bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromosome pairing failure in an intersectional amphiploid of Bromus altissimus × B. arvensis
Authors: Armstrong K. C.
Published: November 2014

An intersectional F1 hybrid between Bromus arvensis and B. altissimus was made with the aid of embryo culture. The hybrid nature of the F1 and the amphiploid were confirmed by karyotyping root-tip cells. Following Giemsa banding, the chromosomes of B. arvensis stained darker than those of B. altissimus. Very little chromosome pairing was observed in the F1 hybrid (11.60 I + 1.08 II + 0.10 III). Chromosome pairing in the amphiploid (2n = 28) varied from almost complete pairing to very little pairing in different samples. The chromosome pairing indicated that very little homology exists between the genomes of B. altissimus and B. arvensis. Pairing failure in the amphiploid may result from the action of pairing control genes which are strong enough to prevent homologous pairing but which are variable in expression because of a sensitivity to endogenous and exogenous factors.Key words: Bromus, amphiploid, chromosome pairing, differential staining.
Inheritance of self-incompatibility in rutabaga (Brassica napus L. ssp. rapifera (Metzg.) Sinsk.)
Authors: Ayotte R. , Harney P. M. , Christie B. R.
Published: November 2014

Self-incompatible and self-compatible lines of Brassica napus L. were crossed and the compatibility status of the F1 and F2 progeny assessed. Compatibility was established by measuring silique and seed set and by microscopic examination of self-pollen behaviour on the stigma and within the style of flowers. Microscopic evaluation was found to be unreliable in determining whether seed set would occur on a plant following self-pollination. The F1 data could not be interpreted because turnip mosaic virus in the greenhouse killed many plants and may have affected the compatibility reaction of the rest. Silique set data for the F2 showed one line (Z) segregated 3:1 self-incompatible to self-compatible, indicating only one locus involved. The 10:6 self-compatible to self-incompatible ratio, obtained for a second line (R) can be explained in the same manner if a dominant modifier (M), which interacts only with S-allele heteozygotes, is also present.Key words: rutabaga, Brassica napus, self-incompatibility, S alleles, genetic.
Inheritance and linkage relationships of gliadin proteins and glume color in durum wheat
Authors: Leisle D. , Kovacs M. I. , Howes N.
Published: November 2014

Reciprocal backcross lines of two crosses were used to study the inheritance and linkage relationships of gliadin bands 42 and 45, as determined by polyacrylimide gel electrophoresis, and glume color in durum wheat (Triticum turgidum L.). Glume color was monogenically inherited, with partial dominance of buff color. Gliadin bands 42 and 45 were each controlled by one gene, located 7.87 ± 2.39 and 10.32 ± 2.44 crossover units, respectively, from the gene for glume color. Gliadin band 42 was always associated with bands 31 and 35. Gluten strength, as determined by sodium dodecyl sulphate sedimentation test, related closely to the genetics of gliadin bands 42 and 45, with the heterozygous band 42/45 types falling midway between the weak gluten homozygous band 42 and strong gluten homozygous band 45 types. Gluten strength data indicated that at least one additional gene, independent of those controlling these gliadins, is also involved.Key words: Triticum, gliadin, glume colour, linkage.
Genome analysis of Thinopyrum bessarabicum and T. elongatum
Authors: Wang Richard R. -C.
Published: November 2014

Thinopyrum bessarabicum (2n = 14; JJ) was successfully crossed with T. elongatum (2n = 14; EE) but the reciprocal cross failed. Five of the 19 F1 plants headed in a greenhouse without being vernalized. Spikes of F1 hybrids were intermediate to those of the parents for number of florets per spike, glume length, and the first rachis internode length, but similar to those of T. bessarabicum and T. elongatum for spike length and number of spikelets per spike, respectively. Karyotypes of mitotic chromosomes in the parental species revealed that three of the seven chromosomes in the J and E genomes were similar in length and arm ratio. Meiosis in the F1 hybrids substantiated the conclusion from karyotype analysis that the other four chromosomes had undergone some structural rearrangements such as reciprocal translocation. Metaphase-I cells in hybrid plants averaged 2.68 I, 4.68 II, 0.27 III, 0.27 IV, and 0.01 V. Although 10% of the pollen grains were stainable with I2–KI, F1 plants of T. bessarabicum × T. elongatum did not set seed upon selfing. It is concluded that the J and E genomes are so closely related that the E genome designation should be changed to Je. The evidence reported here supports the transfer of Lophopyrum elongatum to the genus Thinopyrum. Wheat breeders should be able to utilize the genes in T. bessarabicum as readily as those in T. elongatum.Key words: Genome, mitosis, meiosis, karyotype, idiogram, hybrid.
Cytogenetics of some diploid species of the Solanum nigrum complex
Authors: Ganapathi A. , Rao G. R.
Published: November 2014

A few species of the Solanum nigrum L. complex were selected to determine the relationship among them as revealed by crossability studies and chromosome-pairing behaviour of their hybrids. Cytomorphology of S. americanum Mill., Indian diploid S. nigrum L., S. nodiflorum Jacq., and S. douglasii Dun. was studied. Crosses between S. douglasii and other species were compatible if S. douglasii was used as the male parent. The isolation of S. americanum, Indian diploid S. nigrum, and S. nodiflorum from S. douglasii by hybrid breakdown is most likely due to differences between the parents in chromosome structure as well as gene content. Although the F1 hybrids were normal and fertile, the F2 plants showed meiotic breakdown and reduced fertility. It is suspected that S. nodiflorum, S. nigrum (2x), and S. americanum represent a single biological species, S. americanum. The distinction of S. douglasii as a separate species is justified. Key words: Solanum, diploid, hybrids.
Mise en évidence d'une liaison génétique entre un gène de nanisme et des marqueurs enzymatiques chez le mil pénicillaire (Pennisetum glaucum L.)
Authors: Tostain Serge
Published: November 2014

The genetic linkage relations between the dwarfing (D2, d2) and seven enzymic marker genes were evaluated in three crosses between semidwarf and normal inbred lines of pearl millet (Pennisetum glaucum L.). The seven genes code for the following isoenzymes: alcohol dehydrogenase (Adh A), esterase (Est A), malate dehydrogenase (Mdh D) cathodic peroxydase (Pec A), phosphoglucoisomerase (Pgi A), phospholucomutase (Pgm A), and shikimate dehydrogenase (Skdh A). Semidwarf and normal plants were identified by a discriminant analysis based on 16 morphological height components. Mendelian segregations have been observed for all eight genes. Linkage was shown between Pgi A and Pgm A (4 ± 4 centimorgans (cM)), between Skdh A and Adh A (11 ± 7 cM), between D2 and Skdh A (9 ± 5 cM) and between D2 and Adh A (17 ± 8 cM). The latter three genes are linked in the following order: Adh A – 11 cM – Skdh A – 9 cM – D2. The linkage between the recessive dwarfing gene (d2) and the codominant Skdh A alleles will help in the creation of isogenic semidwarf lines of cultivars. It is highly probable that the D2d2 genotype could be separated from the D2D2 genotype.Key words: isozymes, linkage groups, early selection.
DNA content in Tradescantia
Authors: Martínez Arturo , Ginzo Héctor D.
Published: November 2014

There is a wide variation in the nuclear DNA content and chromosome size between the species belonging to the T. crassifolia and T. virginiana alliances (all the species but one are native to Central and North America). Also the DNA content per genome decreases when the ploidy level increases within the same specific polyploid complex with three ploidy levels (2x, 4x, and 6x). In contrast, no variation was found in the DNA content per genome between different ploidy levels in the T. fluminensis alliance (all the species are native to South America) where they range from 6x to 22x. Since all the species described here are perennials with various life forms, it was possible to analyze the relationship between the DNA content and their vegetative adaptation to the environment. The more specialized species (geophytes and hemicryptophytes) have a higher amount of DNA than the chamaephytes adapted to live in relatively more mesic regions. In the species living in Central and North America there is a positive correlation between the increase in DNA content and the latitude of their native regions.Key words: Tradescantia, DNA content, geographical distribution, life forms, polyploidy.
Neomycin is more efficient than streptomycin in suppressing frameshift mutations
Authors: Phoenix Pauline , Gravel Michel , Herrington Muriel B. , Brakier-Gingras Léa
Published: November 2014

The effects of streptomycin and neomycin on the phenotypic suppression of frameshift mutations in the lacZ gene of Escherichia coli and on the efficiency of suppression of amber mutations in T4 phage by the informational supE tRNA nonsense suppressor were compared. Neomycin stimulated much more efficiently than streptomycin the phenotypic suppression of frameshift mutations. Because neomycin favors mismatches of the central codon base whereas streptomycin favors mismatches of the first codon base, this result suggests that mismatching of the central codon base pair and shifting of the reading frame are two correlated phenomena. In contrast, both streptomycin and neomycin stimulated about equally the efficiency of the tRNA nonsense suppressor, an effect probably related to their interference with the proofreading control in tRNA selection.Key words: streptomycin, neomycin, suppression of frameshift mutations, translational accuracy.
Investigations into the linkage of genes controlling individual quantitative characters in barley
Authors: Powell W. , Caligari P. D. S.
Published: November 2014

Technical innovations in barley breeding have resulted in the ability to reduce generation times. Single seed descent and doubled haploidy have become practical propositions in barley improvement. These Fx samples are also powerful tools for genetical analyses and have been used in this paper together with conventional generations to investigate the linkage of genes controlling quantitative characters. Such investigations are of relevance to barley breeders since the detection of significant levels of repulsion linkages would indicate that the single seed descent (SSD) technique would be preferable to doubled-haploid (DH) methods. The present study indicated that estimates of D (the additive genetic variance) from DH and SSD sampled did not differ significantly. Thus linkage disequilibrium is not an important component of the genetic architecture of the five crosses investigated. Hence F1-derived doubled haploids or SSD will be equally effective in producing desirable recombinant inbred lines.Key words: Hordeum, doubled haploids, linkage disequilibrium.
Chromosomal structure of homozygous common wheat lines obtained from wheat × Agropyron × Aegilops speltoides derivatives. I. A screening of the reciprocal translocations
Authors: Ortiz L. T. , Gonzalez Agueda , Chueca Maria-Cristina , Cauderon Yvonne
Published: November 2014

Fifty-seven homozygous hexaploid lines belonging to five different families obtained by selection in the progenies of the cross between a wheat × Agropyron intermedium substitution line and an Aegilops speltoides promotor of homoeologous pairing were screened for reciprocal translocations. This study was carried out in relation to four Triticum aestivum cultivars: 'Vilmorin 27', Tormes', and 'Ducat' (which were used in the production of these lines), and 'Chinese Spring' that has the primitive structure of the common wheats. None of the lines retained the 5B/7B translocation of 'Vilmorin 27'. For some lines, the translocation of 'Tormes' and 'Ducat' seems to have been maintained. Ten of them show the primitive structure of 'Chinese Spring' even though none of the wheat parents had it. The others carry some original translocations as a result of the effect of Aegilops speltoides on meiotic pairing.Key words: homoeologous pairing, interspecific hybridization, gene transfer, chromosomal rearrangements, Triticum.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. II. The mode of inheritance of spring versus winter growth habit
Authors: Kuspira J. , Maclagan J. , Kerby K. , Bhambhani R. N.
Published: November 2014

The study on the mode of inheritance of spring versus winter growth habit in Triticum monococcum is the first in a diploid wheat species. The results are discussed in light of the information available on the genetics and cytogenetics of this character in Triticum aestivum. Two spring habit and six winter habit lines were used in these investigations. Statistical analyses of progenies in each of these lines clearly established the true-breeding nature of all eight lines with respect to days to heading. Analysis of F1 and F2 results of crosses between the two spring habit lines 68 and 293 showed the following: (i) neither line carries winter habit alleles at any of the major gene loci determining growth habit; and (ii) four of five minor allele pairs determine the phenotypic differences between them. Monohybrid F2 and testcross ratios in crosses between spring habit line 68 and each of the six winter lines lead to the following conclusions: (i) differences between spring and winter growth habit in each cross are due to alleles of one major gene; (ii) the allele for spring habit is completely dominant to that for winter habit in each cross; and (iii) all these lines are genotypically identical or very similar at all modifying gene loci. These results imply that only one major gene determines growth habit in this species. Diallel (critical) crosses among the six recessive lines indicate that complementation does not occur in any of the F1's. Therefore, all these recessive genes represent mutations in the same gene. If these results are characteristic of all winter lines in Triticum monococcum, they permit the initial conclusion that only one major gene determines growth habit in this diploid species. This locus is in all likelihood the VrnI locus since it is the only one of the five major genes identified for growth habit, that is present in the A genome of Triticum aestivum. All six recessive lines respond to natural vernalization. This lends further support to our initial conclusion. Because the six recessive lines head at five different times we conclude that a multiple allelic series occurs at this locus. Specifically, at least three and probably five recessive alleles responsible for different heading dates among the winter lines, and at least one dominant allele for spring habit, occur at this locus.Key words: Triticum, complementation, quantitative, vernalization, alleles, multiple.
Diploid female gametophyte formation in 24-chromosome potatoes: genetic evidence for the prevalence of the second meiotic division restitution mode
Authors: Stelly David M. , Peloquin Stanley J.
Published: November 2014

Half-tetrad genetic analysis of 1431 plants in 26 4x potato (Solanum spp.) families from 2x × 4x crosses revealed that at least 20 of the 26 female parents form 2n female gametophytes that are predominantly or exclusively of the second meiotic division restitution (SDR) type. SDR 2n gametophytes genetically equate to gametophytes that would result from restitution of the second meiotic division. Previous estimates obtained by half-tetrad analysis with 2n pollen placed the yellow-tuber flesh marker, Y, at 13 map units from its centromere. Overall ratios observed herein were slightly discordant with predictions based on that estimate, indicating that the map distance (p) may be slightly greater, around 18.5 map units. An alternative explanation is that most of the tested parents produce a mixture of 2n female gametophytes, composed of mostly SDR but also a smaller proportion of FDR or FDR-NCO 2n female gametophytes. Genetically, FDR and FDR-NCO 2n gametophytes equate to those resulting from meiotic first division restitution, with, or with no crossing-over, respectively. Because the data do not discriminate between these hybpotheses, the segregation data were tested according to both estimates of p. Results with six additional clones were inconclusive regarding the mode of 2n gametophyte formation. The results illustrate limitations of half-tetrad analyses for determining the exact composition of 2n gametophyte populations, where these might result from more than one mechanism of formation. The finding that SDR 2n female gametophytes were most prevalent nevertheless supports the hypothesis that they have contributed significantly to the origin and evolution of the tetraploid cultivated potato, and that SDR × FDR or SDR × FDR-NCO crosses (2x × 2x) may be a meritorious approach for potato improvement.Key words: meiosis, Solanum, evolution, breeding.
Analysis of mitochondrial DNA, chloroplast DNA, and double-stranded RNA in fertile and cytoplasmic male-sterile sunflower (Helianthus annuus)
Authors: Brown Gregory G. , Bussey Howard , DesRosiers Lee J.
Published: November 2014

The extent of variation in the mitochondrial DNAs (mtDNAs), chloroplast DNAs (ctDNAs), and double-stranded RNAs (dsRNAs) of sunflower lines carrying fertile and male-sterility conferring cytoplasms was examined. To minimize nuclear gene effects, efforts were concentrated on two chromosomally isogenic lines, CM400 (fertile) and cmsCM400 (male sterile), which differ only in their cytogenes. A circular 1.45 kilobases (kb) plasmid DNA was found in the mitochondria of the four fertile lines examined, but was absent in the male-sterile line. Restriction enzyme analysis of mtDNAs of the fertile and male-sterile cytoplasms with BamHI, EcoRI, and HindIII revealed no fragment mobility differences between them other than those which could be ascribed to the 1.45-kb circle. Similar restriction analysis of ctDNA showed no differences between fertile and male-sterile cytoplasms. Both CM400 and cmsCM400 contain dsRNA molecules. The number and sizes of these dsRNAs varied from preparation to preparation in both lines. Species of 3.3 and 1.5 kb, which were the only dsRNAs common to all preparations from CM400, were also the only species common to all preparations from cmsCM400. Thus, no consistent differences between the fertile and male-sterile cytoplasms were seen in these molecules. The specific association of the 1.45-kb plasmid with fertile cytoplasm together with the absence of variation in ctDNA and dsRNA, suggests the involvement of mtDNA in sunflower cytoplasmic male sterility.Key words: DNA (mitochondrial), sterility (male), sterility (cytoplasmic), Helianthus, sunflower, DNA chloroplast.
Intergeneric hybrids between × Triticosecale cv. Welsh (2n = 42) and three genotypes of Agropyron intermedium (2n = 42)
Authors: Gupta P. K. , Fedak G.
Published: November 2014

Three genotypes of Agropyron intermedium ssp. trichophorum (2n = 42) were crossed onto × Triticosecale cv. Welsh (2n = 42). Bivalent frequencies per pollen mother cell in the three hybrid combinations were 4.97, 5.64, and 6.94. Pairing was attributed to autosyndesis between two genomes (N and N1) of the paternal parent rather than to genome homology between the two parents.Key words: triticale, hybrids (intergeneric), chromosome pairing, × Triticosecale, agronomy.
Chromosome banding homologies in three species of Aedes (Stegomyia)
Authors: Marchi A. , Rai K. S.
Published: November 2014

The chromosome complements of the mosquitoes Aedes aegypti, Aedes mascarensis, and Aedes albopictus, belonging to the subgenus Stegomyia, gave a uniform response to the Q-, H-, and R-banding techniques. Of the three homomorphic chromosome pairs, only the shortest or sex pair (I) showed a consistent banding pattern. In the three species, a bright yellow intercalary band was present on one arm of both chromosomes of the sex pair after heat treatment and staining with acridine orange. The rest of the chromosome and the other two pairs fluoresced orange–red. The same intercalary region appeared completely dark with the fluorochromes quinacrine and Hoechst 33258, while the rest of the chromosomes fluoresced dull. The same banding pattern was present in males and females. Size variations of the Q- and H-negative and R-positive intercalary bands were observed within each species. The results are interpreted in terms of structural homology of the sex-determining chromosomes, which is retained within the subgenus.Key words: sex-determining chromosomes, banding (Q, H, R), Aedes, mosquitoes.
Effect of different doses of group-2 chromosomes on homoeologous pairing in intergeneric wheat hybrids
Authors: Ceoloni C. , Strauss I. , Feldman M.
Published: November 2014

While an extra dose of chromosome 2A of common wheat, previously reported to carry a pairing promoter on its short arm, did not increase pairing between homoeologous chromosomes in F1 hybrids between common wheat cv. Chinese Spring (CS) and Aegilops variabilis, two doses of chromosome 2D or 2B caused a significant increase in homoeologous pairing. Evidently, chromosomes 2D and 2B carry a pairing promoter(s). Studies of F1 hybrids between aneuploids of CS, either deficient for chromosome 2D or having it in an extra dose, and Ae. variabilis, Ae. longissima, and Secale cereale supported the finding that this chromosome carries a pairing promoter. Using ditelosomic lines, the promoter was found to be located on the short arm of 2D (2DS). It was deduced that the promoter of 2B is also located on the homoeologous short arm, i.e., on 2BS. Evidence was obtained that the long arm of 2D may carry a suppressor(s) of pairing. Thus, the short arm of 2A, 2D, and 2B carries a pairing promoter(s), while the long arm of 2D and possibly of 2A and 2B carry a minor suppressor(s). The promoters are more potent than the suppressors and the overall effect of group-2 chromosomes is pairing promotion.Key words: wheat, homoeologous pairing, pairing promoter, pairing suppressor, intergeneric hybrid, meiosis.
Mapping of a chromosome pairing gene and 5S rRNA genes in Triticum aestivum L. by a spontaneous deletion in chromosome arm 5Bp
Authors: Kota Rama S. , Dvořák Jan
Published: November 2014

A deletion in the p arm of chromosome 5B of Triticum aestivum L. cv. Chinese Spring was identified by C-banding during the production of disomic substitutions of 6B of Aegilops longissima Schweinf. et Muschl. for chromosome 5B of cv. Chinese Spring. The deletion was terminal with a breakpoint just proximal to the interstitial C-band. The degree of metaphase I chromosome pairing in plants homozygous for the deletion indicated that the chromosome pairing promoting gene known to be in the p arm of chromosome 5B is located in the deleted portion of that arm. Additionally, all of the 5S ribosomal RNA genes known to exist on arm 5Bp were mapped to this deleted portion.Key words: C-banding, 5S rRNA genes, Triticum, Aegilops chromosome aberration.
Genetic parameters of growth in rainbow trout, Salmo gairdneri, prior to maturation
Authors: McKay L. R. , Ihssen P. E. , Friars G. W.
Published: November 2014

The relative magnitude of additive genetic effects, nonadditive genetic effects, maternal effects, and common environmental effects was determined for size, growth, and condition factor in rainbow trout of various ages, from the egg to the yearling stage, using a factorial mating system. Heritability estimates for length and weight ranged from 0.09 to 0.32, except for dried egg weight, where no additive genetic variation was detected. Condition factors were more heritable than size, with heritability estimates ranging from 0.24 to 0.46. Maternal effects were only important for dried egg weight and early fry size, and decreased rapidly with age as heritability increased. Egg weight, fry size, and fry condition factors were influenced by common environmental effects and (or) nonadditive genetic effects, but confounding of these sources of variation prevented exact estimation of their relative magnitude. Nonadditive genetic effects were completely absent for yearling size but were present for yearling condition factors. Individual or between-family selection on size should produce some response unless selection is done on very young fry or families are housed separately. For very young fry or where families are not replicated across tanks, within-family selection will be necessary to identify genetically superior fish, because of strong maternal or common environmental effects. Genetic correlations between size or condition factors measured at different ages were all positive, so selection at one stage should improve size or condition factor at another.Key words: rainbow trout, growth, heritability, maternal effects, genetics.
A high-resolution C-banding technique
Authors: Braekeleer M. De , Keushnig Marylinne , Lin C. C.
Published: November 2014

A high-resolution C-banding technique is described. The major advantages of this method are its simplicity and reliability. Because this technique allows the recognition of unusual C-band heteromorphisms, it can be very useful in population cytogenetic studies.Key words: karyotyping, banding (C), heterochromatin, high resolution.
Meiotic pairing in haploids and amphidiploids of spontaneous versus synthetic origin in rape, Brassica napus L.
Authors: Attia T. , Röbbelen G.
Published: November 2014

Newly resynthesized AC amphihaploids, which were characterized by high meiotic pairing and multivalent formulation, after doubling of their chromosome number showed preferential pairing and bivalent formation in the resynthesized amphidiploid Brassica napus (AACC). However, univalents as well as multivalents were also formed indicating that their chromosome behaviour was not fully diploidized. Stabilization of chromosome pairing in newly resynthesized amphidiploids can be achieved through genetic control or structural modification of the homoeologous chromosomes. A comparison of the meiotic behaviour of spontaneous haploids of natural rapeseed with that of the newly synthesized AC amphihaploids provides some evidence that both processes may be involved in the regulation of chromosome pairing in Brassica.Key words: Brassica, amphihaploid, amphidiploid, meiosis, univalents, multivalents.
Interchange polymorphism in natural populations of Allium paniculatum L. (Liliaceae): nature, frequency, effects, and mechanism of maintenance
Authors: Lozano R. , Rejón C. Ruiz , Rejón M. Ruiz
Published: November 2014

A reciprocal translocation was found with a high frequency (average 44.44%) in four natural populations of Allium paniculatum L. (Liliaceae) from the South of Spain. The chromosomes involved are 1 and 7. The translocation is reciprocal and unequal. Chiasma frequency in the chromosomes not involved in the interchange is not affected, but chiasma frequency is decreased in the translocated chromosomes in the heterozygotes. As a satellite chromosome is involved in the interchange, the nucleolus is associated with the quadrivalent and the pattern of nucleolus formation is changed in heterozygotes, which have a lower mean number of nucleoli [Formula: see text] than homozygous standard individuals [Formula: see text]. The spontaneous mutation rate for interchanges during the early stages of microsporogenesis is high (μ = 1.08 × 10−2). No interchange homozygotes were found in any of the four populations analyzed. Furthermore, a comparative analysis of heterozygous (HT) and homozygous standard (HM) individuals in two populations demonstrated that homozygous standard plants show, on the whole, higher fitness than the heterozygotes. This can be attributed to a greater egg cell fertility and seed set. The possible causes of maintenance are discussed: the interchange in A. paniculatum is probably not maintained by overdominance for generative reproductive characters, nor by a mutation–selection equilibrium. One possibility, that heterozygotes have superior vegetative reproduction, still remains open for future investigation.Key words: Allium paniculatum, interchange polymorphism, fitness.
Freezing hardiness in amphiploids of Triticum tauschii (Coss.) Schmal. and T. turgidum L. var. durum
Authors: Le Hoan T. , Reicosky David A. , Olien C. Robert
Published: November 2014

Amphiploids of interspecific hybrids of Triticum tauschii and T. turgidum var. durum were evaluated for freezing hardiness in high and low intensity freeze tests. These amphiploids were compared with a hardy and a moderately hardy cultivar of T. aestivum. In the high and low intensity tests, the amphiploids were not hardier than the hardiest parents of the cross. Freezing hardiness of both species was expressed in the amphiploids with both additive and nonadditive types of gene action. Two amphiploids were as hardy as the T. aestivum cv. Winoka in the high intensity test.Key words: freezing hardiness, hybrids (interspecific), amphiploids.
The third chromosome inversion polymorphisms in northern populations of Drosophila persimilis
Authors: Beckenbach Andrew T.
Published: November 2014

The third chromosome arrangements of northern populations of Drosophila persimilis were reexamined for comparison with their frequencies four decades ago. A total of nine arrangements were found to occur, including four new arrangements. Photographs of all of the arrangements are provided, including homokaryotypes and the most informative of the heterokaryotypes. The frequencies of the most common arrangements have remained relatively constant over the 40-year span since the only previous analysis. The only changes are a slight decrease in the frequency of the Klamath arrangement, with an increase in the frequencies of the rare arrangements.Key words: Drosophila persimilis, chromosome polymorphisms, inversions.
Alien chromosome fragments conditioning resistance to beet cyst nematode in diploid descendants from monosomic additions of Beta procumbens to B. vulgaris
Authors: de Jong J. H. , Speckmann G. J. , de Bock Th. S. M. , Lange W. , Voorst A. van
Published: November 2014

A monosomic addition plant of Beta vulgaris, containing an extra chromosome of B. procumbens with a gene for resistance to the beet cyst nematode, gave rise to a diploid descendant with an additional chromosome fragment. This fragment was found to bear the gene for resistance. A study of its morphology and behaviour made it likely that it represents the short arm of the alien chromosome and may have originated by centric fission of the single addition chromosome at anaphase I or II. The fragment showed incomplete generative transmission. In part of the somatic cells the fragment was missing and occasionally more than one fragment per cell was observed. The transmission of resistance in the telosome addition material was about 10%, which is 2.5 times lower than that of the monosomic addition. The pattern of transmission can be explained by an incomplete centromere, otherwise disturbed centric activity, or chromatid cohesiveness. Comparison with other monosomic addition plants showed that the resistance gene is located on the short arm of the satellite chromosome of B. procumbens and thus is linked to the nucleoar organizer region. The long arm of this chromosome possesses genes influencing annuality and leaf shape.Key words: Beta vulgaris, Beta procumbens, beet cyst nematode, monosomic addition, centric chromosome fragment.
Genetic variation among local populations of jack pine (Pinus banksiana)
Authors: Ross Howard A. , Hawkins Janice L.
Published: November 2014

Genetic variability in three jack pine (Pinus banksiana) populations, spaced 10 km apart in southern Manitoba, was analyzed electrophoretically for 15 enzymes encoded by 20 structural loci. These populations were studied as spatial and temporal controls in an investigation of the effects of long-term gamma irradiation on boreal tree species. Individual populations were, on average, polymorphic at 53.3% of the loci and had 2.0 alleles per locus. Individual trees were heterozygous at 20.7% of their loci. An F-statistic analysis revealed an overall 10% excess of heterozygotes over Hardy–Weinberg expectations. Only 2% of the genetic variation occurred among populations. Consequently Nei's genetic distance between populations was small [Formula: see text]. The amount and disposition of the genetic variation in neighbouring populations resembled that observed by others among widely spaced populations. The similarity of the genetic structure of jack pine populations at the meso- and macro-geographic levels might result from the antagonistic effects of long distance gene flow via pollen transport (increasing homogeneity) and adaptation to fire or other patchily distributed environmental factors (reducing homogeneity).Key words: Jack pine, Pinus banksiana, allozymic variation, genetic structure.
Expression of senescence in Neurospora intermedia
Authors: Griffiths A. J. F. , Kraus S. , Bertrand H.
Published: November 2014

Kalilo cytoplasms of Neurospora intermedia have been shown to express senescence in two ways. First, by the previously reported way of death in a subculture series, and second, as reported here, by growth cessation in a 50-cm race tube. Only those cultures that are sufficiently far advanced in the development of senescence will stop growth in the length of a race tube. Resumption of growth occurs in most cases of growth arrest in race tubes. Although in subculture series growth resumption is rare, there is probably a similar basis: mitochondrial DNA (mtDNA) studies on one such case showed that growth resumption is associated with a resurgence of normal mtDNA and a decline of abnormal genomes. When senescent cultures in race tubes were sampled by removing mycelial cores, longer grown cultures were shown to be able to support less growth than younger cultures of the same genotype, and the growth front was generally able to support less growth than other regions. Therefore senescence in both transfer series and in race tubes involves the accumulation of genetic factors unable to suppport continuous growth. The expression of senescence is considered to be more efficient in subculture series than in race tubes. In such series, conidia or aerial hyphae work equally well as transfer inocula, but 1-mm hyphal tips cut from growing mycelium do not promote senescence when used as inocula. Furthermore, varying the transfer interval does not affect senescence. It is concluded that there is some feature of the development or germination of quiescent cells that enhances the expression of senescence in Neurospora.Key words: Neurospora, senescence, mitochondria, growth.
Chromosome numbers in Antennaria (Asteraceae:Inuleae) from western North America
Authors: Chinnappa C. C.
Published: November 2014

Chromosome numbers were determined for 26 taxa of Antennaria from western North America. These were found to include diploid and polyploid species and their putative hybrids. First counts are reported for A. stenophylla (2n = 28) and A. sedoides (2n = 56). Four polyploid complexes, the A. rosea, A. alpina, A. neodioeca, and A. parvifolia aggregates, were found to have sporophytic chromosomes numbers which included all ploidy levels from diploid (2n = 28) to decaploid (2n = 140). This represents the entire range of euploidy known to occur in the genus. Much of the variation that is encountered in the species of Antennaria is the result of extensive hybridization between diploid and polyploid populations comprised of sexual and partially apomictic individuals, respectively.Key words: Asteraceae, Antennaria, dioecy, agamospermy, polyploid complex.
Sporophytic and gametophytic gene expression in Populus deltoides Marsh., P. nigra L., and P. maximowiczii Henry
Authors: Rajora O. P. , Zsuffa L.
Published: November 2014

Male gametophyte (pollen) isozyme profiles of P. deltoides, P. nigra and their hybrids, and of P. maximowiczii were compared with those of the sporophyte (roots). Fifteen enzyme systems were resolved by starch gel electrophoresis for each species and hybrid, and a total of 51 encoding genes were observed. In P. deltoides, P. nigra, P. deltoides × P. nigra, and P. maximowiczii, respectively, 74, 80, 74, and 76% of the structural genes coding for these enzymes in the sporophyte were also found to be expressed by the male gametophyte. Most of the genes tested were found to be expressed after meiosis, apparently transcribed and translated in the haploid genome.Key words: gene expression, gametophyte, sporophyte, Populus, isozymes.
Relationships between floret size and grain weight in aneuploid lines of homoeologous group-5 chromosomes of common wheat (Triticum aestivum L.) cv. Chinese Spring
Authors: Millet Eitan
Published: November 2014

Various aneuploids of common wheat (Triticum aestivum L.) cv. Chinese Spring were used to study the dosage effect of group-5 chromosomes on spike morphology, size of floral organs, and grain weight. Reduced dosage resulted in smaller floral organs, smaller floret cavities, and lighter grains than in the euploid, while increased dosage had the opposite effects. Chromosome 5A was the most effective in inducing these changes, whereas in most cases 5B was the least effective. Based on the various lines studied, a high linear correlation was found between the weight of the basal grains in the central spikelets and the volume estimates of the florets in which they were developed. The different lines exhibited a considerable similarity between the size distribution of floral organs and the grain weight distribution in the main spike. Pleiotropic effects of genes located on group-5 chromosomes on size of floral organs and grain weight are suggested.Key words: Wheat, aneuploids, group-5 chromosomes.
Chromosome banding in salmonid fishes: nucleolar organizer regions in Oncorhynchus
Authors: Phillips Ruth B. , Zajicek Kerry D. , Utter Fred M.
Published: November 2014

Chromosome banding patterns obtained by silver staining and chromomycin a3 (CMA3) staining were analyzed in six species of Oncorhynchus: O. tshawytscha, O. kisutch, O. keta, O. nerka, and O. gorbuscha from North America and O. masou from Japan. Four different chromosomal locations of the nucleolor organizer regions (NORs) were found in different species. In O. tshawytscha, O. kisutch, and O. masou the NORs comprised the entire short arms of one medium-sized acrocentric chromosome pair. In O. nerka the NORs were found in an interstitial band on the short arms of one submetacentric chromosome pair and in O. gorbuscha proximal to the centromere on one metacentric chromosome pair. In O. keta the NORs were found on the telomeres of one small submetacentric chromosome pair. As in the related genera Salmo and Salvelinus chromomycin A3 positive bands were found at the same sites as the AgNORs in all species. Salmonid fish are assumed to be ancestral tetraploids and the considerable differences in chromosome number between different species are thought to be the result of chromosomal fusions after tetraploidization. In all members of the genus Oncorhynchus the rearrangements have resulted in the consolidation of the NORs on a single chromosome pair. The possible significance of intra- and inter-species NOR polymorphisms is discussed.Key words: nucleolar organizer regions, salmon, Oncorhynchus, chromosomes.
Inheritance and microsporogenesis of a synaptic mutant (sy-2) from Solanum commersonii Dun.
Authors: Johnston S. A. , Ruhde R. W. , Ehlenfeldt M. K. , Hanneman Jr. R. E.
Published: November 2014

A mutant has been found in diploid Solanum commersonii (2n = 2x = 24) in which no bivalents are formed during microsporogenesis. This trait, a simply inherited recessive, has been designated sy-2. It conditions high levels of pollen sterility through random chromosome segregation at anaphase I. Only the nucleolar-associated chromosomes appear to segregate non-randomly, possibly due to the fusion of the nucleoli as cells near diakinesis. Branched spindle configurations result in multipolar telophase I arrangements, yielding from one to seven pollen grains at the tetrad stage. Most of the stainable pollen produced appears to be 2n. The 2n pollen formed by this mechanism should bear the exact genotype of the parent, since no crossing-over occurs.Key words: Solanum, potato, 2n gametes, mutants (meiotic), mutants (synaptic).
The karyotype of the grass Zingeria biebersteiniana (2n = 4) by light and electron microscopy
Authors: Bennett M. D. , Smith J. B. , Seal A. G.
Published: November 2014

The grass Zingeria biebersteiniana is one of only four angiosperm and two monocotyledonous species known with 2n = 4. Its 4C nuclear DNA amount, 7.4 pg, is similar to that of Haplopappus gracilis (4C = 8.2 pg), a dicotyledonous species with 2n = 4. Studies of the karyotype of Z. biebersteiniana using the electron microscope three-dimensional serial thin section reconstruction method showed it to be a highly suitable material in which to examine chromosome placement. Although the two chromosome types have very similar relative volumes (53 and 47%, respectively) and arm volume ratios (1.08 and 1.13, respectively), nevertheless, each chromosome are each arm could be reliably distinguished in single reconstructed cells at each stage of mitosis. Thus, the short arm of chromosome 1 was identified by its unique lighter stained nucleolus organizer region, while the short arm of chromosome 2 was distinguished from the long arm by its relatively smaller arm volume. The two chromosomes and their arms were also easily distinguished at mitotic metaphase in the light microscope by two diagnostic C-bands, one at the telomere of the short arm of chromosome 1 and the other near to, but not at, the short arm telomere of chromosome 2.Key words: Zingeria biebersteiniana (2n = 4), low chromosome number.
Evidence for the existence of endosperm balance number in the true clovers (Trifolium spp.)
Authors: Parrott W. A. , Smith R. R.
Published: November 2014

The endosperm balance number (EBN) hypothesis was first advanced to explain results from interspecific crosses in Solanum and later in Impatiens. According to the EBN hypothesis, normal endosperm development following intra- or inter-specific crosses depends on having a ratio of two EBNs from the female to one EBN from the male in the endosperm tissue. EBNs may differ among related species. Successful hybrids can be obtained between species with the same EBN. The ploidy level of an individual species can be varied to modify its EBN, making it cross compatible with a species sharing its modified EBN. Interspecific crosses within Trifolium have been limited and difficult. Crosses reported in the literature, including evidence from our own study, suggest that EBN is operating in Trifolium and have been used to assign EBN numbers to some clover species. The use of 2n eggs enabled two species, differing in EBN, to be crossed. An understanding of the EBN mechanism that operates in Trifolium should make successful interspecific hybrids easier to obtain in the future.Key words: endosperm balance number, hybrids (interspecific), 2n gametes, Trifolium.
Linkage between the Lr10 gene conditioning resistance to leaf rust, two endosperm proteins, and hairy glumes in hexaploid wheat
Authors: Howes N. K.
Published: November 2014

The possibility that genes controlling the expression of wheat endosperm proteins are linked to the Lr10 gene conditioning resistance to leaf rust (Puccinia recondita f. sp. tritici) race 1 was examined. Derived F3 progeny lines from a cross between two hexaploid spring wheat cultivars (Triticum aestivum) 'Little Club' and line 'Prelude' Lr10 (RL6004), segregated for the Lr10 gene, gliadin component band 50 (54 kilodalton, kDa), a nongliadin endosperm protein (70 kDa), and hairy glumes (Hg). These four characters were each monogenically inherited and were linked, with the gene order being Lr10, (54 and 70 kDa polypeptides), Hg. These genes are located on the short arm of chromosome 1A. The genes Hg and Lr10 could be useful flanking markers to study the fine structure of the complex Gli-A1 locus.Key words: leaf rust, gliadins, glumes (hairy).
Reproduction and the origin of polyploids in hybrid salamanders of the genus Ambystoma
Authors: Bogart James P. , Lichts Lawrence E.
Published: November 2014

Eggs and larvae produced by diploid, triploid, and tetraploid females collected from breeding ponds on Pelee Island in Lake Erie were studied to examine the reproductive mechanism. No instance of parthenogenesis was found as all examined females required sperm to produce viable progeny. Diploid females produced diploid and triploid larvae, triploid females produced triploid and tetraploid larvae, and tetraploid females produced triploid and tetraploid larvae. The majority of the eggs produced by hybrid females do not develop or do not complete embryogenesis. Electrophoretic examination of females and their offspring demonstrate that the male genome is being incorporated in reduced as well as unreduced eggs produced by all three ploidy classes of females. The elevation of ploidy among Pelee Island Ambystoma is attributed to sperm incorporation in unreduced eggs. Triploid as well as tetraploid individuals are constantly being produced. A critical examination of the literature on parthenogenetic or gynogenetic modes of reproduction in North American Ambystoma hybrids shows no conclusive evidence supporting these modes and it is suggested that the reproductive mechanism found among Pelee Island female hybrids may be more generally applied to other hybrid Ambystoma populations.Key words: Ambystoma, polyploids, hybrids, electrophoresis, reproduction.
Rye heterochromatin. I. Studies on clusters of the major repeating sequence and the identification of a new dispersed repetitive sequence element
Authors: Appels R. , Moran L. B. , Gustafson J. P.
Published: November 2014

The structure of appoximately 10 kilobases of DNA originating from the subcloned DNA segments of five lambda clones from rye heterochromatin is described. The sequence data suggested that much of the variation between the 380 base pair (bp) units of the tandem arrays in hetercohromatin must have preceded the amplification events which gave rise to the arrays. Furthermore, evidence for recombination between the tandem arrays of the units (subsequent to the presumed amplification events) was obtained. A single 14-bp region which did not show any variation in sequence was found to be part of a dyad symmetry, characteristic for DNA-binding proteins. The analysis of a molecule which contained a junction between the heterochromatic "350" DNA sequence family and apparently nonheterochromatic DNA is also presented. This nonheterochromatic DNA contains a dispersed repetitive type of sequence ("5.3") which is found adjacent to a wide range of sequences as judged from genomic analyses, in situ hybridization studies and independent isolates of the sequence. The 5.3 sequence is dispersed throughout nonheterochromatic and most heterochromatic regions. However, some heterochromatic regions and the nucleolar organizing region appear not to contain the sequence or else have only very low amounts. The "5.3" element provides a novel probe for further analysis of the rye genome.Key words: rye, heterochromatin, amplification.
Synaptonemal complex spreading in Allium. II. Tetraploid A. vineale
Authors: Loidl Josef
Published: November 2014

In tetraploid Allium vineale four homologous axes are closely aligned in unsynapsed regions at early zygotene. This alignment is brought about by intercalary and terminal associations. The intercalary association sites are possibly targets of forces for long distance attraction of homologues and potential pairing initiation sites. The terminal associations are mediated by dense spherules and result possibly from the attachment of the telomeres to the nuclear envelope. In pachytene the alignment is abolished and the four axes are synapsed two by two, resulting in bivalents or, owing to partner switches in the synapsed axes, in quadrivalents. From the number of partner switches per configuration the number of pairing initiation sites is estimated. Homologous alignment and synapsis are discussed, comparing them with the conditions in a triploid species, which were described in a previous paper.Key words: Allium vineale, synaptonemal complex, polyploids, chromosome pairing, meiosis.