THE EFFECT OF TELOMERIC HETEROCHROMATIN ON CHROMOSOME PAIRING OF HEXAPLOID TRITICALE

1977 ◽  
Vol 19 (3) ◽  
pp. 543-548 ◽  
Author(s):  
D. G. Roupakias ◽  
P. J. Kaltsikes
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Metaphase ◽  
Single Plant ◽  
Hexaploid Triticale ◽  
Telomeric Heterochromatin ◽  
Triticosecale Wittmack

Plants carrying (++) or lacking (−−) most of the telomeric heterochromatic band on the short arm of chromosome 6R(6RS) were isolated from a single plant progeny of Rosner triticale (× Triticosecale Wittmack) heterozygous for this band. Chromosome pairing at first meiotic metaphase was significantly higher in −− than in ++ or +− plants. The changes in chromosome pairing were likely due to the 6RS telomeric heterochromatin which affected the pairing not only of the arm carrying it but of other chromosomes as well.

THE GENOMIC ORIGIN OF THE UNPAIRED CHROMOSOMES IN TRITICALE

1976 ◽  
Vol 18 (4) ◽  
pp. 687-700 ◽  
Author(s):  
J. B. Thomas ◽  
P. J. Kaltsikes
Keyword(s):  
Meiotic Metaphase ◽  
The Other ◽  
Differential Staining ◽  
Hexaploid Triticale ◽  
Genome Chromosome ◽  
Other Hand ◽  
Telocentric Chromosomes ◽  
Telomeric Heterochromatin ◽  
Triticosecale Wittmack ◽  
Terminal Chiasmata

Differential staining of telomeric rye heterochromatin and telocentric chromosomes were used to identify chromosomes which were unpaired at first meiotic metaphase of hexaploid triticale (× Triticosecale Wittmack). Both approaches showed that it was the rye chromosomes which were seen as univalents. Differences in the rate of pairing from triticale to triticale were mostly explained by variation in the pairing of the rye genome. Within the rye genome, chromosome arms with telomeric heterochromatin showed pairing rates much lower than chromosome arms lacking heterochromatin. Wheat telocentrics and heterochromatin-free rye telocentrics which showed intermediate levels of pairing failure (65-90%), had mostly terminal chiasmata. On the other hand rye telocentrics with large heterochromatin bands on the telomeres had mostly nonterminal chiasmata and very low pairing (5-35%). It is concluded that the presence of heterochromatin on certain telomeres of rye chromosomes blocks the formation of terminal chiasmata and this results in desynapsis and univalents at MI.

Effect of chromosome 1B, chromosome 6B, and low temperature on the frequency of chromosome pairing at first meiotic metaphase in hexaploid triticale

1983 ◽  
Vol 25 (3) ◽  
pp. 278-282
Author(s):  
Julian B. Thomas ◽  
P. J. Kaltsikes ◽  
S. Shigenaga
Keyword(s):  
Low Temperature ◽  
Common Wheat ◽  
Chromosome Pairing ◽  
Meiotic Metaphase ◽  
The Other ◽  
Hexaploid Triticale ◽  
Other Hand

Chromosome 1B in 'Rosner' and chromosome 6B in line 125 both reduced the frequency with which chromosomes were paired at first meiotic metaphase of hexaploid triticale. On the other hand, chromosome 6B in 'Rosner' and chromosomes 1B and 6B in line 110 had no such effect. The 1B pairing suppressor in 'Rosner' was located on the short arm of the chromosome (1Bs). Between 10 and 30 °C, pairing frequency was quite stable in 'Rosner' triticale in comparison with common wheat, although the level was consistently lower in the triticale. Some reduction of pairing frequency was noted at 10 °C in 'Rosner'. This effect of low temperature did not interact with 1B dosage to cause a disproportionate decrease in pairing frequency when plants with high 1B dosage were grown at 10 °C.

INDEPENDENCE OF DURATION OF MEIOSIS AND CHROMOSOME PAIRING IN HEXAPLOID TRITICALE

1977 ◽  
Vol 19 (2) ◽  
pp. 345-354 ◽  
Author(s):  
D. G. Roupakias ◽  
P. J. Kaltsikes
Keyword(s):  
Chromosome Pairing ◽  
Total Duration ◽  
Limiting Factor ◽  
Genotypic Differences ◽  
Strong Positive Correlation ◽  
Hexaploid Triticale ◽  
Pollen Maturation ◽  
Secale Cereale L ◽  
Two Stages ◽  
Triticosecale Wittmack

The duration of meiosis, its stages, and pollen maturation at 20 °C were determined in six hexaploid triticales (× Triticosecale Wittmack) which differed in the number of univalents per pollen mother cell at metaphase I (0.67 to 2.43). Meiosis lasted from 46.5 to 53.3 h; these estimates are longer than others previously reported for hexaploid triticale (34–37 h) grown under the same conditions. The quartet stage lasted from 7.1 to 8.0 h while pollen maturation took from 9.5 to 11.2 days. Apart from possible genotypic differences, and subjective judgements as to the beginning of meiosis, the present estimates include the stage of nucleolar fusion (average duration 6.0 h) as part of meiotic prophase. A strong positive correlation (r = 0.99) was found between total duration of meiosis and that of zygotene plus pachytene, the stages during which chromosome pairing is thought to occur. These two stages combined accounted for approximately 46% of the total duration of meiosis; even in the triticale with the shortest meiotic duration these two stages lasted longer than in rye (Secale cereale L.). As no relationship could be demonstrated between the total duration of meiosis, or of zygotene plus pachytene, and the number of univalents per PMC, it is concluded that time is not a limiting factor for chromosome pairing in triticale.

THE EFFECT OF WHEAT CYTOPLASM ON MEIOSIS OF HEXAPLOID TRITICALE

1977 ◽  
Vol 19 (1) ◽  
pp. 39-49 ◽  
Author(s):  
D. G. Roupakias ◽  
P. J. Kaltsikes
Keyword(s):  
Chromosome Pairing ◽  
Hexaploid Wheat ◽  
Mother Cell ◽  
Significant Positive Correlation ◽  
Total Duration ◽  
Continuous Illumination ◽  
Sufficient Time ◽  
Hexaploid Triticale ◽  
Paired Chromosome ◽  
Triticosecale Wittmack

The interrelationships among source of cytoplasm, chromosome pairing and the duration of meiosis were studied in eight combinations of hexaploid triticale (× Triticosecale Wittmack) grown at 20 °C under continuous illumination. The number of paired chromosome arms and univalents per pollen mother cell at MI ranged from 32.32 and 4.89 to 37.26 and 1.37, respectively. Meiosis lasted from 44.14 to 49.35 hours. A significant positive correlation (r = 0.92) was found between total duration of meiosis and the combined duration of zygotene and pachytene, the stages during which chromosome pairing is thought to occur. The origin of the cytoplasm (from tetraploid or hexaploid wheat) had no significant effect of chromosome pairing or meiotic duration. No relationship was found between total duration of meiosis, or that of zygotene and pachytene, and chromosome pairing. It was concluded that lack of sufficient time for homologues to pair cannot account for the presence of rye chromosomes as univalents in triticaie.

COLD HARDINESS IN HEXAPLOID TRITICALE

1985 ◽  
Vol 65 (3) ◽  
pp. 487-490 ◽  
Author(s):  
A. E. LIMIN ◽  
J. DVORAK ◽  
D. B. FOWLER
Keyword(s):  
Cold Hardiness ◽  
Tetraploid Wheat ◽  
Triticum Aestivum L ◽  
Hexaploid Triticale ◽  
D Genome ◽  
Potential Source ◽  
Secale Cereale L ◽  
Cold Hardy ◽  
Triticosecale Wittmack ◽  
X Triticosecale Wittmack

The excellent cold hardiness of rye (Secale cereale L.) makes it a potential source of genetic variability for the improvement of this character in related species. However, when rye is combined with common wheat (Triticum aestivum L.) to produce octaploid triticale (X Triticosecale Wittmack, ABDR genomes), the superior rye cold hardiness is not expressed. To determine if the D genome of hexaploid wheat might be responsible for this lack of expression, hexaploid triticales (ABR genomes) were produced and evaluated for cold hardiness. All hexaploid triticales had cold hardiness levels similar to their tetraploid wheat parents. Small gains in cold hardiness of less than 2 °C were found when very non-hardy wheats were used as parents. This similarity in expression of cold hardiness in both octaploid and hexaploid triticales indicates that the D genome of wheat is not solely, if at all, responsible for the suppression of rye cold hardiness genes. There appears to be either a suppressor(s) of the rye cold hardiness genes on the AB genomes of wheat, or the expression of diploid rye genes is reduced to a uniform level by polyploidy in triticale. The suppression, or lack of expression, of rye cold hardiness genes in a wheat background make it imperative that cold-hardy wheats be selected as parents for the production of hardy triticales.Key words: Triticale, Secale, winter wheat, cold hardiness, gene expression

Variation in induction of homoeologous pairing among chromosomes of 6x Hordeum parodii as a result of three triticale (×Triticosecale Wittmack) cultivars

1986 ◽  
Vol 28 (3) ◽  
pp. 420-425 ◽  
Author(s):  
P. K. Gupta ◽  
George Fedak
Keyword(s):  
Control Mechanism ◽  
Intergeneric Hybrids ◽  
Meiotic Pairing ◽  
Homoeologous Pairing ◽  
Telomeric Heterochromatin ◽  
Triticosecale Wittmack ◽  
Heterochromatin Content

Intergeneric hybrids were obtained between Hordeum parodii Covas s.1. (6x) and three cultivars of triticale (×Triticosecale) at frequencies of 0.47 to 1.21% of pollinated florets. The triticale cultivars varied in their chromosome constitutions of the rye genome as well as the telomeric heterochromatin content of some of the rye chromosomes. The average chiasmata frequency per cell varied from 0.58 to 13.14 in different hybrid combinations. The differences in the chiasmata frequencies in the different hybrid combinations were attributed to a meiotic pairing control mechanism in H. parodii whose function was affected primarily by the rye chromosome constitutions of the triticale cultivars and to a lesser extent by the heterochromatin content of the rye chromosomes.Key words: hybrids (intergeneric), Hordeum, meiotic pairing control, chiasma.

THE EFFECT OF COLCHICINE ON CHROMOSOME PAIRING

1977 ◽  
Vol 19 (2) ◽  
pp. 231-249 ◽  
Author(s):  
J. B. Thomas ◽  
P. J. Kaltsikes
Keyword(s):  
Aqueous Solution ◽  
Chromosome Pairing ◽  
Close Association ◽  
Tetraploid Wheat ◽  
Continuous Illumination ◽  
Hexaploid Triticale ◽  
Homologous Chromosomes ◽  
Wheat Hybrids ◽  
Bouquet Stage

Beginning at 120 hours prior to first metaphase of meiosis (MI) a 0.03% aqueous solution of colchicine was injected into the boot of pentaploid (hexaploid triticale × tetraploid wheat) hybrids developing at 20 °C ± 1° under continuous illumination. Colchicine applied 40 h or less prior to MI had no effect on chromosome pairing, while its application 40 h or more prior to MI induced a steady decline, culminating in a 40% reduction in chromosome pairing at about 80 h from MI. Between 48 and 35 h before MI (late premeiotic interphase to early zygotene) meiocytes underwent a period of active nucleolar fusion. The time, therefore, at which the colchicine sensitive aspects of chromosome pairing were completed coincided with the completion of nucleolar fusion. From comparison with other findings it was concluded that there is a colchicine sensitive bouquet stage which appears in leptotene and early zygotene; this bouquet is responsible for active nucleolar fusion and final close association between homologous chromosomes.

CHROMOSOME PAIRING IN HEXAPLOID TRITICALE

1971 ◽  
Vol 13 (3) ◽  
pp. 621-624 ◽  
Author(s):  
J. B. Thomas ◽  
P. J. Kaltsikes
Keyword(s):  
Durum Wheat ◽  
Normal Level ◽  
Chromosome Pairing ◽  
Tetraploid Wheat ◽  
Meiotic Pairing ◽  
Hexaploid Triticale ◽  
Secale Montanum

A durum wheat background was shown to suppress the meiotic pairing of chromosomes of Secale montanum Guss. with homoeologues of S. cereale L. in hexaploid triticale. This effect was attributed to the activity of the 5BL diploidising system, apparently active in tetraploid wheat. It was considered unlikely that the SBL system was important in conditioning the normal level of pairing failure found in disomic triticales.

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