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.

NONSTRUCTURAL CHROMOSOME DIFFERENTIATION AMONG WHEAT CULTIVARS, WITH SPECIAL REFERENCE TO DIFFERENTIATION OF CHROMOSOMES IN RELATED SPECIES

Genetics ◽  
1981 ◽  
Vol 97 (2) ◽  
pp. 391-414
Author(s):  
Jan Dvořák ◽  
Patrick E McGuire
Keyword(s):  
Chinese Spring ◽  
Structural Changes ◽  
Wheat Cultivar ◽  
Chromosome Complement ◽  
Triticum Aestivum L ◽  
Substitution Lines ◽  
Structural Differentiation ◽  
Chromosome Differentiation ◽  
Mother Cells ◽  
Homoeologous Chromosomes

ABSTRACT Wheat cultivar Chinese Spring (Triticum aestivum L. em. Thell.) was crossed with cultivars Hope, Cheyenne and Timstein. In all three hybrids, the frequencies of pollen mother cells (PMCs) with univalents at metaphase I (MI) were higher than those in the parental cultivars. No multivalents were observed in the hybrids, indicating that the cultivars do not differ by translocations. Thirty-one Chinese Spring telosomic lines were then crossed with substitution lines in which single chromosomes of the three cultivars were substituted for their Chinese Spring homologues. The telosomic lines were also crossed with Chinese Spring. Data were collected on the frequencies (% of PMCs) of pairing of the telesomes with their homologues at MI and the regularity of pairing of the remaining 20 pairs of Chinese Spring chromosomes in the monotelodisomics obtained from these crosses. The reduced MI pairing in the intercultivar hybrids was caused primarily by chromosome differentiation, rather than by specific genes. Because the differentiation involved a large part of the chromosome complement in each hybrid, it was concluded that it could not be caused by structural changes such as inversions or translocations. In each case, the differentiation appeared to be unevenly distributed among the three wheat genomes. It is proposed that the same kind of differentiation, although of greater magnitude, differentiates homoeologous chromosomes and is responsible, together with structural differentiation, for poor chromosome pairing in interspecific hybrids.

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.

CYTOLOGY AND FERTILITY OF PENTAPLOID WHEAT HYBRIDS WITH INDUCED PAIRING BETWEEN HOMOEOLOGOUS CHROMOSOMES

1982 ◽  
Vol 24 (4) ◽  
pp. 397-408 ◽  
Author(s):  
U. Kushnir ◽  
G. M. Halloran
Keyword(s):  
Chromosome Pairing ◽  
Hexaploid Wheat ◽  
Triticum Turgidum ◽  
Triticum Aestivum L ◽  
The Other ◽  
Homoeologous Chromosome ◽  
D Genome ◽  
Homoeologous Chromosome Pairing ◽  
Wheat Hybrids ◽  
Homoeologous Chromosomes

Two mutants, each promoting homoeologous chromosome pairing in hexaploid wheat (Triticum × aestivum L. emend gr. aestivum), in the cultivar Chinese Spring, ph1b at the Ph locus on chromosome 5BL and the other, ph2, on chromosome 3DS, were compared for their influence on chromosome pairing and fertility in pentaploid hybrids with Triticum turgidum L. emend var. dicoccoides (Korn. in litt. in Schweinf.). The mutants induced increased multivalent frequency over the normal pentaploid. Lower univalent frequencies in the ph2-pentaploid, compared with the normal pentaploid, indicated that D-genome chromosomes of the former were substantially involved in homoeologous pairing. Certain differences in other meiotic processes and fertility among the pentaploids may reflect differences in the activity of the pairing genes. There appeared to be a higher level of univalent elimination in pollen and egg cells in the ph2-, compared with the ph1b-pentaploid. Tetrad formation was close to normal in the ph2- pentaploid but exhibited high levels of abnormality (monads, dyads, triads and apolar tetrads) in the ph1b-pentaploid. Fertility levels in crosses of the pentaploids with hexaploid wheat, while low, were much lower for the ph1b-, compared with the ph2-pentaploid.

scholarly journals Aegilops × Secale hybrids: the production and cytology of diploid hybrids

1971 ◽  
Vol 17 (1) ◽  
pp. 17-31 ◽  
Author(s):  
B. N. Majisu ◽  
J. K. Jones
Keyword(s):  
Embryo Culture ◽  
Interspecific Hybrids ◽  
Diploid Species ◽  
Genetic Mechanism ◽  
Genetic Incompatibility ◽  
Homologous Chromosomes ◽  
Homoeologous Chromosomes

SUMMARYHybrids between four diploid species of Aegilops and species of Secale were obtained by using embryo culture. There was a marked incompatibility in the crosses between Secale species and each of the four species in Section Sitopsis of Aegilops and Ae. mutica. It is suggested that this genetic incompatibility with Secale species is an additional similarity between these species of Aegilops and the diploid species of Triticum.Most chromosomes of Aegilops (A) and Secale (S) are univalent during meta-anaphase of meiosis in these hybrids, but some appeared to associate and others to pair as apparently normal chiasmate bivalents. Analysis of non-chiasmate and chiasmate associations showed that the frequencies of autosyndetic (AA and SS) and allosyndetic (AS) associations fitted the 3AA: 7AS: 3SS ratio expected if association and pairing is at random. Any deviations from random involved a deficiency rather than an excess of Aegilops-Secale pairing. There is no evidence that the chromosomes of Secale are homologous with those of Ae. caudata, Ae. comosa and Ae. umbel-lulata, and it is suggested that the genome of Secale species does not show any homology with the genomes of the genera Aegilops. This does not preclude the presence of homologous segments. It is suggested that the possibility of random association of chromosomes should be considered when occasional pairing in interspecific hybrids is analysed, and that identification of chromosomes and recognition of chiasmata are required. The possibilities of chiasmata between non-homologous chromosomes, of a genetic mechanism in rye which suppresses the pairing of homoeologous chromosomes, and of other factors causing asynapsis and pseudo-synapsis between genetically similar chromosomes are discussed.

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.

scholarly journals LATENT NONSTRUCTURAL DIFFERENTIATION AMONG HOMOLOGOUS CHROMOSOMES AT THE DIPLOID LEVEL: CHROMOSOME 6Be OF AEGILOPS LONGISSIMA

Genetics ◽  
1986 ◽  
Vol 114 (2) ◽  
pp. 579-592
Author(s):  
Rama S Kota ◽  
Patrick E McGuire ◽  
Jan Dvořák
Keyword(s):  
Chromosome Pairing ◽  
Chinese Spring ◽  
Constitutive Heterochromatin ◽  
Diploid Species ◽  
Triticum Aestivum L ◽  
Homologous Chromosomes ◽  
B Genome ◽  
Aegilops Longissima ◽  
Chinese Spring Wheat ◽  
Diploid Level

ABSTRACT Previous work has shown that chromosome pairing at metaphase I (MI) of wheat homologous chromosomes from different inbred lines (heterohomologous chromosomes) is reduced relative to that between homologous chromosomes within an inbred line (euhomologous chromosomes). In order to determine if a potential for this phenomenon exists in diploid species closely related to the wheat B genome, MI chromosome pairing was investigated between euhomologous and heterohomologous 6Be (=6Se) chromosomes, each from a different population of Aegilops longissima Schweinf. et Muschl. (2n = 2x = 14) substituted for chromosome 6B of Chinese Spring wheat (Triticum aestivum L., 2n = 6x = 42). Euhomologous and heterohomologous monotelodisomics, i.e., plants with one complete chromosome 6Be and a telosome of either 6Bep or 6Beq, were constructed in the isogenic background of Chinese Spring. Pairing at MI of the Ae. longissima chromosomes was reduced in heterohomologous monotelodisomics compared to that in the corresponding euhomologous monotelodisomics. The remaining 20 pairs of Chinese Spring chromosomes paired equally well in the euhomologous and heterohomologous monotelodisomics. Thus, the cause of the reduced pairing must reside specifically in the Ae. longissima heterohomologues. In the hybrids between the Ae. longissima lines that contributed the substituted chromosomes, pairing between the heterohomologous chromosomes was normal and did not differ from that of the euhomologous chromosomes. These data provide evidence that a potential for reduced pairing between the heterohomologues is present in the diploid species, but is expressed only in the polyploid wheat genetic background. The reduction in heterohomologous chromosome pairing was greater in the p arm than in the q arm, exactly as in chromosome 6B of wheat. It is concluded that the reduced pairing between Ae. longissima heterohomologues has little to do with constitutive heterochromatin. The value of chromosome pairing as an unequivocal means of determining the origin of genomes in polyploid plants is questioned.

Genetic control of meiotic chromosome pairing in polyploids in the genus Hordeum

1985 ◽  
Vol 27 (5) ◽  
pp. 515-530 ◽  
Author(s):  
P. K. Gupta ◽  
George Fedak
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Meiotic Chromosome ◽  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Major Locus ◽  
In The Wild ◽  
Hordeum Species ◽  
Homoeologous Chromosomes ◽  
Existing Data

Existing data on meiosis in hexaploid and tetraploid species of Hordeum, their respective polyhaploids, and intergeneric – interspecific hybrids indicate that a meiotic pairing control system exists in this genus. The system is probably polygenic and it is therefore unlikely that a major locus such as Ph in Triticum controls chromosome pairing. It is more efficient in the tetraploids than hexaploids, permitting some intergenomic pairing in the latter. In the polyhaploids the pairing control is somewhat hemizygous ineffective. The pairing of homoeologous chromosomes in the wild polyploid Hordeum species is generally inhibited by H. vulgare and variably enhanced by genomes of Secale species.Key words: Hordeum, synapsis regulation, intergeneric hybrid, polyhaploids, hemizygous.

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.

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