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.

Assessment of chromosome associations in haploids and their parental accessions in Hordeum

Genome ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 204-210 ◽  
Author(s):  
R. von Bothmer ◽  
N. C. Subrahmanyam
Keyword(s):  
Genetic Variation ◽  
Chromosome Pairing ◽  
Diploid Species ◽  
Meiotic Behaviour ◽  
Meiotic Pairing ◽  
Homoeologous Pairing ◽  
Homoeologous Chromosome ◽  
Homologous Pairing ◽  
Homoeologous Chromosome Pairing ◽  
Chromosome Associations

Meiotic pairing was studied in the following species and their haploid derivatives: Hordeum cordobense 2x, H. marinum 2x and 4x, H. secalinum 4x, H. capense 4x, H. jubatum 4x, H. brachyantherum 4x and 6x, H. lechleri 6x, and H. procerum 6x. The study revealed (i) homologous pairing in diploid species and very little nonhomologous associations in their mono-haploids; (ii) the alloploid nature of the polyploid taxa; (iii) a certain degree of homoeologous pairing in polyhaploids despite the diploid-like meiotic behaviour of the polyploids; (iv) genetic variation in the suppression of homoeologous chromosome pairing in different Hordeum species.Key words: Hordeum, meiotic pairing, haploids.

THE EFFECT OF GENES CONTROLLING DIFFERENT DEGREES OF HOMOEOLOGOUS PAIRING ON QUADRIVALENT FREQUENCY IN INDUCED AUTOTETRAPLOID LINES OF TRITICUM LONGISSIMUM

1976 ◽  
Vol 18 (2) ◽  
pp. 357-364 ◽  
Author(s):  
Lydia Avivi
Keyword(s):  
Chromosome Pairing ◽  
Chiasma Frequency ◽  
Spatial Separation ◽  
Meiotic Pairing ◽  
Homoeologous Pairing ◽  
Homologous Pairing ◽  
Homologous Chromosomes ◽  
Chromosomal Pairing ◽  
Per Se ◽  
Quadrivalent Frequency

Different genotypes of Triticum longissimum are known to either promote or suppress chromosome pairing in crosses with polyploid wheats. Lines that promote homoeologous pairing are here designated as intermediate pairing lines, while those which have no such effect or suppress pairing are known as low pairing lines. To determine a possible effect of these genotypes on homologous pairing, tetraploidy was induced in both lines and chromosomal pairing was studied at first metaphase of meiosis. While the two induced autotetraploids did not differ in chiasma frequency or in the number of paired chromosomal arms, they differed significantly in multivalent frequency; the intermediate-pairing autotetraploid exhibited the same multivalent frequency as that expected on the basis of two telomeric initiation sites, while the low pairing autotetraploid exhibited a significantly lower frequency. It is assumed that in the autotetraploid the low pairing genotype does not affect meiotic pairing per se, but modifies the pattern of homologous association in a similar manner to that known in polyploids and caused by diploidization genes. It is speculated that the tendency for bivalent pairing in the low pairing autotetraploid is due to spatial separation of the four homologous chromosomes in somatic and premeiotic cells into two groups of two.

FERTILITY AND MEIOTIC BEHAVIOUR IN TETRAPLOID BARLEY

1975 ◽  
Vol 17 (1) ◽  
pp. 121-123 ◽  
Author(s):  
George Fedak
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Behaviour ◽  
Preferential Pairing ◽  
Subsequent Fertility ◽  
Structural Differences ◽  
Hordeum Leporinum ◽  
Metaphase I

Chromosome pairing at metaphase I and distribution at anaphase I were examined in 3 autotetraploid and 3 amphidiploid parents and their F1 hybrids and related to spike fertility of the respective plants. Structural differences translocated from the Hordeum leporinum chromosomes to H. vulgare did not significantly enhance preferential pairing and subsequent fertility in the latter as anticipated. Quadrivalent formation was not related but regular disjunction at anaphase I was related to spike fertility.

Chromosome pairing and aneuploidy in tetraploid triticale. II. Unstabilized karyotypes

Genome ◽  
1987 ◽  
Vol 29 (4) ◽  
pp. 562-569 ◽  
Author(s):  
Adam J. Lukaszewski ◽  
Barbara Apolinarska ◽  
J. Perry Gustafson ◽  
K.-D. Krolow
Keyword(s):  
Key Words ◽  
Chromosome Pairing ◽  
Homoeologous Pairing ◽  
Polyploid Species ◽  
C Banding ◽  
Group 4 ◽  
Genome Recombination ◽  
Segregation Ratios ◽  
Homoeologous Chromosomes

In the progeny of tetraploid triticale plants that segregated for either one, two, or three pairs of homoeologous wheat chromosomes, plants were selected that had 13 pairs of homologues and 1 pair of presumed wheat homoeologues. Segregation ratios of "homoeologues" were close to 1:2:1 except for group 4, where no 4B homozygotes were recovered. Aneuploid frequency among 190 progeny of the segregating plants was 4.74%. C-banding at meiosis showed that "homoeologues" paired with frequencies ranging from 0.1 to 1.74 paired arms per chromosome. The only exception was the 4A–4B pair, which did not synapse. It was concluded that the high pairing frequencies between "homoeologous" chromosomes were due to translocations that had accumulated during line development. With few exceptions, translocations could not be detected by C-banding. The results demonstrate that genome recombination in polyploid species may occur at two levels simultaneously: by segregation of complete chromosomes and by translocations between homoeologues. Key words: C-banding, homoeologous pairing, translocations.

A reassessment of genome relationships between Thinopyrum bessarabicum and T. elongatum of the Triticeae

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 903-914 ◽  
Author(s):  
Prem P. Jauhar
Keyword(s):  
Chromosome Pairing ◽  
Chiasma Frequency ◽  
Parental Species ◽  
Preferential Pairing ◽  
Chromosome Configuration ◽  
Synaptic Competition ◽  
Ring Bivalents ◽  
The Mean ◽  
Quadrivalent Frequency ◽  
Thinopyrum Bessarabicum

Chromosome pairing and chiasma frequency in diploid (2n = 2x = 14; JE genomes), amphidiploid (2n = 4x = 28; JJEE), and triploid (2n = 3x = 21; JJE) hybrids between Thinopyrum bessarabicum (2n = 2x = 14; JJ) and T. elongatum (2n = 2x = 14; EE) were analyzed. The diploid hybrids (JE) showed a mean pairing of < 0.01V + 0.30IV + 0.28III + 4.98II + 1.97I with 8.36 chiasmata per cell. The pairing was rather poor, most bivalents being rod-shaped; some were clearly hetero-morphic and loosely paired (probably pseudochiasmate). The diploid hybrids were sterile, showing the reproductive isolation of the parental species. The JJE triploid had a mean chromosome configuration of < 0.01VI + 0.06IV + 1.53III + 5.46II + 5.20I with a chiasma frequency of 13.45 per cell. Chromosomes of the duplicated genome JJ showed preferential pairing, forming mostly ring bivalents with two or even three chiasmata each, as in the T. bessarabicum parent; most chromosomes of the E genome remained as univalents. Thus, the E genome chromosomes offered little synaptic competition to the chromosomes of the duplicated JJ genome. The degree of preferential pairing was even stronger in the JJEE amphidiploids, which predominantly showed bivalent pairing with up to 14 ring bivalents in some cells. They had a mean pairing of 0.01VI + 0.55IV + 0.26III + 11.75II + 1.42I; the mean quadrivalent frequency per cell varied from 0.10 to 1.53. Thus J and E genomes essentially maintained their meiotic integrity at the 4x level. This pattern of chromosome pairing in hybrids at different ploidies and the sterility of diploid hybrids show that J and E are distinct genomes and that there is little justification for merging them, as suggested by previous workers. The J and E are homoeologous at best. The merger of Lophopyrum (E genome) with the genus Thinopyrum (J genome) would be improper. Although the J and E genomes are close enough to permit some intergenomic gene flow, which may be exploited in plant breeding, they are certainly not close enough to have the same genomic designation. The JJEE amphidiploids are meiotically stable and may be a useful source of genes for wheat improvement.Key words: genome, meiosis, chromosome pairing, phylogenetic relationships, Thinopyrum, interspecific hybrid, autoallo-triploid, amphidiploid.

Chromosome complement and nucleoli in the Festuca pallescens alliance from South America

1991 ◽  
Vol 69 (12) ◽  
pp. 2756-2761 ◽  
Author(s):  
Jorge Dubcovsky ◽  
Arturo J. Martínez
Keyword(s):  
South America ◽  
Key Words ◽  
Chromosome Pairing ◽  
Chromosome Complement ◽  
Meiotic Behaviour ◽  
Root Tips ◽  
Festuca Pallescens ◽  
Secondary Constrictions

The karyotypes, chromosomes with secondary constrictions, and maximum number of nucleoli of 14 hexaploid (2n = 42) species of Festuca native to South America are described to complete the cytological characterization of the Festuca pallescens alliance. The species analyzed were Festuca acanthophylla E. Desv., Festuca argentinensis (St.-Yves) Türpe, Festuca chrysophylla Phil., Festuca circinata Griseb., Festuca cirrosa (Speg.) Parodi, Festuca gracillima J. D. Hook, Festuca kurtziana St.-Yves, Festuca monticola Phil., Festuca pallescens (St.-Yves) Parodi, Festuca scabriuscula Phil., Festuca scirpifolia (Presl.) Kunth, Festuca thermarum Phil., Festuca tunicata E. Desv., and Festuca ventanicola Speg. They have symmetric and uniform karyotypes but differed (p < 0.01) in arm ratio values. The species had similar maxima in the number of nucleoli in the root tips (9–12), microspores (5–7), and chromosomes with secondary constrictions (10–14). The arrangement of chromosomes in homomorphic pairs and their meiotic behaviour suggest that the species are allohexaploids. The size, shape, and number of chromosomes bearing secondary constrictions confirm that these species are members of the same alliance. Key words: Festuca, karyotype, nucleolus, chromosome pairing.

Synthesis and cytological characterization of trigeneric hybrids of durum wheat with and without Ph1

Genome ◽  
2004 ◽  
Vol 47 (6) ◽  
pp. 1173-1181 ◽  
Author(s):  
Prem P Jauhar ◽  
M Doğramaci ◽  
T S Peterson
Keyword(s):  
In Situ Hybridization ◽  
Chromosome Pairing ◽  
Genetic Recombination ◽  
Genomic In Situ Hybridization ◽  
Homoeologous Pairing ◽  
Alien Gene Transfer ◽  
Chromosome 5B ◽  
Alien Gene ◽  
Trigeneric Hybrids

Wild grasses in the tribe Triticeae, some in the primary or secondary gene pool of wheat, are excellent reservoirs of genes for superior agronomic traits, including resistance to various diseases. Thus, the diploid wheatgrasses Thinopyrum bessarabicum (Savul. and Rayss) Á. Löve (2n = 2x = 14; JJ genome) and Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) are important sources of genes for disease resistance, e.g., Fusarium head blight resistance that may be transferred to wheat. By crossing fertile amphidiploids (2n = 4x = 28; JJEE) developed from F1 hybrids of the 2 diploid species with appropriate genetic stocks of durum wheat, we synthesized trigeneric hybrids (2n = 4x = 28; ABJE) incorporating both the J and E genomes of the grass species with the durum genomes A and B. Trigeneric hybrids with and without the homoeologous-pairing suppressor gene, Ph1, were produced. In the absence of Ph1, the chances of genetic recombination between chromosomes of the 2 useful grass genomes (JE) and those of the durum genomes (AB) would be enhanced. Meiotic chromosome pairing was studied using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH). As expected, the Ph1-intergeneric hybrids showed low chromosome pairing (23.86% of the complement), whereas the trigenerics with ph1b (49.49%) and those with their chromosome 5B replaced by 5D (49.09%) showed much higher pairing. The absence of Ph1 allowed pairing and, hence, genetic recombination between homoeologous chromosomes. Fl-GISH analysis afforded an excellent tool for studying the specificity of chromosome pairing: wheat with grass, wheat with wheat, or grass with grass. In the trigeneric hybrids that lacked chromosome 5B, and hence lacked the Ph1 gene, the wheat–grass pairing was elevated, i.e., 2.6 chiasmata per cell, a welcome feature from the breeding standpoint. Using Langdon 5D(5B) disomic substitution for making trigeneric hybrids should promote homoeologous pairing between durum and grass chromosomes and hence accelerate alien gene transfer into the durum genomes.Key words: alien gene transfer, chiasma (xma) frequency, chromosome pairing, fluorescent genomic in situ hybridization (fl-GISH), homoeologous-pairing regulator, specificity of chromosome pairing, wheatgrass.

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.

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.

A WHEAT MUTATION CONDITIONING AN INTERMEDIATE LEVEL OF HOMOEOLOGOUS CHROMOSOME PAIRING

1982 ◽  
Vol 24 (6) ◽  
pp. 715-719 ◽  
Author(s):  
E. R. Sears
Keyword(s):  
Chromosome Pairing ◽  
Triticum Aestivum L ◽  
Terminal Segment ◽  
Intermediate Level ◽  
Homoeologous Pairing ◽  
Homoeologous Chromosome ◽  
X Ray ◽  
Homoeologous Chromosome Pairing ◽  
Homozygous Line ◽  
A Minor

An X-ray-induced mutation in common wheat (Triticum aestivum L.), designated ph2, conditions an intermediate level of homoeologous chromosome pairing in hybrids with Triticum kotschyi var. variabilis. The number of chromosomes paired averaged 9.2 per sporocyte, compared with 2.0 in the control and 27.9 in the same hybrid involving ph1b, an apparent deficiency for Ph1 obtained in the same mutation experiment. The ph2 mutation is located on chromosome 3D and is believed to be a deficiency for a terminal segment of the short arm that includes the locus of Ph2, a minor suppressor of homoeologous pairing. Although no pairing of the ph2-carrying chromosome with telosome 3DS was observed, the mutation is clearly not a deficiency for the entire arm. It has little effect on pairing in wheat itself. Male transmission of the mutation is approximately normal, and fertility, while reduced, is sufficient for easy maintenance of the homozygous line.

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