CYTOLOGY AND FERTILITY OF PENTAPLOID WHEAT HYBRIDS WITH INDUCED PAIRING BETWEEN HOMOEOLOGOUS CHROMOSOMES

1982 ◽  
Vol 24 (4) ◽  
pp. 397-408 ◽  
Author(s):  
U. Kushnir ◽  
G. M. Halloran
Keyword(s):  
Chromosome Pairing ◽  
Hexaploid Wheat ◽  
Triticum Turgidum ◽  
Triticum Aestivum L ◽  
The Other ◽  
Homoeologous Chromosome ◽  
D Genome ◽  
Homoeologous Chromosome Pairing ◽  
Wheat Hybrids ◽  
Homoeologous Chromosomes

Two mutants, each promoting homoeologous chromosome pairing in hexaploid wheat (Triticum × aestivum L. emend gr. aestivum), in the cultivar Chinese Spring, ph1b at the Ph locus on chromosome 5BL and the other, ph2, on chromosome 3DS, were compared for their influence on chromosome pairing and fertility in pentaploid hybrids with Triticum turgidum L. emend var. dicoccoides (Korn. in litt. in Schweinf.). The mutants induced increased multivalent frequency over the normal pentaploid. Lower univalent frequencies in the ph2-pentaploid, compared with the normal pentaploid, indicated that D-genome chromosomes of the former were substantially involved in homoeologous pairing. Certain differences in other meiotic processes and fertility among the pentaploids may reflect differences in the activity of the pairing genes. There appeared to be a higher level of univalent elimination in pollen and egg cells in the ph2-, compared with the ph1b-pentaploid. Tetrad formation was close to normal in the ph2- pentaploid but exhibited high levels of abnormality (monads, dyads, triads and apolar tetrads) in the ph1b-pentaploid. Fertility levels in crosses of the pentaploids with hexaploid wheat, while low, were much lower for the ph1b-, compared with the ph2-pentaploid.

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.

EFFECT OF RYE ON HOMOEOLOGOUS CHROMOSOME PAIRING IN WHEAT × RYE HYBRIDS

1977 ◽  
Vol 19 (3) ◽  
pp. 549-556 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Triticum Aestivum L ◽  
Homoeologous Chromosome ◽  
Wheat Genotype ◽  
Hybrid Plants ◽  
Homoeologous Chromosome Pairing ◽  
Secale Cereale L ◽  
Polygenic System

The number of chiasmata per cell at metaphase I was scored in eight haploid plants of Triticum aestivum L. emend. Thell. cv. 'Chinese Spring' and 100 hybrid plants of Chinese Spring × Secale cereale L. Mean chiasma frequency per cell ranged from 0.00 to 3.59 in the hybrids and from 0.17 to 0.35 in the haploids. Since the same wheat genotype was present in both the haploids and hybrids, it is concluded that some of the rye genotypes promoted homoeologous chromosome pairing. The absence of distinct segregation classes among the hybrids suggests that these genes constitute a polygenic system.

GENETIC SUPPRESSION OF HOMOEOLOGOUS CHROMOSOME PAIRING IN HEXAPLOID WHEAT

1972 ◽  
Vol 14 (1) ◽  
pp. 39-42 ◽  
Author(s):  
C. J. Driscoll
Keyword(s):  
Chromosome Pairing ◽  
Hexaploid Wheat ◽  
Homoeologous Pairing ◽  
Homoeologous Group ◽  
Homoeologous Chromosome ◽  
Chromosome 5B ◽  
Homoeologous Chromosome Pairing ◽  
Genetic Complexity ◽  
Genetic Suppression ◽  
Group 3

Greater genetic complexity has been revealed for the control of bivalency in hexaploid wheat. A suppressor of homoeologous pairing has been detected on chromosome 3A. Thus, there are two suppressors in homoeologous group 3. The 3A suppressor may be homoeoallelic to either the suppressor on 3Dβ or the promoter, detected in this study, on 3Dα. Individually these two suppressors are less effective than the suppressor on the long arm of chromosome 5B; however, their combined effect is yet to be studied. This greater complexity suggests that hexaploid wheat may not be too dissimilar to other polyploids as regards genetic control of bivalency. The mode of action of these suppressors appears to be consistent with a heteromultimeric hypothesis.

REDUCTION OF CHROMOSOME PAIRING BY A SPONTANEOUS MUTATION ON CHROMOSOMAL ARM 5DL OF TRITICUM AESTIVUM

1980 ◽  
Vol 22 (4) ◽  
pp. 569-575 ◽  
Author(s):  
Wanda S. Viegas ◽  
T. Mello-Sampayo ◽  
Moshe Feldman ◽  
Lydia Avivi
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Secale Cereale ◽  
Chinese Spring ◽  
Spontaneous Mutation ◽  
Triticum Aestivum L ◽  
Homoeologous Chromosome ◽  
Homoeologous Chromosome Pairing ◽  
Promoter Allele

In a plant of Triticum aestivum L. em. Thell. cultivar Chinese Spring which was disomic for a mutant isochromosome of the long arm of chromosome 5D (di-isosomic 5DLM), partial chromosome asynapsis was detected at meiosis. Chromosome pairing in F1 hybrids from crosses of T. aestivum plants carrying the mutant isochromosome with Secale cereale, an intermediate pairing line of T. longissimum and with T. sharonensis disclosed that 5DLM carried a gene that reduced homoeologous chromosome pairing. This gene, designated Ph3 is less potent than its assumed homoeoallele on chromosomal arm 5BL, i.e., Ph1. The possibility of Ph1 being transferred from 5BL to 5DL through homoeologous chromosome pairing and recombination was discarded. Rather, it seems more likely that this allele resulted from a spontaneous mutation of the pairing-promoter allele known to be located on 5DL.

The evolution of polyploid wheats: identification of the A genome donor species

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Jan Dvořák ◽  
Pantaleo di Terlizzi ◽  
Hong-Bin Zhang ◽  
Paolo Resta
Keyword(s):  
Nucleotide Sequence ◽  
Chromosome Pairing ◽  
Hexaploid Wheat ◽  
Triticum Turgidum ◽  
Nucleotide Sequences ◽  
The Other ◽  
Genome Donor ◽  
A Genome ◽  
Sequence Profiles ◽  
Donor Species

Cytogenetic work has shown that the tetraploid wheats, Triticum turgidum and T. timopheevii, and the hexaploid wheat T. aestivum have one pair of A genomes, whereas hexaploid T. zhukovskyi has two. Variation in 16 repeated nucleotide sequences was used to identify sources of the A genomes. The A genomes of T. turgidum, T. timopheevii, and T. aestivum were shown to be contributed by T. urartu. Little divergence in the repeated nucleotide sequences was detected in the A genomes of these species from the genome of T. urartu. In T. zhukovskyi one A genome was contributed by T. urartu and the other was contributed by T. monococcum. It is concluded that T. zhukovskyi originated from hybridization of T. timopheevii with T. monococcum. The repeated nucleotide sequence profiles in the A genomes of T. zhukovskyi showed reduced correspondence with those in the genomes of both ancestral species, T. urartu and T. monococcum. This differentiation is attributed to heterogenetic chromosome pairing and segregation among chromosomes of the two A genomes in T. zhukovskyi.Key words: phylogeny, Triticum, Aegilops, repeated nucleotide sequences.

Effect of nullisomy for D-genome chromosomes and chromosome 5B on the cytological characteristics of pentaploid Triticum aestivum × T. dicoccoides hybrids

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 221-224
Author(s):  
G. Ganeva ◽  
B. Bochev
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Functional Ability ◽  
Meiotic Chromosome ◽  
Specific Effect ◽  
Homoeologous Chromosome ◽  
D Genome ◽  
Chromosome 5B ◽  
Homoeologous Chromosome Pairing ◽  
Cytological Characteristics

The effect of nullisomy for D-genome chromosomes and chromosome 5B on the meiotic behaviour of pollen mother cell chromosomes of pentaploid F1 hybrids of Triticum aestivum (cv. Bezostaya 1) × T. dicoccoides (Körn) was studied. The functional ability of female gametes with diverse chromosome constitution and the frequency of their inheritance in BC1 was assessed. Absence of individual T. aestivum D-genome chromosomes had a specific effect on meiotic chromosome pairing. The genetic systems involving chromosome 5B of the two species did not have the same effect on homologous and homoeologous chromosome pairing. Chromosome 5B of T. dicoccoides reduced bivalent pairing and increased multivalent associations. In BC1 the frequency of female gametes with n = 16–18 chromosomes was highest. Key words: nullisomy, chromosome pairing, Triticum, pentaploid hybrids.

The biology and ecology of hexaploid wheat (Triticum aestivum L.) and its implications for trait confinement

2008 ◽  
Vol 88 (5) ◽  
pp. 997-1013 ◽  
Author(s):  
C. J. Willenborg ◽  
R. C. Van Acker
Keyword(s):  
Triticum Aestivum ◽  
Gene Flow ◽  
Hexaploid Wheat ◽  
Triticum Turgidum ◽  
Cropping Systems ◽  
Pollen Viability ◽  
Triticum Aestivum L ◽  
Genetically Engineered ◽  
Wide Range ◽  
Trait Confinement

This review summarizes the biological and ecological factors of hexaploid wheat (Triticum aestivum L.) that contribute to trait movement including the ability to volunteer, germination and establishment characteristics, breeding system, pollen movement, and hybridization potential. Although wheat has a short-lived seedbank with a wide range of temperature and moisture requirements for germination and no evidence of secondary dormancy, volunteer wheat populations are increasing in relative abundance and some level of seed persistence in the soil has been observed. Hexaploid wheat is predominantly self-pollinating with cleistogamous flowers and pollen viability under optimal conditions of only 0.5 h, yet observations indicate that pollen-mediated gene flow can and will occur at distances up to 3 km and is highly dependent on prevailing wind patterns. Hybridization with wild relatives such as A. cylindrica Host., Secale cereale L., and Triticum turgidum L. is a serious concern in regions where these species grow in field margins and unmanaged lands, regardless of which genome the transgene is located on. More research is needed to determine the long-term population dynamics of volunteer wheat populations before conclusions can be drawn with regard to their role in trait movement. Seed movement has the potential to create adventitious presence (AP) on a larger scale than pollen, and studies tracing the movement of wheat seed in the grain handling system are needed. Finally, the development of mechanistic models that predict landscape-level trait movement are required to identify transgene escape routes and critical points for gene containment in various cropping systems. Key words: Triticum, coexistence, gene flow, genetically-engineered, herbicide-resistant, trait confinement

scholarly journals Comparative Mapping of Genes for Brittle Rachis in Triticum

2011 ◽  
Vol 41 (No. 2) ◽  
pp. 39-44 ◽  
Author(s):  
N. Watanabe ◽  
N. Takesada ◽  
Y. Fujii ◽  
P. Martinek
Keyword(s):  
Triticum Turgidum ◽  
Aegilops Tauschii ◽  
Dominant Gene ◽  
Introgression Line ◽  
Triticum Aestivum L ◽  
Grass Species ◽  
Brittle Rachis ◽  
D Genome ◽  
Adaptive Value ◽  
Group 3

The brittle rachis phenotype is of adaptive value in wild grass species because it causes spontaneous spike shattering. The genes on the homoeologous group 3 chromosomes determine the brittle rachis in Triticeae. A few genotypes with brittle rachis have also been found in the cultivated Triticum. Using microsatellite markers, the homoeologous genes for brittle rachis were mapped in hexaploid wheat (Triticum aestivum L.), durum wheat (Triticum turgidum L. conv. durum /Desf./) and Aegilops tauschii Coss. On chromosome 3AS, the gene for brittle rachis, Br<sub>2</sub>, was linked with the centromeric marker, Xgwm32, at the distance of 13.3 cM. Br<sub>3 </sub>was located on chromosome 3BS and linked with the centromeric marker,<br />Xgwm72 (14.2 cM). Br<sub>1 </sub>was located on chromosome 3DS. The distance from the centromeric marker Xgdm72 was 23.6 cM. The loci Br<sub>1</sub>, Br<sub>2</sub> and Br<sub>3</sub> determine disarticulation of rachides above the junction of the rachilla with the rachis so that a fragment of rachis is attached below each spikelet. The rachides of Ae. tauschii are brittle at every joint, so that the mature spike disarticulates into barrel type. The brittle rachis was determined by a dominant gene, Br<sup>t</sup>, which was linked to the centromeric marker, Xgdm72 (19.7 cM), on chromosome 3DS. A D-genome introgression line, R-61, was derived from the cross Bet Hashita/Ae. tauschii, whose rachis disarticulated as a wedge type. The gene for brittle rachis of R-61, tentatively designated as Br<sup>61</sup>, was distally located on chromosome 3DS, and was linked with the centromeric marker, Xgdm72 (27.5 cM). We discussed how the brittle rachis of R-61 originated genetically. &nbsp; &nbsp;

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