Chromosome pairing in octoploid F1 and octoploid amphiploid hybrids between Bromus inermis and B. pumpellianus

1985 ◽  
Vol 27 (5) ◽  
pp. 538-541 ◽  
Author(s):  
K. C. Armstrong
Keyword(s):  
Chromosome Pairing ◽  
Bromus Inermis ◽  
Chromosome Differentiation ◽  
Bivalent Formation ◽  
Tetraploid Cytotypes

Chromosome pairing in the amphiploid (8x) of 4x Bromus pumpellianus ssp. dicksonii × 4x B. inermis was compared with pairing in the F1 hybrids between natural octoploid cytotypes of B. inermis and B. pumpellianus and the octoploid parents. Predominantly bivalent pairing was found in both the amphioctoploid, octoploid F1 hybrids, and octoploid parents. Bivalent formation in the amphioctoploid could be based on chromosome differentiation between the tetraploid cytotypes of B. inermis and B. pumpellianus. These results suggest that the evolution of the octoploid cytotypes of B. inermis and B. pumpellianus could have involved hybridization of the tetraploid cytotypes.Key words: Bromus, chromosome pairing, octoploid, F1 hybrid, amphiploid.

Chromosomal evidence for autotetraploidy in the Turnera ulmifolia complex (Turneraceae)

1991 ◽  
Vol 69 (6) ◽  
pp. 1302-1308 ◽  
Author(s):  
Joel S. Shore
Keyword(s):  
Chromosome Pairing ◽  
Goodness Of Fit ◽  
Chromosome Counts ◽  
Goodness Of Fit Test ◽  
Bivalent Formation ◽  
Pairing Model ◽  
Turnera Ulmifolia ◽  
Variety Show ◽  
A Minor ◽  
Tetraploid Cytotypes

The hypothesis that tetraploids of two taxonomic varieties of the Turnera ulmifolia complex, vars. elegans and intermedia, have had autopolyploid origins, was tested. Chromosome counts within each variety show that two cytotypes occur with somatic numbers of 2n = 10 and 2n = 20. Tetrapoloids of both var. intermedia and var. elegans have pollen fertility approximately 13% less than that of diploids. Synthetic tetraploids produced by colchicine doubling exhibit pollen fertilities virtually identical to those of the natural tetraploids. While diploids exhibited only bivalent formation, tetraploids showed varying frequencies of univalents, bivalents, trivalents, and quadrivalents. The chromosome pairing model of R. C. Jackson and D. P. Hauber (1982. Am. J. Bot. 69: 644–646) and a minor modification of the goodness-of-fit test for that model, were used to test the hypothesis of an autopolyploid origin. For four of the six populations studied meiotically, the data fit the model. The data indicate that the tetraploid cytotypes of T. ulmifolia vars. elegans and intermedia have had autopolyploid origins. Key words: Turnera ulmifolia, autotetraploid, chromosome pairing model.

CHROMOSOME PAIRING IN POA ANNUA L.

1973 ◽  
Vol 15 (3) ◽  
pp. 549-551 ◽  
Author(s):  
W. M. Ellis ◽  
B. T. O. Lee ◽  
D. M. Calder
Keyword(s):  
Chromosome Pairing ◽  
Breeding System ◽  
Tetraploid Plant ◽  
Poa Annua ◽  
Diploid Population ◽  
Bivalent Formation

Cytological studies carried out on six tetraploid and one diploid population and a synthesized tetraploid plant have shown regular bivalent formation at meiosis. This regularity appears to be genetically controlled in this species. Plants from all the populations behave as diploids. The implications of this regular disomic chromosome pairing on recombination, variation and the breeding system of P. annua are considered.

CHROMOSOME DIFFERENTIATION IN POLYPLOID SPECIES OF ELYTRIGIA, WITH SPECIAL REFERENCE TO THE EVOLUTION OF DIPLOID-LIKE CHROMOSOME PAIRING IN POLYPLOID SPECIES

1981 ◽  
Vol 23 (2) ◽  
pp. 287-303 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Special Reference ◽  
Normal Level ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Triticum Aestivum L ◽  
Polyploid Species ◽  
Chromosome Differentiation

Triticum aestivum L. em Thell ditelosomics 7AL and 7DS and T. aestivum-Elytrigia elongata (Host) Holub (2n = 2x = 14) ditelosomic additions were crossed with "E. elongata 4x" (2n = 4x = 28), E. caespitosa (C. Koch) Nevski (2n = 4x = 28), and E. intermedia (Host) Nevski (2n = 6x = 42). The effect of each Elytrigia genotype on homoeologous (heterogenetic) chromosome pairing was assessed by comparing the pairing frequencies of T. aestivum cv. Chinese Spring telosomes 7AL and 7DS in the hybrids with the pairing frequency of telosome 7AL in haploid Chinese Spring. The genotype of "E. elongata 4x" had no effect on heterogenetic pairing in the hybrids. Although some genotypes of E. caespitosa and E. intermedia promoted heterogenetic pairing in the hybrids, others had no effect. Telosome VS of E. elongata interacted in a complementary fashion with the genotype of "E. elongata 4x," but not with the genotypes of Chinese Spring and E. caespitosa, and it promoted heterogenetic pairing. In hybrids in which the wheat diploidizing genes were active at the normal level, the E. elongata telosomes paired with chromosomes of "E. elongata 4x" in 5.8% to 24.6% of the cells, with chromosomes of E. caespitosa in 0.0% to 1.0% of the cells, and with chromosomes of E. intermedia in 0.0% to 2.8% of the cells. A model of chromosome differentiation is discussed and special attention is devoted to the origin of diploid-like pairing in polyploid species.

Evidence for genetic suppression of heterogenetic chromosome pairing in polyploidy species of Solanum, sect. Petota

1983 ◽  
Vol 25 (5) ◽  
pp. 530-539 ◽  
Author(s):  
Jan Dvořák
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Diploid Species ◽  
Diploid Hybrid ◽  
Polyploid Species ◽  
Chromosome Differentiation ◽  
Genetic Suppression ◽  
Solanum Sect ◽  
Paradoxical Results

Data on chromosome pairing in haploids and interspecific hybrids of Solanum, sect. Petota reported in the literature were used to determine whether the diploidlike chromosome pairing that occurs in some of the polyploid species of the section is regulated by the genotype or brought about by some other mechanism. The following trends emerged from these data. Most of the polyploid × polyploid hybrids had high numbers of univalents, which seemed to indicate that the polyploid species were constructed from diverse genomes. Haploids, except for those derived from S. tuberosum, had incomplete chromosome pairing. All hybrids from diploid × diploid crosses had more or less regular chromosome pairing, which suggested that all investigated diploid species have the same genome. Likewise, hybrids from polyploid × diploid crosses had high levels of chromosome pairing. These paradoxical results are best explained if it is assumed that (i) the genotypes of most polyploid species, but not those of the diploid species, suppress heterogenetic pairing, (ii) that nonstructural chromosome differentiation is present among the genomes of both diploid and polyploid species, and (iii) the presence of the genome of a diploid species in a polyploid × diploid hybrid results in promotion of heterogenetic pairing. It is, therefore, concluded that heterogenetic pairing in most of the polyploid species is genetically suppressed.

A AND B GENOME HOMOEOLOGIES IN TETRAPLOID AND OCTOPLOID CYTOTYPES OF BROMUS INERMIS

1979 ◽  
Vol 21 (1) ◽  
pp. 65-71 ◽  
Author(s):  
K. C. Armstrong
Keyword(s):  
Chromosome Pairing ◽  
Convincing Evidence ◽  
Bromus Inermis ◽  
Open Pollination ◽  
Homoeologous Chromosome ◽  
Genome Chromosome ◽  
B Genome ◽  
Homoeologous Chromosome Pairing ◽  
A Genome ◽  
Structural Differences

Homoeology between the A and B genomes of allotetraploid (2n = 4x = 28) AiAiBiBi and autoallooctoploid (2n = 8x = 56) AIAIAIAIBIBIBIBI cytotypes of B. inermis Leyss. was studied in a tetraploid F1 hybrid (AeAeAiBi) from 4x B. erectus × 4x B. inermis and in a haplo-triploid (AIeAIeBI) which occurred spontaneously in the F2 from open-pollination among plants of the hexaploid F1 hybrid (AeAeAIAIBIBI) from 4x B. erectus × 8x B. inermis. Chromosome pairing at metaphase I in both the tetraploid (AeAeAiBi) and haplo-triploid (AIeAIeBI) indicated that for each A genome chromosome there was a corresponding B genome homoeologue. There was no convincing evidence of gross structural differences between the two homoeologous genomes. The frequency of trivalent formation in the haplo-triploid was approximately one-half that found in two pentaploids (2n = 5x = 35) AIeAIeAIBIBI. This indicates that the pairing affinity between the A and B genomes is one-half that between homologues as expressed by trivalent formation in triploids of the type AAB and AAA. Homoeologous chromosome pairing (A with B) may be controlled by a gene which is hemizygous ineffective.

THE SIGNIFICANCE OF MEIOTIC CHROMOSOME PAIRING IN TETRAPLOID (2n = 28) BROMUS PUMPELLIANUS SCRIBN. SSP. DICKSONII

1972 ◽  
Vol 14 (4) ◽  
pp. 763-771 ◽  
Author(s):  
K. C. Armstrong
Keyword(s):  
Chromosome Pairing ◽  
High Frequency ◽  
Chiasma Frequency ◽  
Karyotype Analysis ◽  
Meiotic Chromosome ◽  
Low Frequency ◽  
Meiotic Chromosome Pairing ◽  
Ring Bivalents ◽  
Bivalent Formation

Bivalent formation was predominant at meiosis in B. pumpellianus ssp. dicksonii. The average in 15 plants ranged from 11.38 to 13.77 bivalents per cell. The high chiasma frequency (23.41-26.74) was a reflection of the high frequency of ring bivalents (9.48-12.42). A low frequency of quadrivalents occurred (0.06-1.22). A karyotype of this species was presented from both a highly contracted and moderately contracted cell and the differences between these two were noted. Four satellites were found, two large and two minute. There were 3-5 submedian and 5-7 median chromosomes depending on the cell studied. In addition two subterminal chromosomes were present. The meiotic and karyotype analysis suggest a deviation from an autotetraploid behaviour, but the presence of quadrivalents and similarities between pairs in the karyotype suggested closely related genomes. Alternatively it was considered that the quadrivalents could be due to translocation heterozygotes. The implications of these results were discussed in relation to the reported meiotic events in the octoploids, B. inermis and B. pumpellianus.

GENOME RELATIONSHIPS IN BROMUS ERECTUS, B. PUMPELLIANUS SSP. DICKSONII AND B. PUMPELLIANUS

1975 ◽  
Vol 17 (3) ◽  
pp. 391-394
Author(s):  
K. C. Armstrong
Keyword(s):  
Genetic Control ◽  
Chromosome Pairing ◽  
Low Frequency ◽  
Homoeologous Chromosome ◽  
Homoeologous Chromosome Pairing ◽  
Bivalent Formation ◽  
Bromus Erectus

Chromosome pairing was studied in hexaploid (2n = 42) hybrids of B. erectus (2n = 28) × B. pumpellianus (2n = 56) and B. pumpellianus ssp. dicksonii (2n = 28) × B. pumpellianus. Chromosome pairing in the B. erectus × B. pumpellianus hybrid was complete with predominantly bivalent formation and a low frequency of quadrivalents. The pairing results support the contention that B. pumpellianus is an autoalloploid with an AAAABBBB genome formula. The B. pumpellianus ssp. dicksonii × B. pumpellianus hybrid has an AAABBB genome formula. The presence of quadrivalents, hexavalents and cells containing a total number of bivalents or bivalents plus trivalents in excess of 14 indicated pairing between the A and B genomes. However, a high univalent frequency showed that the A and B genomes were homoeologous rather than homologous. Evidence for genetic control of homoeologous chromosome pairing and homoeologous differentiation between the genomes of the species is discussed.

Meiotic pairing in haploids and amphidiploids of spontaneous versus synthetic origin in rape, Brassica napus L.

1986 ◽  
Vol 28 (3) ◽  
pp. 330-334 ◽  
Author(s):  
T. Attia ◽  
G. Röbbelen
Keyword(s):  
Brassica Napus ◽  
Chromosome Number ◽  
Chromosome Pairing ◽  
Structural Modification ◽  
Meiotic Pairing ◽  
Chromosome Behaviour ◽  
Preferential Pairing ◽  
Brassica Napus L ◽  
Bivalent Formation ◽  
Homoeologous Chromosomes

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.

Hybrids of Hordeum californicum and 2x H. brevisubulatum s.l. with Agropyron caninum

1985 ◽  
Vol 27 (4) ◽  
pp. 380-386 ◽  
Author(s):  
P. K. Gupta ◽  
George Fedak
Keyword(s):  
Chromosome Pairing ◽  
Floral Morphology ◽  
Embryo Rescue ◽  
Intergeneric Hybrid ◽  
Bivalent Formation ◽  
The Difference ◽  
Agropyron Caninum ◽  
Hordeum Species

Two diploid Hordeum species, H. californicum (2n = 2x = 14) and H. brevisubulatum s.l. (2n = 2x = 14), were used successfully to produce hybrids with Agropyron caninum (2n = 4x = 28) through embryo rescue techniques. The floral morphology of the hybrids was intermediate between the parents in each case. Both hybrids were triploids (2n = 3x = 21), and chromosome pairing exhibited a mean of 3.86 bivalents in the hybrid with H. californicum and a mean of 5.53 bivalents in the hybrid with H. brevisubulatum. Bivalent formation was attributed to a common genome between the diploid Hordeum species and the tetraploid A. caninum. It could not be ascertained whether the difference in the two hybrids was due to a difference in the degree of homology or difference in meiotic control mechanisms.Key words: Hordeum, Agropyron, homeology, triploid, intergeneric hybrid.

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