bluuebunny/crossref_metadata_2025 huggingface dataset:
Segregation of molecular markers supports an allotetraploid structure for Medicago sativa × Medicago papillosa interspecific hybrid
Authors: McCoy T. J. , Echt C. S. , Mancino L. C.
Published: April 2011

Cytogenetic analysis has indicated there is little genomic affinity between the genomes of Medicago sativa L. and Medicago papillosa Boiss. The objective of this study was to determine whether disomic segregation of alleles at isozyme and restriction fragment length polymorphism (RFLP) loci occurs in F1 hybrids of M. sativa × M. papillosa. We examined segregation of alleles at seven isozyme loci and 13 RFLP loci. Of the 20 loci analyzed, 11 exhibited a disomic pattern of inheritance, indicative of strict species-specific chromosome pairing in the M. sativa × M. papillosa hybrids. The other nine loci generally followed disomic inheritance, with exceptions. The results provide significant evidence in support of the concept that M. sativa × M. papillosa hybrids are basically allotetraploids with limited genomic affinity between the genomes. This report also represents the first documentation of the utility of RFLP markers in genetic analysis of alfalfa, a species with an essentially nonexistent genetic map.Key words: isozymes, genomic affinity, alfalfa, introgression, restriction fragment length polymorphism.
Wide hybridization of Hordeum vulgare × Zea mays
Authors: Chen F. Q. , Hayes P. M. , Rivin C. J.
Published: April 2011

Two barley (Hordeum vulgare L.) varieties ('Klages' and 'Harrington') were crossed with an array of maize (Zea mays L.) stocks carrying active transposons. From 1204 florets pollinated and cultured, 98 embryos were rescued. Forty-one of these embryos germinated to give green plants, 38 of which were haploid (2n = 7) and 3 of which were diploid (2n = 14). The overall efficiency of barley haploid production was 4.7% with 'Klages' and 1.5% with 'Harrington'. No maize DNA introgression was detected cytologically or in DNA hybridizations using maize transposable elements and highly repeated sequences as probes.Key words: barley, maize, haploids, DNA hybridization.
Cytological characterisation of heterochromatin in mitotic and meiotic chromosomes of the Old World screwworm fly, Chrysomya bezziana (Diptera: Calliphoridae)
Authors: Bedo D. G.
Published: April 2011

Mitotic and meiotic chromosomes of the Old World screwworm fly, Chrysomya bezziana, were studied using C-banding and quinacrine and counterstain-enhanced fluorescence techniques. The five autosomes in the karyotype are evenly graded in size, with somewhat variable arm ratios. Distinguishing all autosomes on these features alone can be difficult. C-banding produces small centromeric bands in the autosomes, whereas the much longer X and Y chromosomes have extensive dark C-band blocks with intermediate background staining. Most bright fluorescence occurs in the sex chromosomes, particularly the X chromosome, which has remarkable banding detail. Band resolution is greatly increased in mitotic metaphase cells from embryos. Quinacrine staining of mitotic chromosomes produces bright fluorescence at the centromere regions of chromosomes 2, 3, and 4, assisting in their identification. Meiotic chromosomes have distinctly reduced brightness and resolution of fluorescent bands and show marked chromatid asynapsis in the brighter regions of the sex chromosomes. Fluorochromes staining A∙T-rich DNA (quanacrine and 4,6-diamidino-2-phenylindole (DAPI)) produce bright staining in a large proportion of the sex chromosomes. By contrast chromomycin, which binds preferentially to G∙C-rich DNA, stains a much smaller proportion of the sex chromosomes than expected from reciprocal staining. Together with the asynapsis data this indicates that much of the heterochromatin in the sex chromosomes has unusual structural properties.Key words: Chrysomya bezziana, screwworm, karyotype, C-banding, fluorescence, heterochromatin.
Patterns of genetic diversity in the sumac gall aphid, Melaphis rhois
Authors: Hebert Paul D. N. , Finston Terrie L. , Foottit Robert
Published: April 2011

In contrast to prior work on aphids, which has focused on pest species, the present study involved the analysis of genetic diversity in Melaphis rhois, a species that employs sumac and moss as alternate hosts. The life cycle involves a spring migration to sumac, with each sexual female producing a single offspring, which elicits a gall and subsequently proliferates clonally within it. Allozyme surveys at 52 sites in Ontario and Quebec established the absence of migration among galls and indicated that this species shares the low level of genetic diversity found in pest aphids. Genotypic frequencies in local populations of M. rhois showed frequent heterozygote deficits, suggesting the prevalence of inbreeding. Gene frequency divergence among populations was exceptionally pronounced, providing further evidence that gene flow was restricted. The unusual genetic attributes of this species suggest the important interaction among host-plant characteristics and the dispersal ability of aphids and their genetic systems.Key words: aphid, Melaphis, parthenogenesis, allozyme, cyclic parthenogen.
Evolutionary DNA variation in Papaver
Authors: Srivastava Sangeeta , Lavania U. C.
Published: April 2011

In 23 species of Papaver L., 2C nuclear DNA amounts range from 4.64 pg in Papaver persicum (2n = 14) to 22.43 pg in Papaver orientale (2n = 42), revealing a fivefold variation within the genus. However, such variation is limited to only twofold among the species that have the same chromosome number (2n = 14). The distribution of DNA is discontinuously spread over six groups in the genus. A strong positive correlation exists between nuclear DNA content and metaphase chromosome length. Viewed in the context of evolutionary divergence, it is revealed that DNA reduction has taken place in conjunction with speciation. This is achieved by equal reduction to each chromosome independent of chromosome size, as apparent from the estimated DNA values for individual chromosomes within the complements. The diminution in DNA amount with evolutionary specialisation appears to be a genomic strategy to dispense with the less important DNA associated with heterochromatic segments. The uniform distribution of such dispensible DNA throughout the complement is probably nucleotypically conducive to allow the genomic loss to be adaptationally operative, lest it affects the very survival of the evolving species.Key words: Papaver, evolution, DNA content, DNA systematics.
In situ enzymatic denaturation and random oligonucleotide priming of DNA selectively stains centromeric heterochromatin in Triturus marmoratus (Salamandridae: Caudata)
Authors: Herrero P. , Bella J. L. , Torre J. de la , Gosálvez J.
Published: April 2011

Enzymatic production of single-stranded DNA with the HaeIII restriction endonuclease and exonuclease III has been used for chromosome labelling involving random primer extension and incorporation of biotinylated nucleotides with the Klenow polymerase on fixed chromosomes of Triturus marmoratus. Results show repetitive and selective labelling of centromeric heterochromatin, while remaining heterochromatin does not exhibit a positive response. This method of chromosome labelling permits the characterization of specific fractions of the heterochromatin and can be used for the analysis of heterochromatin heterogeneity within a given genome.Key words: Triturus marmoratus, cytogenetics, heterochromatin, restriction endonuclease DNA denaturation, random priming.
Chloroplast genome differentiation in Asian cultivated rice
Authors: Ishii Takashige , Tsunewaki Koichiro
Published: April 2011

Restriction endonuclease analysis of chloroplast DNA was carried out to clarify the chloroplast genome differentiation between Asian varieties of Oryza sativa. Based on the restriction fragment patterns obtained with six endonucleases, i.e., EcoRI, HindIII, PstI, PvuII, SmaI, and XhoI, chloroplast genomes of 68 local varieties from 15 Asian countries could be classified into five types (types 1, 3, 10, 11, and 12). Among these types, four length mutations and two base substitutions were found; these changes were located on the PstI physical map of rice chloroplast DNA. In a dendrogram showing genetic relationships among five chloroplast genomes, they are mainly divided into two groups, which we have named as the Japonica (types 1, 11, and 12) and Indica (types 3 and 10) chloroplast genome groups. Both groups are distributed widely in Asian countries. The Japonica isozyme group classified by J.C. Glaszmann (1985. Rice Genetics. International Rice Research Institute, Manila, Philippines, pp. 83–90) carries only the Japonica chloroplast genome, whereas the Indica isozyme group contains both Japonica and Indica chloroplast genomes.Key words: Oryza sativa, Asian varieties, chloroplast DNA, restriction endonuclease analysis, chloroplast genome differentiation.
The desynaptic mutant of maize as a combined defect of synaptonemal complex and chiasma maintenance
Authors: Maguire M. P. , Paredes A. M. , Riess R. W.
Published: April 2011

The phenotype of the desynaptic (dy) mutant of maize in microsporocytes at meiotic prophase was compared with normal microsporocytes of a closely related strain and with microsporocytes of a maize inbred line (KYS) assumed to be normal. Strikingly more univalents and open arms of bivalents were found in the mutant cells than in normal cells at diakinesis, and where there was heterozygosity for a distal knob (heterochromatic region), separation was usually equational, indicating the occurrence of normal crossing-over followed by failure of chiasma maintenance in the mutant. Differences found in the mutant by electron microscopy were a statistically significant wider dimension of the synaptonemal complex central region and also less twisting of synapsed configurations at pachytene. It is suggested that these are side-effect symptoms of a defect in the synaptonemal complex (or associated substance), which is expressed later as sporadic loss of chiasma maintenance.Key words: desynaptic, chiasma maintenance, synaptonemal complex.
Gametophytic selection in a winter × spring barley cross
Authors: Schön C. C. , Hayes P. M. , Blake T. K. , Knapp S. J.
Published: April 2011

Segregation distortion and the consequences of gametophytic selection were assessed in a winter × spring barley cross by comparing segregation of enzyme, storage protein, DNA, and morphological markers in three populations derived from the same cross: a control F2 (F2C), a doubled-haploid (DH) population, and an F2 derived from F1 plants self-pollinated at 10 °C (F2T). Segregation distortion was present in the F2T and the doubled-haploid population. Based on a comparison of the F2C and the F2T, gametophytic selection as a consequence of self-pollination at 10 °C was operative on chromosome 7 in regions linked to Rrn2. Segregation distortion in favor of the winter parent was found in the doubled-haploid population. There were significant deviations from expected segregation ratios at two loci, but only at one of the loci was the gene number significantly different from the F2C. Despite segregation distortion, the doubled-haploid population should be suitable for linkage analyses, as estimates of recombination based on F2 and doubled-haploid data were in close agreement.Key words: Hordeum vulgare, segregation distortion, doubled haploids, gametophytic selection, cold tolerance.
Intergeneric hybrids between Hordeum vulgare and Elymus trachycaulus resistant to Russian wheat aphid
Authors: Aung Taing
Published: April 2011

Intergeneric hybrids between cultivated barley (Hordeum vulgare L.) (2n = 2x = 14) and slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), PI 531691 (2n = 4x = 28), were produced. This slender wheatgrass accession carries resistance to Russian wheat aphid, Diuraphis noxia Mordvilko, and was used as pollen parent. The seven hybrid plants were also resistant to Russian wheat aphid. The hybrids were produced at a frequency of 0.21% of emasculated and hand-pollinated florets. Chromosome pairing in all the euploid hybrids was very low (average chiasma frequency per cell, 0.30). This indicates that the I genome from H. vulgare is remotely related to the SH genomes of E. trachycaulus. Expression of resistance to Russian wheat aphid in all the hybrid plants demonstrates that the nuclear gene or genes for insect resistance contributed by E. trachycaulus are either dominant or hemizygous effective. Five of the seven hybrid plants were vigorous and produced well-developed flowering spikes; however, they did not shed viable pollen. Since all the vegetatively cloned plants of these hybrids exhibited a high degree of perennial characteristics and could be induced to flower under a favourable light and temperature regime, they appear congenial for chromosome doubling and backcrossing. Preliminary observations suggest that successful backcrossing could be achieved using the F1 hybrids as pistillate parent and H. vulgare as pollen parent.Key words: Russian wheat aphid resistance, intergeneric hybrids, genomic relationship, chromosome pairing, Hordeum vulgare, Elymus trachycaulus.
Salt tolerance and ionic relations of wheat as affected by individual chromosomes of salt-tolerant Lophopyrum elongatum
Authors: Omielan J. A. , Epstein E. , Dvořák J.
Published: April 2011

Bread wheat cv. Chinese Spring (CS), an amphiploid from a cross between CS and salt-tolerant Lophopyrum (= Agropyron) elongatum (Host) Löve, 19 of 21 possible disomic substitution lines of L. elongatum chromosomes for CS homoeologues, and a check cultivar, PI 178704, were grown in a replicated field trial under two levels of salinity and control conditions. Under salinity, the amphiploid greatly outperformed CS in grain yield, biomass, and other characters, indicating that it is more salt tolerant than CS. Of the seven L. elongatum chromosomes, six increased salt tolerance in disomic substitution lines; the most dramatic increase was conferred by chromosome 3E. Increased salt tolerance of the amphiploid was associated with the exclusion of Na+ and Cl− and inclusion of K+ as well as retranslocation of K+. Lophopyrum chromosomes controlling these physiological characters were identified. Some of the chromosomes had multiple effects, where as others affected only a specific character. The largest effects were associated with chromosome 3E. In addition, several wheat chromosomes controlled the exclusion or inclusion of these ions; the most notable effects were by chromosome 4D. Salt tolerance correlated negatively with Na+ and positively with K+ concentration in the flag leaf and with the K+/Na+ ratios. The relationships were strong enough to be exploited as selection tools in the breeding of salt-tolerant wheat cultivars.Key words: salt tolerance, wheat, Lophopyrum elongatum.
Nucleocytoplasmic interactions stabilize ploidy level in wheat interspecific hybrids
Authors: Maan S. S. , Endo T. R.
Published: April 2011

The cytoplasm of Aegilops squarrosa L. (2n = 14; DD) is compatible with the nuclei of Triticum aestivum L. (2n = 42; AABBDD) and the pentaploid F1 (2x = 35; AABBD), but not with the euploid nucleus of Triticum turgidum L. (2n = 28; AABB). To identify D-genome chromosomes with the genes conditioning differential nucleocytoplasmic compatibility, ae and sq 5x F1, having cytoplasms of T. aestivum and Ae. squarrosa, respectively, were reciprocally crossed to the seven doubled ditelosomics (d-dts) of the D-genome chromosomes (including four control crosses of d-dts 1A, 1B, and sq 5x F1). The 32 progeny were examined for the presence or absence of unpaired telosomes, monosomes, and the maximum number of bivalents at the meiotic metaphase I in the pollen mother cells for comparison with the transmission of ae and sq male and ae and sq female gametes carrying different numbers of D-genome chromosomes. The sq gametes with 1D, 5D, and other D-genome chromosomes had a strong functional advantage. In contrast, the ae gametes with 1D and other D genome chromosomes, except 5D, had a functional disadvantage. The sq and ae 5x F1 transmitted chromosome 5D through 80.0 and 72.2% of the male and 58.6 and 44.8% of the female gametes, respectively. We concluded that the sq gametes tended to increase and ae gametes tended to reduce the ploidy levels of the progeny.Key words: preferential gamete transmission, alloplasmic wheat, Triticum, Aegilops, polyploidy, aneuploidy.
Chromosome structure in spermatogenesis of Anabolia furcata (Trichoptera)
Authors: Wolf Klaus Werner , Novák Karel , Marec František
Published: April 2011

The structure of metaphase chromosomes was analysed in spermatogonia and spermatocytes of the caddis-fly, Anabolia furcata (Trichoptera: Limnephilidae), using ultrathin serial sections and electron microscopy. In metaphase spermatogonia, about 40% of the chromosomal length was covered with a compact kinetochore plate. Subjectively estimated, secondary spermatocytes were not significantly different in this respect. However, in primary spermatocytes, each bivalent showed four kinetochores, two at each poleward surface, connected with the chromosome. The kinetochores were not located at the chromosome portions most proximal to the spindle poles, but attached laterally in a more equatorial position. When the orientation of individual kinetochore plates in metaphase I bivalents was not roughly at right angles with respect to the spindle axis, gaps and holes were visible in the plates. This possibly indicates the presence of compound kinetochores in A. furcata. The center of the bivalents contains less dense material than the periphery. The structural features of chromosomes in this Trichoptera species are very similar to those described in Lepidotera species with a comparable chromosome number. Taken together with similarities in other karyotype characteristics, such as female heterogamety and the lack of chiasmata in female meiosis, this further corroborates the notion that Lepidoptera and Trichoptera have strong phylogenetic affinities.Key words: caddis-fly, metaphase chromosomes, kinetochore, microtubules, spindle.
Potato germplasm enhancement with disomic tetraploid Solanum acaule. I. Efficiency of introgression
Authors: Watanabe Kazuo , Arbizu Carlos , Schmiediche P. E.
Published: April 2011

The wild potato species Solanum acaule (acl) was used as a model of a disomic tetraploid Solanum species to develop systematic methods of germplasm enhancement for disomic tetraploid species. The objective was to develop a genetically efficient method to overcome the inherent technical problems encountered in the utilization of disomic tetraploid wild species. Accessions of acl were selected from CIP's wild germplasm collection and from the collection of University of Birmingham, with emphasis on genetic attributes such as PLRV resistance and (or) PSTV resistance. Four methods were tested: (i) triploids from crosses between 4x acl × 2x potato were selected for 2n gametes production and were crossed to tetraploids or to diploids with 2n egg production; (ii) axillary buds of triploid hybrids were treated with colchicine to double chromosome numbers to generate hexaploids; (iii) in vitro chromosome doubling to obtain hexaploids from triploid hybrids; and furthermore (iv) the selected acl clones were directly crossed to tetraploid potatoes followed by a combination of second compatible pollinations with IvP 35 and subsequent embryo rescue. The combination of second compatible pollination and embryo rescue was found to be the most genetically efficient method for the utilization of the valuable genetic attributes of acl.Key words: inter-EBN crosses, ploidy manipulation, polyploid, potato breeding, wild species
Evaluation of transgenic canola plants under field conditions
Authors: Arnoldo M. , Baszczynski C. L. , Bellemare G. , Brown G. , Carlson J. , Gillespie B. , Huang B. , MacLean N. , MacRae W. D. , Rayner G. , Rozakis S. , Westecott M. , Kemble R. J.
Published: April 2011

Eleven independent transgenic canola (Brassica napus ssp. oleifera L. cv. Westar and Regent) lines were evaluated in the field. The plants carried a neomycin phosphotransferase (NPTII) gene for kanamycin resistance that was introduced via Agrobacterium-mediated transformation. NPTII enzyme assays, Southern blot hybridizations and progeny analysis, confirmed the stable, heritable integration and expression of the introduced NPTII gene. A number of agronomic characteristics evaluated under field conditions, including maturity, yield, and oil and protein content, were all statistically comparable between the transformed and nontransformed plants. These results indicate that canola can be genetically engineered successfully, and that the Agrobacterium-based transformation system employed does not induce any adverse effects on the intrinsic agronomic and qualitative traits critical to the agricultural industry.Key words: transgenic field trial, canola, Agrobacterium-mediated transformation, vectors.
Characterization and assessment of an avian repetitive DNA sequence as an icterid phylogenetic marker
Authors: Quinn J. S. , Guglich E. , Seutin G. , Lau R. , Marsolais J. , Parna L. , Boag P. T. , White B. N.
Published: April 2011

The first tandemly repeated sequence examined in a passerine bird, a 431-bp PstI fragment named pMAT1, has been cloned from the genome of the brown-headed cowbird (Molothrus ater). The sequence represents about 5–10% of the genome (about 4 × 105 copies) and yields prominent ethidium bromide stained bands when genomic DNA cut with a variety of restriction enzymes is electrophoresed in agarose gels. A particularly striking ladder of fragments is apparent when the DNA is cut with HinfI, indicative of a tandem arrangement of the monomer. The cloned PstI monomer has been sequenced, revealing no internal repeated structure. There are sequences that hybridize with pMAT1 found in related nine-primaried oscines but not in more distantly related oscines, suboscines, or nonpasserine species. Little sequence similarity to tandemly repeated PstI cut sequences from the merlin (Falco columbarius), saurus crane (Grus antigone), or Puerto Rican parrot (Amazona vittata) or to HinfI digested sequence from the Toulouse goose (Anser anser) was detected. The isolated sequence was used as a probe to examine DNA samples of eight members of the tribe Icterini. This examination revealed phylogenetically informative characters. The repeat contains cutting sites from a number of restriction enzymes, which, if sufficiently polymorphic, would provide new phylogenetic characters. Sequences like these, conserved within a species, but variable between closely related species, may be very useful for phylogenetic studies of closely related taxa.Key words: tandemly repeated sequences, satellite DNA, tribe Icterini.
5-Methylcytosine content in Gryllotalpa fossor (Orthoptera)
Authors: Sarkar Soma , Rao S. R. V. , Gupta V. S. , Hendre R. R.
Published: April 2011

The MspI-HpaII digestion patterns of Gryllotalpa fossor (Scudder) DNA indicated the methylation of internal cytosine in the sequence 5′ -CCGG-3′. The amount of 5-methylcytosine (5mC) was estimated by HPLC analysis to be about 0.6–0.8%, which constitutes approximately 3% of the total cytosine in the genome. This is the first example of a non-mammalian animal with appreciable levels of 5mC.Key words: insect genome, 5-methylcytosine, DNA methylation.
Diploid ancestry and evolution of Triticum kotschyi and T. peregrinum examined using variation in repeated nucleotide sequences
Authors: Zhang Hong-Bin , Dvořák Jan , Waines J. Giles
Published: April 2011

Triticum peregrinum Hackel (syn. Aegilops variabilis Eig) and T. kotschyi (Boiss.) Bowden (syn. Ae. kotschyi Boiss.) are closely related allotetraploid species. Previous research indicated that they have a pair of U genomes from diploid T. umbellulatum (Zhuk.) Hackel and a pair of S genomes from a diploid species of Triticum section Sitopsis. To reinvestigate the origin of their genomes, we identified diagnostic bands in Southern blots hybridized with 27 cloned repeated nucleotide sequences and one 5S rRNA gene clone for all diploid species of Triticum L. sensu Bowden. The presence of each diagnostic band was then determined in the two tetraploid species. One pair of the genomes in both tetraploid species was found to be virtually identical to the U genome of T. umbellulatum and the other to the S1 genome of T. longissimum (Schweif. et Muschl.) Bowden or T. sharonense (Eig) Waines &Johnson (syn. Aegilops sharonensis Eig) or the internode in the phylogenetic tree of Triticum immediately preceding the divergence of T. longissimum and T. sharonense. The source of the S genomes in T. kotschyi and T. peregrinum inferred from our data differs from that inferred from cpDNA. This indicates the need to investigate the origin of nuclear genomes with nuclear genetic markers. No evidence for an extensive modification of the S genome relative to that of T. longissimum or T. sharonense was found in either tetraploid.Key words: phylogeny, polyploids, Triticum, Aegilops, Aegilops kotschyi, Aegilops variabilis, genome origin, genome modification.
The polytene chromosomes of Drosophila triauraria and D. quadraria, sibling species of D. auraria
Authors: Mavragani-Tsipidou P. , Scouras Z. G. , Haralampidis K. , Lavrentiadou S. , Kastritsis C. D.
Published: April 2011

The polytene chromosomes of Drosophila triauraria and D. quadraria, two of the sibling species of D. auraria, were examined. The polytene chromosomes of all three species exhibit very clear homology. Unlike the stock of D. auraria that we studied, D. triauraria and D. quadraria carry heterozygous paracentric inversions. In both species, 2R and 3R are the arms where these inversions are concentrated. In addition, in D. quadraria, the 3L chromosome arm is very complicated because of heterozygous inversions. The mode of inheritance of these rearrangements was studied. A homozygous strain for all chromosome arms of D. triauraria was isolated, while a homozygous strain was obtained only for the arms X, 2L, 3L, and 4 of D. quadraria. Like D. auraria, both species show a large number of inverted tandem duplications in the paired condition, even in the chromosomes of their hybrids. Small deletions were also detected, one of which, in D. triauraria, is homozygous terminal. Hypotheses are discussed concerning the relationships of the species and the existence of inverted tandem duplications.Key words: Drosophila, duplications, inversions, deletions, evolution.
Variation in telomeric heterochromatin in somaclones of rye
Authors: Karp A. , Owen P. G. , Steele S. H. , Bebeli P. J. , Kaltsikes P. J.
Published: April 2011

Somaclonal variation in telomeric heterochromatin was detected by in situ hybridization with the het 1 probe, which hybridizes to a 380-bp repeated sequence family. In a control cultivar, Gazelle, large blocks of signal were detected at the telomeres but not at the centromeres or the secondary constrictions. In the donor line, 7R–, labelling was restricted to small telomeric dots, confirming that the large telomeric blocks had been removed in selection of this line. In situ hybridization with the het 1 probe to chromosomes of selfed progeny from 50 plants regenerated from independent cultured immature embryos of the 7R– line revealed variant patterns for three regenerants. In the progeny of two regenerants, a new interstitial hybridization site was detected on the short arm of a submetacentric chromosome. This site was not at the nucleolus organizer. In the progeny of the third regenerant two changes were detected: an enlarged telomeric block on the long arm of an unidentified chromosome and an interstitial site on the long arm of chromosome 6. All three regenerated plants had shown normal morphology and meiotic behaviour. The identification of somaclonal variants in telomeric heterochromatin provides further evidence for variation in repeated DNA sequences in plant tissue culture.Key words: rye (Secale cereale), somaclonal variation, in situ hybridization, repeated sequence, heterochromatin, telomere.
Innate and acquired variation of nuclear DNA contents of marine copepods
Authors: Escribano Ruben , McLaren Ian A. , Breteler W. C. M. Klein
Published: April 2011

Feulgen staining revealed significant geographical differences in mean DNA contents of somatic nuclei of adult female Calanus glacialis and Pseudocalanus acuspes from the Canadian arctic and Nova Scotia; the latter exhibited seasonal differences near Halifax in 1987 but not 1989–1990. Female P. elongatus reared for 96 generations in the laboratory had significantly less DNA per nucleus than did first-generation females from the same North Sea wild stock. Nuclei of C. glacialis reared from juvenile stages (copepodid III) in four food–temperature treatments had significantly more DNA at high food and low temperature. There were also significant treatment effects in P. elongatus and P. acuspes reared from egg to adult. There were always significant differences in DNA contents among females within samples and treatments. Increased variance among nuclei within individual C. glacialis may have resulted from suboptimal laboratory conditions. Body lengths in rearing experiments were positively correlated with nuclear DNA contents in C. glacialis and P. elongatus; there was no correlation of lengths with nucleus number in P. acuspes. Development rate of late-stage C. glacialis was negatively related to nuclear DNA contents. The slight, but significant, differences among females within and among samples and treatments suggest that their DNA contents are both inherent and subject to slight environmental effects. Results are also consistent with earlier indications that body sizes and development rates of copepods, because of restricted variation in cell number, are partly under nucleotypic control.Key words: Copepoda, genome size, intraspecific variation, nucleotypic effects, body size, development rate.
DNA fingerprinting analysis in the solitary bee Megachile rotundata: variability and nest mate genetic relationships
Authors: Blanchetot Alain
Published: April 2011

The most conventional approach for evaluating genetic variability in an insect population involves assessing the degree of enzyme polymorphism. Hymenoptera display a relatively low level of genetic variability compared with most insect species. DNA probes consisting of tandemly repeated sequences are powerful tools for detecting polymorphisms when employed to develop DNA fingerprinting (DNAfp) profiles in a wide range of organisms. This report describes genetic variability in the solitary bee species Megachile rotundata as assessed by DNAfp using the Ml3 sequence and a synthetic oligonucleotide sequence homologous to a hypervariable region of the α-globin gene. DNAfp comparisons among offspring were used to analyze genealogical structure in M. rotundata nests. The results indicate that polyandry, by a large number of males, is not a common phenomenon in M. rotundata bee species. In the present analysis, it is likely that the broods raised in single nests are mostly the offspring of one singly mated female. However, the data does not preclude that for certain nests two males could have been involved in the mating process.Key words: Megachile rotundata, DNA fingerprinting, M13 sequence, α-globin hypervariable sequence, intra-nest genetic relationships.
Electrophoretic karyotype analysis of the button mushroom, Agaricus bisporus
Authors: Royer John C. , Hintz W. E. , Kerrigan R. W. , Horgen P. A.
Published: April 2011

An efficient procedure is presented for the generation of protoplasts from shake flask cultures of the commercial mushroom Agaricus bisporus. Orthogonal field electrophoresis (OFAGE) of high molecular weight DNA from lysed protoplasts resolved the genome of A. bisporus into at least 10 bands, ranging in size from 1.2 to 4 Mb. The illustrated electrophoretic karyotypes of two homokaryons were highly polymorphic. A heterokaryon of the two homokaryons contained a mixture of the two electrophoretic patterns, though the ratio of nuclear types was not equal. A number of RFLP and RAPD markers and the rDNA repeat have been localized to specific chromosomes. Based on ethidium bromide staining intensity and autoradiography, we have estimated the chromosome number of A. bisporus to be 13.Key words: Agaricus bisporus, orthogonal field electrophoresis, RFLP, rDNA.
Genetics of Glossina morsitans morsitans (Diptera: Glossinidae). XIV. Map locations of the loci for phosphoglucomutase and glucose-6-phosphate isomerase
Authors: Gooding R. H. , Rolseth B. M.
Published: April 2011

The locus for phosphoglucomutase (Pgm) was mapped at less than 1.2 recombination units from the locus for arginine phophokinase (Apk) in linkage group I, the X chromosome. Linkage group III loci were mapped in the order sabr (long scutellar apical bristles in females), Mdh (malate dehydrogenase), and Pgi (glucose-6-phosphate isomerase). The loci sabr and Mdh were separated by 39.3 ± 4.6 recombination units, and Mdh and Pgi were separated by 45.5 ± 4.7 recombination units. Intrachromosomal recombination was rare or did not occur in males. Previously published recombination distances are summarized as a linkage map for the 16 loci that have been mapped in Glossina morsitans morsitans.Key words: tsetse, linkage map, phosphoglucomutase, glucose-6-phosphate isomerase.
The S genome in Triticum syriacum
Authors: Yen Yang , Kimber Gordon
Published: April 2011

Triticum syriacum (= Aegilops vavilovi, 2n = 42, DDMMSS) was hybridized with induced autotetraploids of T. longissimum (= Ae. longissima, 2n = 28, S1S1S1S1), T. bicorne (= Ae. bicornis, 2n = 28, SbSbSbSb), and T. speltoides (= Ae. speltoides, 2n = 28, SSSS). Meiotic analysis showed that no genome in T. syriacum seems to be identical to the genome of any of the induced autotetraploid parents. However, our data indicates that T. syriacum contains a substantially modified S genome.Key words: meiosis, chromosome pairing, hybrid, phylogenesis.
Genetic variability in a family of satellite DNAs from tilapia (Pisces: Cichlidae)
Authors: Franck J. P. C. , Wright J. M. , McAndrew B. J.
Published: April 2011

We have cloned and sequenced members of a family of satellite DNAs from three genera of the tilapiine tribe of fishes: Oreochromis, Sarotherodon, and Tilapia. The satellite DNAs, visualized as intensely staining bands following electrophoretic separation of EcoRI-digested genomic DNA, consist of three size variants differentially distributed in the various tilapiine species. The sizes of the monomers are approximately 237 bp (type I), 230 bp (type II), and 209 bp (type III). Several cloned monomers were sequenced from Oreochromis niloticus (type III), Oreochromis placidus (types I and II), Sarotherodon galilaeus (type I), Tilapia zillii (type I), and Tilapia rendalli (type I). Comparison of derived consensus sequences for the monomer units of the satellite DNAs revealed sequence identities within and between species that ranged from 89 to 96%. The type II and type III size variants appear to have arisen by deletions of 9 and 29 bp, respectively, within different regions of the type I satellite. Hybridization of a cloned monomer satellite from O. niloticus (type III) to PalI digests of genomic DNA from all three genera detected polymorphic, high molecular weight restriction fragments that produced fingerprint-like patterns. The complexity of these DNA fingerprints varied from one species to another, suggesting a markedly different genomic organization for these polymorphic satellite DNAs.Key words: satellite DNA, polymorphic, DNA fingerprints, tilapia.
An RFLP-based linkage map of oats based on a cross between two diploid taxa (Avena atlantica × A. hirtula)
Authors: O'Donoughue L. S. , Wang Z. , Röder M. , Kneen B. , Leggett M. , Sorrells M. E. , Tanksley S. D.
Published: April 2011

A restriction fragment length polymorphism (RFLP) map for the A genome of Avena has been developed using F3 families from the cross A. atlantica × A. hirtula. The main source of markers were an oat cDNA and a barley cDNA library. A total of 194 RFLP markers was used, 192 of which were mapped or assigned to linkage groups. Seven main linkage groups, presumably corresponding to the seven chromosomes of the haploid genome, were identified. The linkage groups varied in size from 30 to 118 cM for a total map length of 614 cM. This map provides a tool for the interpretation of genome organization in Avena and for marker selection in the development of a map of hexaploid oats.Key words: restriction fragment length polymorphism, Avena, mapping.
A better way to construct recombinant chromosome lines and their controls
Authors: Yen Yang , Baenziger P. Stephen
Published: April 2011

Previous procedures to construct chromosome monosomic, substitution, recombinant chromosome lines and their controls underestimated cultivar heterogeneity, which can increase background effects. Modifications are proposed to increase background homogeneity and to eliminate interference of genetic or structural heterogeneity of the target chromosomes in parental populations. To achieve this goal, a single plant or plants of single-seed descendants of disomic, monosomic, and substitution lines should be used as the parents to construct recombinant chromosome lines and the controls (i.e., the recreated disomic recurrent parent and the recreated disomic substitution line). Intracultivar variations can thus be avoided. The mating plan is carefully designed so that the resultant recombinant chromosome lines and their controls will have a similar genetic background. All the resultant lines will share the same cytoplasm and the same target chromosomes or chromosome segments that came from the parent plant(s). Therefore, we are able to largely reduce the heterogeneity in the genetic background, eliminate the potential intracultivar cytoplasm variations, and be free from the structural or genetic heterogeneity of the target chromosome. In addition, the background heterogeneity, if it exists, could be measured by comparing individual control lines.Key words: quantitative trait, cytogenetics, background heterogeneity, aneuploidy, substitution.
2n gametes in Solanum commersonii and cytological mechanisms of triplandroid formation in triploid hybrids of Solanum commersonii × Solanum gourlayi
Authors: Masuelli R. W. , Camadro E. L. , Mendiburu A. O.
Published: April 2011

Solanum commersonii Dun. (cmm) is a diploid wild species of potential value for potato breeding. Ploidy level manipulations are necessary to cross this species with the common potato. This could be achieved by the use of "bridge" species and sexual polyploidization in which 2n gametes are involved. Eight introductions of cmm were screened for production of (i) diplandroids, through cytological observations confirmed by controlled 4x Solanum acaule Bitt. (acl) × 2x cmm crosses, and (ii) diplogynoids, by controlled 2x cmm × 2x Solanum gourlayi Haw. (grl) crosses. Eleven plants produced 1–3% large size pollen and one plant produced more than 3% of this type of pollen. Twelve triploid and seven tetraploid hybrids were obtained when these plants were used in crosses with acl. On the other hand, 75 triploid hybrids were obtained from the second type of cross. The average pollen stainability in the diplogynoid triploid cmm × grl hybrids was 18.9%, with a range of 2–34.4%. Forty-four to 54.6% of meiocytes with parallel spindles in metaphase II and anaphase II were observed in microsporogenesis of these hybrids. For each clone, the frequency of triplandroids predicted according to the frequency of meiocytes with parallel, fused and tripolar spindles in anaphase II were 52.3, 36.6, and 45.2%, respectively. These values were highly superior to the frequency of triplandroids predicted according to the number of dyads and triads observed, 8.8, 0.7, and 3.9%, respectively. However, triplandroid frequencies predicted according to the frequencies of fused and tripolar spindles agree with the triplandroid frequencies observed. The frequencies of stainable pollen grains are not completely accounted for by the formation of fused and tripolar spindles. In view of the variability encountered in size, it is assumed that a high proportion of gametophytes with aneuploid chromosome numbers are also stainable. A hypothesis is put forward regarding the possible genetic control of triplandroid formation in the diplogynous triploid hybrids analyzed.Key words: 2n gametes, triploid hybrids, spindle orientation, Solanum commersonii Dun.
Detection of polymorphic loci in Arachis germplasm using random amplified polymorphic DNAs
Authors: Lanham Patrick G. , Fennell Sarah , Moss J. P. , Powell W.
Published: April 2011

The development of easily scoreable genetic markers in Arachis will facilitate the introgression of desirable traits from wild species into adapted germplasm. We have used random amplified polymorphic DNAs (RAPDs) to identify polymorphic molecular markers in a range of wild and cultivated Arachis species. From a total of sixty 10-mer oligonucleotide primers, 49 polymorphic loci were identified between a cultivated A. hypogaea type (TMV-2) and a synthetic amphidiploid (B × C)2 created from a A. batizocoi and A. chacoense cross. The inheritance of polymorphic markers, both in the amphidiploid and in the F1 progeny in a TMV-2 × (B × C)2 cross, has also been demonstrated. The potential exploitation of RAPD markers in groundnut improvement programs is discussed.Key words: groundnut, Arachis species, RAPDs, amphidiploid.
Banding in mitotic chromosomes of Brassica campestris var. pekinensis with a trypsin–Giemsa method
Authors: Nishibayasahi Soryu
Published: April 2011

In Brassica campestris var. pekinensis cv. CR-strong, the karyotype comprised 12 median, 6 submedian, and 2 sub-terminal chromosomes. Secondary constrictions were observed in the two subterminal chromosomes. Banding pattern appeared very clearly in metaphase chromosomes with a trypsin–Giemsa method. It was possible to classify the chromosomes into 10 types (C1–C10), based on the chromosome size, shape, and banding pattern.Key words: Brassica campestris var. pekinensis, mitotic chromosomes, G-banding.
Silver staining two types of meiotic nodules
Authors: Sherman Jamie D. , Herickhoff Lisa A. , Stack Stephen M.
Published: April 2011

We have developed a reliable method for silver staining nodules on synaptonemal complexes (SCs) of tomato (Lycopersicon esculentum). This technique involves hypotonically bursting primary microsporocytes, fixing SC spreads with paraformaldehyde, and incubating the spreads at 40 °C in a 33% aqueous silver nitrate solution covered with nylon mesh. When tomato SCs were stained by this method, nodules were observed with the same distribution and frequency as nodules stained with uranyl acetate and lead citrate. Incubation in silver nitrate at higher temperatures caused the loss of some or all nodules. The pattern of loss suggests that two types of nodules coexist during late zygonema and early pachynema and that one type becomes the late nodules of mid-pachynema through early diplonema.Key words: Lycopersicon esculentum, silver staining, synaptonemal complex.
Genomic relationships of N-genome Triticum species
Authors: Yen Yang , Kimber Gordon
Published: April 2011

Induced autotetraploids of Triticum uniaristatum, T. tauschii, and T. umbellulatum were used to study the genomes of the polyploid species T. ventricosum, T. neglecta, and T. recta. The N genome in T. ventricosum is homologous to the N genome in the putative diploid donor T. uniaristatum and has undergone little modification. The D genome in T. ventricosum is also essentially unmodified. The U genome of T. neglecta appears to be unchanged from the U genome of T. umbellulatum. Two of the genomes of T. recta are the same as the genomes in T. neglecta (U and a presumed modified M genome). The presence of a U genome in T. recta has also been independently confirmed. The origin of the third genome in T. recta has not been confirmed.Key words: chromosomes, meiosis, genome analysis, wheat.
Mapping quantitative powdery mildew resistance of barley using a restriction fragment length polymorphism map
Authors: Heun M.
Published: April 2011

To map the genes underlying the quantitative resistance (QR) of the spring barley cultivars Proctor and Nudinka to powdery mildew, the relative pustule number of F1-derived doubled haploids (DHs) was determined and combined with the restriction fragment length polymorphism (RFLP) mapping data of these DHs via MAPMAKER/QTL. Applying a log-likelihood (LOD) threshold of 2.50, two putative quantitative trait loci (QTLs) were found in two different genome areas that accounted for 19.8% of the observed variance. One of the QR-related RFLPs (Xcnl.CDO36) is located on chromosome 1S, the other one (Xcnl.CDO749) is tightly linked with the nucleolus organizer region on chromosome 7. By comparing the means of subpopulations of DHs carrying alternative parental marker alleles, it was found that both RFLPs were also linked with some genes causing thousand kernel weight differences in this population. For the QR trait measured, LOD scores < 1.00 were found for the Mla12 region on chromosome 5S indicating that the Mla12 virulent isolate used neutralized this major resistance gene and that no residual effect of that locus occurred.Key words: barley, powdery mildew, restriction fragment length polymorphism, quantitative trait loci.
Phaseolin nucleotide sequence diversity in Phaseolus. I. Intraspecific diversity in Phaseolus vulgaris
Authors: Kami James A. , Gepts Paul
Published: April 2011

Most information about the molecular biology of phaseolin, the major seed storage protein in Phaseolus vulgaris, has been obtained from the T-type phaseolin, which is characteristic of the Andean gene pool of the species. In the work reported here, two cDNA clones for the S-type phaseolin representing the other major, Middle American gene pool were isolated and sequenced. Analysis of the DNA sequences revealed the presence of two subtypes of S phaseolin, α and β, depending on the presence or absence, respectively, of a 27-bp direct repeat. These are similar to the α- and β-phaseolin subtypes found in the Andean, T phaseolin; however, the additional 15-bp direct repeat also found in the T α-phaseolin gene type was apparently absent from the S α-phaseolin genes. The overall sequence identity was greater between the α or β subtypes of different gene pools than between the a or p subtypes within gene pools. This implies that the gene subtypes were formed prior to the formation of the two major gene pools of P. vulgaris. Analysis of the putative amino acid sequence revealed that both the 'Sanilac' phaseolin subtypes contained an additional methionine, however, not at the same site. This opens the possibility of increasing the nutritionally limiting methionine level in phaseolin either through protein engineering or by screening accessions for recombinant phaseolin sequences that combine both substitutions.Key words: seed storage protein, multigene family, direct repeat.