narrow the search for the gene in question. For example, this strategy has been pursued in the effort to characterize the gene responsible for familial adenomatous polyposis. When a target region has been narrowed to about 1 centiMorgan, corresponding to roughly a million base pairs in physical distance, other techniques of molecular biology can be brought to bear to isolate and clone the actual gene.Key words: genetic linkage, chromosome maps, DNA markers, chromosome 17, chromosome 10, genetic disease, familial adenomatous polyposis.
Hybrids involving wheat relatives and autotetraploid Triticum umbellulatum
Authors: Kimber Gordon , Yen Yang
Published: April 2011

Genomic analysis based on chromosome pairing is perhaps the most reliable method of determining the major evolutionary pathways in allopolyploid series. Difficulties can arise when genomes have become modified, since then they will not correspond exactly to the genomes used as analysers. Some resolution of this type of problem is possible when the interpretation of meiotic data is enhanced by numerical methods. However, providing conclusive evidence of which chromosomes are pairing rather than just how many remains a problem unless specific chromosomes can be recognized. One possible solution is to make hybrids between natural polyploids and autotetraploids of the putative diploid progenitors. The recognition of specific pairing patterns in such hybrids will provide substantial evidence of which chromosomes are pairing at metaphase I. Hybrids between an autotetraploid Triticum umbellulatum and the natural U-genome polyploids T. kotschyi, T. neglecta, T. ovatum, T. macrochaetum, T. columnare, T. triunciale, and T. juvenale demonstrate that the U-genome of most of them is very closely related to the U-genome of the diploid T. umbellulatum. The U-genome in four hybrids in two accessions of T. ovatum does differ from its diploid progenitor, T. columnare shows some heterogeneity, and T. juvenale may show differentiation.Key words: autotetraploid, evolution, genome analysis, Triticum species, pivotal–differential evolution.
Meiotic chromosome segregation in human t(11;22)(q23;q11) carriers: a theoretical consideration
Authors: Koduru Prasad R. K. , Chaganti R. S. K.
Published: April 2011

The t(11;22)(q23;q11) translocation is the most frequently encountered familial reciprocal translocation in humans. In the majority of reported cases ascertainment has been through the birth of a child with the chromosomal constitution 47,XX, +der(22) or 47,XY, +der(22), i.e., tertiary trisomy. Previous segregation analysis of familial cases showed a number of interesting features. Thus, euploid unbalanced genotypes resulting from adjacent segregation are absent in the progeny, and only tertiary trisomic offspring are recovered. To explain this unusual progeny output we present here a model for the meiotic behavior of this translocation in the carriers based on an analysis of cytogenetic data of progeny of carriers. This model predicts the formation of a chain trivalent with chromosome order 11-der(11)-22 during prophase I and its predominant alternate orientation at metaphase I.Key words: human, t(11;22)(q23;q11), meiosis, segregation.
Synaptonemal complex formation and metaphase I configuration patterns in a translocation heterozygote of rye (Secale cereale)
Authors: Jong J. H. de , Eden J. van , Sybenga J.
Published: April 2011

Four rye plants heterozygous for translocation 248, involving chromosomes 1R and 6R, were used for a comparative study of synaptonemal complex formation at midprophase I and chromosome configurations at metaphase I. Synaptonemal complexes were obtained with a cell-spreading technique and studied with electron microscopy. The total length of the synaptonemal complexes in the 28 analyzable pachytene nuclei varied considerably, both within and among plants. The variation of synaptonemal complex lengths of the bivalents in a nucleus was partly stage dependent; i.e., it was greater at early than at late pachytene. In all but one pachytene nucleus, pairing in the quadrivalent was regular, and the four pairing arms were usually easy to identify. Most noticeable was the variation of pairing saturation at the breakpoint of the quadrivalent. Pairing in the breakpoint region was delayed with respect to the pairing in the bivalents. Variation in the arm lengths of the quadrivalent was the result of incomplete and nonhomologous pairing at the breakpoint as well as differential contraction rates among chromosome segments. It was shown that the completion of delayed pairing throughout pachytene is mainly long-arm pairing. The actual breakpoint was therefore not in the middle of the unpaired segments, but more distal. The analysis of metaphase I nuclei revealed that chiasma frequency in this material was higher than in similar material used in former studies. When one of the translocation segments lacked a chiasma, this was in most cases the short translocated segment 1RS, the terminal segment of the satellite of chromosome 1R. Positive chiasma interference was demonstrated between the interstitial and exchanged segment in 1RS. This agreed with the observation of a negative correlation in extent of pairing between these two segments. Other interference phenomena, which have been described for this translocation in other material, remained undetected because of lack of variation in chiasma formation owing to high chiasma frequency.Key words: Secale cereale, meiosis, translocation, synaptonemal complex, metaphase I.
Male gametophyte development in monosomics of maize
Authors: Zhao Zuo-Yu , Weber David F.
Published: April 2011

The development of male gametophytes in diploid and monosomic-1, -2, -3, -4, -6, -7, -8, -9, and -10 maize plants was characterized. Developmental differences due to nullisomy in the gametophyte were evaluated by comparing the development of haploid and nullisomic microspores formed by monosomic plants, while differences due to gene dosage in the sporophyte were evaluated by comparing the development of haploid microspores in monosomic plants with those in diploids. These analyses show that (i) male gametophytes nullisomic for the chromosomes analyzed are developmentally delayed and eventually abort; (ii) male gametophytes nullisomic for chromosome 2 or 6 can reach the first mitosis, but those nullisomic for chromosomes 1, 3, 4, 7, 8, 9, or 10 do not reach the first division; and (iii) monosomy of chromosome 1, 2, 3, 4, 6, 7, 8, or 9 interferes with normal male gametophyte development, and monosomic-2 and -9 plants specifically cannot support pollen maturation.Key words: aneuploidy, monosome, nullisome, microspore, r-X1, deficiency.
Maize microsporogenesis
Authors: Chang Ming T. , Neuffer M. Gerald
Published: April 2011

The use of maize (Zea mays L.) pollen for basic scientific research has been well documented, but the progression of clear cytological features of maize microsporogenesis has not been fully documented. This study was undertaken to identify cytologically the different developmental stages of maize pollen and to correlate them with morphological features of the developing maize tassel. Morphological changes in the length of the tassel, floret, and anther were recorded and correlated with six cytologically defined stages of microsporogenesis: premeiosis, meiosis, uninucleate stage, first pollen mitosis, second pollen mitosis, and mature pollen.Key words: cytogenetics, gametophyte, maize, microsporogenesis, pollen.
Evolutionary history of Drosophila buzzatii. XV. Meiosis of inversion heterozygotes in backcross hybrids between D. buzzatii and its sibling D. koepferae
Authors: Naveira H. , Hauschteck-Jungen E. , Fontdevila A.
Published: April 2011

Interspecific F1 hybrid females between Drosophila koepferae and D. buzzatii are fertile, but hybrid males are sterile. By successive backcrossing of hybrid females to D. buzzatii males, it was possible to reduce progressively the genomic contribution of D. koepferae to the hybrid karyotype. Finally, only selected chromosome sections containing inversions restricted to D. koepferae were individually left in the otherwise D. buzzatii karyotype, namely: 2 C2b – F4a (j9m9n9), 3 C5a – G1b (k2), 4 E2a – G2f (m), and 5 C5d – F2h[Formula: see text]. Any of these sections produces hybrid male sterility in heterozygous condition. The present paper deals with the influence of these chromosome sections on meiosis. The observed abnormalities varied according to the introgressed segment borne by the hybrid males. The section from chromosome 2 of D. koepferae, representing about 6.7% of the total polytene karyotype, had the most drastic effect, giving rise to the same phenotype observed in the F1 hybrids, which was characterized by the complete lack of meiotic stages. The disruption produced by the chromosome section containing inversion 3 k2 (4.9% of the karyotype) was only a little more severe than that containing [Formula: see text] (4.2% of the karyotype), and both may be distinguished only quantitatively. Anaphase I exhibited precocious separation of sister chromatids and aberrant segregations; metaphase II was also always abnormal, with the chromosomes separated into their constituent chromatids and no apparent junction between sister centromeres; anaphase II rarely took place, and then it was always highly abnormal, with aberrant segregations and frequent tripolar or tetrapolar spindles; finally, cytokinesis also failed quite often, giving rise to multinuclear spermatids. The introgression of the chromosome segment containing inversion 4 m (3.2% of the karyotype) produced the least deviation from normal meiosis, which consisted simply of a relative increase in the number of metaphase II among the cells undergoing meiosis. These results show a positive correlation between the size of the introgressed segments and the importance of the disturbances they bring about. A similarity with some described meiotic-sterile mutations is suggested.Key words: Drosophila, hybrids, meiosis, chromosomal inversions.
The direct measurement of ribosomal RNA gene activity in wheat–rye hybrids
Authors: Capesius I. , Appels R.
Published: April 2011

Cloned rDNA segments, from wheat (Triticum aestivum) and rye (Secale cereale), which included the entire spacer region plus parts of the flanking 18S and 26S rRNA genes, were used to assay transcripts formed in the nuclei from wheat–rye hybrids. The tetraploid triticales (× Triticosecale Wittmack) carrying a complete rye chromosome complement and a combination of wheat chromosomes, as well as wheat and rye per se, were studied. Nuclei isolated from young leaves were incubated in the presence of [32P]UTP for 10 min, after which the total RNA was isolated. Hybridization of this radioactive RNA to the cloned rDNA segments showed that the suppression of rye NOR activity, measured cytologically, can be directly related to a major reduction in rRNA synthesis.Key words: NOR suppression, RNA transcripts, isolated nuclei.
Interspecific diploid hybrids in Avena
Authors: Leggett J. M.
Published: April 2011

Chromosome pairing in the diploid hybrids Avena longiglumis Dur. × A. canariensis Baum, Rajhathy, et Sampson, A. strigosa Schreb. × A. canariensis, and A. damascena Rajhathy et Baum × A. strigosa is described in relation to the genomic affinities between them. The cytological data complete the picture of chromosome pairing between the A and modified A genome taxa and are compared with some previously reported Avena hybrids.Key words: Avena, hybrids interspecific, chromosome pairing, phylogeny.
Chromocentre polymorphism in polytene chromosomes of Simulium costatum (Diptera: Simuliidae)
Authors: Brockhouse C. , Bass J. A. B. , Straus N. A.
Published: April 2011

The polytene chromosomes of the black fly species Simulium (Nevermannia) costatum are joined at the centromeres in a strongly heterochromatic chromocentre. Examination of the larval salivary gland chromosomes revealed two populations with a unique polymorphism for attachment to the chromocentre involving all centromeres. All three homologous pairs of chromosomes are polymorphic for centromeres that do not join to the chromocentre. Samples from one of these populations were large enough for thorough study. In this population, the attachment polymorphism is in Hardy-Weinberg equilibrium for two of the centromeres and was in the same frequency for 2 successive years of sampling. The polymorphism could be either primary, retained from an ancestral nonchromocentric state, or secondary, evolving independently or introduced via hybrid introgression. The evolution of chromocentres is discussed in the context of species in the Simulium vernum group.Key words: black fly, polytene chromosome, chromocentre, polymorphism, evolution.
Absence of population structure in black flies as revealed by enzyme electrophoresis
Authors: Feraday R. M. , Leonhardt K. G.
Published: April 2011

Analysis of allozyme variation by the FST-statistic in Simulium decorum and several other black fly species reveals very little genetic variation that could be attributed to genetic drift. This is consistent with what is known about the rates of migration of black flies and supports the idea that there is a lack of population subdivision in these insects. This picture of population structure is quite different from that presented by chromosome inversion polymorphisms. Chromosomal variation, however, can reasonably be attributed to selection and suggests that the role of inversions in black fly evolution is similar to population subdivision in the shifting balance process.Key words: black flies, allozymes, population structure, evolution.
Cytogenetic studies of progenies from crosses between 'Centurk' wheat and its doubled haploids derived from anther culture
Authors: Youssef Sawsan S. , Morris R. , Baenziger P. S. , Papa C. M.
Published: April 2011

Karyotype stability, which is essential when using wheat (Triticum aestivum L.) doubled haploids in a breeding program, was evaluated in 14 anther-derived doubled-haploid lines after at least three generations of selfing, by crossing them as females with the parent cultivar 'Centurk' and doing cytological studies on the progenies. There were no deviations from the hexaploid chromosome number (2n = 42) in root tips. Meiotic chromosome pairing was as stable as that in the control ('Centurk' × 'Centurk') in most progenies. Chromosomal structural changes and (or) behavioral deviations were detected at the metaphase I, anaphase I, telophase I, and quartet stages of meiosis in a minor proportion of the cells. The frequencies of multivalents, lagging bivalents and univalents, bridges, and micronuclei were higher in some progenies than in the control. Chromosomal fragments were infrequent. The ranges in percentages of normal cells were 72.4–90.0 at anaphase I, 76.4–92.6 at telophase I, and 82.6–93.2 at quartet stages in the doubled-haploid progenies, compared with 95–100, 92–100, and 94–96, respectively, in the control. On the basis of these results, the doubled-haploid lines should produce enough normal gametes to provide adequate seed supplies when they are used as parents in wheat cultivar and population improvement.Key words: Triticum aestivum, chromosome pairing, chromosome aberrations, gametoclonal variation.
Comparaison des profils plasmidiques de mutants oligosporogènes chez Bacillus thuringiensis var. kurstaki HD-1 après traitement à l'ozone et à la nitrosoguanidine
Authors: Rivard Sylvain R. , Côté Jean-Charles , Chung Young Sup
Published: April 2011

Two strains of Bacillus thuringiensis were used in order to isolate sporeless and crystalliferous mutants. These strains, B. thuringiensis var. kurstaki HD-1 and var. israelensis Q-2, produce a crystalline inclusion, δ-endotoxin, which is lethal for lepidopteran and dipteran larvae, respectively. Mutants derived from strain HD-1 were easily isolated because of their characteristic morphology. By comparing different plasmidic patterns of the strains, we can confirm the relationship existing between a DNA extrachromosomic element and the production of δ-endotoxin in B. thuringiensis. However, the absence of toxic crystallin protein does not necessarily mean that all plasmids are absent.Key words: Bacillus thuringiensis, oligosporogenous, ozone, nitrosoguanidine, plasmids.
Detection of cryptic bands by AluI in eukaryotic chromosomes
Authors: Gosálvez J. , López-Fernández C. , Goyanes V.
Published: April 2011

Selective digestion of fixed chromatin with the restriction endonuclease AluI (which cuts the sequence AG CT) uncovers a specific and repeatable pattern of bands within the euchromatin of two species of grasshoppers and of the L929 mouse cell line, which are not detectable by means of other banding techniques such as C-bands, specific fluorochromes, or other restriction endonucleases. It is tentatively suggested that this chromatin represents a special class of repetitive DNA embedded in the euchromatin, not containing the AluI restriction site to the same extent as in euchromatin and not associated with C-banded heterochromatic material.Key words: heterochromatin, restriction endonucleases, cytogenetics.
Changes in triticale chromosome heterochromatin visualized by C-banding
Authors: Jouve Nicolas , Galindo Carmen , Mesta Montserrat , Diaz Fernando , Albella Beatriz , Garcia Pilar , Soler Consuelo
Published: April 2011

The distribution and characterization of heterochromatin in a series of cultivars, parents, new amphiploids and progeny of hexaploid triticale were comparatively studied using C-banding and morphometric analysis. A high level of intervarietal polymorphism was detected for the banding pattern. The chromosome pairs 4A and 1R presented the most constant pattern of heterochromatin distribution among 31 triticale lines studied. A total of 126 bands have been catalogued, from which 28, 59, and 39 belong, respectively, to the A, B and R genomes. The ratio of polymorphic bands per genome was 23/28, 36/59, and 30/39. The chromosomes displayed heterochromatin modifications consistent in both presence–absence and relative length of their content per genome, when passed from the parents to the amphiploids. Variations in the heterochromatin were also observed among sister plants coming from crosses between wheat and triticale. The heterochromatin content showed gradual tendencies either to increase or decrease in each genome during successive self-cross generations after that cross. The existence of a systematic process of variation of heterochromatin content in triticale is assumed, and the nature of this phenomenon is discussed.Key words: triticale, tetraploid wheat, rye, C-banding, heterochromatin.
Polymorphic regions in plant genomes detected by an M13 probe
Authors: Zimmerman P. A. , Lang-Unnasch N. , Cullis C. A.
Published: April 2011

A sequence containing two clusters of 15 base pair repeats from the protein III gene in the bacteriophage M13 has been shown to detect hypervariable minisatellites in many animal species. We have shown that this M13 fragment will detect similar sequences in higher plants including monocots, dicots, and gymnosperms. In addition, polymorphisms were demonstrated in three dicot species. The amount of this sequence has no relationship with the size of the genome, chromosome number, or amount of repetitive DNA in the species tested.Key words: bacteriophage M13, monocot, dicot, gymnosperm, restriction fragment length polymorphism.
Genetic analysis of the avirulence of wheatgrass powdery mildew fungus on common wheat
Authors: Tosa Y.
Published: April 2011

F1 hybrid cultures between Erysiphe graminis f.sp. agropyri (wheatgrass mildew fungus) and E. graminis f.sp. tritici (wheat mildew fungus) were produced by using a common host of the two formae spéciales. When three common wheat cultivars, Triticum aestivum cv. Norin 4, T. aestivum cv. Norin 10, and T. compactum cv. No. 44, were inoculated with a population of F1 cultures, avirulent and virulent cultures segregated in a 3:1 ratio. This indicated that two major genes are involved in the avirulence of E. graminis f.sp. agropyri, Ak-1, on each of the three cultivars. Further analyses revealed that the three pairs of avirulence genes have one gene in common. On T. aestivum cv. Shin-chunaga, T. aestivum cv. Norin 26, and a strain of T. macha, the F1 population segregated in the same pattern as on T. aestivum cv. Norin 4, indicating that the same pair of avirulence genes is operating on these four cultivars. On T. aestivum cv. Red Egyptian the distribution of F1 phenotypes was continuous, suggesting that no major genes are involved in the avirulence of Ak-1 on this cultivar.Key words: powdery mildew, Erysiphe graminis, avirulence, wheat, wheatgrass.
Meiotic chromosome association in diploid and tetraploid Avena strigosa Schrel.
Authors: Zadoo S. N. , Choubey R. N. , Gupta S. K. , Sybenga J.
Published: April 2011

In diploid Avena strigosa the frequency and distribution of open (rod) bivalents suggest that a limited number of chromosomes, possibly two, fail to have a chiasma in one (short) arm in over 60% of the cells. In the tetraploid these are expected to form bivalents instead of quadrivalents at metaphase I of meiosis in a high frequency. In addition, interstitial chiasmata are expected in the long arms of these chromosomes, when involved in quadrivalents. In the tetraploid the frequency of quadrivalents is indeed low, and the configurations with interstitial chiasmata are distributed as expected. However, application of Sybenga's models suggests that the pairing system rather than the chiasma system would be responsible for the low quadrivalent frequency. It is suggested that apparent negative chiasma interference across the point of pairing partner exchange, resulting from variation in its location, invalidates application of these models to the present material. Negative interference results in an even higher than expected open bivalent frequency, in combination with a relatively high ring quadrivalent frequency. In addition, not only the subacrocentric chromosomes but also the more metacentric chromsomes, by this same mechanism, tend to form open bivalents more often than in the diploid.Key words: meiosis, bivalent, quadrivalent, diploid, tetraploid, Avena strigosa
Identification of crossbred buffalo genotypes and their chromosome segregation patterns
Authors: Harisah M. , Azmi T. I. , Hilmi M. , Vidyadaran M. K. , Bongso T. A. , Nava Z. M. , Momongan V. , Basrur P. K.
Published: April 2011

Chromosome analysis on different breed types of water buffaloes (Bubalus bubalis) was undertaken to identify their karyotypes and to determine the pattern of chromosome segregation in crossbred water buffaloes. Altogether, 75 purebred and 198 crossbred buffaloes including 118 from Malaysia and 80 from the Philippines, were analyzed in this study. The diploid chromosome number of the swamp buffalo from both countries was 48 and.that of the river buffalo was 50, while all F1 hybrids exhibited 49 chromosomes. The F2 hybrids consisted of three different karyotype categories (2n = 48, 2n = 49, and 2n = 50), whereas the backcrosses included two different karyotype categories each, with 2n = 48 and 2n = 49 in the three quarters swamp types and 2n = 49 and 2n = 50 in the three quarters river types. Chi-square tests on pooled data from Malaysia and the Philippines indicated that the distribution of different karyotype categories of F2 animals did not deviate significantly from the 1:2:1 ratio expected if only balanced gametes with 24 and 25 chromosomes were produced by the F1 hybrids. In the three quarters swamp and three quarters river types, the respective karyotypic categories were in ratios approximating 1:1. The distribution of chromosome categories among the F2 hybrids and backcrosses suggests that only genetically balanced gametes of the F1 hybrids are capable of producing viable F2 and backcross generations.Key words: buffaloes, chromosome segregation, genotype, buffalo hybrids.
Genetic deficiency of purine nucleoside phosphorylase in the mouse. Characterization of partially and severely enzyme deficient mutants
Authors: Mably Ellen R. , Fung Ernest , Snyder Floyd F.
Published: April 2011

Two independent mutations of purine nucleoside phosphorylase were identified in the first-generation progeny of male mice that had been treated with the mutagen N-ethylnitrosourea and mated to untreated females. The common allele in inbred strains is Np-1a and the mutants are assigned the gene symbols Np-1e and Np-1f. Heterozygotes had approximately half normal purine nucleoside phosphorylase activity in erythrocytes and activity of homozygotes was 17 and 5% of NP-1A for NP-1E and NP-1F, respectively. The following properties are consistent with both Np-1e and Np-1f being point mutations: the expression of residual but markedly reduced activity with normal Michaelis constants for inosine and phosphate, altered isoelectric points, and increased thermal lability. The reduction in erythrocyte activity was also evident in other tissues. A metabolic consequence of the mutations was increased purine nucleoside excretion. Inosine and guanosine, total 150 ± 84 μM, and inosine, deoxyinosine, guanosine, and deoxyguanosine, total 1490 ± 190μM, were present in urine of Np-1e/Np-1e and Np-1f/Np-1f mice, respectively, but not in normal urine, < 10μM.Key words: purine nucleoside phosphorylase, enzyme deficiency, mouse model, mutagenesis.
Synaptic mutants in potato, Solanum tuberosum L. II. Concurrent reduction of chiasma frequencies in male and female meiosis of ds-1 (desynapsis) mutants
Authors: Jongedijk E. , Ramanna M. S.
Published: April 2011

Chiasma frequencies in pollen mother cells and megaspore mother cells from both normal and desynaptic (ds-1ds-1) diploid potato clones were estimated on the basis of chiasmate chromosome arm association in metaphase I. In desynaptic mutants both the mean chiasma and bivalent frequencies per cell and the mean chiasma frequency per bivalent proved to be significantly lower. Despite significant differences in within-cell chiasma frequency variation among and particularly between normal and desynaptic clones, no clear effects of the ds-1 gene on the distribution of chiasmata over chromosomes in a cell were detected. The distribution of chiasmata over chromosomes appeared to be more or less random in both normal and desynaptic plants, which suggests that the ds-1 gene similarly affects chiasma frequencies in all chromosomes. Genetic data reported in the literature indicate that the ds-1 gene affects both the overall chiasma frequency and the chiasma distribution along individual chromosomes rather than chiasma maintenance. Sex differences in chiasma formation were not observed among normal plants or among desynaptic mutants, which indicates that chiasma formation in male and female meiosis of potato is governed by a single control system that is similarly expressed in both sexes.Key words: Solanum, desynapsis, chiasma frequency, male meiosis, female meiosis.
Relationship between mitotic instability and accumulation of B chromosomes in males and females of Locusta migratoria
Authors: Viseras E. , Camacho J. P. M. , Cano M. I. , Santos J. L.
Published: April 2011

Mitotic instability of B chromosomes has been studied in males and females from two Spanish populations of Locusta migratoria. This instability is a common feature in embryos, adult somatic tissues such as gastric caeca, and ovariole wall cells and male and female germ lines. While B chromosomes accumulate in the male germ line independently of the existence or absence of intraindividual variation in the number of B chromosomes in gastric caeca cells, they do not accumulate in the female germ line despite meiotic instability. The relationship between the mitotic instability of the B chromosomes in germ lines and their mode of transmission is discussed.Key words: Locusta migratoria, B chromosomes, mitotic instability, accumulation.
Molecular evidence on the origin of wheat chromosomes 4A and 4B
Authors: Dvořák J. , Resta P. , Kota R. S.
Published: April 2011

The genome allocation of the Triticum aestivum L. chromosomes denoted 4A and 4B was based on an erroneous inference. Since neither chromosome pairs with the chromosomes of putative ancestors of wheat, molecular tools were employed to clarify the origin of the two chromosomes. Disomic substitutions for T. aestivum chromosomes 4A or 4B by chromosomes 4 from T. speltoides (Tausch) Gren., a putative ancestor of the wheat B genome, T. longissimum (Schweinf. et Muschl.) Bowden (a close relative of T. speltoides), or T. monococcum L. ssp. aegilopoides (Link) Thell., a close relative of the ancestor of the wheat A genome, were produced. The ability of the substituted chromosome to compensate in the disomic substitution lines, the C-banding patterns of the chromosomes, electrophoretic alleles at the Adh-1 and Lpx-1 loci, and in situ hybridization with an interspersed repeated sequence all were consistent in showing that the chromosome previously denoted as 4A belongs to the B genome and the chromosome previously denoted as 4B is a rearranged chromosome of the A genome. Chromosome 4A is consequently reallocated to the B genome and chromosome 4B to the A genome in T. turgidum L. em. Morris et Sears and T. aestivum. To reflect the fact that the chromosome previously denoted as 4B has only a homoeologous relationship to chromosome 4A of T. urartu (the ancestor of the A genome in polyploid wheats), the chromosome is designated 4Aa.Key words: repeated nucleotide sequence, alcohol dehydrogenase, lipoxygenase, in situ hybridization, chromosome evolution.
Chromosomal localization of genes in the R genome causing hybrid necrosis in rye and triticale
Authors: Ren Z. L. , Lelley T.
Published: April 2011

By using a set of primary hexaploid triticale lines monosomic for each of the seven rye chromosomes and with the help of a complete series of monosomic wheat–rye addition lines the two genes Ner1 and Ner2 were chromosomally localized in the rye genome. These two genes condition hybrid necrosis in rye through a dominant complementary interaction. Interacting with the corresponding necrosis genes in the B genome of wheat, Ne1 and Ne2, these two genes in rye also cause hybrid necrosis in triticale. The Ner1 locus was localized on the long arm of chromosome 5R and the Ner2 locus on the long arm of chromosome 7R. The results provide further evidence for a strong phylogenetic relationship of these two cereal species.Key words: hybrid necrosis, rye, triticale, chromosomal localization, monosomies, addition lines.
Attempts to overcome prefertilization incompatibility in interspecific and intergeneric crosses involving Oryza sativa L.
Authors: Sitch L. A. , Romero G. O.
Published: April 2011

The wild relatives of rice are a valuable source of desirable agronomic traits, but prefertilization barriers operate in crosses of Oryza sativa L. with the wild Oryza species and related genera. Pollen germination was normal in crosses with O. brachyantha, O. eichingeri, O. officinalis, and O. ridleyi and slightly inhibited in crosses with Rhynchoryza subulata. Stigmal penetration of O. brachyantha and R. subulata pollen tubes was inhibited, while O. ridleyi pollen tubes showed both incompatible and weakly compatible reactions. Pollen tubes of O. eichingeri, O. officinalis, and O. ridleyi penetrated the stigma, but growth was frequently inhibited in the style or ovary wall, particularly in O. eichingeri crosses. The effect of postpollination application of boric acid, the immunosuppressant ε-aminocaproic acid (EACA), and gibberellic acid (GA3) and of ambient temperature (29 and 35 °C) on germination and pollen tube growth was investigated. Boric acid, EACA, and GA3 inhibited germination of O. brachyantha pollen, and boric acid and EACA inhibited pollen tube growth of O. brachyantha, O. eichingeri, O. ridleyi (35 °C), and R. subulata (29 °C). Pollen tube growth in the control and GA3 treatments was similar. Temperature had no effect on pollen germination and pollen tube growth was stimulated in O. ridleyi crosses at 35 °C only. The nature of incompatibility operating in these crosses is discussed.Key words: incompatibility, pollen tube growth, fertilization, Oryza, interspecific cross, intergeneric cross.
Generation of alien chromosome addition lines from synthetic Brassica napus: morphology, cytology, fertility, and chromosome transmission
Authors: McGrath J. Mitchell , Quiros Carlos F.
Published: April 2011

The chromosome complement of Brassica oleracea (2n = 18) was dissected by means of alien chromosome addition lines generated by successive backcrosses of either of two B. campestris accessions (2n = 20) to the resynthesized B. napus 'Hakuran' (2n = 38). Alien chromosome addition lines were characterized by chromosome counts, morphology, pollen and seed fertility, and transmission of chromosome-specific markers. Mean chromosome number in the first backcross generation was approximately 23.5 and was little influenced by the B. campestris accession. Fertility and isozyme marker transmission were also not affected by choice of B. campestris accession. Transmission of chromosome-specific markers to the BC2 was more variable than to the BC1, and appeared to be affected by the B. campestris recurrent accession. Twenty-five monosomic addition lines (2n = 21) were recovered in the second backcross generation, representing 7 of the 9 B. oleracea synteny groups. One monosomic alien chromosome decreased seed fertility but not pollen fertility. Only one monosomic addition could be reliably identified morphologically.Key words: chromosome markers, aneuploidy, restriction fragment length polymorphism, isoymes.
Quantitative karyotyping of barley chromosomes by image analysis methods
Authors: Fukui K. , Kakeda K.
Published: April 2011

Barley chromosomes were analyzed by the chromosome image analyzing system, CHIAS. Stained and unstained diploid metaphase spreads were automatically scanned and their locations on the glass slide were detected. With stained chromosomes, detection efficiency of good metaphase plates exceeded on average 90%. Three image parameters, length, area, and density volume, of each chromosome were defined and measured for 250 haploid chromosome plates. Of these parameters, total length and the arm ratio of the length were the most informative for chromosome identification. A quantitative idiogram of the N-banded barley chromosomes was established from numerical data of phase-contrast images and the image analysis of N-banded chromosomes.Key words: Hordeum vulgare, CHIAS, image analysis, automatic scanning, quantitative idiogram.
Chromosome pairing in triploid hybrids and amphidiploids involving Lolium and diploid Festuca species
Authors: Morgan W. G.
Published: April 2011

Chromosome homology between Lolium and Festuca complements are assessed in triploid and tetraploid hybrids with variable doses of the different diploid genomes. In general, the chromosome pairing observed in the triploid hybrid gave a better prediction of the meiotic behaviour of the tetraploid amphidiploids than that found in the diploid hybrids. Differences in chromosome size between the complements allowed the precise identification of the chromosomes in chiasmate associations and there was evidence that most chromosome pairing was between homologues. In the triploid hybrids, associations between nonhomologous chromosomes were recorded. The results, based on chromosome pairing data, are briefly discussed in relation to genome homologies and phylogenetic relationships in the Lolium-Festuca complex.Key words: Lolium, Festuca, chromosome pairing, nonhomologous, triploid hybrids, amphidiploids.
Inheritance of supernumerary spikelets in a tetraploid wheat cross
Authors: Klindworth D. L. , Williams N. D. , Joppa L. R.
Published: April 2011

The supernumerary spikelet (SS) trait of durum wheat (Triticum turgidum L.), including the four-rowed and ramified spike types, is characterized by an increased number of spikelets per spike. To determine the inheritance of this trait, the tetraploid ramified spike cultivar PI349056 was crossed reciprocally to normal-spike 'Langdon' durum, and the F1 was backcrossed to each parent. The F1, F2, F3, BC1F1, and BC1F2 were classified for SS expression. Additionally, PI349056 was crossed to the 'Langdon' 2D(2A) disomic substitution line to study linkage of SS genes. The SS trait was recessive to normal spike, and both four-rowed spike and ramified spike progeny were observed in the segregating generations. Segregation in F3 and BC1F2 families indicated that SS in PI349056 was quantitatively inherited, controlled by a major recessive gene and numerous minor genes. Normal-spiked plants selected in families homozygous for the major gene indicated that the major gene did not produce SS when the minor genes were absent. Selection of normal-spiked plants in the F3 and F4 of 'Langdon' 2D(2A) disomic substitution/PI349056 indicated that the minor SS genes were not linked to the major gene on chromosome 2A.Key words: Triticum, branched spike, ramified spike, four-rowed spike.
Inheritance of the blue aleurone trait in diverse wheat crosses
Authors: Keppenne V. D. , Baenziger P. S.
Published: April 2011

The blue aleurone trait has been suggested as a useful genetic marker in wheat (Triticum aestivum L.). However, little information is available on its transmission in diverse backgrounds and on its use to identify hybrid seed. UC66049, a hexaploid spring wheat with a spontaneous translocation that included the gene for the blue aleurone trait (Ba) from Agropyron elongatum (Host) P.B. (synonymous with Elytrigia pontica (Podp.) Holub), was crossed to seven wheat cultivars to test the transmission of the trait. UC66049 was crossed to male-sterile red wheat lines to evaluate the blue aleurone trait as a marker for confirming hybridity. Ba segregated as a dominant gene that was transmitted normally through the male and female gametes. For 6 of 7 crosses with diverse pedigrees, we experienced problems with misclassification of the aleurone color in the F2 seed generation, determined by the F3 seed family data. The blue aleurone trait is a good genetic marker; however, progeny testing may be needed to confirm the F2 genotypes in some environments or genetic backgrounds. Moreover, Ba is useful in determining the amount of controlled hybridity as opposed to self-fertility and (or) outcrossing in genetic male-sterile wheat lines. The use of Ba to confirm doubled haploidy was proposed.Key words: Agropyron elongatum, seed color, genetics, Triticum aestivum, Elytrigia pontica.
Lack of correlation between crossing-over and chromosome distance between inversions in Drosophila ananassae
Authors: Singh B. N. , Mohanty Sujata
Published: April 2011

Two linked inversions, AL and ZE, located in the opposite limbs of the second chromosome of Drosophila ananassae are separated from each other by nearly 32% of the total length of the second chromosome. Crossing-over between these inversions when heterozygous was studied in females and males by the salivary-gland smear technique using karyotypically homozygous stocks. The results of recombination experiments show that there is a strong suppression of recombination between inversions when heterozygous, in spite of a large euchromatic distance available for crossing-over between them. Thus there is no correlation between chromosome distance and crossing-over between heterozygous inversions in the second chromosome of D. ananassae when studied cytologically.Key words: crossing-over, linked inversions.
Genome size and karyotype evolution in Tradescantia section Cymbispatha (Commelinaceae)
Authors: Kenton Ann , Drakeford Andrew
Published: April 2011

Karyotype morphology and nuclear DNA content are compared in species of Tradescantia section Cymbispatha from North and South America. Comparison of DNA amounts confirms the polyploid ancestry previously suggested for several cytotypes and shows that basic genome size has been unaffected by the Robertsonian fusions constituting a major evolutionary change in this group. The 2C-values of Mexican tetraploids are double those of their Central American diploid relative Tradescantia gracillima. The 2C-value of the South American tetraploid T. cymbispatha is comparatively lower as a result of a reduction in the size of some chromosomes. This reduction is most likely to have been achieved by Robertsonian fusions in a hybrid whose parental chromosome sets differed in size. The results provide evidence for selection of ancestral diploids with low C-value as mechanism for reduction of genome size in polyploids.Key words: Tradescantia, genome size, polyploidy, Robertsonian fusion, DNA reduction.
Natural autotriploidy in salamanders
Authors: Lowcock Leslie A. , Licht Lawrence E.
Published: April 2011

The frequency of autotriploidy in naturally occurring diploid populations of salamanders was investigated by use of flow cytometry of erythrocyte nuclei. Eight autotriploids were discovered from among a sample of over 1700 individuals representing 16 species of North American salamanders. Information from published records of autopolyploidy in natural and laboratory populations of urodeles is compiled and the possible role of autotriploidy in the evolution of this group is discussed.Key words: salamanders, polyploidy, amphibia, autotriploidy, nuclear DNA, flow cytometry.
Rye C-banding patterns and meiotic stability of hexaploid triticale (× Triticosecale) selections differing in kernel shriveling
Authors: Papa Charles M. , Morris R. , Schmidt J. W.
Published: April 2011

Two winter hexaploid triticale populations derived from the same cross were selected on the basis of grain appearance and agronomic performance. The five lines from 84LT402 showed more kernel shriveling than the four lines from 84LT401. The derived lines were analyzed for aneuploid frequencies, rye chromosome banding patterns, and meiotic stability to detect associations with kernel development. The aneuploid frequencies were 16% in 84LT401 and 18% in 84LT402. C-banding showed that both selection groups had all the rye chromosomes except 2R. The two groups had similar telomeric patterns but differed in the long-arm interstitial patterns of 4R and 5R. Compared with lines from 84LT402, those from 84LT401 had significantly fewer univalents and rod bivalents, and more paired arms at metaphase I; fewer laggards and bridges at anaphase I; and a higher frequency of normal tetrads. There were no significant differences among lines within each group for any meiotic character. Since there were no differences within or between groups in telomeric banding patterns, the differences in kernel shriveling and meiotic stability might be due to genotypic factors and (or) differences in the interstitial patterns of 4R and 5R. By selecting plump grains, lines with improved kernel characteristics along with improved meiotic stability are obtainable.Key words: triticale, meiotic stability, C-banding, Secale cereale, heterochromatin.
Breeding system and genome size of the rhabdocoel turbellarian Mesostoma ehrenbergii
Authors: Hebert Paul D. N. , Beaton Margaret J.
Published: April 2011

Rhabdocoel turbellarians, such as Mesostoma ehrenbergii, are hermaphrodites which produce both subitaneous and resting eggs. Both genotypic frequencies in natural populations as well as parent–offspring genotypes at a polymorphic allozyme locus confirm that, under natural conditions, M. ehrenbergii produces subitaneous eggs via self-fertilization and resting eggs probably by outcrossing. Chromosome counts show, contrary to an earlier report, that North American populations of the species possess the same chromosome number as European populations. However, other karyotypic differences do exist between Old World and New World populations. DNA quantification studies revealed that M. ehrenbergii possesses one of the largest haploid genome sizes (14.8 pg) yet reported for an invertebrate. Among organisms showing similar genome size, this species appears to be unique for its rapid developmental rate.Key words: Turbellaria, allozyme, breeding system, genome size, cytogenetics, selfing.
New distinctions between regions of centromeric heterochromatin in human chromosomes by treatments with the isoschizomers NdeII–Sau3AI
Authors: Ludeña P. , Sentís C. , Fernández-Peralta A. M. , Gonzalez-Aguilera J. , Fernández-Piqueras J.
Published: April 2011

The isoschizomers NdeII-Sau3AI (↓GATC) have been used to characterize heterochromatic regions in human chromosomes. The findings with NdeII are identical with those previously published with MboI, but the results with Sau3AI provide evidence for new distinctions of centromeric heterochromatin in chromosomes 5 and 6. The results are discussed in relation to the chromatin organization at these regions an the mechanisms of the action of restriction endonucleases.Key words: human heterochromatin, in situ digestion, NdeII–Sau3AI isoschizomers.