The potential for diploidizing Lolium multiflorum × L. perenne tetraploids

1985 ◽  
Vol 27 (5) ◽  
pp. 506-509 ◽  
Author(s):  
Taing Aung ◽  
G. M. Evans
Keyword(s):  
Pollen Mother Cell ◽  
Chromosome Pairing ◽  
Interspecific Hybrid ◽  
Mother Cell ◽  
Lolium Multiflorum ◽  
Genetically Modify ◽  
Hybrid Progeny ◽  
Homoeologous Pairing ◽  
Homologous Chromosomes

The possibility of diploidizing meiosis in tetraploid hybrids of the two closely related Lolium species, L. multiflorum and L. perenne, was investigated using specific genotypes of both parents. Both these parental genotypes had previously been shown to reduce homoeologous pairing in a separate but wider cross with the inbreeder L. temulentum. A preponderance of bivalents was recorded at first metaphase of meiosis in several of the hybrid progeny with the frequency of multivalents being reduced to 0.6/pollen mother cell in one plant. Although it is not unambiguously established that the bivalents so formed are solely between homologous chromosomes, it is highly likely that this is so. It is concluded that it is feasible to genetically modify the pattern of meiosis even in tetraploid hybrids of species of similar karyotypes.Key words: chromosome pairing, Lolium, interspecific hybrid.

Identification of a diploidizing genotype of Lolium multiflorum

1985 ◽  
Vol 27 (5) ◽  
pp. 498-505 ◽  
Author(s):  
G. M. Evans ◽  
Taing Aung
Keyword(s):  
Mathematical Models ◽  
Chromosome Pairing ◽  
Interspecific Hybrid ◽  
Lolium Multiflorum ◽  
Hybrid Progeny ◽  
Single Plant ◽  
Homoeologous Chromosome ◽  
High Incidence ◽  
Species Hybrids ◽  
Diploid Populations

Thirty diploid populations of Lolium multiflorum were screened for genes that were capable of modifying meiosis in species hybrids. A standard genotype of L. temulentum was used as the tester species. Modified pairing at first metaphase of meiosis was identified in some of the hybrid progeny of a single plant from a population from Uruguay and also in one from Portugal. Evidence is presented to show that the high incidence of univalents in diploid hybrids of L. temulentum × L. multiflorum from Uruguay was due to the suppression of homoeologous chromosome association only. A proportion of equivalent triploid and tetraploid hybrids had an excess of bivalents at first metaphase of meiosis. This was confirmed by comparison of the observed meiotic data with that expected from three separate mathematical models. It is concluded that this single plant from the Uruguayan population was heterozygous for genes that suppress chiasmate association of homoeologous chromosomes.Key words: interspecific hybrid, Lolium, chromosome pairing.

scholarly journals Meiotic Chromosome Behavior and Capsule Setting in Doritaenopsis Hybrids

2008 ◽  
Vol 133 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Pablo Bolaños-Villegas ◽  
Shih-Wen Chin ◽  
Fure-Chyi Chen
Keyword(s):  
Cell Division ◽  
Pollen Mother Cell ◽  
Chromosome Pairing ◽  
Chromosomal Aberrations ◽  
High Frequency ◽  
Mother Cell ◽  
Seed Set ◽  
Pollen Viability ◽  
High Pollen ◽  
Mother Cells

The development of new cultivars in Doritaenopsis Guillaum. & Lami orchids is often hindered by factors such as low seed count in hybrids. Cytological study may offer the ability to develop new hybrids by revealing cultivars with good chromosome pairing and high pollen viability, which are somewhat difficult to obtain under current breeding programs. Cross pollination, pollen viability, and chromosomal behavior during meiosis were analyzed to reveal the relation between seed fertility and capsule set in Doritaenopsis hybrids. The number of mature capsules harvested and their relative seed content were used as indices of crossing availability. The results of meiosis were evaluated according to pollen viability detected by fluorescein diacetate and quantification of sporad types by acid fuchsin staining. Chromosome number and pairing at meiosis were observed in root tips or in samples of pollen mother cells. A positive relation was found among high seed set, high frequency of viable tetrads, high degree of chromosome pairing, and low frequency of chromosomal aberrations such as inversions and translocations. On the basis of these factors, three types of hybrids could be distinguished. In type one hybrids, chromosomes paired as bivalents, pollen mother cells divided into tetrads, and capsule setting occurred after pollination of pollen acceptors. In type two hybrids, chromosomes remained mainly as univalents that developed into micromeiocytes, pollen mother cell division was disrupted, and seed recovery was low after pollination. Type three hybrids showed chromosomes paired mostly as multivalents, chromosome bridges, pollen mother cell division with massive failure, and little fertility. In Doritaenopsis orchids, high pollen viability and high fertility depends on a high frequency of normal tetrads, and low seed set in cross-pollination is predicted with micronuclei in the end products of meiosis. The occurrence of chromosomal aberrations may suggest a process of genome differentiation that could compromise breeding efforts if not taken into consideration.

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 MATHEMATICS OF CHROMOSOME PAIRING

Genetics ◽  
1980 ◽  
Vol 95 (1) ◽  
pp. 159-169
Author(s):  
C J Driscoll ◽  
G H Gordon ◽  
G Kimber
Keyword(s):  
Chromosome Pairing ◽  
Related Species ◽  
Homoeologous Pairing ◽  
Homologous Chromosomes ◽  
Species Hybrids

ABSTRACT Analysis of frequencies of chromosome configurations in wheat-related species hybrids is extended to include cases involving homoeologous groups of size six. Further, the expected frequencies of the various configurations emanating from homologous and homoeologous pairing events have been determined for groups consisting of two and three homoeologous pairs of homologous chromosomes. Analysis of configuration frequencies of nullisomic 5B of wheat, in which both homologous and homoeologous pairing occurs, led to estimation of the relative frequencies of homologous and homoeologous pairing events as 17.9: 1. In the samples analyzed, slightly less than one homoeologous exchange occurred per gamete.

Intergeneric hybrids between × Triticosecale cv. Welsh (2n = 42) and three genotypes of Agropyron intermedium (2n = 42)

1986 ◽  
Vol 28 (2) ◽  
pp. 176-179 ◽  
Author(s):  
P. K. Gupta ◽  
G. Fedak
Keyword(s):  
Pollen Mother Cell ◽  
Chromosome Pairing ◽  
Mother Cell ◽  
Intergeneric Hybrids ◽  
Agropyron Intermedium ◽  
Genome Homology ◽  
Paternal Parent

Three genotypes of Agropyron intermedium ssp. trichophorum (2n = 42) were crossed onto × Triticosecale cv. Welsh (2n = 42). Bivalent frequencies per pollen mother cell in the three hybrid combinations were 4.97, 5.64, and 6.94. Pairing was attributed to autosyndesis between two genomes (N and N1) of the paternal parent rather than to genome homology between the two parents.Key words: triticale, hybrids (intergeneric), chromosome pairing, × Triticosecale, agronomy.

scholarly journals Cytological Evidence for the Sterility of an Interspecific Alstroemeria Hybrid

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 855B-855
Author(s):  
Chunsheng Lu ◽  
Mark Bridgen
Keyword(s):  
Pollen Mother Cell ◽  
Late Stage ◽  
Interspecific Hybrid ◽  
Mother Cell ◽  
Seed Set ◽  
Pollen Viability ◽  
Pollen Grains ◽  
Cytological Evidence ◽  
Stage Of Development ◽  
Hybrid Plants

Self-pollinations of a diploid (2n = 2x = 16) interspecific hybrid from the cross of Alstroemeria aurea × A. caryophyllaea resulted in no seed set. Pollen viability studies with the hybrid demonstrated that only 5% of the pollen grains were viable. Cytological observations with the hybrid pollen mother cell (PMC) revealed abnormal chromosome behaviors, such as no pairing in Prophase I and Metaphase I, and bridges in the Anaphase I and II. Although the development of microspores appeared normal in shape until the stage of tetrad release, some chromosomes did not remain in the nucleus after completing meiosis, formed isolated groups of 1 to 4, and remained in the cytoplasm. This genetic imbalance of the microspores could be one of the causes for the abortion of the pollen grains in the late stage of development. Additional meiotic cytological studies with colchicine-induced tetraploids (2n = 4x = 32) derived from the hybrid plants showed that chromosome pairings were normal in most cases. However, self-pollination with the tetraploid plants failed to set seeds. These studies with the tetraploids further demonstrate that the sterility of the hybrid is due not only to chromosomal differences, but also to complex genic interactions.

Synthesis and cytological characterization of trigeneric hybrids of durum wheat with and without Ph1

Genome ◽  
2004 ◽  
Vol 47 (6) ◽  
pp. 1173-1181 ◽  
Author(s):  
Prem P Jauhar ◽  
M Doğramaci ◽  
T S Peterson
Keyword(s):  
In Situ Hybridization ◽  
Chromosome Pairing ◽  
Genetic Recombination ◽  
Genomic In Situ Hybridization ◽  
Homoeologous Pairing ◽  
Alien Gene Transfer ◽  
Chromosome 5B ◽  
Alien Gene ◽  
Trigeneric Hybrids

Wild grasses in the tribe Triticeae, some in the primary or secondary gene pool of wheat, are excellent reservoirs of genes for superior agronomic traits, including resistance to various diseases. Thus, the diploid wheatgrasses Thinopyrum bessarabicum (Savul. and Rayss) Á. Löve (2n = 2x = 14; JJ genome) and Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) are important sources of genes for disease resistance, e.g., Fusarium head blight resistance that may be transferred to wheat. By crossing fertile amphidiploids (2n = 4x = 28; JJEE) developed from F1 hybrids of the 2 diploid species with appropriate genetic stocks of durum wheat, we synthesized trigeneric hybrids (2n = 4x = 28; ABJE) incorporating both the J and E genomes of the grass species with the durum genomes A and B. Trigeneric hybrids with and without the homoeologous-pairing suppressor gene, Ph1, were produced. In the absence of Ph1, the chances of genetic recombination between chromosomes of the 2 useful grass genomes (JE) and those of the durum genomes (AB) would be enhanced. Meiotic chromosome pairing was studied using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH). As expected, the Ph1-intergeneric hybrids showed low chromosome pairing (23.86% of the complement), whereas the trigenerics with ph1b (49.49%) and those with their chromosome 5B replaced by 5D (49.09%) showed much higher pairing. The absence of Ph1 allowed pairing and, hence, genetic recombination between homoeologous chromosomes. Fl-GISH analysis afforded an excellent tool for studying the specificity of chromosome pairing: wheat with grass, wheat with wheat, or grass with grass. In the trigeneric hybrids that lacked chromosome 5B, and hence lacked the Ph1 gene, the wheat–grass pairing was elevated, i.e., 2.6 chiasmata per cell, a welcome feature from the breeding standpoint. Using Langdon 5D(5B) disomic substitution for making trigeneric hybrids should promote homoeologous pairing between durum and grass chromosomes and hence accelerate alien gene transfer into the durum genomes.Key words: alien gene transfer, chiasma (xma) frequency, chromosome pairing, fluorescent genomic in situ hybridization (fl-GISH), homoeologous-pairing regulator, specificity of chromosome pairing, wheatgrass.

Inferences from genetical evidence on the course of meiotic chromosome pairing in plants

1977 ◽  
Vol 277 (955) ◽  
pp. 313-326 ◽  
Keyword(s):  
Chromosome Pairing ◽  
Developmental Stages ◽  
Meiotic Chromosome ◽  
Critical Assessment ◽  
Gene Control ◽  
Meiotic Pairing ◽  
Homologous Chromosomes ◽  
Meiotic Chromosome Pairing ◽  
Combined Use ◽  
Or Gene

Meiotic chromosome pairing is a process that is amenable to genetic and experimental analysis. The combined use of these two approaches allows for the process to be dissected into several finite periods of time in which the developmental stages of pairing can be precisely located. Evidence is now available, in particular in plants, that shows that the pairing of homologous chromosomes, as observed at metaphase I, is affected by events occurring as early as the last premeiotic mitosis; and that the maintenance of this early determined state is subsequently maintained by constituents (presumably proteins) that are sensitive to either colchicine, temperature or gene control. A critical assessment of this evidence in wheat and a comparison of the process of pairing in wheat with the course of meiotic pairing in other plants and animals is presented.

scholarly journals Synaptonemal complex antigen location and conservation.

1987 ◽  
Vol 105 (1) ◽  
pp. 93-103 ◽  
Author(s):  
P B Moens ◽  
C Heyting ◽  
A J Dietrich ◽  
W van Raamsdonk ◽  
Q Chen
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Structural Integrity ◽  
Genetic Recombination ◽  
Positive Control ◽  
Western Blots ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Recombination Nodules ◽  
Grain Distribution

The axial cores of chromosomes in the meiotic prophase nuclei of most sexually reproducing organisms play a pivotal role in the arrangement of chromatin, in the synapsis of homologous chromosomes, in the process of genetic recombination, and in the disjunction of chromosomes. We report an immunogold analysis of the axial cores and the synaptonemal complexes (SC) using two mouse monoclonal antibodies raised against isolated rat SCs. In Western blots of purified SCs, antibody II52F10 recognizes a 30- and a 33-kD peptide (Heyting, C., P. B. Moens, W. van Raamsdonk, A. J. J. Dietrich, A. C. G. Vink, and E. J. W. Redeker, 1987, Eur. J. Cell Biol., 43: 148-154). In spreads of rat spermatocyte nuclei it produces gold grains over the cores of autosomal and sex chromosomes. The cores label lightly during the chromosome pairing stage (zygotene) of early meiotic prophase and they become more intensely labeled when they are parallel aligned as the lateral elements of the SC during pachytene (55 grains/micron SC). Statistical analysis of electronically recorded gold grain positions shows that the two means of the bimodal gold grain distribution coincide with the centers of the lateral elements. At diplotene, when the cores separate, the antigen is still detected along the length of the core and the enlarged ends are heavily labeled. Shadow-cast SC preparations show that recombination nodules are not labeled. The continued presence suggests that the antigens serve a continuing function in the cores, such as chromatin binding, and/or structural integrity. Antibody III15B8, which does not recognize the 30- and 33-kD peptides, produces gold grains predominantly between the lateral elements. The grain distribution is bimodal with the mean of each peak just inside the pairing face of the lateral element. The antigen is present where and while the cores of the homologous chromosomes are paired. From the location and the timing, it is assumed that the antigen recognized by III15B8 functions in chromosome pairing at meiotic prophase. The two anti-rat SC antibodies label rat and mouse SCs but not rabbit or dog SCs. A positive control using human CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) anti-centromere serum gives equivalent labeling of SC centromeres in the rat, mouse, rabbit, and dog. It is concluded that the SC antigens recognized by II52F10 and III15B8 are not widely conserved. The two antibodies do not bind to cellular or nuclear components of somatic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

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