Origin of B chromosomes in cultivated rye

Genome ◽  
1995 ◽  
Vol 38 (2) ◽  
pp. 307-312 ◽  
Author(s):  
K. Niwa ◽  
S. Sakamoto
Keyword(s):  
Secale Cereale ◽  
Natural Populations ◽  
B Chromosomes ◽  
Standard Type ◽  
Monophyletic Origin ◽  
Pollen Mother Cells ◽  
Somatic Metaphase ◽  
Pistillate Parent ◽  
Mother Cells ◽  
Cytogenetic Relationship

Cultivated rye (Secale cereale) and its weedy relative (S. segetale) carry B chromosomes. The B chromosomes are known to be morphologically alike at somatic metaphase and they are of the standard type in natural populations. To clarify the cytogenetic relationship between the standard B chromosomes of S. cereale and those of S. segetale, we made four crosses between Afghan S. segetale with two standard B chromosomes as a pistillate parent and Turkish, Iranian, Korean, and Japanese S. cereale, all with two standard B chromosomes as pollen parents. We observed the pairing of B chromosomes at diakinesis in pollen mother cells in all F1 hybrids with four standard B chromosomes, two from each of the pistillate and the pollen parents. The degree of pairing of B chromosomes in all F1 hybrids with four standard B chromosomes was similar to or somewhat lower than, that in parental strains with four standard B chromosomes. These results showed that the standard B chromosomes in S. segetale from Afghanistan are homologous with those in S. cereale from Turkey, Iran, Korea, and Japan. We therefore propose monophyletic origin of the standard B chromosomes in S. segetale and S. cereale.Key words: Secale, B chromosomes, origin, cultivated rye, weedy rye.

Ultrastructure of meiotic pairing in B chromosomes of Crepis capillaris. I. One-B and two-B pollen mother cells

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 611-621 ◽  
Author(s):  
G. H. Jones ◽  
J. A. F. Whitehorn ◽  
S. M. Albini
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Complex Surface ◽  
B Chromosome ◽  
B Chromosomes ◽  
Meiotic Pairing ◽  
Pollen Mother Cells ◽  
Crepis Capillaris ◽  
Axis Length ◽  
Mother Cells

Chromosome pairing of a small metacentric B chromosome in Crepis capillaris has been studied by synaptonemal complex surface spreading of pollen mother cells containing either one or two B chromosomes. The B-chromosome axis, on average, represents about 8.7% of the axis length of the standard A-chromosome set, which is less than the corresponding values for DNA content (10.6%) and mitotic chromosome volume (13.6%). Single B chromosomes commonly undergo fold-back pairing to give a symmetrical hairpin loop, which supports earlier suggestions that this B chromosome is an isochromosome. Two B chromosomes may show interarm pairing, exclusively, or interchromosome pairing, exclusively, or combinations of the two. Near the centromeres pairing occurs preferentially between arms of the same chromosome, but chromosome ends show random association. Some B chromosomes show anomalous pairing configurations, which may reflect further orders of reverse repeats within arms or, alternatively, nonhomologous pairing. The period of B-chromosome pairing is confined almost exclusively to zygotene, when the standard A chromosomes are pairing, but within this period their pairing is delayed relative to the A set. Individual B chromosomes at zygotene contain from one to three separate synaptonemal complex segments. These are widely distributed within the chromosomes, mainly in distal and interstitial regions; pairing is delayed around the centromere.Key words: B chromosomes, isochromosomes, synaptonemal complex.

Relative rate of development of aneuploid and euploid microspores in a tertiary trisomic of rye, Secale cereale L.

1985 ◽  
Vol 27 (4) ◽  
pp. 393-398 ◽  
Author(s):  
J. Janse
Keyword(s):  
Mitotic Index ◽  
Secale Cereale ◽  
Time Scale ◽  
Relative Rate ◽  
Pollen Mitosis ◽  
Rate Of Development ◽  
Pollen Mother Cells ◽  
Secale Cereale L ◽  
First Pollen Mitosis ◽  
Mother Cells

Meiotic configurations were studied in pollen mother cells of a tertiary trisomic of rye. Chains of five and chains of three, in alternate orientation, were the most frequent configurations. Assuming loss of univalents in anaphase I or single chromatids in anaphase II, a total of 58.1% of the viable gametes resulting after meiosis were expected to contain the normal haploid complement, whereas 41.9% were expected to have the translocated chromosome in addition. The percentages of uninucleate and binucleate microspores in anthers containing dividing microspores provided a time scale for the development of euploid and aneuploid spores during first pollen mitosis. Microspores containing the extra translocated chromosome tended to divide at a later stage than euploid microspores. The slower development was also illustrated by the course of the mitotic index of both types. It was found that 58.1% of all microspores passing through pollen mitosis contained seven chromosomes and 41.9% contained eight chromosomes, which means that up to the end of first pollen mitosis aneuploid spores were not lost significantly more than euploid spores. It is likely that the delay in development already starts immediately after meiosis.Key words: rye, tertiary trisomic, euploid microspores, aneuploid microspores, rate of development.

Nucleolus organization and meiotic behaviour of B chromosomes in Hepatica nobilis

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 853-859 ◽  
Author(s):  
T. Mabuchi
Keyword(s):  
Chromosome Complement ◽  
B Chromosomes ◽  
The Other ◽  
Chromosome 7 ◽  
Meiotic Behaviour ◽  
Pollen Mother Cells ◽  
Small Satellites ◽  
C Banding ◽  
End To End ◽  
Mother Cells

The C-banding karyotype of Hepatica nobilis indicates the A chromosome complement and B chromosomes (Bs) to be banded in the terminal regions. The A chromosomes (As) of this species comprise mainly euchromatin (89.7%) and a small amount of heterochromatin (10.3%). Bs of H. nobilis have terminal centromeres at one end and possess small satellites at the other end. Bs cause an increase in the number of nucleoli per cell, with a decrease in the size of each nucleolus. During meiosis, Bs associate as bivalents and multivalents up to pentavalents. These associate loosely with the short arm of satellited chromosome 7 (end to end association) at diakinesis in some pollen mother cells. Bivalent or trivalent Bs associate with a nucleolus at diakinesis. B chromosomes of H. nobilis thus appear to contain nucleolus organizing regions and may have originated from the satellited chromosome 7 and other members of As.Key words: Hepatica, satellited B, end to end association, origin, nucleolus organizing regions.

Effect of auxins and cytokinins upon the start of meiosis in cultured anthers of rye (Secale cereale L.)

1985 ◽  
Vol 27 (6) ◽  
pp. 759-765 ◽  
Author(s):  
J. Rueda ◽  
A. M. Vázquez
Keyword(s):  
Anther Culture ◽  
Plant Hormones ◽  
Secale Cereale ◽  
Meiotic Division ◽  
Basic Medium ◽  
Differential Capacity ◽  
Pollen Mother Cells ◽  
Secale Cereale L ◽  
Mother Cells

Anthers of rye excised at premeiotic interphase were cultured in vitro on a basic medium and on a series of auxin- and cytokinin-containing media to ascertain the effect of these plant hormones upon the start of meiosis. Only in the hormone-containing media was it possible to find anthers in which pollen mother cells had started the meiotic division. The different hormones and concentrations tested exhibited a differential capacity to induce the start of meiosis, the percentages of anthers with pollen mother cells in meiosis varying from 0% in one medium to more than 60% in two other media. In some media, pollen mother cells were able to complete the whole meiotic division, while in others they were arrested at different stages of meiosis.Key words: Secale cereale, meiosis induction, anther culture, plant hormones.

The duration of meiosis in pollen mother cells of wheat, rye and Triticale

1971 ◽  
Vol 178 (1052) ◽  
pp. 259-275 ◽  
Keyword(s):  
Triticum Aestivum ◽  
Dna Synthesis ◽  
Secale Cereale ◽  
Sampling Methods ◽  
Tritiated Thymidine ◽  
Pollen Mother Cells ◽  
Mother Cells

The duration of meiosis and its stages at 20 °C has been determined in wheat ( Triticum aestivum 2 n = 6 x = 42), in rye ( Secale cereale 2 n = 14) and in Triticale (2 n = 8 x = 56) by sampling methods and by timing the intervals between the pre-meiotic DNA synthesis and meiotic stages following the incorporation of tritiated thymidine. The results from all the methods used were in general agreement. Meiosis takes about 24 h in wheat, 21 h in Triticale and about 51 h in rye. The lengths of the meiotic stages relative to that of the division correspond reasonably well in the three forms studied but zygotene and pachytene were much longer in rye than in wheat and Triticale .

A separate control for frequency and within-bivalent distribution of chiasmata in rye (Secale cereale L.)

Genome ◽  
1987 ◽  
Vol 29 (3) ◽  
pp. 419-424 ◽  
Author(s):  
V. Lein ◽  
T. Lelley
Keyword(s):  
Secale Cereale ◽  
Chiasma Frequency ◽  
Positional Distribution ◽  
Pollen Grains ◽  
Female Parent ◽  
Close Correlation ◽  
Strong Negative Correlation ◽  
Pollen Mother Cells ◽  
Chiasma Distribution ◽  
Mother Cells

Six genetically different inbred genotypes of spring-type rye Secale cereale with differences in the average number and in the positional distribution of chiasmata were used in this study. The line with the lowest chiasma frequency was chosen as the female parent and crossed with the other five lines. Parental, F1, and F2 data were collected on chiasma number and on chiasma distribution between and within bivalents. Evidence for a polygenic control of both phenomena was found. Chiasma distribution between bivalents within pollen mother cells obviously follows a binomial distribution. This is effected by a mechanism that prevents the formation of a second chiasma on a chromosome arm as long as chromosome arms without chiasma remain; i.e., with 14 chiasmata seven ring bivalents will generally be formed. This mechanism causes a very strong negative correlation between frequency and between-cell variance of chiasmata. The number of chiasmata is independent of their position within the bivalents. A very close correlation between the number of pollen mother cells without univalents and the number of fertile pollen grains was found. Key words: inbred rye, genetic control, chiasma frequency, chiasma distribution, heterosis.

Chromosome localization of genes that control synchronous development of pollen mother cells in wheat

Caryologia ◽  
2003 ◽  
Vol 56 (3) ◽  
pp. 275-279 ◽  
Author(s):  
Wei Li ◽  
Jun Yang ◽  
You-Fu Pan ◽  
Guang-Qin Guo ◽  
Guo-Chang Zheng
Keyword(s):  
Chromosome Localization ◽  
Pollen Mother Cells ◽  
Synchronous Development ◽  
Mother Cells

An ultrastructural study of cytomixis in tobacco pollen mother cells

PROTOPLASMA ◽  
2011 ◽  
Vol 248 (4) ◽  
pp. 717-724 ◽  
Author(s):  
Sergey R. Mursalimov ◽  
Elena V. Deineko
Keyword(s):  
Ultrastructural Study ◽  
Pollen Mother Cells ◽  
Tobacco Pollen ◽  
Mother Cells

Persisting demibivalents: a unique meiotic behaviour in Cuscuta babylonica Choisy

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 63-66 ◽  
Author(s):  
Batia Pazy ◽  
Uzi Plitmann
Keyword(s):  
Key Words ◽  
Chromosome Segregation ◽  
Meiotic Behaviour ◽  
Chromosome Behaviour ◽  
Chromosome Movement ◽  
Pollen Mother Cells ◽  
Key Words Meiosis ◽  
Mother Cells ◽  
Telomeric Association

Idiosyncratic chromosome behaviour during meiosis was found in pollen mother cells of Cuscuta babylonica Choisy, a thread-like holoparasitic herb. Its main features are among the following: (i) telomeric association between homologues through most stages of the process, which leads to persisting chromatid bivalents (= "demibivalents"); (ii) uncommon chromosome segregation in first and second anaphase; and (iii) prolonged intensified heterochromatinization. Although "regular" in its own way, this process leads to the formation of unviable products. Its further investigation might contribute to our understanding of the role of the spindle and chromosome movement in the ordinary process of meiosis. Key words: meiosis (abnormal), persisting demibivalents, Cuscuta babylonica.

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