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.

Genetic control of meiosis in rice, Oryza sativa L. IV. Cytogenetical analyses of asynaptic mutants

1984 ◽  
Vol 26 (3) ◽  
pp. 264-271 ◽  
Author(s):  
Kunio Kitada ◽  
Takeshi Omura
Keyword(s):  
Oryza Sativa ◽  
Genetic Control ◽  
Chromosome Pairing ◽  
Chiasma Frequency ◽  
Oryza Sativa L ◽  
Recessive Gene ◽  
The Other ◽  
Normal Plant ◽  
Meiotic Stage ◽  
The Mean

One complete asynaptic mutant, MM-19, and two partial ones, MM-4 and MM-16, of Oryza sativa L. induced by N-methyl-N-nitrosourea (MNU) were cytogenetically investigated. No chromosome pairing occurred from zygotene to pachytene and 24 univalents appeared at diakinesis and metaphase 1 in MM-19. On the other hand, a partial lack of chromosome pairing was observed from zygotene to pachytene and various numbers of univalents occurred at metaphase I in MM-4 and MM-16. The mean chiasma frequency per bivalent as well as per cell decreased to different extents in MM-4 and MM-16, and the correlation between both the amount of chromosome pairing from zygotene to pachytene and the chiasma frequency per cell at diakinesis was recognized. Judging from the development of anthers in each meiotic stage, the duration of the stage forming the synizetic knot, at which chromosome pairing took place, was longer in MM-4 and MM-16 than in the normal plant, and was in MM-19 almost as long as in the normal plant. The results of gene analyses indicate that each of the three asynaptic mutants is controlled by a recessive gene and that, at least for MM-4 and MM-16, these genes are located at different loci.Key words: asynaptic, rice, Oryza, chiasma frequency, synizesis.

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.

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.

scholarly journals Correlation between geography and cytogenetic diversity in Pomegranate (Punica granatum L.) cultivars in Iran

2012 ◽  
Vol 26 (4) ◽  
pp. 953-965 ◽  
Author(s):  
Masoud Sheidai ◽  
Sakineh Kolahizadeh ◽  
Zahra Noormohammadi ◽  
Nasim Azani ◽  
Mehrnoosh Nikoo
Keyword(s):  
Negative Correlation ◽  
Chromosome Pairing ◽  
Significant Positive Correlation ◽  
Punica Granatum ◽  
Significant Negative Correlation ◽  
Annual Rainfall ◽  
Positive Correlation ◽  
Ring Bivalents ◽  
The Mean ◽  
Punica Granatum L

Pomegranate (Punica granatum L.) is an important horticultural plant with several cultivated forms planted in different regions of Iran. Due to its economic importance, studies have been carried out to illustrate the genetic diversity at the chromosomal and molecular levels in different pomegranate cultivars growing in this region. This study analyzed chromosome pairing and B-chromosomes of 21 pomegranate cultivars and tried to investigate the effects of geographical parameters like altitude and longitude as well as elevation and the mean annual rainfall on cytogenetic diversity of these taxa. An ANOVA test revealed the presence of a significant difference for chiasmata and chromosome pairing among the cultivars, indicating their genetic differences. A positive significant correlation was observed between total chiasma frequency and terminal chiasmata, intercalary chiasmata and the mean number of quadrivalents. A significant positive correlation was observed between annual rainfall and the mean number of rod bivalents, while a significant negative correlation was found for the number of ring bivalents. Altitude did not show any correlation with the cytogenetic characters studied, but showed a significant negative correlation with the number of univalents. Longitude showed significant positive correlation with the number of ring bivalents and a negative correlation with the number of univalents and intercalary chiasmata. PCA analysis showed that both geographical and cytological features contribute greatly in the diversity observed in the pomegranate cultivars. The occurrence of multipolar cells and unreduced pollen grains were observed in some of the cultivars.

THE CYTOGENETIC POSITION OFAVENA DAMASCENAAMONG THE DIPLOID OATS

1978 ◽  
Vol 20 (3) ◽  
pp. 399-404
Author(s):  
H. Cahana ◽  
G. Ladizinsky
Keyword(s):  
Chromosome Pairing ◽  
Parental Species ◽  
Marker Gene ◽  
High Potential ◽  
Chromosome Rearrangements ◽  
Preferential Pairing ◽  
Partial Fertility

The diploid oat Avena damascena was successfully crossed with the diploids A. prostrata and A. strigosa. Chromosome pairing in A. strigosa × A. damascena hybrid indicated that the two parental species differ by three translocations. This hybrid also was completely sterile. The greater affinity of A. damascena to A. prostrata than to A. strigosa could be concluded from the smaller number of multivalents and the partial fertility of the A. prostrata × A. damascena hybrid. Although the number of chromosome rearrangements between A. damascena and A. strigosa was compatible with those found between A. prostrata and these two species, a marked difference in the frequency of the various translocations was noted. Predominantly bivalent pairing characterized the A. prostrata × A. damascena amphidiploid. The lack of segregation of a marker gene in the F2indicated conspicuous preferential pairing in this amphidiploid. A comparison of the number of bivalents per cell in this and in other amphidiploids involving the strigosa-like species suggests that the A. damascena genome has a high potential for preferential pairing.

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.

An assessment of genome analysis based on chromosome pairing in hybrids of perennial Triticeae

Genome ◽  
1989 ◽  
Vol 32 (2) ◽  
pp. 179-189 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Chromosome Pairing ◽  
Genome Analysis ◽  
Correlation Coefficients ◽  
Diploid Hybrid ◽  
Preferential Pairing ◽  
Triticeae Species ◽  
Relative Affinity ◽  
C Value ◽  
The Mean ◽  
Lower Correlation

Genome analysis based on chromosome pairing in diploid hybrids of perennial Triticeae species was examined along with those interpretations based on data of triploid and tetraploid hybrids and (or) species. The mean arm pairing frequency, c, of diploid hybrids with known genome combinations was used as a measure of chromosome homology. The mean trivalent frequency and the averaged sum of trivalents and quadrivalents were used as indices of pairing in triploids and tetraploids, respectively, to assess the validity of the diploid c values. The relative affinity, x value, of the respective triploid hybrids was also used to assess the c value of a diploid combination. Positive correlation coefficients were found between c values of diploid hybrids and trivalent frequencies in triploid hybrids (r = 0.97) as well as between the former and sums of trivalents and quadrivalents in tetraploid hybrids or amphidiploids (r = 0.92). A lower correlation coefficient (r = 0.65) was found for the comparison between diploid and amphidiploid hybrids involving annual Triticeae species. The c values of diploid combinations were negatively correlated (r = −0.79) with the x values of triploid hybrids. These relationships indicate that chromosome relatedness can be measured by the level of pairing in diploid hybrids of perennial Triticeae. It is also suggested that if the diploid hybrid has a c value of about 0.5, a conclusion regarding the genome relationship should be based on additional evidence, such as karyotype data. It is shown that assignment of genome symbols cannot be guided by the presence or absence of preferential pairing in polyploids. Genes regulating chromosome pairing pose problems for genome analysis but should not invalidate either genome analysis as a whole or that of diploid hybrids in particular.Key words: genome, karyotype, meiosis, hybrid, amphidiploid, triploid, diploid, Triticeae.

scholarly journals DISTRIBUTION OF NONSTRUCTURAL VARIATION ALONG THREE CHROMOSOME ARMS BETWEEN WHEAT CULTIVARS CHINESE SPRING AND CHEYENNE

Genetics ◽  
1984 ◽  
Vol 106 (2) ◽  
pp. 309-324
Author(s):  
Anne Crossway ◽  
Jan Dvořák
Keyword(s):  
Chinese Spring ◽  
Continuous Distribution ◽  
Inbred Lines ◽  
Wheat Cultivars ◽  
Chromosome Variation ◽  
Homologous Chromosomes ◽  
Ring Bivalents ◽  
Chromosome Arm ◽  
Parental Inbred ◽  
The Mean

ABSTRACT Metaphase I (MI) pairing of wheat homologous chromosomes is usually reduced in hybrids between cultivars relative to the parental inbred lines. Previous work suggested that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The present work investigated the distribution of this variation along three selected chromosome arms between cultivars Chinese Spring and Cheyenne. Chinese Spring ditelosomics 3Aq, 6Ap and 6Bp were crossed with disomic substitutions of Cheyenne chromosomes 3A, 6A and 6B in Chinese Spring, respectively. The resulting F1 plants, called substituted monotelodisomics, were crossed with the respective Chinese Spring monosomics, producing potentially "recombinant" substituted monosomics. When these "recombinant" chromosomes were combined with the parental Chinese Spring telosomes, marked reductions in mean telosome-pairing frequency were found compared with the corresponding Chinese Spring monotelodisomics. The mean pairing frequencies of the "recombinant" chromosomes showed a continuous distribution between those of the substituted and Chinese Spring monotelodisomics. The results suggest that the nonstructural variation that reduces MI pairing between chromosomes of different wheat cultivars is not localized in a specific site but distributed along each chromosome arm. Little variation was found among monotelodisomics for either the number of ring bivalents per cell or the number of univalents other than those constituting the heteromorphic pair. This implies that the reductions in MI pairing between the Cheyenne and Chinese Spring chromosomes are caused by something residing within these specific chromosomes that does not affect the pairing of the remaining Chinese Spring chromosomes in the same cell. Furthermore, the absence of parental types among the "recombinant"-substituted monotelodisomics suggests that the sequences involved in the variation studied here are capable of converting heterohomologous chromosomes to something intermediate in nature in the span of only a single generation.

The synaptic behaviour of the wild forms of Triticum turgidum and T. timopheevii

Genome ◽  
2001 ◽  
Vol 44 (4) ◽  
pp. 517-522 ◽  
Author(s):  
M Martínez ◽  
T Naranjo ◽  
C Cuadrado ◽  
C Romero
Keyword(s):  
Synaptonemal Complex ◽  
Triticum Turgidum ◽  
Genetic System ◽  
Wild Wheat ◽  
Homologous Chromosomes ◽  
Tetraploid Wheats ◽  
Ring Bivalents ◽  
In The Wild ◽  
The Mean ◽  
Wild Accessions

Different wild allopolyploid species of Triticeae show extensive bivalent formation at zygotene while a considerable number of multivalents is present in cultivated polyploid wheats. To study the chromosome behaviour at early meiotic stages in wild forms of tetraploid wheats Triticum turgidum and T. timopheevii (2n = 4x = 28) we have analysed the synaptic pattern in fully traced spread nuclei at mid- and late zygotene and at pachytene of wild accessions of these species. The mean number of synaptonemal complex (SC) bivalents at mid-zygotene ranged from 12.22 to 13.14 among the accessions studied indicating a strong restriction of synapsis initiation to homologous chromosomes. The mean of bivalents increased at pachytene because of the transformation of multivalents into bivalents. Ring bivalents observed at metaphase I support that SC bivalents were formed by homologous chromosomes. The average values of SC bivalents at mid-zygotene in the wild forms are much higher than the average values observed in the cultivated tetraploid wheats but similar to that of a mutant line of T. turgidum with a duplication that includes Ph1, the major homoeologous pairing suppressor locus. These results suggest that the efficiency of the mechanism operating in the homologous recognition for synapsis is higher in wild wheat populations than in cultivated varieties. Apparently, a relatively detrimental modification of the pairing regulating genetic system accompanied the domestication of the wild wheat forms.Key words: Ph1 locus, Triticum turgidum, Triticum timopheevii, synaptonemal complex, diploidisation.

CHROMOSOMAL INSTABILITY IN A HYBRID BETWEEN HORDEUM VULGARE AND SECALE VAVILOVII

1982 ◽  
Vol 24 (2) ◽  
pp. 207-212 ◽  
Author(s):  
George Fedak ◽  
Chiharu Nakamura
Keyword(s):  
Hordeum Vulgare ◽  
Chromosome Number ◽  
Chiasma Frequency ◽  
Chromosomal Instability ◽  
Chromosome Instability ◽  
Somatic Tissue ◽  
Unreduced Gamete ◽  
Hordeum Vulgare L ◽  
The Mean

A hybrid was obtained between Hordeum vulgare L. cv. Betzes (2n = 2x = 14) and Secale vavilovii [Nürn. (2n = 2x = 14)] in which chromosome instability was observed in somatic and meiotic tissues. In somatic tissue the chromosomes per cell varied from 7 to 24 with a mean of 19.7. Similarly in meiotic tissue the chromosome number varied from 14 to 26 with a mean of 18.3. The mean chiasma frequency was 12.9 consisting of an average Ml configuration of 0.02IV + 0.3III + 6.68II + 3.92I. It was concluded that the hybrid was derived from the union of an unreduced gamete from Betzes barley with a normal gamete from S. vavilovii.

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