A cytological study of intraspecific variation in Ceratopteris thalictroides

1979 ◽  
Vol 57 (16) ◽  
pp. 1694-1700 ◽  
Author(s):  
Leslie G. Hickok
Keyword(s):  
Spore Germination ◽  
Cytological Study ◽  
Meiotic Pairing ◽  
Spore Viability ◽  
Polymorphic Species ◽  
Structural Differences ◽  
Pairing Behavior ◽  
Ceratopteris Thalictroides ◽  
Low Levels ◽  
Intraspecific Hybrids

A cytological study of meiotic pairing behavior in intraspecific hybrids was undertaken utilizing seven different collections of Ceratopteris thalictroides. Two mutant gametophyte stocks with nonfunctional spermatozoids were utilized to facilitate the synthesis of intraspecific hybrids. Low levels of univalent and quadrivalent formation were found in most of the hybrids, indicating that some structural differences existed, but major pairing homologies were still evident. The fertility of hybrids ranged from 10 to 75% spore germination. One collection, from Hawaii, showed high levels of univalent formation and very low spore viability. In that this stock is both biologically and morphologically distinct, it should be given taxonomic recognition. The study, in general, is in agreement with the most recent taxonomic treatment of Ceratopteris in that it shows a significant amount of cytological variation within the polymorphic species C. thalictroides.

Structural hybridity and supernumerary chromosomes in a diploid Tradescantia hirsuticaulis

1975 ◽  
Vol 53 (5) ◽  
pp. 456-465 ◽  
Author(s):  
C. C. Chinnappa
Keyword(s):  
Reciprocal Translocation ◽  
Cytological Study ◽  
B Chromosomes ◽  
The Other ◽  
Meiotic Pairing ◽  
Structural Hybridity ◽  
Supernumerary Chromosomes

Cytological study of a diploid (2n = 12) population of Tradescantia hirsuticaulis Small from Stone Mountain, Georgia, revealed striking variation in four plants growing in a cluster, indicating that they constitute different genotypes. The occurrence of B chromosomes, fragments, and aneusomaty in the plants is associated with structural hybridity in the chromosomes. Two plants were homozygotes with simple meiotic pairing, one was heterozygous for a reciprocal translocation, and the other was a heterozygote for two interchanges as well as for inversions. The behavior and the origin of B chromosomes, fragments, and structural hybridity are discussed.

Can abortive early homologous associations promote increased crossing-over in an adjacent rearranged segment?

Genome ◽  
1988 ◽  
Vol 30 (4) ◽  
pp. 469-472 ◽  
Author(s):  
Marjorie P. Maguire
Keyword(s):  
Crossing Over ◽  
Meiotic Pairing ◽  
Pairing Behavior ◽  
Chromosome Segments

Meiotic pairing behavior of rearranged chromosome segments is compared across an informative series of combinations. The question is raised whether the simplest explanation for some peculiar findings may include a sequence of synaptic precursor events at leptotene or zygotene, the course of which may eventually strongly affect crossover frequency.Key words: meiosis, synapsis, crossing-over, rearrangement.

scholarly journals Role of Dipicolinic Acid in the Germination, Stability, and Viability of Spores of Bacillus subtilis

2008 ◽  
Vol 190 (14) ◽  
pp. 4798-4807 ◽  
Author(s):  
Anil Magge ◽  
Amanda C. Granger ◽  
Paul G. Wahome ◽  
Barbara Setlow ◽  
Venkata R. Vepachedu ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Small Molecules ◽  
Spore Germination ◽  
Dipicolinic Acid ◽  
Great Majority ◽  
Lytic Enzyme ◽  
Spore Proteins ◽  
Low Levels ◽  
Made In

ABSTRACT Spores of Bacillus subtilis spoVF strains that cannot synthesize dipicolinic acid (DPA) but take it up during sporulation were prepared in medium with various DPA concentrations, and the germination and viability of these spores as well as the DPA content in individual spores were measured. Levels of some other small molecules in DPA-less spores were also measured. These studies have allowed the following conclusions. (i) Spores with no DPA or low DPA levels that lack either the cortex-lytic enzyme (CLE) SleB or the receptors that respond to nutrient germinants could be isolated but were unstable and spontaneously initiated early steps in spore germination. (ii) Spores that lacked SleB and nutrient germinant receptors and also had low DPA levels were more stable. (iii) Spontaneous germination of spores with no DPA or low DPA levels was at least in part via activation of SleB. (iv) The other redundant CLE, CwlJ, was activated only by the release of high levels of DPA from spores. (v) Low levels of DPA were sufficient for the viability of spores that lacked most α/β-type small, acid-soluble spore proteins. (vi) DPA levels accumulated in spores prepared in low-DPA-containing media varied greatly between individual spores, in contrast to the presence of more homogeneous DPA levels in individual spores made in media with high DPA concentrations. (vii) At least the great majority of spores of several spoVF strains that contained no DPA also lacked other major spore small molecules and had gone through some of the early reactions in spore germination.

scholarly journals PAIRING COMPETITION BETWEEN IDENTICAL AND HOMOLOGOUS CHROMOSOMES IN AUTOTETRAPLOID RYE. I. SUBMETACENTRIC CHROMOSOMES

Genetics ◽  
1985 ◽  
Vol 111 (4) ◽  
pp. 933-944
Author(s):  
J Orellana ◽  
J L Santos
Keyword(s):  
Genetic Control ◽  
Secale Cereale ◽  
Inbred Lines ◽  
Meiotic Pairing ◽  
Homologous Chromosomes ◽  
Partner Exchange ◽  
Pairing Behavior ◽  
Chromosome 1R ◽  
Heterochromatin Content

ABSTRACT Meiotic pairing preferences between identical and homologous but not identical chromosomes were analyzed in ten induced tetraploid/diploid chimaeral rye plants (Secale cereale) heterozygous for telomeric heerochromatin C-bands in both arms of chromosome 1R. These plants were the progeny of two crosses between only one plant of cv. Petkus, used as male, and two plants of the inbred lines E and R, respectively. Different pairing preferences for chromosome 1R were found: (1) between plants, (2) between chromosome arms within the same plant and (3) between bivalents and multivalents within the same plant. The possible influence in the preferences of several factors such as differences in C-heterochromatin content in the chromosomes analyzed, specific genetic control and independence in pairing behavior between both arms and partner exchange is discussed.

scholarly journals PAIRING COMPETITION BETWEEN IDENTICAL AND HOMOLOGOUS CHROMOSOMES IN RYE AND GRASSHOPPERS

Genetics ◽  
1983 ◽  
Vol 104 (4) ◽  
pp. 677-684
Author(s):  
J L Santos ◽  
J Orellana ◽  
R Giraldez
Keyword(s):  
Secale Cereale ◽  
Banding Pattern ◽  
Chromosome Pair ◽  
Meiotic Pairing ◽  
Homologous Pairing ◽  
Eyprepocnemis Plorans ◽  
Homologous Chromosomes ◽  
Random Pairing ◽  
Structural Differences ◽  
Telomeric Heterochromatin

ABSTRACT Meiotic pairing preferences between identical and homologous but not identical chromosomes were analyzed in spontaneous tetraploid/diploid chimeras of three male grasshoppers (Eyprepocnemis plorans) whose chromosome pair 11 were heterozygous for C-banding pattern and in four induced tetraploid/diploid chimaeral rye plants (Secale cereale) heterozygous for telomeric heterochromatin C-bands in chromosomes 1R and 2R. In the grasshoppers, a preference for identical over homologous pairing was observed, whereas in rye both a preference for homologous rather than identical pairing and random pairing between the four chromosomes of the set was found. From the results in rye, it can be deduced that pairing preferences do not depend exclusively on the similarities between chromosomes involved. It is suggested that genotypic or cryptic structural differences between the homologous chromosomes of each pair analyzed might be responsible for the pairing preferences found. This hypothesis can also explain the results obtained in grasshoppers, although the possibility of premeiotic association cannot be excluded in this material.

Molecular Cytogenetic Analysis and Meiotic Pairing Behavior of Progenies Originating from a Hexaploid Triticale (×Triticosecale, Wittmack) and Bread Wheat (Triticum aestivum, L.) Cross

2020 ◽  
Vol 160 (1) ◽  
pp. 47-56
Author(s):  
Aybeniz J. Aliyeva ◽  
András Farkas ◽  
Naib Kh. Aminov ◽  
Klaudia Kruppa ◽  
Márta Molnár-Láng ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Chromosome Pairing ◽  
Addition Line ◽  
Meiotic Pairing ◽  
Hexaploid Triticale ◽  
Substitution Lines ◽  
Molecular Cytogenetic ◽  
Triticale Line ◽  
Pairing Behavior

The chromosomal constitution of 9 dwarf (D) and 8 semidwarf (SD) lines derived by crossing hexaploid Triticale line NA-75 (AABBRR, 2n = 6x = 42) with Triticumaestivum (AABBDD, 2n = 6x = 42) cv. Chinese Spring was investigated using molecular cytogenetic techniques: fluorescence in situ hybridization and genomic in situ hybridization. A wheat-rye translocation (T4DS.7RL), 8 substitution lines, and a ditelosomic addition line (7RSdt) were identified. In the substitution lines, 1, 2, or 4 pairs of wheat chromosomes, belonging to the A, B, or D genome, were replaced by rye chromosomes. Substitutions between chromosomes belonging to different wheat genomes [5B(5A), 1D(1B)] also occurred. The lines were genetically stable, each carrying 42 chromosomes, except the wheat-rye ditelosomic addition line, which carried 21 pairs of wheat chromosomes and 1 pair of rye telocentric chromosomes (7RS). The chromosome pairing behavior of the lines was studied during metaphase I of meiosis. The chromosome pairing level and the number of ring bivalents were different for each line. Besides rod bivalents, univalent and multivalent associations (tri- and quadrivalents) were also detected. The main goal of the experiment was to develop genetically stable wheat/Triticale recombinant lines carrying chromosomes/chromatin fragments originating from the R genome of Triticale line NA-75. Introgression of rye genes into hexaploid wheat can broaden its genetic diversity, and the newly developed lines can be used in wheat breeding programs.

Relationship in annual spceies of Medicago. III. The complex M. littoralis Rhode-M. truncatula Gaertn

1967 ◽  
Vol 15 (1) ◽  
pp. 35 ◽  
Author(s):  
JP Simon ◽  
AJ Millington
Keyword(s):  
Interspecific Hybrids ◽  
Seed Set ◽  
Chromosomal Rearrangements ◽  
Chromosome Translocation ◽  
Pollen Sterility ◽  
Multivalent Formation ◽  
Structural Differences ◽  
Intraspecific Hybrids ◽  
Adult Plants ◽  
Cytological Behaviour

A programme of interspecific hybridization, involving species from subsections Pachyspirae, Leptospirae, and Rotatae of section Spirocarpos, resulted in only one successful combination out of the 20 attempted. Viable hybrids were obtained with ease in crosses between different accessions of M. littoralis and M. truncatula. The morphology, fertility, and cytological behaviour of interspecific hybrids involving seven strains of M. truncatula and three strains of M. littoralis was compared with intraspecific hybrids of each species. With the exception of those with N.2829, which was differentiated from the other strains by one chromosome translocation, intraspecific hybrids of M. truncatula were fully fertile. Considerable pollen sterility and reduced seed set were observed in intraspecific crosses of M. littoralis, but there was no evidence of chromosomal rearrangements. The morphology of the hybrids between M. littoralis and M. truncatula was intermediate between the parents. Chlorophyll deficiency in seedlings and adult plants, dwarfism, and other morphological irregularities were observed in F2 plants. In some FT1s failure of pairing, multivalent formation at metaphase I, and other irregularities at meiosis indicated chromosome rearrangements. Up to three independent translocations and one inversion in the hybrid combinations and pronounced sterility were observed in both FT1s and FT2s. The pollen sterility of the hybrids could be explained in several instances by structural differences, but these do not account completely for the results obtained. Inheritance studies of three possible strain markers indicated simple monohybrid segregation in most intraspecific crosses, but in the interspecific and partially fertile intraspecific crosses, ratios were disturbed and phenotypes abnormal. The agronomic implications of these studies are discussed.

The Mechanisms Responsible for Large Near-Surface Vertical Vorticity within Simulated Supercells and Quasi-Linear Storms

2020 ◽  
Vol 148 (10) ◽  
pp. 4281-4297 ◽  
Author(s):  
Christian H. Boyer ◽  
Johannes M. L. Dahl
Keyword(s):  
Severe Weather ◽  
Common Mechanism ◽  
Near Surface ◽  
Vertical Vorticity ◽  
Convective Systems ◽  
Structural Differences ◽  
History Of ◽  
Low Levels

AbstractDespite their structural differences, supercells and quasi-linear convective systems (QLCS) are both capable of producing severe weather, including tornadoes. Previous research has highlighted multiple potential mechanisms by which horizontal vorticity may be reoriented into the vertical at low levels, but it is not clear in which situation what mechanism dominates. In this study, we use the CM1 model to simulate three different storm modes, each of which developed relatively large near-surface vertical vorticity. Using forward-integrated parcel trajectories, we analyze vorticity budgets and demonstrate that there seems to be a common mechanism for maintaining the near-surface vortices across storm structures. The parcels do not acquire vertical vorticity until they reach the base of the vortices. The vertical vorticity results from vigorous upward tilting of horizontal vorticity and simultaneous vertical stretching. While the parcels analyzed in our simulations do have a history of descent, they do not acquire appreciable vertical vorticity during their descent. Rather, during the analysis period relatively large horizontal vorticity develops as a result of horizontal stretching, and therefore this vorticity can be effectively tilted into the vertical.

Factors affecting spread of Cronartiumcomptoniae on the sweetfern host

1981 ◽  
Vol 11 (2) ◽  
pp. 401-409 ◽  
Author(s):  
Dale L. K. Smeltzer ◽  
D. W. French
Keyword(s):  
Spore Germination ◽  
Free Water ◽  
Dispersal Distance ◽  
Growth Chamber ◽  
Spore Viability ◽  
Factors Affecting ◽  
Temperature Range ◽  
Field Plots

Infection of sweetfern plants (Comptoniaperegrina (L.) Coult.) by Cronartiumcomptoniae Arth. was observed at a maximum of 30 m from the aeciospore source on two field plots in northeastern Minnesota, U.S.A. Amount of infection per spores trapped decreased significantly as dispersal distance increased from the source of inoculum. Infection of sweetfern was limited most by the decrease in spore viability, but lack of rain may have limited infection at least twice during the summer. Inoculations of sweetfern with aeciospores and uredospores in a growth chamber resulted in infection at 0–28 °C, a wider temperature range than for spore germination on agar. Infection occurred after 1 h in a humid chamber and was inhibited by light, especially high intensities. Free water and spores on the undersurface of the sweetfern leaf were required for infection.

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