The effect of B-chromosomes of rye on chiasma frequency in Triticum aestivum

Genetica ◽  
1979 ◽  
Vol 51 (1) ◽  
pp. 69-75 ◽  
Author(s):  
W. S. Viegas
Keyword(s):  
Triticum Aestivum ◽  
Chiasma Frequency ◽  
B Chromosomes

B Chromosomes in Wheat, Triticum aestivum L.

Nature ◽  
1964 ◽  
Vol 202 (4932) ◽  
pp. 623-624
Author(s):  
JUAN-RAMÓN LACADENA
Keyword(s):  
Triticum Aestivum ◽  
Triticum Aestivum L ◽  
B Chromosomes

GENETIC VARIATION IN TRITICUM AFFECTING THE LEVEL OF CHROMOSOME PAIRING IN INTERGENERIC HYBRIDS

1970 ◽  
Vol 12 (2) ◽  
pp. 278-282 ◽  
Author(s):  
C. J. Driscoll ◽  
C. J. Quinn
Keyword(s):  
Triticum Aestivum ◽  
Genetic Variation ◽  
Natural Selection ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Chiasma Frequency ◽  
Intergeneric Hybrids ◽  
Homoeologous Chromosome ◽  
Homoeologous Chromosome Pairing ◽  
Aegilops Variabilis

Genetic differences which affect the extent of homoeologous chromosome pairing in intergeneric hybrids have been demonstrated between varieties of Triticum aestivum. Each of seven varieties of Triticum was crossed with the same strain of Aegilops variabilis. Significant differences in chiasma frequencies between varieties were found. Varieties Eureka, Gamut and Chinese Spring constitute one group with a relatively low chiasma frequency and varieties A. R. Falcon, Federation and Poso constitute a distinct second group with a relatively high chiasma frequency. The variety Bearded Yalta is intermediate to the two groups. Thus, this genetic variation appears to be common among varieties of Triticum. Presumably this variation does not become subject to natural selection as long as chromosome pairing in the parental varieties remains strictly homologous.

THE EFFECTS OF SUPERNUMERARY CHROMATIN IN THREE SPECIES OF GRASSHOPPER

1974 ◽  
Vol 16 (2) ◽  
pp. 285-296 ◽  
Author(s):  
Gilbert L. Schroeter ◽  
Godfrey M. Hewitt
Keyword(s):  
Life Cycle ◽  
Chiasma Frequency ◽  
Genetic Material ◽  
B Chromosomes ◽  
Population Variability ◽  
The Other ◽  
Direct Effects ◽  
Apparent Effect ◽  
Other Hand ◽  
The Mean

The chiasma frequencies in males of three species of grasshopper with and without B-chromosomes and supernumerary segments were scored at diplotene. The partially heterochromatic B's found in some individuals of Chimarocephala pacifica pacifica have no effect on chiasma frequencies. On the other hand, heterochromatic supernumerary segments in Oedaleonotus phryneicus males significantly increase the mean chiasma frequencies over individuals without them but not the between-cell variances. In Camnula pellucida neither the mitotically unstable B's nor supernumerary segments have any apparent effect on chiasma.frequencies. The supernumerary elements in Chimarocephala pacifica and Camnula pellucida may, however, produce other effects during the life cycle These and previous observations suggest that polymorphism involving extra genetic material in grasshoppers can result in increased population variability via two different means: (1) by producing variation in chiasma frequency or (2) through direct effects in the individuals possessing it. The importance of such a mechanism for producing variation is discussed.

scholarly journals Population Cytology of the Genus Phaulacridium VI. Seasonal Changes in the Frequency of the B Chromosome in a Population of Ph. vittatum

1977 ◽  
Vol 30 (4) ◽  
pp. 329 ◽  
Author(s):  
M Westerman ◽  
J Dempsey
Keyword(s):  
Seasonal Changes ◽  
Chiasma Frequency ◽  
Sequential Sampling ◽  
Late Summer ◽  
B Chromosome ◽  
B Chromosomes ◽  
Adult Males ◽  
University Campus ◽  
Maximum Value ◽  
Significant Difference

Sequential sampling of adult males from the La Trobe University campus population of Ph. Vittatum has been carried out over two successive years. Within each year there is seen to be a similar change in frequency of males carrying a large, mitotically stable B chromosome. Early in the summer, when adults first appear, the B frequency of the population is low; it then rises to a maximum value in late summer and then declines once more. Possible reasons for this change in B frequency are discussed. Chiasma frequency scores of individuals with and without B chromosomes were also recorded for each sample. It was found that although at anyone time there was no significant difference between individuals with and without B chromosomes, due no doubt to the small numbers sampled, nonetheless the chiasma frequency of the former was always higher than the latter. Since this was the finding for collections over three years, it is concluded that the B chromosomes of Ph. vittatum, like those of other acridids, raise mean cell chiasma frequency.

Relationship between pachytene synapsis, metaphase I associations, and transmission of 2B and 4B chromosomes in rye

Genome ◽  
2000 ◽  
Vol 43 (2) ◽  
pp. 232-239 ◽  
Author(s):  
Guillermo Jiménez ◽  
Silvia Manzanero ◽  
María J Puertas
Keyword(s):  
Secale Cereale ◽  
Maternal Effect ◽  
Chiasma Frequency ◽  
Transmission Rate ◽  
Chiasma Formation ◽  
B Chromosomes ◽  
Bivalent Formation ◽  
The Relationship ◽  
Variable Efficiency ◽  
Metaphase I

2B rye plants selected for high (H) or low (L) B transmission rate were studied at pachytene and metaphase I of meiosis to determine the relationship between synapsis, bivalents at metaphase I, and B transmission rate. The results show that the 2 B chromosomes (Bs) form bivalents at pachytene in both the H and L lines, whereas the frequency of bivalents at metaphase I is much higher in the H than in the L line. This demonstrates that B transmission is mainly related to the proper association of Bs at metaphase I, as well as that synapsis of the 2 Bs in the L line is normal, but the bivalent is not consolidated by a chiasma in most cases. Crosses were made between 2B plants of the H and L lines in all combinations (H × H, H × L, L × H, and L × L) to obtain 4B plants. Similarly, bivalent formation at pachytene and metaphase I was studied. The results show that 4B plants of the H × H and L × L classes differ significantly at pachytene and metaphase I since the former forms more bivalents. The heterozygous 4 Bs of the H × L and L × H classes show intermediate values. The relation H × H > H × L > L × H > L × L was consistently found for the variables transmission rate, bivalents at pachytene, bivalents at metaphase I, and B mean chiasma frequency. A maternal effect was also found. Our data suggest that there are two separate mechanisms acting upon synapsis and chiasma formation in H and L B chromosomes: (i) there is variable efficiency of the control of synapsis at early stages of meiosis; and (ii) there is variable efficiency of the control of the number of chiasmata. Key words: B chromosomes, synaptonemal complex, Secale cereale.

Enhanced meiotic chromosome pairing in intergeneric hybrids between Triticum aestivum and diploid Inner Mongolian Agropyron

Genome ◽  
1992 ◽  
Vol 35 (1) ◽  
pp. 98-102 ◽  
Author(s):  
Qin Chen ◽  
Joseph Jahier ◽  
Yvonne Cauderon
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Inner Mongolia ◽  
Meiotic Chromosome ◽  
Embryo Rescue ◽  
Genetic System ◽  
Intergeneric Hybrids ◽  
B Chromosomes ◽  
Meiotic Pairing ◽  
Reciprocal Hybrids

Triticum aestivum cv. Chinese Spring (2n = 6x = 42, ABD genomes) was crossed with diploid Inner Mongolian Agropyron Gaertn. species A. cristatum and A. mongolicum and reciprocal hybrids between them (2n = 2x = 14, P genome, with or without B chromosomes). Intergeneric hybrids with 2n = 27, 28, 32, and 33 chromosomes were produced by the aid of embryo rescue. The extra chromosomes in two hybrids were assumed to be B chromosomes transmitted by the male Agropyron parent. Average meiotic pairing in the euploid hybrid with 28 chromosomes was 14.38 univalents + 4.92 bivalents + 1.26 trivalents. This level of pairing higher than expected was likely due to homeologous associations between wheat chromosomes. This data indicates that the P genome of diploid as well as tetraploid Agropyron originating from Inner Mongolia possess a genetic system interfering with 5B homoeologous restricting system of wheat.Key words: intergeneric hybrids, Triticum aestivum, diploid Agropyron species, chromosome pairing.

EFFECT OF CULTIVAR COMBINATION ON MEIOSIS IN BARLEY-WHEAT HYBRIDS

1982 ◽  
Vol 24 (5) ◽  
pp. 575-582 ◽  
Author(s):  
George Fedak
Keyword(s):  
Triticum Aestivum ◽  
Hordeum Vulgare ◽  
Chinese Spring ◽  
Chiasma Frequency ◽  
Wheat Hybrids

Hordeum vulgare cultivars Betzes, Bonus, and Emir were crossed with Triticum aestivum cultivars Chinese Spring and Koga. Variable cultivar effects on chiasma frequency in hybrids were observed. Chiasma frequencies per cell varied from 0.38 in the Emir × Chinese Spring hybrid to 3.27 in the Bonus × Koga hybrid. Paired configurations involved homeologous wheat chromsomes.

B chromosomes of the grasshopper Heteracris littoralis: meiotic behaviour and endophenotypic effects in both sexes

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 797-801 ◽  
Author(s):  
M. I. Cano ◽  
J. L. Santos
Keyword(s):  
Chiasma Frequency ◽  
Main Type ◽  
Natural Populations ◽  
Meiotic Drive ◽  
B Chromosome ◽  
B Chromosomes ◽  
Female Meiosis ◽  
Accumulation Mechanism ◽  
Cell Variance ◽  
High Level

A main type of a large supernumerary B chromosome has been found in several natural populations of the grasshopper Heteracris littoralis. A study on the geographical distribution of the polymorphism and the meiotic behavior of Bs in both sexes has been carried out with special reference to their effect on two endophenotypic parameters: recombination level and macrospermatid production. Male B bivalents are characterized by a high level of pairing and a strict proximal localization of chiasmata. In the females the B chromosome always divides reductionally at anaphase I indicating the possible existence of an accumulation mechanism based on meiotic drive. There is no effect of Bs on either mean chiasma frequency or between-cell variance in either of the sexes. However, in males a positive correlation between the number of Bs and production of abnormal spermatids (macrospermatids) was found.Key words: B chromosomes, chiasma frequency, female meiosis.

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