CYTOLOGICAL STUDIES IN KRIGIA (ASTERACEAE)

1981 ◽  
Vol 23 (4) ◽  
pp. 671-678 ◽  
Author(s):  
C. C. Chinnappa
Keyword(s):  
Meiotic Pairing ◽  
Polyploid Species ◽  
High Polyploid ◽  
Karyotype Morphology

The genus Krigia Schreb. consists of nine species representing diploid and polyploid taxa. Karyotype morphology and meiotic pairing of chromosomes for five species are described. Krigia cespitosa (2n = 8) and K. biflora (2n = 10) are diploids. Krigia montana with 2n = 20 is a tetraploid. Diploid and tetraploid forms of K. virginica with 2n = 10 and 20 were also studied. Krigia dandelion 2n = 60 is a high polyploid species.

Senecio L. (Asteraceae) in Australia: Rcombination systems of a polyploid series

1985 ◽  
Vol 33 (2) ◽  
pp. 209 ◽  
Author(s):  
M.E. Lawrence
Keyword(s):  
Chromosome Number ◽  
Breeding System ◽  
Chromosome Numbers ◽  
Native Species ◽  
Polyploid Species ◽  
Ploidy Levels ◽  
Basic Chromosome ◽  
High Polyploid ◽  
Evolutionary Changes ◽  
Extreme Phenotypes

Recombination systems of 32 species of Senecio are discussed in terms of chromosome number, chiasma frequency and position, breeding system and generation length. Darlington's recombination index cannot be applied to Senecio as several ploidy levels are represented. Increases in basic chromosome numbers promote recombination but increases by polyploidy buffer intermediate genotypes and retard evolutionary changes when selection is for homozygous or extreme phenotypes. High polyploid species of Senecio may therefore have recombination systems as restrictive as those produced by aneuploid reduction. When viewed in this manner, the majority of native species examined have recombination systems that contain a balance of restrictive and expansive factors regulating recombination.

scholarly journals On the Origin of Tetraploid Vernal Grasses (Anthoxanthum) in Europe

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 966
Author(s):  
Zuzana Chumová ◽  
Terezie Mandáková ◽  
Pavel Trávníček
Keyword(s):  
Flow Cytometry ◽  
In Situ Hybridization ◽  
Crucial Role ◽  
Evolutionary History ◽  
Essential Role ◽  
Grass Species ◽  
Polyploid Species ◽  
Anthoxanthum Odoratum ◽  
European Populations

Polyploidy has played a crucial role in the evolution of many plant taxa, namely in higher latitudinal zones. Surprisingly, after several decades of an intensive research on polyploids, there are still common polyploid species whose evolutionary history is virtually unknown. Here, we addressed the origin of sweet vernal grass (Anthoxanthum odoratum) using flow cytometry, DNA sequencing, and in situ hybridization-based cytogenetic techniques. An allotetraploid and polytopic origin of the species has been verified. The chromosome study reveals an extensive variation between the European populations. In contrast, an autopolyploid origin of the rarer tetraploid vernal grass species, A. alpinum, has been corroborated. Diploid A. alpinum played an essential role in the polyploidization of both European tetraploids studied.

Male Sterility and Meiotic Drive Associated With Sex Chromosome Rearrangements in Drosophila: Role of X-Y Pairing

Genetics ◽  
1998 ◽  
Vol 149 (1) ◽  
pp. 143-155 ◽  
Author(s):  
Bruce D McKee ◽  
Kathy Wilhelm ◽  
Cynthia Merrill ◽  
Xiao-jia Ren
Keyword(s):  
Male Sterility ◽  
Sex Chromosome ◽  
Meiotic Drive ◽  
Repeated Sequence ◽  
Meiotic Pairing ◽  
Intergenic Spacers ◽  
Male Specific ◽  
The Relationship ◽  
Novel Model

Abstract In Drosophila melanogaster, deletions of the pericentromeric X heterochromatin cause X-Y nondisjunction, reduced male fertility and distorted sperm recovery ratios (meiotic drive) in combination with a normal Y chromosome and interact with Y-autosome translocations (T(Y;A)) to cause complete male sterility. The pericentromeric heterochromatin has been shown to contain the male-specific X-Y meiotic pairing sites, which consist mostly of a 240-bp repeated sequence in the intergenic spacers (IGS) of the rDNA repeats. The experiments in this paper address the relationship between X-Y pairing failure and the meiotic drive and sterility effects of Xh deletions. X-linked insertions either of complete rDNA repeats or of rDNA fragments that contain the IGS were found to suppress X-Y nondisjunction and meiotic drive in Xh−/Y males, and to restore fertility to Xh−/T(Y;A) males for eight of nine tested Y-autosome translocations. rDNA fragments devoid of IGS repeats proved incapable of suppressing either meiotic drive or chromosomal sterility. These results indicate that the various spermatogenic disruptions associated with X heterochromatic deletions are all consequences of X-Y pairing failure. We interpret these findings in terms of a novel model in which misalignment of chromosomes triggers a checkpoint that acts by disabling the spermatids that derive from affected spermatocytes.

Effect of the Pairing Gene Ph1 and Premeiotic Colchicine Treatment on Intra- and Interchromosome Pairing of Isochromosomes in Common Wheat

Genetics ◽  
1998 ◽  
Vol 150 (3) ◽  
pp. 1199-1208 ◽  
Author(s):  
Juan M Vega ◽  
Moshe Feldman
Keyword(s):  
Common Wheat ◽  
Homologous Chromosome ◽  
Colchicine Treatment ◽  
Crossing Over ◽  
Meiotic Pairing ◽  
Factors Affecting ◽  
Homologous Chromosomes ◽  
Polyploid Wheat ◽  
Main Gene ◽  
Ph1 Gene

Abstract The analysis of the pattern of isochromosome pairing allows one to distinguish factors affecting presynaptic alignment of homologous chromosomes from those affecting synapsis and crossing-over. Because the two homologous arms in an isochromosome are invariably associated by a common centromere, the suppression of pairing between these arms (intrachromosome pairing) would indicate that synaptic or postsynaptic events were impaired. In contrast, the suppression of pairing between an isochromosome and its homologous chromosome (interchromosome pairing), without affecting intrachromosome pairing, would suggest that homologous presynaptic alignment was impaired. We used such an isochromosome system to determine which of the processes associated with chromosome pairing was affected by the Ph1 gene of common wheat—the main gene that restricts pairing to homologues. Ph1 reduced the frequency of interchromosome pairing without affecting intrachromosome pairing. In contrast, intrachromosome pairing was strongly reduced in the absence of the synaptic gene Syn-B1. Premeiotic colchicine treatment, which drastically decreased pairing of conventional chromosomes, reduced interchromosome but not intrachromosome pairing. The results support the hypothesis that premeiotic alignment is a necessary stage for the regularity of meiotic pairing and that Ph1 relaxes this alignment. We suggest that Ph1 acts on premeiotic alignment of homologues and homeologues as a means of ensuring diploid-like meiotic behavior in polyploid wheat.

scholarly journals Chromatid and chromosome type breakage-fusion-bridge cycles in wheat (Triticum aestivum L.).

Genetics ◽  
1995 ◽  
Vol 140 (3) ◽  
pp. 1069-1085 ◽  
Author(s):  
A J Lukaszewski
Keyword(s):  
Triticum Aestivum ◽  
Ring Chromosome ◽  
Triticum Aestivum L ◽  
Aleurone Layer ◽  
Meiotic Pairing ◽  
Chromosome Type ◽  
Root Tips ◽  
Morphological Marker ◽  
Bfb Cycle ◽  
Tandem Duplications

Abstract During the development of disomic additions of rye (Secale cereale L.) chromosomes to wheat (Triticum aestivum L.), two reverse tandem duplications on wheat chromosomes 3D and 4A were isolated. By virtue of their meiotic pairing, the reverse tandem duplications initiated the chromatid type of the breakage-fusion-bridge (BFB) cycle. This BFB cycle continued through pollen mitoses and in the early endosperm divisions, but no clear evidence of its presence in embryo mitoses was found. The chromosome type of BFB cycle was initiated by fusion of two broken chromosome ends resulting in a dicentric or a ring chromosome. Chromosome type BFB cycles were detected in embryo mitoses and in root tips, but they did not persist until the next meiosis and were not transmitted to the progeny. Active BFB cycles induced breakage of other wheat chromosomes that resulted in additional reverse tandem duplications and dicentric and ring chromosomes. Four loci, on chromosome arms 2BS, 3DS, 4AL, and most likely on 7DL, were particularly susceptible to breakage. The BFB cycles produced high frequency of variegation for pigmentation of the aleurone layer of kernels and somatic chimeras for a morphological marker. With the exception of low mutation rate, the observed phenomena are consistent with the activity of a Ds-like element. However, it is not clear whether such an element, if indeed present, was of wheat or rye origin.

Meiotic pairing and segregation of translocation quadrivalents in yeast

Chromosoma ◽  
1998 ◽  
Vol 107 (4) ◽  
pp. 247-254 ◽  
Author(s):  
J. Loidl ◽  
Q.-W. Jin ◽  
M. Jantsch
Keyword(s):  
Meiotic Pairing

Putative diploid ancestors of 80-chromosome Glycine tabacina

Genome ◽  
1992 ◽  
Vol 35 (1) ◽  
pp. 140-146 ◽  
Author(s):  
R. J. Singh ◽  
K. P. Kollipara ◽  
F. Ahmad ◽  
T. Hymowitz
Keyword(s):  
Adventitious Roots ◽  
Chromosome Doubling ◽  
Colchicine Treatment ◽  
Meiotic Pairing ◽  
B Genome ◽  
Specific Hybridization ◽  
A Genome ◽  
Genome Homology ◽  
Glycine Tabacina ◽  
Natural Mutation

The objective of this study was to discover the diploid progenitors of 80-chromosome Glycine tabacina with adventitious roots (WAR) and no adventitious roots (NAR). Three synthetic amphiploids were obtained by somatic chromosome doubling. These were (i) (G. latifolia, 2n = 40, genome B1B1,) × (G. microphylla, 2n = 40, genome BB) = F1(2n = 40, genome BB1) – 0.1% colchicine treatment (CT) – 2n = 80, genome BBB1B1; (ii) (G. canescens, 2n = 40, genome AA) × G. microphylla, 2n = 40, genome BB) = F1 (2n = 40, genome AB) – (CT) – 2n = 80, genome AABB; (iii) (G. latifolia, 2n = 40, B1B1) × G. canescens, 2n = 40, AA) = F1 (2n = 40, genome AB1) – (CT) – 2n = 80, genome AAB1B1. The segmental allotetraploid BBB1B1 was morphologically similar to the 80-chromosome G. tabacina (WAR), but meiotic pairing data in F1 hybrids did not support the complete genomic affinity. Despite normal diploid-like meiosis in allotetraploids AABB and AAB1B1, AABB was completely fertile, while pod set in AAB1B1 was very sparse. Morphologically, allotetraploid AABB was indistinguishable from the 80-chromosome G. tabacina (NAR) but in their F1 hybrids, the range of univalents at metaphase I was wide (4–44). The allotetraploid AAB1B1 did not morphologically resemble the 80-chromosome G. tabacina (NAR). However, the F1 hybrid of AABB × AAB1B1 showed normal meiosis with an average chromosome association (range) of 1.7 I (0–4) + 39.2 II (38–40). Based on this information, we cannot correctly deduce the diploid progenitor species of the 80-chromosome G. tabacina (NAR). The lack of exact genome homology may be attributed to the geographical isolation, natural mutation, and growing environmental conditions since the inception of 80-chromosome G. tabacina. Thus, it is logical to suggest that the 80-chromosome G. tabacina (NAR) is a complex, probably synthesized from A genome (G. canescens, G. clandestina, G. argyrea, G. tomentella D4 isozyme group) and B genome (G. latifolia, G. microphylla, G. tabacina) species, and the 80-chromosome G. tabacina (WAR) complex was evolved through segmental allopolyploidy from the B genome species.Key words: Glycine spp., allopolyploidy, colchicine, genome, intra- and inter-specific hybridization, polyploid complex.

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.

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