CYTOLOGICAL DIPLOIDIZATION IN THE CULTIVATED OCTOPLOID STRAWBERRY FRAGARIA × ANANASSA

1976 ◽  
Vol 18 (4) ◽  
pp. 653-659 ◽  
Author(s):  
D. Byrne ◽  
G. Jelenkovic
Keyword(s):  
Chromosome Pairing ◽  
Fragaria Ananassa ◽  
Late Prophase ◽  
Multivalent Formation ◽  
Bivalent Association ◽  
Prophase Of Meiosis

Chromosome pairing during meiosis was studied in 9 cultivated genotypes and 32 seedlings produced by selfing several different genotypes of the octoploid strawberry Fragaria × ananassa Duch. (2n = 8x = 56). In all genotypes studied the chromosomes paired exclusively as bivalents indicating cytological diploidization. Meiotic studies of one of the S1 plants, which was completely sterile, revealed that the chromosomes were paired at pachytene but desynapsed during diplotene, so that very little bivalent association was observed in late prophase of meiosis. The pairing in the F. × ananassa × F. nubicola pentaploid hybrids showed an average of 11.6 bivalents per PMC and frequent multivalent formation. There is thus an indication of residual homology between the ancestral genomes of the octoploid strawberry.

Synaptic mutants in hexaploid oats (Avena sativa L.)

Genome ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 1-7 ◽  
Author(s):  
H. W. Rines ◽  
S. S. Johnson
Keyword(s):  
Chromosome Pairing ◽  
Sodium Azide ◽  
Avena Sativa ◽  
Seed Set ◽  
Single Gene ◽  
Inheritance Pattern ◽  
Late Prophase ◽  
Homologous Chromosomes ◽  
Breeding Station ◽  
Meiotic Synapsis

Three meiotic synapsis-deficient mutants of oats (Avena sativa L.) were analyzed to determine their inheritance pattern, detailed chromosomal behavior, and location to chromosome. These highly sterile mutants, one in the cultivar 'Stout' and two in 'Noble', had been recovered from progeny of sodium azide mutagenized populations. Each segregated as a single gene recessive. The only synapsis-deficient variants previously described in hexaploid oats have been nullisomics or ditelosomics. Mutant 'Stout 1212' was classified as asynaptic due to deficiencies in chromosome pairing at all meiotic stages. Mutants 'Noble 1362' and 'Noble 1911' were classified as desynaptic since their homologous chromosomes were paired in early meiosis but they disassociated prematurely in late prophase I. Using a partial monosomic series from the Welsh Plant Breeding Station, mutant 1212 was mapped to monosome XII and is probably a mutation in Syn-5, a gene previously defined only by its nulli effect. Mutants 1362 and 1911 were mapped to monosome IV and are probably mutations in Syn-1, a gene also previously defined only by its nulli effect. Seed set on the synaptic mutant plants in the field was less than 0.2% of that on fertile sibs and likely resulted from pollination by surrounding fertile plants. This seed may serve as a source of unique aneuploid stocks in oats.Key words: meiotic mutants, gene mapping, monosomics, nullisomics, oat cytogenetics.

scholarly journals The external mechanics of the chromosomes III-Meiosis in triploids

1936 ◽  
Vol 121 (823) ◽  
pp. 290-300 ◽  
Keyword(s):  
Sexual Reproduction ◽  
Chromosome Pairing ◽  
Natural Experiment ◽  
Diploid Species ◽  
Homologous Chromosomes ◽  
Normal Series ◽  
Mitosis And Meiosis ◽  
Meiosis I ◽  
Prophase Of Meiosis ◽  
The Way

Triploid organisms have three homologous chromosomes of each kind instead of the two of diploids. The regular mechanism of heredity fails in these circumstances. The triploid is incapable of breeding true by sexual reproduction. But the way in which it carries out the process of chromosome pairing and segregation is of great significance. The processes take place in normal series, but the relationships they establish are abnormal. A triploid thus provides a natural experiment, with the diploid of its own species as a control for one variable, and with triploids of different species as controls for others. In Tulipa and Hyacinthus I have made use of this experiment for inducing the principles of the external mechanics of chromosomes during the prophase of meiosis. I have inferred from them the relationships between the forces working in mitosis and meiosis. The triploid forms of various Fritillaria species make it possible to test the principles of metaphase mechanics induced from observations on structural hybrids and other polyploids (Darlington, 1932, b , and 1933, c ) as well as from the exceptional behaviour in the diploid species of Fritillaria already discussed.

Two well-known mutants of chiasma maintenance function in maize are allelic

Genome ◽  
1998 ◽  
Vol 41 (3) ◽  
pp. 417-421
Author(s):  
Marjorie P Maguire ◽  
Janet Day Jackson
Keyword(s):  
Nuclear Membrane ◽  
Membrane System ◽  
Late Prophase ◽  
Prophase I ◽  
Essentially Normal ◽  
Independent Origin ◽  
Stage Separation ◽  
Bivalent Association ◽  
Diakinesis Stage ◽  
System Breakdown

By a series of traditional crosses, allelism has been tested for two maize recessive mutants of independent origin, dy1 and dsy1, both called desynaptic. These mutants both display loss of chiasmate association during diakinesis (late prophase I) but at differing frequencies. This chiasma loss happens before nucleolar loss and nuclear membrane system breakdown. That crossovers have occurred to establish the chiasmata in the first place has been documented by diakinesis-stage separation of heterozygous heterochromatic regions in univalents formed by bivalent-association breakdown. In the present work, the two mutants have been found to be allelic by the outcome of traditional crosses that produced variant plants which were heterozygous for the two alleles. These plants express a unique phenotype at diakinesis, but are essentially normal at pachytene, metaphase I, anaphase I, and later stages of meiosis.Key words: chiasma, crossover, complementation.

FUSION OF CHROMOCENTERS IN PREMEIOTIC INTERPHASE OF SECALE CEREALE AND ITS POSSIBLE RELATIONSHIP TO CHROMOSOME PAIRING

1977 ◽  
Vol 19 (2) ◽  
pp. 313-321 ◽  
Author(s):  
J. G. Bowman ◽  
Tibor Rajhathy
Keyword(s):  
Chromosome Pairing ◽  
Secale Cereale ◽  
Disruptive Effect ◽  
Immature Inflorescence ◽  
Multivalent Formation ◽  
Relationship Of ◽  
The Relationship ◽  
Metaphase I

The premeiotic interphase of rye has been found to exhibit a synchronized fusion of chromocenters. This results in a solid knot of heterochromatin localized to one side of the nucleus. Colchicine injected into the immature inflorescence of diploid rye has been found to induce univalent and multivalent formation at metaphase I. The early premeiotic interphase was the phase of development most sensitive to colchicine. Colchicine was also found to have a similar disruptive effect on fusion of chromocenters in the premeiotic interphase. The relationship of these observations to chromosome pairing is discussed.

CHROMOSOME ASSOCIATIONS AT DIAKINESIS IN THE CULTIVATED STRAWBERRY

1971 ◽  
Vol 13 (2) ◽  
pp. 231-236 ◽  
Author(s):  
D. W. S. Mok ◽  
W. D. Evans
Keyword(s):  
Chromosome Pairing ◽  
Genetic Data ◽  
Cytological Evidence ◽  
Tetrasomic Inheritance ◽  
Secondary Pairing ◽  
Multivalent Formation ◽  
Chromosome Associations

The analysis of chromosome pairing in the cultivated strawberry revealed that multivalent formation occurs in each of the nine cultivars examined. Secondary pairing and a loose association of bivalents were also observed. The cytological evidence suggests that tetrasomic inheritance should be considered in the interpretation of genetic data.

NON-RANDOM CHROMOSOME ASSOCIATIONS AT DIPLOTENE AND DIAKINESIS IN A TETRAPLOID CLONE OF VACCINIUM AUSTRALE SMALL

1971 ◽  
Vol 13 (2) ◽  
pp. 270-276 ◽  
Author(s):  
G. Jelenkovic ◽  
E. Harrington
Keyword(s):  
Meiotic Division ◽  
Great Majority ◽  
Late Prophase ◽  
Multivalent Formation ◽  
Chromosome Associations ◽  
Tetraploid Genotype

In a cultivated tetraploid genotype (2n=4x=48) of Vaccinium australe Small the chromosome associations at late prophase of the first meiotic division and the separation of the chromosomes at anaphase I and anaphase II were investigated.Of the 223 PMC's analyzed one quarter of them displayed only bivalent associations; the remaining displayed both bivalent and quadrivalent associations. In about 3% of the PMC's, hexavalents were observed. No univalents, trivalents or pentavalents were found. The non-randomness of the chromosome associations is interpreted as resulting from obligatory pairing and localized distal chiasma.In spite of multivalent formation, in 115 PMC's studied, separation of the chromosomes at anaphase I is regular and in 95 daughter nuclei 24 chromosomes were counted. At anaphase II, the great majority of the nuclei revealed regular separation of the chromosomes and consequently numerically balanced gametes are produced.

scholarly journals Haploid Arabidopsis Thaliana Callus and Plants From Anther Culture

1972 ◽  
Vol 25 (2) ◽  
pp. 259 ◽  
Author(s):  
PM Gresshoff ◽  
CH Doy
Keyword(s):  
Arabidopsis Thaliana ◽  
Hordeum Vulgare ◽  
Callus Formation ◽  
Defined Medium ◽  
Dark Cycle ◽  
Late Prophase ◽  
General Application ◽  
High Auxin ◽  
Haploid Callus ◽  
Prophase Of Meiosis

Haploid callus and plants were cultured from the anthers of diploid A. thaliana. This depends on removing anthers during late prophase of meiosis, selecting a genotype favouring callus formation from dividing sporocytes on a high auxin-low kinetin concentration, fully defined medium, then inducing differentiation by transfer to a low auxin-high kinetin concentration, fully defined medium, with a light-dark cycle. Attempts to produce embryoids directly from' anthers were unsuccessful. The view that our approach may have Ii. more general application is discussed in relation to the work of others and our culture of haploid callus and plantlets from tomato (LycoperBicon eBculentum) and haploid callus from barley (Hordeum vulgare).

Chromosome pairing affinity and quadrivalent formation in polyploids: do segmental allopolyploids exist?

Genome ◽  
1996 ◽  
Vol 39 (6) ◽  
pp. 1176-1184 ◽  
Author(s):  
J. Sybenga
Keyword(s):  
Key Words ◽  
Chromosome Pairing ◽  
Meiotic Behaviour ◽  
Homoeologous Pairing ◽  
Preferential Pairing ◽  
Multivalent Formation ◽  
Well Differentiated ◽  
Quadrivalent Frequency ◽  
Segmental Allopolyploid ◽  
Clear Cases

When polyploid hybrids with closely related genomes are propagated by selfing or sib-breeding, the meiotic behaviour will turn into essentially autopolyploid behaviour as soon as the affinity between the genomes is sufficient to permit occasional homoeologous pairing. An allopolyploid will only be formed when the initial differentiation is sufficient to completely prevent homoeologous pairing (in some cases enhanced by specific genes), or when segregational dysgenesis prevents transmission of recombined chromosomes. A new polyploid hybrid may be considered a segmental allopolyploid and may show reduced multivalent formation as a result of preferential pairing between the least differentiated genomes. An established polyploid is either an autopolyploid or an allopolyploid. In exceptional cases it is thinkable that a stable segmental allopolyploid arises, in which some sets of chromosomes are well differentiated and behave as in an allopolyploid, whereas other sets are not well differentiated and behave as in an autopolyploid. No clear cases have been found in the literature so far. Key words : chromosome, pairing affinity, quadrivalent frequency, segmental allopolyploidy.

Investigations in the Triticinae II. The cytology and fertility of intergeneric and interspecific F1 hybrids and their derived amphidiploids

1953 ◽  
Vol 43 (1) ◽  
pp. 105-115 ◽  
Author(s):  
G. D. H. Bell ◽  
Leo Sachs
Keyword(s):  
Chromosome Pairing ◽  
Intergeneric Hybrids ◽  
F1 Hybrids ◽  
Cytological Evidence ◽  
Structural Chromosome ◽  
Multivalent Formation ◽  
Bivalent Formation ◽  
Low Incidence ◽  
High Degree ◽  
Differential Affinity

1. Chromosome pairing has been studied in twenty-two different sterile F1 hybrids involving the genera Aegilops, Agropyron and Triticum, together with their colchicine derived amphidiploids having chromosome numbers of 2n = 42, 56 and 70. Cytological evidence has been correlated with male and female fertility, while chromosome pairing in the parents has been studied in relation to their amphidiploids.2. Some of the sterile F1 hybrids showed little or no pairing, while in others the pairing was appreciable. There was an association of the amount of pairing with the parental combinations used in the production of the hybrids in that the interspecific hybrids were characterized by a relatively high degree of pairing, particularly those with 28 chromosomes, while the intergeneric hybrids either lacked pairing or showed a low incidence.3. In the A1 amphidiploid generation, chromosome pairing was in all cases high, and in some cases almost complete. In all cases multivalent formation in the amphidiploid was lower than bivalent formation in its undoubted F1 hybrid. Different amphidiploids showed various degrees of differential affinity. Univalent formation occurred in some amphidiploids, while bivalent formation in some was increased by a loss of chromosomes.4. In all cases there was a reduction in chiasmata per nucleus and chiasmata per bivalent in the amphidiploid compared with its parent species. Reduction values were not directly associated with any increase in chromosome number of the amphidiploid, nor with the presence of multivalents.5. No confirmation could be obtained of the view that multivalent formation in amphidiploids is a more generally sensitive index of chromosome homology than bivalent formation in the undoubted F1 hybrid. The absence of multivalents in an amphidiploid does not disprove the existence of structural chromosome homologies between the two parents.

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