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.

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.

Cytogenetic studies of interspecific hybrids between diploid species of Festuca

1986 ◽  
Vol 28 (6) ◽  
pp. 921-925 ◽  
Author(s):  
W. G. Morgan ◽  
Hugh Thomas ◽  
M. Evans ◽  
M. Borrill
Keyword(s):  
Genome Size ◽  
Chromosome Pairing ◽  
Dna Content ◽  
Interspecific Hybrids ◽  
Parental Species ◽  
Diploid Species ◽  
Chromosome Size ◽  
Cytogenetic Studies ◽  
The Difference

Chromosome pairing in hybrids between diploid species of Festuca is described. The chromosome complements of the species from different taxonomic sections vary in chromosome size and DNA content. In interspecific hybrids involving species of the section Montanae there was a relationship between the difference in DNA content of the parental species and chromosome pairing in the F1 hybrids. The larger the difference between the DNA content of the parental species, the more pronounced the failure of chromosome pairing in the F1 hybrids. Factors other than divergence in genome size were also shown to have an effect on chromosome pairing in other hybrid combinations.Key words: chromosome pairing, DNA content, Festuca, hybrids (interspecific).

Cytogenetic analysis of interspecific hybrids and amphiploids between two diploid crested wheatgrasses, Agropyron mongolicum and A. cristatum

Genome ◽  
1989 ◽  
Vol 32 (6) ◽  
pp. 1079-1084 ◽  
Author(s):  
Catherine Hsiao ◽  
Kay H. Asay ◽  
Douglas R. Dewey
Keyword(s):  
Chromosome Pairing ◽  
Morphological Variation ◽  
Reciprocal Translocation ◽  
Interspecific Hybrids ◽  
Diploid Species ◽  
Structural Rearrangements ◽  
Short Chromosome ◽  
Cytological Data ◽  
Broad Array ◽  
Pairing Behavior

Agropyron mongolicum Keng, the narrow linear-spiked diploid species (2n = 14), was hybridized with the broad pectinate-spiked diploid (2n = 14), A. cristatum (L.) Gaertner. The F1 hybrids were all diploids and morphologically intermediate to their parents. Chromosome pairing at metaphase I in the hybrids averaged 1.40 I, 5.59 II, 0.35 III, and 0.09 IV per cell, demonstrating that the two parental genomes are very similar. The F1 hybrids were partially fertile. The F2 progeny showed a broad array of variations in spike morphology and chromosome pairing behavior. Cytological data of the F1 hybrids and the F2 progeny revealed that these two diploid species contain the same basic P genome but differ by structural rearrangements of some chromosomes. The patterns of multivalent associations were the result of a heterozygous reciprocal translocation between a long and a very short chromosome segment. The colchicine-induced C0 amphiploids were fully fertile with regular chromosome pairing behavior. These two diploid species are the likely source of morphological variation in the tetraploid crested wheatgrasses.Key words: Agropyron, cytogenetics, chromosome pairing, interspecific hybrids.

Chromosomal distribution of genes in diploid Elytrigia elongata that promote or suppress pairing of wheat homoeologous chromosomes

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 34-40 ◽  
Author(s):  
Jan Dvořák
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Diploid Species ◽  
Triticum Aestivum L ◽  
Hordeum Bulbosum ◽  
Triticum Urartu ◽  
Substitution Lines ◽  
Chromosomal Distribution ◽  
Key Words Wheat ◽  
Homoeologous Chromosomes

Triticum aestivum L. lines with added or substituted chromosomes of Elytrigia elongata (Host) Nevski were hybridized with Hordeum bulbosum L. to obtain haploids and with Triticum urartu Thum. to obtain interspecific hybrids. Chromosome pairing at metaphase I was investigated in the resulting haploids and hybrids and the parental addition and substitution lines. Genes that promoted pairing of homologous or homoeologous chromosomes were found on chromosome arms 3ES, 3EL, 4ES, 5Ep, and chromosome 6E of E. elongata. Genes that suppressed pairing of homoeologous chromosomes were found on chromosome arms 4EL and 7Eq. It is concluded that genes promoting or suppressing pairing of homoeologous chromosomes are ubiquitous among diploid species. Key words: wheat, Triticum, wheatgrass, Elytrigia elongata, heterogenetic pairing, chromosome pairing, pairing promotion, pairing suppression.

Chromosome pairing in the Triticum monococcum complex: evidence for pairing control genes

Genome ◽  
1989 ◽  
Vol 32 (2) ◽  
pp. 216-226 ◽  
Author(s):  
X. M. Shang ◽  
R. C. Jackson ◽  
H. T. Nguyen ◽  
J. Y. Huang
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Diploid Species ◽  
Triticum Monococcum ◽  
Control Gene ◽  
Unpaired Chromosome ◽  
Meiotic Analyses ◽  
Diploid Level ◽  
And Behavior ◽  
Chromosome Segments

The occurrence and behavior of pairing control genes at the diploid level were analyzed by using the models and equations developed by Jackson and co-workers. It appears that all pairing control genes are codominant and they are detectable only as heterozygotes in diploids. The phenotypic expressions of such genes are the production of univalents, and this is positively correlated with the occurrence of unpaired chromosome segments at pachytene. Analyses of a large number of accessions of the Triticum monococcum complex and various hybrid combinations have also shown that pairing control gene alleles occur within accessions of the same diploid species and in intraspecific and interspecific hybrids. Strength differences among the pairing control alleles are indicated by different frequencies of univalents at the diploid level, and the occurrence of pairing control genes is not correlated with taxonomic units.Key words: mathematical models, meiotic analyses, pairing control gene, heterozygotes, pachytene, Triticum diploids.

CHROMOSOME RELATIONSHIPS BETWEEN THE CULTIVATED OAT AVENA SATIVA (6x) AND A. VENTRICOSA (2x)

1970 ◽  
Vol 12 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Hugh Thomas
Keyword(s):  
Chromosome Pairing ◽  
Avena Sativa ◽  
Diploid Species ◽  
Meiotic Behaviour ◽  
Hexaploid Species ◽  
C Genome

Chromosome pairing in the F1 hybrid between the cultivated oat Avena sativa and a diploid species A. ventricosa, and in the derived amphiploid, shows that the diploid species is related to one of the genomes of the hexaploid species. The amount of chromosome pairing observed in complex interamphiploid hybrids demonstrates further that A. ventricosa is related to the C. genome of A. sativa. However, the chromosomes of the diploid species have become differentiated from that of the C genome of A. sativa and this is readily apparent in the meiotic behaviour of both the F1 hybrid and the amphiploid.

CHROMOSOME PAIRING IN TWO INTERSPECIFIC HYBRIDS OF TRIFOLIUM

1970 ◽  
Vol 12 (4) ◽  
pp. 790-794 ◽  
Author(s):  
Chi-Chang Chen ◽  
Pryce B. Gibson
Keyword(s):  
Phylogenetic Relationship ◽  
Chromosome Pairing ◽  
Trifolium Repens ◽  
Interspecific Hybrids ◽  
Triploid Hybrid ◽  
Close Phylogenetic Relationship ◽  
Metaphase I

Both Trifolium repens (2n = 32) and T. nigrescens (2n = 16) formed bivalents during meiosis. However, their triploid hybrid showed an average of 4.27 trivalents per microsporocyte at metaphase I. The frequency of trivalents in the hybrid between T. nigrescens and autotetraploid T. occidentale (2n = 32) was 5.69. The data are interpreted to indicate: (1) a possible autotetraploid origin of T. repens; and (2) a close phylogenetic relationship among T. repens, T. nigrescens and T. occidentale.

scholarly journals Speciation towards tetraploidization after intermediate processes of non-sexual reproduction

2008 ◽  
Vol 363 (1505) ◽  
pp. 2921-2929 ◽  
Author(s):  
Carina Cunha ◽  
Ignacio Doadrio ◽  
Maria M Coelho
Keyword(s):  
Sexual Reproduction ◽  
Mating Systems ◽  
Diploid Hybrid ◽  
Polyploid Species ◽  
Animal Evolution ◽  
Sex Ratio Bias ◽  
First Time ◽  
Normal Meiosis ◽  
Experimental Crosses ◽  
Hybrid Forms

Polyploidy, hybridization and variation in mating systems are central issues for a deeper understanding of animal evolution. The Iberian species Squalius alburnoides represents an example combining all three phenomena. Previous studies showed that S. alburnoides populations are mainly composed of triploid and diploid hybrid forms (mainly females), and that the tetraploid forms are rare or absent. Both populations from the Douro drainage reveal a distinct scenario: tetraploid individuals represent 85.6–97.5% of the population, with no sex ratio bias observed. Based on the flow cytometry measurements of blood and spermatozoa cells, microsatellite loci and experimental crosses, we describe here, for the first time, two symmetric allotetraploid populations (CCAA) that resumed normal meiosis after undergoing intermediate processes of non-sexual reproduction to give rise to a new sexually reproducing polyploid species. Prezygotic (habitat selection and assortative mating) and postzygotic mechanisms (nonviable embryos) are responsible for the reproductive isolation from other forms of the S. alburnoides complex (e.g. CA, CAA). This example illustrates how hybrid polyploid complexes may lead to speciation.

Evidence for the presence of an intercontinental genome in the Australian hexaploid alliance of Hibiscus Sect. Furcaria

1980 ◽  
Vol 28 (3) ◽  
pp. 369 ◽  
Author(s):  
MY Menzel ◽  
DW Martin
Keyword(s):  
Sri Lanka ◽  
South America ◽  
Interspecific Hybrids ◽  
New World ◽  
Hawaiian Islands ◽  
Diploid Species ◽  
Australian Species ◽  
Data Support ◽  
North And South America ◽  
North And South

Genomes of the G group in Hibiscus sect. Furcaria have been found previously in one African diploid species and in various ailoploid combinations in Africa, India and Sri Lanka, North and South America and the Hawaiian Islands. Study of 11 interspecific hybrids between the Australian species H. heterophyllus and H. splendens and G-genome testers indicates that genomes somewhat related to the G group are present in the Australian allohexaploid alliance. These genomes are designated G′. Several of the intercontinental hybrids studied were weak, inviable or morphologically abnormal. The data support the interpretation that the genomes of the Australian alliance have diverged more from African and New World genomes than the latter two have from each other.

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