bluuebunny/crossref_metadata_2025 huggingface dataset:
Intraspecific differentiation of Setaria italica (L.) P.B.: study of abnormalities (weakness, segregation distortion, and partial sterility) observed in F1 and F2 generations
Authors: Croullebois M. L. , Barreneche M. T. , Cherisey H. de , Pernes J.
Published: April 2011

Hybrid weakness, segregation distortion, and partial sterility were observed in the offspring of Setaria italica (L.) P.B. following intraspecific crosses. These perturbations occurred in hybrids involving strains from two different geographical origins (China and Europe). However, the parental lines were morphologically similar. In this study, the F1 and F2 generations arising from crosses between Chinese and French varieties were analysed. We hypothesized that the genetic determination of weakness may be due to two complementary recessive genes. The segregation distortion for Adh isozyme could be due to a selection on one type of gamete. Partial sterility was also studied. No meiotic perturbation was observed in semisterile plants, but the tapetal cells were abnormal. The study of F2 generations suggests that the sterility is controlled by a few major genes.Key words: foxtail millet, intraspecific sterility, F2 weakness, segregation distortion, genetic differentiation.
Genetic variation in body weight of pink salmon (Oncorhynchus gorbuscha)
Authors: Beacham Terry D.
Published: April 2011

A factorial mating design was used in which three males were mated to either two or three females in each of the three sets of pink salmon (Oncorhynchus gorbuscha), and the juveniles were reared for 420 days after fry emergence. The parents used were derived from pink salmon that had been reared for one generation in captivity. Pink salmon families from this captive second generation were characterized by low growth rates, high within-family variance in juvenile weight, and low (< 0.11) heritability of juvenile weight. Maternal effects were estimated to account for about 20% of the observed variation in juvenile weight after the juveniles had been reared for 420 days. The observed results were postulated to be accounted for by variation in egg quality in the parental generation, presumably a consequence of an inadequate diet.Key words: development, genetics, growth, pink salmon, size.
Developmentally related changes in the production and expression of endo-β-1,4-glucanases in Aspergillus nidulans
Authors: Bagga P. S. , Sharma S. , Sandhu D. K.
Published: April 2011

The production and electrophoretic expression of endoglucanase(s) were compared in the wild-type and three developmental mutants of Aspergillus nidulans. In the wild type, the production of endoglucanase and its distribution in extracellular and intracellular fractions varied with the age of the culture and the yield was better in stable cultures (production of conidia and cleistothecia) as compared with shake cultures (vegetative hyphae only). Two developmental mutants, aco-T69 and aco-40, which lack the development of conidia and cleistothecia, produced low levels of endoglucanase enzymes as compared with the wild type grown under similar conditions. On the other hand, in aco-90, a mutant capable of producing cleistothecia but no conidia, endoglucanase production was better. The results indicate a correlation between cleistothecial development and endoglucanase level. The electrophoretic studies revealed the presence of three forms of endoglucanase, i.e., EGI, EGII, and EGIII. The first two were detectable in the wild type as well as in mutant strains when grown under various experimental conditions and at all the stages of development. However, the third form could be observed only during cleistothecial development, indicating that this isozyme is developmentally regulated.Key words: endoglucanases, development, Aspergillus nidulans.
Organisation of the mitochondrial genome from Atlantic salmon (Salmo salar)
Authors: Davidson William S. , Birt Tim P. , Green John M.
Published: April 2011

A restriction map of Atlantic salmon mitochondrial DNA was constructed. The smallest XbaI fragment of the salmon mitochondrial genome was cloned and subjected to partial DNA sequence analysis. This fragment contains the genes for ATPase 6 and cytochrome oxidase III. The putative organisation of the mitochondrial genome relative to the physical map is shown.Key words: salmonid, mitochondrial DNA, restriction map, sequence analysis.
Speciation in black flies
Authors: Rothfels Klaus
Published: April 2011

In many Simuliidae, patterns of spatial and temporal relationships among the most closely related species are more readily interpreted in terms of sympatric speciation than of allopatric speciation. Specific examples are (i) the allotriploid taxa in Gymnopais and other genera, (ii) the black fly faunas of geologically recent islands (Tahiti), and (iii) species in Prosimulium onychodactylum, a prototype of a continental multisibling species complex. A model of sympatric speciation is presented based on coadaptation of polymorphic sex chromosomes in pairs reinforced by progressive development of assortative mating. This model predicts that (i) populations should frequently exhibit sex-chromosome polymorphism, (ii) these sex-chromosome polymorphisms, and autosomal ones, should in some cases display linkage or association disequilibria, (iii) species pairs or complexes should be incurred that differ only in sex chromosomes and that share extensive ancestral autosomal polymorphisms, and (iv) such species should differ in their biology and perhaps their present-day distribution. Recent publications and observations are in accordance, in general, with predictions from the model. Genetic control, e.g., of diapause, larval developmental timing, and niche preference or ethology, could substitute as a basis of incipient cleavage. The evidence for sympatric speciation is purely inferential, but this is equally true for the allopatric interpretation, and in black flies the circumstantial evidence for prevalence of sympatric speciation appears more compelling. This is not to deny the efficacy of allopatry and founder effect in the origin of some species complexes.Key words: sympatric speciation, black fly, evolution.
The role of sex chromosomes in black fly evolution
Authors: Feraday R. M. , Leonhardt K. G. , Brockhouse C. L.
Published: April 2011

Sex chromosomes have been repeatedly implicated in the process of speciation of black flies and other nemotocerans. Arguments are presented here against the case that frequent differences between species in their sex chromosomes are based on (i) different average rates of differentiation of sex-linked and autosomal loci or (ii) the fact that the X and Y chromosomes are less numerous than autosomal chromosomes and so are more subject to the effects of drift and the random fixation of chromosome rearrangements. The argument is made that speciation in black flies and many other groups is an adaptive process and that differentiated sex-chromosome systems play a role in this process.Key words: black flies, sex chromosomes, speciation, evolution.
A cytological study of Simulium ruficorne (Diptera: Simuliidae) and its relationship to the S. ornatipes species complex
Authors: Bedo D. G.
Published: April 2011

Polytene chromosome banding patterns in Simulium ruficorne populations from two island and a continental African locality were analyzed and a standard map was prepared. Distinct arrays of fixed and polymorphic rearrangements characterize unique cytotypes in Santiago Island, Tenerife, and Ivory Coast populations. Sex-chromosome differentiation where an inversion linked to the male determiner marks a Y chromosome also occurs in the Santiago Island population. No sibling species can be defined at present because of the absence of sympatric population samples. Comparison of banding patterns between S. ruficorne and the S. ornatipes–neornatipes species complex in Australia and New Caledonia shows striking similarities. Banding homology is readily established with about 90% of polytene banding recognizable between the two standards. Three inversions are shared between the lineages, further emphasizing their similarity. These results provide independent corroboration of the close relationship between S. ruficorne and S. ornatipes established from conventional taxonomy. The validity of using shared inversions and common breakpoints in phylogenetic comparisons is discussed in relation to the possibility of confusing similar but distinct rearrangements and the inversion-generating role of transposable elements. The possibility of transposable element mediated identical, independently derived, rearrangements seems unlikely, but in all studies the confusion of phylogenies by similar inversions must be carefully considered.Key words: Simulium ruficorne, polytene chromosome, inversion phylogeny.
Tetrasomic inheritance and chromosome pairing behaviour in the naturally occurring autotetraploid Heuchera grossulariifolia (Saxifragaceae)
Authors: Wolf Paul G. , Soltis Pamela S. , Soltis Douglas E.
Published: April 2011

Inheritance patterns at four allozyme loci and chromosome pairing behaviour at diakinesis were examined in the naturally occurring autotetraploid Heuchera grossulariifolia. Segregation patterns for Tpi, Pgi, Pgm-2, and Lap deviated significantly from all possible disomic models. All patterns were consistent with tetrasomic inheritance of these marker loci. No chromatid segregation was detected electrophoretically. Meiotic chromosome configurations at diakinesis in 45 cells were compared with a previously published model to test for autopolyploid-like chromosome pairing. Using the observed chiasma frequencies, the frequency of quadrivalents was consistent with the expectations for an autotetraploid. We suggest that the low frequency of quadrivalents at diakinesis in Heuchera grossulariifolia is due to small chromosome size, which results in a low chiasma frequency.Key words: autopolyploidy, tetrasomic inheritance, chromosome pairing, isozyme genetics, Heuchera.
Biochemical evidence for the existence of a null allele at the leucine aminopeptidase-2 (Lap-2) locus in the oyster Crassostrea virginica (Gmelin)
Authors: Katoh Masaya , Foltz David W.
Published: April 2011

The existence of a null activity allele at the leucine aminopeptidase-2 (Lap-2) locus in the oyster Crassostrea virginica (Gmelin) was previously inferred from anomalous segregation patterns observed in offspring from pair crosses, and from the occurrence of individuals lacking Lap-2 bands on gels (presumed null homozygotes). The present research was done to determine whether leucine aminopeptidase specific activity was significantly reduced in oysters presumed from breeding experiments to be heterozygous for a Lap-2 null allele. Approximately thirty 4-month-old oysters from each of two crosses were analyzed. In each cross, LAP specific activity was significantly reduced (P < 0.001) in active/null heterozygotes, compared with full-sib oysters that were active/active heterozygotes. On average, active/null heterozygotes had 57% of the activity of the corresponding active/active heterozygotes.Key words: oysters, null allele, leucine aminopeptidase.
Effect of temperature on meiosis and fertility in Festuca mairei × Festuca arundinacea var. glaucescens
Authors: Kopyto Renata , Crane Charles F. , Sleper David A.
Published: April 2011

This study considered the effects of three continuous growth temperatures (14, 21, and 28 °C) on apparent genomic structure, apparent chromosome arm ratio, pollen abortion, and meiotic nonreduction in full-sib genotypes of Festuca mairei × F. arundinacea var. glaucescens. Ten genotypes were sampled for meiosis and 20 for pollen. The metaphase I (MI) data for each sampled combination of genotype, temperature, and replication were subjected to a bootstrap algorithm that calculated 95% confidence limits for each class of meiotic figure and for the ratio of ring bivalents to total bivalents, the total number of chromosomes in multivalents per cell, and the mean arm-binding frequency. These confidence limits permitted an evaluation of the significance of differences among genotypes, temperatures, and replications. The MI data were also subjected to two types of numerical models to investigate apparent genomic structure and mean effective chromosome arm ratio, i.e., pairing regulation and extent of chiasma interference across the centromere. The hybrids overall exhibited a 2:2 (AABB) genomic structure, but there were significant differences among genotypes in arm-binding frequency and frequencies of univalents, rod bivalents, and ring bivalents. Except for desynapsis and impaired chromosome contraction in one genotype at 28 °C, temperature had little effect; optimized genomic structure was slightly more 2:1:1 (like AABC) at 14 °C and chiasma interference increased slightly at 28 °C. One genotype was monosomic but meiotically normal. Pollen stainability was significantly depressed at 14 °C, while microspore micronuclei were more numerous. Pollen diameter was least at 21 °C regardless of degree of abortion.Key words: meiosis, meiotic modeling, temperature, pollen fertility, Festuca.
Linearity of offspring–parent regression in barley
Authors: Choo T. M.
Published: April 2011

A study was conducted to test the linearity of offspring–parent regression in barley. Forty-two F2 familes and 398 F∞ (i.e., doubled haploid) lines were derived from 7 × 7 diallel crosses. The F2 families, F∞ lines, and their parents were evaluated in hill plots with five replications. Three types of regression analysis (F2 family on midparent, F∞ family on midparent, and F∞ line on midparent) were carried out for grain yield, heading date, plant height, and number of spikes per hill. The linear regression mean square was significant in most cases, but the quadratic regression mean square was not significant in all cases. These results suggest that the true regression of offspring on midparent is linear, although dominance, additive × additive epistasis, and maternal effects were detected for the four traits of the same materials in previous studies.Key words: barley, Hordeum vulgare L., curvilinearity, regression, heritability.
The genetics of abnormal abdomen, incomplete abdomen, and bobbed in Drosophila buzzatii
Authors: Knibb W. R. , Barker J. S. F. , Oakeshott J. G.
Published: April 2011

Five stocks of Drosophila buzzatii with superficially similar abdominal disruptions including partial tergite and sternite loss were isolated by inbreeding. Three of the stocks have indistinguishable phenotypes, the inheritance of which is maternally influenced. This phenotype and its mode of inheritance bear similarities with those of Abnormal abdomen in D. melanogaster. The phenotype in the fourth stock is slightly different and is due to a single autosomal recessive gene, which we denote incomplete abdomen. In the fifth stock the trait is limited to females, and in appearance and mode of inheritance resembles bobbed in D. melanogaster. Furthermore, only in this stock are rDNA deletions evident. The combined frequencies of the three types of abdominal aberration were found to be around 1% in several samples from wild and laboratory populations of D. buzzatii.Key words: Drosophila, abnormal abdomen, ribosomal DNA, selection.
Comparisons of unweighted with weighted least squares methods of fitting a genetic model to a diallel cross
Authors: Tyson Hugh
Published: April 2011

Data on mean seed weight from the F1 of a complete 6 by 6 diallel cross with flax (Linum usitatissimum), grown in a randomized block design, were used to evaluate the benefits of weighted compared with unweighted least squares fitting of a genetical model for this type of cross. The model examines combining abilities and reciprocal differences. Matrix methods were employed in this study for weighted and unweighted least squares solutions. These methods accommodate rapid modification of appropriate models through changes in the corresponding design matrices, the use of various types of weight, the handling of missing data, the construction of orthogonal sets of parameters, the calculation of sums of squares accounted for by one or more of the parameters in the model, and the analysis of variance of the data. Weights used here were reciprocals of variances of diallel cell means, i.e., a variance reflecting variation among replicate mean values for a given cell. Weighted fitting with sequential elimination of redundant parameters in the original model extracted the minimum adequate model. Predicted values, generated from significant parameters in weighted or unweighted fittings of the model to overall F1 and parental means, were compared. Deliberate, increasing distortion of data in one replicate of the randomized block design showed that weighted fitting of the model distinguished consistent diallel data from distorted, giving predicted values reflecting the more reliable observations.Key words: diallels, weighted versus unweighted fitting.
Isozyme analysis, chromosome pairing, and fertility of Lycopersicon esculentum × Solanum lycopersicoides diploid backcross hybrids
Authors: Chetelat Roger T. , Rick Charles M. , DeVerna Joseph W.
Published: April 2011

The wild nightshade Solanum lycopersicoides possesses potentially valuable traits for tomato (Lycopersicon esculentum) improvement. Male sterility of the intergenic F1 hybrid and its stylar rejection of tomato pollen have until recently prevented introgression. In the work herein described, ovule fertility was detected in the F1 hybrid following pollinations with S. lycopersicoides. Pollinations of the F1 with L. pennellii derived bridging hybrids resulted in a BC1 population of 65 plants. BC2 seed was obtained from most BC1 individuals. Male fertility of the BC1 plants ranged from 0 to 66% acetocarmine-stainable pollen. Of the 43 plants scored, 41 were diploids (2n = 24) and 2 were aneuploids (2n = 25 and 2n = 26). Chromosome pairing of the BC1 at diakinesis and metaphase I averaged 11.1 bivalents per pollen mother cell. BC1 and BC2 plants were scored for 19 isozyme and morphological markers covering 10 of the 12 S. lycopersicoides chromosomes. Significant deviations from Mendelian segregation were observed for seven loci, with an excess of homozygotes (+/+) in all cases. Wa, which controls the white anther trait of S. lycopersicoides, was mapped to within 15 centiMorgans (cM) of Got-4, while Mdh-4 was closely linked to Pgi-1 (<2 cM). Plants heterozygous for the S. lycopersicoides allele (+/s) at Dia-2, Skdh-1, Wa, and Aco-1 showed significantly lower pollen stainability than homozygotes (+/+). Skdh-1 and Got-3 heterozygotes had less chromosome pairing at meiosis than homozygotes. These hybrids will permit the introgression of novel traits from S. lycopersicoides into tomato.Key words: tomato, segregation, linkage mapping, quantitative trait loci, intergeneric hybridization.
Genome relationship between Thinopyrum bessarabicum and T. elongatum: revisited
Authors: Wang Richard R.-C. , Hsiao Catherine
Published: April 2011

New meiotic pairing data on triploids and amphidiploids derived from the diploid hybrids between Thinopyrum bessarabicum (Savul. &Rayss) A. Love (2n = 14; JJ) and T. elongatum (Host) D. R. Dewey (2n = 14; JeJe) are presented, which support the close relationship between the genomes of these two species. Three triploids having the JJJe genome constitution were analyzed. Two (both derived from backcrossing amphidiploids of T. bessarabicum × T. elongatum with T. bessarabicum) had an averaged metaphase I pairing pattern of 3.89 I + 0.96 rod II + 3.30 ring II + 2.75 III + 0.06 chain IV + 0.01 ring IV in spikes from a field-grown plant and two greenhouse-grown plants sampled in early spring. Another, which was the F1 triploid progeny of T. bessarabicum × T. elongatum as the result of fertilization of an unreduced megaspore (JJ) by a reduced microspore (Je), had 3.62 I + 2.16 rod II + 1.34 ring II + 3.28 III + 0.10 chain IV + 0.02 ring IV in spikes of a field-grown plant. The first triploid plant had an averaged metaphase I pairing of 4.60 I + 0.74 rod II + 4.03 ring II + 2.19 III + 0.06 chain IV + 0.01 V in spikes sampled in a warmer greenhouse. The amphidiploids exhibited variable pairing patterns with a wide range of multivalent frequency. It is interpreted that the J and Je genomes are essentially homologous, with difference due mainly to two translocations. A genetic mechanism for a "bivalentization" appeared to be present in most, if not all, amphidiploids and the triploids derived from them. Meiotic pairing patterns reported here for triploid hybrids T. junceiforme (Love &Love) A. Love (2n = 28; JJJeJe) × T. bessarabicum, its reciprocal, and T. bessarabicum × T. scirpeum (K. Presl) D. R. Dewey (2n = 28; JeJeJeJe) also support the conclusion that J and Je genomes are homologous. The network of meiotic data supports the conclusion that J and Je are two versions of the same basic genome.Key words: genome, meiosis, hybrid, amphiploid, bivalent formation.
Evidence on wheat for gene-for-gene relationship between formae speciales of Erysiphe graminis and genera of gramineous plants
Authors: Tosa Y.
Published: April 2011

The avirulence of Erysiphe graminis f.sp. agropyri, Ak-1, on Triticum aestivum 'Norin 4' is conditioned by two major genes. When an F2 population derived from the cross between 'Norin 4' and a susceptible cultivar was inoculated with F1 hybrids between Ak-1 and E. graminis f.sp. tritici, Tk-1, resistant and susceptible seedlings segregated in either a 15:1 or a 3:1 ratio. The F1 cultures producing a 15:1 segregation and those producing a 3:1 segregation occurred in a ratio of 1:2. These results suggested that the resistance of 'Norin 4' to Ak-1 is conditioned by two major genes corresponding to the two avirulence genes. 'Norin 4' carries a resistance gene, Pm10, which operates on an F1 hybrid culture, Gw-34, but not on another F1 culture, Gw-180. Triticum compactum 'No. 44' carries another resistance gene, Pm11, which operates on Gw-180 but not on Gw-34. When these cultivars were inoculated with F2 cultures derived from the cross Gw-34 × Gw-180, avirulent and virulent cultures segregated in a 1:1 ratio. The segregation patterns on the two cultivars were independent. These results indicated that, for each of Pm10 and Pm11, there is one corresponding avirulence gene. These genes were considered to be derived from the wheatgrass mildew fungus, Ak-1. The two series of experiments strongly suggest that the forma specialis – genus specificity in the E. graminis – gramineous plant system follows the gene-for-gene theory.Key words: powdery mildew, Erysiphe graminis, wheat, wheatgrass.
The mode of inheritance of a type of dwarfism in common wheat
Authors: Knott D. R.
Published: April 2011

A type of dwarfism found in crosses involving the wheat (Triticum aestivum L.) cultivar Webster and a stem rust (Puccinia graminis tritici Erik. &Henn.) susceptible line, LMPG, proved to be due to a dominant gene from cv. Webster and a recessive gene from LMPG. The dominant gene is closely linked to the gene Sr30, which conditions stem rust resistance in cv. Webster and is on chromosome 5D. The dwarf plants have short, dark green, stiff leaves and rarely develop more than two leaves before dying.Key words: dwarfism, Triticum aestivum, Puccinia graminis tritici, stem rust.
The timing of chromosome elimination in hexaploid wheat × maize crosses
Authors: Laurie D. A. , Bennett M. D.
Published: April 2011

Early seed development in crosses between the hexaploid wheat genotype 'Chinese Spring' and the maize genotype 'Seneca 60' was studied to determine the timing of elimination of the maize chromosomes. Elimination of one or more maize chromosomes occurred in about 70% of zygotic mitoses. Metaphase nuclei from two-celled embryos had 5 to 10 maize chromosomes, most of which were lost during the second cell division. About half the metaphase nuclei from four-celled embryos had no maize chromosomes, and the remainder had one to five. Anaphase or telophase nuclei from four-celled embryos showed no maize chromosomes in about half the cells and one or more pairs of lagging maize daughter chromosomes in the remainder. No maize chromosomes were seen in metaphase preparations from embryos with eight or more cells. These data strongly suggest that all maize chromosomes were lost during the first three cell-division cycles in most embryos. All embryos with four or more cells had micronuclei, showing that embryo development was dependent on fertilization. The only primary endosperm metaphase obtained in the experiment had 42 wheat and 10 maize chromosomes and the presence of micronuclei in most developing endosperms showed that at least 85% were of hybrid origin. Few endosperm nuclei were formed in comparison with self-pollinated 'Chinese Spring' caryopses, and many were abnormal. The implications of the results for wheat haploid production and gene transfer from maize to wheat are discussed.Key words: wheat, maize, wide hibridization, chromosome elimination.
Inheritance of male fertility restoration and allelism of restorer genes for the Polima cytoplasmic male sterility system in oilseed rape
Authors: Fang G. H. , McVetty P. B. E.
Published: April 2011

The inheritance of male fertility restoration for the pol cytoplasmic male sterility (CMS) system in summer rape (Brassica napus L.) was determined. Male fertility:sterility segregation ratios observed in F2 and backcross generations derived from crosses and backcrosses between two pol CMS A lines and the male fertility restorer gene(s) sources Italy and UM2353 were used in this study. Italy and UM2353 were found to possess a single Mendelian dominant gene with high male fertility restoration capabilities for the pol CMS system. Tests for allelism of the restorer genes were also conducted using male fertility:sterility segregation ratios observed in F3 families derived from crosses between F1 plants containing genes for male fertility restoration from the Italy and UM2353 restorer gene sources. The male fertility restorer gene from Italy (designated Rfp1) was found to be different (i.e., nonallelic) from the restorer gene possessed by UM2353 (designated Rfp2).Key words: Brassica napus L., oilseed rape, male fertility restoration, pol cytoplasmic male sterility.
C-banding in meiosis: an approach to the study of wheat and rye genome interactions in triticale
Authors: Galindo C. , Jouve N.
Published: April 2011

Meiosis in four primary hexaploid triticale lines, in their component two tetraploid wheat and two rye parents, and in the hybrids obtained by crossing within each ploidic level was studied using Giemsa banding. The individual chromosomes were identified and their meiotic behaviour at first metaphase was analyzed in each line. In each new triticale line, the level of pairing for wheat chromosomes was moderately reduced and for rye chromosomes was very significantly reduced, in comparison with that of the wheat and rye parents used to synthesize it. The pairing intensity observed suggests the presence of a strong negative intergenomic interaction between the rye and wheat genomes in triticale, irrespective of whether the rye is in a homozygous or heterozygous genotypic condition. The homozygosity or heterozygosity in the wheat constituent does not appear to effect the behaviour of the rye chromosomes in triticale.Key words: triticale, meiosis, C-banding, heterosis.
Restriction fragment length polymorphism in Oryza sativa L.
Authors: Wang Z. Y. , Tanksley S. D.
Published: April 2011

Seventy varieties of rice, representing the breadth of the species Oryza sativa, were assayed with 10 rice restriction fragment length polymorphism markers. Polymorphism was detected for all probes and 58 of 70 varieties tested could be uniquely distinguished from one another by combining all probe – enzyme combinations. Within-population variation, usually in the form of homozygous variant alleles, was found for 26% of the varieties. Based on genetic distance calculations, the ratio of the genetic variation between versus within rice varieties was estimated to be approximately 12:1. A restriction fragment length polymorphism based dendrogram has also been constructed depicting genetic distances among rice varieties.Key words: Oryza sativa, rice, polymorphism, genetic variation, restriction fragment length polymorphism.
Isolation of Ht genome chromosome additions from polyploid Elymus trachycaulus (StStHtHt) into common wheat (Triticum aestivum)
Authors: Morris Kay L. D. , Raupp W. John , Gill Bikram S.
Published: April 2011

A combination of cytological and biochemical methods were used to isolate and identify six Triticum aestivum 'Chinese Spring' – Elymus trachycaulus (= Agropyron trachycaulum, 2n = 28, genomes StStHtHt) Ht genome disomic and ditelosomic chromosome addition lines. Protein and morphological markers indicated that Elymus chromosomes 1Ht, 1Htp, 5Ht, 6Ht, 7Ht, and 7Htp have been added to the wheat genome. Two alloplasmic addition lines, 1Ht and 1Htp, were determined to have favorable nucleocytoplasmic interactions by the presence of vegetative vigor and fertility restoration. The gene(s) for vigor and fertility restoration were located on the short arm of 1Ht. The Elymus chromosomes of each line were found to affect plant morphology and fertility, with the exception of disomic addition 6Ht, which appeared similar to 'Chinese Spring'. Phenotypic differences between each line may be attributed to the expression of genes from specific Elymus chromosomes, the cumulative dosage of homoeoalleles, or nucleocytoplasmic interactions. These morphological traits, in combination with biochemical markers, provide evidence of the gene synteny relationships between the Elymus and Triticum species. Knowledge of the homoeologous relationships among wheat and Elymus chromosomes may be useful for the eventual transfer of disease-resistance genes from Elymus to wheat.Key words: Elymus, wheat, addition line, polyploidy.
A tandem fusion in the fish Gobius paganellus (Gobiidae, Perciformes), a karyotypically polymorphic species
Authors: Amores A. , Giles V. , Thode G. , Alvarez M. C.
Published: April 2011

In 1 of 384 cytologically analyzed specimens of the polymorphic fish Gobius paganellus a new type of chromosome was observed. On the basis of the conventional and C-banding analysis, centromeric–telomeric fusion, involving the heterochromatin, of two different acrocentrics is suggested to be responsible for the observation.Key words: Gobiidae, tandem fusion, heterochromatin.
Chromosomal organization of the amplified esterase B1 gene in organophosphate-resistant Culex pipiens quinquefasciatus Say (Diptera, Culicidae)
Authors: Nance Eric , Heyse Denise , Britton-Davidian Janice , Pasteur Nicole
Published: April 2011

In Culex pipiens quinquefasciatus from California, high resistance to organophosphorus insecticides is due to an increased production of the detoxifying esterase B1 resulting from a 250-fold amplification of the structural gene. The chromosomal organization of this amplified gene was studied by in situ hybridization techniques. Esterase B1 gene copies were found to be clustered on a single chromosome, tentatively identified as chromosome II.Key words: gene amplification, insecticide resistance, chromosomes, in situ hybridization, mosquitoes.
Adding the heterochromatic YL arm to an X chromosome reduces reproductive fitnesses in Drosophila melanogaster: implications for the evolution of rDNA, heterochromatin, and reproductive isolation
Authors: Frankham R.
Published: April 2011

For X–Y exchange to be of importance in the coevolution of X and Y rDNA, there must be a mechanism to maintain cytologically normal X chromosomes in the face of continual infusions of X.YL chromosomes produced by X–Y exchanges. Replicated populations were founded with different frequencies of isogenic X and X.YL chromosomes. The X.YL chromosome declined in frequency over time in all lines. Relative fitnesses, estimated from chromosome frequency trajectories, were 0.40, 1.01, and 1.0 for X.YL/X.YL, X.YL/X, and X/X females and 0.75 and 1.0 for X.YL/Y and X/Y males, respectively. The equilibrium frequency for the X.YL chromosome due to the balance between X–Y exchange and selection was predicted to be 4–16 × 10−4. The results strengthen the evidence for the involvement of X–Y exchange in the coevolution of X and Y rDNA arrays. Conditions for the evolution of reproductive isolation by sex-chromosome translocation are much less probable than previously supposed since the X.YL translocation chromosome is at a selective disadvantage to cytologically normal X chromosomes. Additional heterochromatin was not neutral but was only deleterious beyond a threshold, as one dose of the heterochromatic XL arm did not reduce female reproductive fitness, but two doses did.Key words: Drosophila, rRNA, heterochromatin, fitness, speciation.
Isozyme markers in rice: genetic analysis and linkage relationships
Authors: Pham J. L. , Glaszmann J. C. , Sano R. , Barbier P. , Ghesquière A. , Second G.
Published: April 2011

Segregations of rice isozymes made it possible to ascertain the genetic control of 13 enzymes by 30 loci. In addition to numerous cases of independence, several linkages were observed. Got-2 and Enp-1 were localized on chromosome 3 and a linkage group composed of Pox-3, Pox-4, and Est-1 was identified. Inconsistencies of recombination rates between linked loci among different crosses were noted. Several cases of distorted segregations and pseudolinkages were recorded. The relationships between these results and the study of genome organization in cultivated rice are discussed.Key words: Oryza, isozyme, genetic analysis, segregation distortion, linkage.
Morphology and cytology of induced hexaploid of Elymus canadensis and its backcross derivatives—pentaploids, tetrasomics, and trisomics
Authors: Park C. H. , Walton P. D.
Published: April 2011

A tissue culture induced octoploid of Elymus canadensis was crossed with two accessions ("Canada" and "Montana") of the same tetraploid species to produce hexaploids. Hexaploid (2n = 42) and near-hexaploid progeny (2n = 43 or 40) obtained from the crosses were morphologically vigorous but either partially or completely sterile. Mean frequencies of univalents and trivalents in the hexaploid pollen mother cells at metaphase I were 3 or 4 and 2 to 4 per cell, respectively. In view of the genomic constitution of the parents, the hexaploids were expected to be genomically double triploids. Nevertheless, bivalents, averaging 14–17 per cell, predominated. This might be due to the failure of chiasma formation and chiasma terminalization. One hexaploid plant was backcrossed to the tetraploid. The progeny consisted of one pentaploid and five aneuploids including one tetrasomic and two trisomics. All of the progeny from the backcrosses were less vigorous than aneuploids at the near-hexaploid level. Tetrasomics and trisomics had stainable pollen and a 17–19% seed set. Two trisomic plants were morphologically indistinguishable from each other and predominantly showed chromosome pairing of 14 II + 1 I. This indicates failure of chiasma formation and chiasma terminalization between homologous chromosomes.Key words: Elymus canadensis, hexaploids, tetrasomics, trisomics, meiosis.
Cytological evidence supporting a procedure for directing and enhancing pairing between maize and Tripsacum
Authors: Kindiger B. , Beckett J. B.
Published: April 2011

A homozygous B–A translocation, TB-9Sb, was utilized in a maize × Tripsacum dactyloides backcrossing procedure in an attempt to enhance and direct pairing between homoeologous regions of the maize and Tripsacum genomes. Cytological observations of root tip preparations and microsporocyte specimens isolated a 38-chromosome BC2 hybrid with one set of chromosomes from Tripsacum and two sets from maize, but which lacked a portion of the short arm of one maize chromosome 9. Because the distal 0.6 of the normal maize chromosome lacked a homologous pairing partner, it was available for pairing and presumably crossing over with a homoeologous Tripsacum chromosome, if sufficient homology existed. The frequent occurrence of what appeared to be a particular trivalent at metaphase I supports the conclusion that B–A translocations are effective tools for moving particular Tripsacum chromosomes and crossover derivatives into maize. A backcrossing program involving a large number of B–A translocations should effectively incorporate much of the Tripsacum genome into maize.Key words: B–A translocations, cytogenetics, hybridization, introgression, corn breeding.
Transfer to hexaploid wheat of linked genes for adult-plant leaf rust and seedling stem rust resistance from an amphiploid of Aegilops speltoides × Triticum monococcum
Authors: Kerber E. R. , Dyck P. L.
Published: April 2011

A partially dominant gene for adult-plant leaf rust resistance together with a linked, partially dominant gene for stem rust resistance were transferred to the hexaploid wheat cultivar 'Marquis' from an amphiploid of Aegilops speltoides × Triticum monococcum by direct crossing and backcrossing. Pathological evidence indicated that the alien resistance genes were derived from Ae. speltoides. Differential transmission of the resistance genes through the male gametes occurred in hexaploid hybrids involving the resistant 'Marquis' stock and resulted in distorted segregation ratios. In heterozygotes, pairing between the chromosome arm with the alien segment and the corresponding arm of the normal wheat chromosome was greatly reduced. The apparent close linkage between the two resistance genes, 3 ± 1.07 crossover units, was misleading because of this decrease in pairing in the presence of the 5B diploidizing mechanism. The newly identified gene for adult-plant leaf rust resistance, located on chromosome 2B, is different from adult-plant resistance genes Lr12, Lr13, and Lr22 and from that in the hexaploid accession PI250413; it has been designated Lr35. It is not known whether the newly transferred gene for stem rust resistance differs from Sr32, also derived from Ae. speltoides and located on chromosomes 2B.Key words: hexaploid, Triticum, Aegilops, aneuploid, Puccinia graminis, Puccinia recondita.
Variation in the ribosomal DNA repeat unit within single-oospore isolates of the genus Pythium
Authors: Martin Frank N.
Published: April 2011

Restriction analyses of the DNA repeat unit coding for the production of 5.8S, 17S, and 26S ribosomal RNA (rDNA) isolated from several different Pythium species revealed polymorphic forms within a single-oospore isolate. Restriction mapping of cloned rDNA from Pythium paroecandrum indicated that two major forms were present in approximately equal ratios (A and B, 11.6 and 11.9 kb in size, respectively), which differed in the nontranscribed spacer region for numbers and locations of restriction sites for HaeIII, SalI, and KpnI and an insertion–deletion adjacent to the 3′ end of the 26S RNA coding region. The insertion–deletion makes form B 0.27 kb larger than form A. An additional insertion–deletion in both forms of approximately 60 bp in the same region makes a total of four polymorphic types in the isolate investigated. Similar results also were obtained for Pythium spinosum following restriction digestion of purified rDNA. A survey of other Pythium species indicates that the presence of polymorphic forms in the same isolate, variation in the number or polymorphic forms in different isolates of the same species, and insertions–deletions in multiples of approximately 60 bp adjacent to the 3′ end of the 26S coding region are common in the genus.Key words: Pythium spp., rDNA.
Species-specific in situ hybridization of Hordeum bulbosum chromosomes
Authors: Xu Jie , Procunier J. D. , Kasha K. J.
Published: April 2011

BamHI-digested genomic DNA from three barley cultivars and four Hordeum bulbosum accessions was hybridized in Southern blots with two rye (Secale cereale) repetitive DNA sequences, clones pSc119.1 and pSc119.2. Both clones showed exclusive hybridization to H. bulbosum DNA. The pSc119.1 probe exhibited two strong and two weak bands on Southern blots of all four H. bulbosum accessions (two diploid and two autotetraploid). The two diploid H. bulbosum accessions exhibited a five-step ladder of DNA fragments with a periodicity of about 600 bp in Southern blots with pSc119.2. The band pattern of the two autotetraploids differed from the diploids as well as from each other. In in situ hybridizations with biotin-labelled probes, pSc119.1 hybridized predominantly to centromere regions of H. bulbosum chromosomes, with some interstitial sites, whereas pSc119.2 hybridized predominantly to a few telomeric sites. Three of the accessions exhibited one telomeric site on up to 6 chromosomes, while one accession had telomeric sites on up to 12 chromosomes, with one chromosome sometimes exhibiting hybridization at both telomeres. pSc119.2 hybridization to the satellite of H. bulbosum chromosome 6 revealed that two of the four accessions were heterozygous for the presence of DNA hybridization with this probe. No in situ hybridization was revealed on barley chromosomes with either probe. As discussed, these rye repetitive DNA probes could be used to detect the transfer of segments of H. bulbosum chromosomes, or from a number of other species, into barley.Key words: Southern blot, biotin labelling, barley, rye, repetitive DNA.
On the nature of meiotic associations involving heterochromatic ends in grasshoppers
Authors: Santos J. L. , Esteban M. R.
Published: April 2011

The nature of "terminal" associations between three heterochromatic short (S) bivalents of Schistocerca gregaria, and a heterochromatic and a euchromatic segment of an M7 bivalent of Euchorthippus pulvinatus has been investigated using a silver-staining technique that visualizes a core-like structure that extends through each homologous chromosome and forms cross-shaped configurations at chiasmata. It is concluded that most of these associations, about 99% in Schistocerca and 98% in Euchorthippus, are chiasmate. The problems concerning the nature of terminal associations involving heterochromatic ends in grasshoppers are discussed.Key words: silver-stained cores, chiasma, terminal association, heterochromatin, grasshoppers.
Variation in the heterochromatin and nucleolar organizing regions of Allium subvillosum L. (Liliaceae)
Authors: Jamilena M. , Rejón C. Ruiz , Rejón M. Ruiz
Published: April 2011

Two kinds of polymorphisms have been found in a wild population of Allium subvillosum L. (Liliaceae): (i) extra C-bands and supernumerary chromosome segments on three chromosome pairs and (ii) the absence of the nucleolar organizing region (NOR) in one member of the third chromosome pair (there are two other NOR-bearing chromosome pairs in the karyotype of this species). The fluorescence pattern (chromomycin A3 (CMA3) positive and 4,6-diamidino-2-phenylindole (DAPI) negative) of the extra heterochromatin is similar to that of the standard. The absence of the NOR on the third chromosome pair is related to a variation in the NOR-associated heterochromatin (the chromosomes with no NOR do not have the distal C-band from the satellite, but the proximal C-band may be present). The characteristics of the karyotype of this species, its heterochromatin distribution, and the possible mechanisms by which the polymorphisms may originate are discussed.Key words: Allium, supernumerary segments, heterochromatin, polymorphisms, nucleolar organizing regions.
Cytogenetics of decaploid Agropyron elongatum (Elytrigia elongata) (2n = 70). I. Frequency of decavalent formation
Authors: Muramatsu Mikio
Published: April 2011

The multivalents that appeared in the decaploid strain of Agropyron elongatum (2n = 10x = 70), a relative of wheat, ranged from trivalent to decavalent. Few univalents occurred. The metaphase I chromosome association in 12 cells where all configurations could clearly be identified averaged 0.42 ring X + 0.17 chain X + 0.42 ring VIII + 0.17 branched VIII + 0.25 chain VIII + 0.17 chain VII + 1.17 ring VI + 0.33 branched VI + 0.5 chain VI + 1.67 ring IV + 0.42 branched IV + 0.58 chain IV + 0.08 branched III + 0.17 chain III + 12.58 ring II + 3.75 open II + 0.25 I. The occurrence of decavalents, up to two in one cell, and of a cell with five multivalents, each of which involved more than five chromosomes, and many multivalents of ring shape indicated that the strain is autodecaploid.The chromosome associations of each cell can be interpreted as seven groups of 10 homologous chromosomes. The high frequency of bivalents indicated a tendency toward reduced multivalent formation, for which an explanation is suggested.Key words: Agropyron elongatum, meiotic configuration, decaploid, multivalent.
Intergeneric hybrids between Thinopyrum and Psathyrostachys (Triticeae)
Authors: Wang Richard R.-C.
Published: April 2011

Intergeneric hybrids were synthesized for the first time from the diploid crosses Thinopyrum elongatum (JeJe) × Psathyrostachys juncea (NjNj), T. elongatum × P. fragilis (NfNf), T. bessarabicum (JbJb) × P. huashanica (NhNh), and T. bessarabicum × P. juncea, as well as from a cross between the amphidiploid of T. bessarabicum × T. elongatum (JbJbJeJe) and P. juncea. Spikes of these hybrids are morphologically intermediate between those of the parental species. Double spikelets occurred occasionally at central nodes of the spikes. Glaucous blue leaves appeared in the F1 only in the cross T. bessarabicum × P. huashanica, suggesting that the gene(s) for glaucous blue leaves in T. bessarabicum is (are) recessive to a gene(s) for green leaves in P. juncea but is (are) dominant to that for yellowish green leaves in P. huashanica. Meiotic pairing at metaphase I in these diploid (JN) and triploid (JJN) hybrids revealed a very low level of homology between the basic J and N genome. Therefore, the J and N genomes are nonhomologous and justifiably represented by different genome symbols. The triploid hybrids exhibited a pattern of chromosome associations that substantiated the earlier conclusion that the genomes in T. bessarabicum and T. elongatum are two versions of a basic genome (J). These hybrids will be useful in genome analysis, forming new Leymus species with the J and N genomes and broadening the diversity in the genus Pascopyrum with the SHJN genomes.Key words: hybrid, Thinopyrum, Psathyrostachys, genome.
Synaptonemal complex spreading in Allium cepa and Allium fistulosum. III. The F1 hybrid
Authors: Albini S. M. , Jones G. H.
Published: April 2011

Synaptonemal complexes (SCs) were analysed, by surface spreading, in the F1 hybrid between Allium cepa and Allium fistulosum. These closely related species have a similar karyomorphology, but the A. cepa genome has 27% more DNA than A. fistulosum. At metaphase I, in the hybrid, heteromorphic bivalents were observed, and the pollen mother cell chiasma frequency in the F1 hybrid was reduced when compared with the parents. Synapsis was incomplete and disturbed to some extent in all the prophase I nuclei observed. The reduced level of synapsis at late zygotene – mid pachytene in the hybrid (mean percent homoeologous synapsis is 60%) corresponds to the percent reduction in chiasma frequency. It is suggested that failure of synapsis is the main cause of reduction of chiasma frequency in the F1 hybrid. The chiasma distribution in the hybrid is most similar to that of the A. cepa parent. Although some proximal chiasmata were observed (10% of total), none of the bivalents observed had only proximally localised chiasmata as found in the A. fistulosum parent. In the F1 hybrid, synapsis of the centromeric regions of the bivalents was invariably disturbed throughout prophase I. It is suggested that there are major DNA differences in these regions preventing regular synapsis or progression of synapsis and possibly proximal chiasma formation. Nonhomoeologous synapsis occurred within axes, giving foldback SCs, and between axes, resulting in multivalent formation. It is proposed that disturbance of synapsis is due to DNA differences. There is no indication of any rearrangement or adjustment of synapsis during prophase I either to give perfectly synapsed bivalents or to resolve multivalents into bivalents.Key words: synaptonemal complex, Allium, incomplete pairing, chiasma, nonhomologous pairing, DNA content.