scholarly journals Homoeologous pairing of a chromosome from Agropyron elongatum with those of Triticum aestivum and Aegilops speltoides

1967 ◽  
Vol 10 (1) ◽  
pp. 63-71 ◽  
Author(s):  
Roy Johnson ◽  
Gordon Kimber
Keyword(s):  
Triticum Aestivum ◽  
Average Rate ◽  
Aegilops Speltoides ◽  
Homoeologous Pairing ◽  
Agropyron Elongatum ◽  
Telocentric Chromosome ◽  
Telocentric Chromosomes ◽  
Group 6 ◽  
Genetic Compensation ◽  
Homoeologous Chromosomes

1. Complex hybrids were produced having twenty-nine chromosomes, consisting of one telocentric and twenty complete chromosomes of T. aestivum (2n = 6x = 42), seven complete chromosomes of Ae. speltoides (2n = 2x = 14) and one telocentric chromosome derived from A. elongatum (2n = 10x = 70). The presence of the Ae. speltoides genome permitted pairing between homoeologous chromosomes at meiosis and the behaviour of the two telocentric chromosomes was observed.2. The A. elongatum chromosome was seen to pair with chromosomes homoeologous to those of group 6. There was no evidence that it paired with chromosomes of any other group.3. When the A. elongatum telocentric and those of 6A and 6D occurred in the same configuration it was evident that the telocentrics 6A and 6D were for corresponding chromosome arms, and the A. elongatum telocentric for the opposite arm.4. The average rate of pairing was much lower for the A. elongatum telocentric than for wheat telocentrics. Previous studies had indicated very good genetic compensation of the A. elongatum chromosome for chromosomes 6A and 6D. It was therefore indicated that genetic equivalence and pairing affinity were not closely related in this case. Some implications of this are discussed.

scholarly journals Wheat mutants permitting homoeologous meiotic chromosome pairing

1971 ◽  
Vol 18 (3) ◽  
pp. 311-328 ◽  
Author(s):  
A. M. Wall ◽  
Ralph Riley ◽  
Victor Chapman
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Secale Cereale ◽  
Meiotic Chromosome ◽  
Meiotic Pairing ◽  
Homoeologous Pairing ◽  
Homozygous Condition ◽  
Meiotic Chromosome Pairing ◽  
Homoeologous Chromosomes

SUMMARYPlants of Triticum aestivum (2n = 6x = 42) ditelocentric 5BL were treated with EMS in order to produce mutations in the 5B system by which meiotic pairing between homoeologous chromosomes is normally prevented. To check for the occurrence of mutation T. aestivum ditelo-5BL plants were pollinated with rye (Secale cereale 2n = 14) and meiosis was examined in the resulting hybrids.Wheat-rye hybrids were scored for the presence of mutants when the wheat parents were either the EMS-treated wheat plants, or their selfed derivatives, or their progenies obtained after pollination with untreated euploid individuals.Mutants were detected by each of these procedures and mutant gametes were produced by the treated ditelocentric plants with frequencies between 1·5 and 2·5%, but there were differences between the mutants in the extent to which homoeologous pairing occurred in the derived wheat-rye hybrids. The differences may have resulted from the occurrence of mutation at different loci or to different extents at the same locus.Two mutants, Mutant 10/13 and Mutant 61, were fixed in the homozygous condition. Mutant 10/13 was made homozygous both in the 5BL ditelocentric and in the euploid conditions but these genotypes regularly formed 21 bivalents at meiosis, and there was no indication of homoeologous pairing although the mutant 10/13 gave rise to homoeologous pairing in wheat-rye hybrids.

GENETIC VARIABILITY IN AEGILOPS SPELTOIDES AFFECTING HOMOEOLOGOUS PAIRING IN WHEAT

1972 ◽  
Vol 14 (2) ◽  
pp. 371-380 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Aegilops Speltoides ◽  
Homoeologous Pairing ◽  
Addition Lines ◽  
Single Population ◽  
Polyploid Wheat ◽  
Hybrid Plants ◽  
Telocentric Chromosomes ◽  
Two Factors ◽  
The Mean ◽  
Speltoides Chromosome

Three Chinese Spring ditelocentric lines and four Agropyron telocentric addition lines were crossed with a single population of Aegilops speltoides. Chromosome pairing was studied in the hybrid plants. The mean chiasma frequencies per cell in different hybrid plants indicate the existence of three different genotypes in the population of Ae. speltoides each differing significantly in ability to suppress the diploidizing mechanism in polyploid wheat. Plants at the three levels of pairing showed means of 6.4, 10.4 and 15.0 chiasmata per cell, respectively.Agropyron telocentric chromosomes did not pair with their wheat homoeolgues at the lowest pairing level. At intermediate and high pairing levels they did pair with wheat chromosomes. The increase in pairing of Agropyron telocentrics paralleled the increase in chiasma frequency per cell.The action of genes controlling homoeologous synapsis is discussed and it is suggested that pairing affinity between chromosomes may result from the interaction between two factors: homology in nucleotide sequences at specific sites in chromosomes, and degree of activation of these sequences.

scholarly journals The position of a locus on chromosome 5B of Triticum aestivum affecting homoeologous meiotic pairing

1971 ◽  
Vol 18 (3) ◽  
pp. 329-339 ◽  
Author(s):  
A. M. Wall ◽  
Ralph Riley ◽  
M. D. Gale
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Single Locus ◽  
Meiotic Pairing ◽  
Homoeologous Pairing ◽  
Chromosome 5B ◽  
Homoeologous Chromosome Pairing ◽  
Mutant Locus ◽  
Homoeologous Chromosomes ◽  
Pairing Behaviour

SUMMARYAn investigation was made of the chromosomal position of the mutant locus, in Mutant 10/13 of Triticum aestivum (2n = 6x = 42), affecting homoeologous chromosome pairing at meiosis. In hybrids between Mutant 10/13 and rye (Secale cereale 2n = 14), homoeologous chromosomes frequently pair at meiosis although normally, in wheat-rye hybrids, this happens infrequently.The association of the mutant condition with chromosome 5B was determined by (i) the absence of segregation in hybrids obtained when Mutant 10/13 monosomic 5B was pollinated by rye; (ii) the occurrence of trisomie segregation for pairing behaviour in 28-chromosome wheat-rye hybrids, obtained from SB trisomie wheat parents with two 5B chromosome from a non-mutant and one from a mutant parent; (iii) the absence of segregation for pairing behaviour in the 29-chromosome wheat-rye hybrids obtained from the same trisomie wheat parents.The alternative pairing behaviours segregated independently of the centromere when wheat plants that were simultaneously heteromorphic, 5BL telocentric/5B complete, and heterozygous for the Mutant 10/13 state, were pollinated by rye. The alternative chromosome-pairing patterns segregated to give a ratio not different from 1:1, so that the association of homoeologous pairing with Mutant 10/13 probably derived from the occurrence of mutation at a single locus on 5BL. In the disomic heteromorphic state, 5BL was 91 map units in length.Trisomie wheats with two complete 5B chromosomes and one 5BL telocentric, that were also heterozygous for the Mutant 10/13 condition, were pollinated by rye. Among the resulting 28-chromosome hybrids there was a 2:1 segregation of hybrids with low pairing: high (homoeologous) pairing and also of hybrids with complete 5B: telocentric 5BL. However, there was no evidence of linkage in this trisomie segregation. All the 29-chromosome hybrids from this cross had low pairing and it could be concluded that the single mutant allele, in Mutant 10/13, was recessive. In the trisomie condition, relative to a simplex situation, 5BL was 33·05 map units in length.The critical locus on 5BL was designated Pairing homoeologous. The normal dominant allele was symbolized Ph and the recessive allele, in Mutant 10/13, ph.The prevention of homoeologous pairing by the activity of a single locus makes the evolution of the regular meiotic behaviour of T. aestivum more readily comprehensible.

Complex genome rearrangements reveal evolutionary dynamics of pericentromeric regions in the Triticeae

Genome ◽  
2006 ◽  
Vol 49 (12) ◽  
pp. 1628-1639 ◽  
Author(s):  
Lili Qi ◽  
Bend Friebe ◽  
Bikram S. Gill
Keyword(s):  
Triticum Aestivum ◽  
Hexaploid Wheat ◽  
Evolutionary Dynamics ◽  
Triticum Aestivum L ◽  
Genome Rearrangements ◽  
Aegilops Speltoides ◽  
Agropyron Elongatum ◽  
B Genome ◽  
Group 4 ◽  
Pericentric Inversions

Most pericentromeric regions of eukaryotic chromosomes are heterochromatic and are the most rapidly evolving regions of complex genomes. The closely related genomes within hexaploid wheat ( Triticum aestivum L., 2n = 6x = 42, AABBDD), as well as in the related Triticeae taxa, share large conserved chromosome segments and provide a good model for the study of the evolution of pericentromeric regions. Here we report on the comparative analysis of pericentric inversions in the Triticeae, including Triticum aestivum, Aegilops speltoides , Ae. longissima, Ae. searsii, Hordeum vulgare , Secale cereale , and Agropyron elongatum . Previously, 4 pericentric inversions were identified in the hexaploid wheat cultivar ‘Chinese Spring’ (‘CS’) involving chromosomes 2B, 4A, 4B, and 5A. In the present study, 2 additional pericentric inversions were detected in chromosomes 3B and 6B of ‘CS’ wheat. Only the 3B inversion pre-existed in chromosome 3S, 3Sl, and 3Ss of Aegilops species of the Sitopsis section, the remaining inversions occurring after wheat polyploidization. The translocation T2BS/6BS previously reported in ‘CS’ was detected in the hexaploid variety ‘Wichita’ but not in other species of the Triticeae. It appears that the B genome is more prone to genome rearrangements than are the A and D genomes. Five different pericentric inversions were detected in rye chromosomes 3R and 4R, 4Sl of Ae. longissima, 4H of barley, and 6E of Ag. elongatum. This indicates that pericentric regions in the Triticeae, especially those of group 4 chromosomes, are undergoing rapid and recurrent rearrangements.

A spontaneous translocation that transfers wheat curl mite resistance from decaploid Agropyron elongatum to common wheat

Genome ◽  
1988 ◽  
Vol 30 (3) ◽  
pp. 289-292 ◽  
Author(s):  
E. D. P. Whelan ◽  
G. E. Hart
Keyword(s):  
Common Wheat ◽  
Dominant Gene ◽  
Triticum Aestivum L ◽  
Translocation Line ◽  
Structural Genes ◽  
Agropyron Elongatum ◽  
Selfed Progeny ◽  
Wheat Curl Mite ◽  
Group 6 ◽  
Homoeologous Chromosomes

The wheat curl mite (Eriophyes tulipae Keifer) is the vector of wheat streak mosaic virus, a damaging disease of winter wheat. A translocation between a common wheat (Triticum aestivum L.) chromosome and a group 6 chromosome (6Ag) from decaploid Agropyron elongatum (Host) Beauv. resulted in transfer of resistance to colonization by the wheat curl mite. Transmission of resistance through the pollen and the egg were similar and not significantly different from 50%. The frequency of resistance in the F2 generation (65.6%) was lower than expected for a single, dominant gene. In the F2, 26.7% of the resistant plants were homozygous for resistance. Selfed progeny from monosomic and disomic F1 plants from crosses between the translocation line and monosomics for 6A and 6B segregated with frequencies similar to normal F2 progeny but the progeny of monosomics for 6D were primarily resistant (93.2%). Crosses between the translocation line and chromosome 6D telocentrics and studies of four enzymes that are encoded by genes on the group 6 homoeologous chromosomes showed that the translocated chromosome consists of the q arm of chromosome 6D of 'Rescue' and the p arm of chromosome 6 of A. elongatum. Because the new stock was derived from a double monosomic, the translocation was probably a Robertsonian fusion of misdivided centromeres. The resistance is being backcrossed into winter wheat.Key words: Agropyron elongatum, Thinopyron, Elytrigia, Lophopyrum, Robertsonian translocation, isozyme structural genes, wheat curl mite.

METAPHASE I PAIRING FREQUENCIES OF INDIVIDUAL AGROPYRON ELONGATUM CHROMOSOME ARMS WITH TRITICUM CHROMOSOMES

1979 ◽  
Vol 21 (2) ◽  
pp. 243-254 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Chromosome Complement ◽  
Triticum Aestivum L ◽  
Diploid Hybrid ◽  
Agropyron Elongatum ◽  
D Genome ◽  
Telocentric Chromosomes ◽  
Metaphase I

Ten telocentric chromosomes of diploid Agropyron elongatum (Host.) P.B. (2n = 14) were added to the chromosome complement of Triticum aestivum L. emend. Thell. The ditelosomic additions were crossed with Triticum speltoides (Tausch) Gren. ex Richter, and in the tetraploid hybrids the pairing frequencies of the telosomes were determined, expressed as percent of PMC's in which a telosome paired at metaphase I. All Agropyron telosomes paired with Triticum chromosomes. The pairing frequencies ranged from 4.4% to 41.2% of the PMC's, it is concluded that none of the ten Agropyron chromosome arms has a homologous partner among the four Triticum genomes involved. The pairing frequencies did not correlate with the lengths of the telosomes. Pairing of the Agropyron telosomes in these tetraploid hybrids approximated the chromosome pairing that occurred in a diploid hybrid T. tauschii (Coss.) Schmal. (the donor of the D genome of T. aestivum) × A. elongatum.

HOMOEOLOGY BETWEEN AGROPYRON ELONGATUM CHROMOSOMES AND TRITICUM AESTIVUM CHROMOSOMES

1980 ◽  
Vol 22 (2) ◽  
pp. 237-259 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Male Gametophyte ◽  
Chromosome Complement ◽  
Wheat Chromosome ◽  
Triticum Aestivum L ◽  
Homoeologous Group ◽  
Agropyron Elongatum ◽  
Group 2 ◽  
Genetic Compensation

Genetic compensation of Agropyron chromosomes for wheat chromosomes in the male gametophyte and compensation of Agropyron chromosomes for wheat chromosomes in disomic substitutions were used to investigate relationships between the chromosomes of Agropyron elongatum (Host.) P.B. (2n = 2x = 14) and Triticum aestivum L. emend. Thell. (2n = 6x = 42). Gametophytic compensation indicated that A. elongatum chromosomes I, II, III, IV, and VII were related to wheat chromosomes of homoeologous groups 1, 7, 4, 3, and 6, respectively, and were designated 1E, 7E, 4E, 3E, and 6E. Chromosomes V and VI appeared to be related to homoeologous group 2. Other analyses showed that chromosomes V and VI originated from arm exchanges between chromosome 2E and other Agropyron chromosomes. An unaltered disome of Agropyron chromosome 2E was added to the wheat chromosome complement. In the disomic substitutions Agropyron chromosomes 1E, 6E, and 7E compensated for all three wheat homoeologues of the respective homoeologous groups. Chromosome 4E fully compensated for chromosome 4D but only partially for chromosomes 4A and 4B. Chromosomes V and VI compensated poorly or not at all for wheat chromosomes of group 2.

scholarly journals Equivalence of the A genome of bread wheat and that of Triticum urartu

1976 ◽  
Vol 27 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Victor Chapman ◽  
T. E. Miller ◽  
Ralph Riley
Keyword(s):  
Triticum Aestivum ◽  
Hexaploid Wheat ◽  
Homoeologous Pairing ◽  
Triticum Urartu ◽  
B Genome ◽  
Chromosome 5B ◽  
A Genome ◽  
Telocentric Chromosomes ◽  
Mother Cells ◽  
Pairing Behaviour

SUMMARYLines of Triticum aestivum Chinese Spring (2n = 6x = 42) which were ditelocentric or doubly ditelocentric, in turn, for the 14 chromosomes of the A and B genomes were pollinated by Triticum urartu (2n = 14). The behaviour of the marked telocentric chromosomes was scored in the 14 distinct hybrids obtained from these pollinations. In 6 of the hybrids in which different A genome chromosomes were marked by telocentrics there were from 50 to 80% of the pollen mother cells in which the telocentrics were paired. In the seven hybrids in which different B genome chromosomes were marked the telocentrics were never paired. It was concluded that the genome of T. urartu matched very closely the A genome of hexaploid wheat and that it did not correspond, as had been proposed by Johnson, to the B genome. The pairing behaviour of the 14 T. aestivum × T. urartu hybrids was compared with earlier results obtained from hybrids between T. aestivum and T. boeoticum. It was proposed that the higher trivalent frequencies seen in the T. boeoticum hybrids could be due to homoeologous pairing and that the genotype of T. boeoticum has the capacity partly to suppress the activity of the Ph locus of chromosome 5B of wheat, as a result of which homoeologous pairing is normally prevented.

Chromosomal structure of homozygous common wheat lines obtained from wheat × Agropyron × Aegilops speltoides derivatives. I. A screening of the reciprocal translocations

1986 ◽  
Vol 28 (1) ◽  
pp. 69-75 ◽  
Author(s):  
L. T. Ortiz ◽  
Agueda Gonzalez ◽  
Maria-Cristina Chueca ◽  
Yvonne Cauderon
Keyword(s):  
Triticum Aestivum ◽  
Chinese Spring ◽  
Chromosomal Rearrangements ◽  
Aegilops Speltoides ◽  
Homoeologous Pairing ◽  
Reciprocal Translocations ◽  
Chromosomal Structure ◽  
The Common ◽  
Primitive Structure ◽  
Wheat Lines

Fifty-seven homozygous hexaploid lines belonging to five different families obtained by selection in the progenies of the cross between a wheat × Agropyron intermedium substitution line and an Aegilops speltoides promotor of homoeologous pairing were screened for reciprocal translocations. This study was carried out in relation to four Triticum aestivum cultivars: 'Vilmorin 27', Tormes', and 'Ducat' (which were used in the production of these lines), and 'Chinese Spring' that has the primitive structure of the common wheats. None of the lines retained the 5B/7B translocation of 'Vilmorin 27'. For some lines, the translocation of 'Tormes' and 'Ducat' seems to have been maintained. Ten of them show the primitive structure of 'Chinese Spring' even though none of the wheat parents had it. The others carry some original translocations as a result of the effect of Aegilops speltoides on meiotic pairing.Key words: homoeologous pairing, interspecific hybridization, gene transfer, chromosomal rearrangements, Triticum.

GENOTYPIC INTERACTION FOR CHIASMA FORMATION AT LOW TEMPERATURE IN THE HYBRID BETWEEN TRITICUM AESTIVUM 'CHINESE SPRING' AND AEGILOPS SPELTOIDES DEFICIENT FOR CHROMOSOME 5D

1977 ◽  
Vol 19 (3) ◽  
pp. 471-475 ◽  
Author(s):  
T. Attia ◽  
T. Lelley ◽  
G. Röbbelen
Keyword(s):  
Triticum Aestivum ◽  
Low Temperature ◽  
Chinese Spring ◽  
Chiasma Formation ◽  
Aegilops Speltoides ◽  
Homoeologous Pairing ◽  
Chromosome 5B ◽  
Analogous System ◽  
Two Systems

In F1 plants from crosses between Triticum aestivum var. 'Chinese Spring' monosomic 5D and Aegilops speltoides Tausch. var. aucheri (Boiss) it was found that at a temperature of 12 °C the presence of chromosome 5D is necessary to maintain the level of homoeologous pairing and chiasma formation observed under greenhouse conditions. Some genotypes of Ae. speltoides, however, were more efficient than others in compensating for the absence of chromosome 5D. The differences in compensating ability indicate the existence of several alleles in Ae. speltoides that counteract the low-temperature pairing system on chromosome 5D. An analogous system of alleles previously reported in Ae. speltoides that suppresses the chromosome 5B diploidising system of wheat was substantiated by the present study. The results indicate, however, that the two systems are independent.

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