The segregation ratio in waxy-heterozygous barley plants

SummaryIn seven experiments the segregation ratio in barley plants heterozygous for the waxy-gene was studied. Each experiment entailed the scoring of more than 40000 iodine-stained pollen grains from ten spikes. A significant over-representation of blue pollen grains was found in all experiments, with the segregation distortion (measured as a conversion force) ranging from 0·0063 to 0·0143. The distortion was unaffected by which of two mutations was used and which genetic background the plants had, but was stronger in 1988 than in 1987. Different statistical, methodological and biological explanations of the results are discussed.

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Laboratory Exercise on the Segregation of Flower Color and Related Genes Using Salpiglossis sinuata

HortScience ◽

10.21273/hortsci.33.3.555b ◽

1998 ◽

Vol 33 (3) ◽

pp. 555b-555

Author(s):

Chiwon W. Lee

Keyword(s):

Phenotypic Expression ◽

Pollen Grains ◽

Flower Color ◽

Segregation Ratio ◽

Crop Breeding ◽

Flower Opening ◽

Pigmentation Pattern ◽

Laboratory Exercise ◽

Demonstration Plant ◽

Corolla Color

Velvet flower (Salpiglossis sinuata, Solanaceae) can be used as an excellent demonstration plant for horticultural crop breeding classes. Salpiglossis produces large trumpet-like flowers exhibiting an assortment of corolla color and pigmentation pattern. The pistil is large (3 to 4 cm long) with a sticky stigmatal tip and anthers can be easily emasculated prior to anthesis. The large pollen grains are shed in tetrads, which can be separated and individually placed on the stigma. It takes 8 to 9 weeks from seeding to blooming, with a prolific flowering cycle repeated in flushes. Numerous seeds (about 750/capsule) are obtained in 3 weeks after self- or cross-pollination. The influences of three genes that control flower color and pigmentation pattern can be conveniently demonstrated with their dominant and recessive alleles. The R gene controls flower color with red (RR or Rr) being dominant over yellow (rr) flower color. The D gene controls the density of pigmentation with solid (DD or Dd) color being dominant over dilute (dd) color. Corolla color striping is controlled by the St gene with striped (stst) being recessive to non-striped (StSt or Stst) pattern. For example, by using diploid lines of genotypes RRDD (red, solid), RRdd (red, dilute), or rrdd (yellow, dilute) and their crosses, students can easily learn a dominant phenotypic expression in the F1 hybrid and the digenic 9:3:3:1 segregation ratio in the F2 progeny. Another gene (C) that controls flower opening can also be used to show its influence on cleistogamous (closed, self-pollinated, CC or Cc) versus normal chasmogamous (open-pollinated, cc) corolla development. In addition, the induction and use of polyploid (4X, 3X) plants in plant breeding can be effectively demonstrated using this species.

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Mapping segregation distortion loci and quantitative trait loci for spikelet sterility in rice (Oryza sativa L.)

Genetics Research ◽

10.1017/s0016672305007779 ◽

2005 ◽

Vol 86 (2) ◽

pp. 97-106 ◽

Cited By ~ 83

Author(s):

CHUNMING WANG ◽

CHENGSONG ZHU ◽

HUQU ZHAI ◽

JIANMIN WAN

Keyword(s):

Oryza Sativa ◽

Segregation Distortion ◽

Quantitative Trait ◽

Oryza Sativa L ◽

Segregation Ratio ◽

Chromosome 8 ◽

Spikelet Fertility ◽

Spikelet Sterility ◽

Multipoint Method ◽

Two Populations

Markers with segregation ratio distortion are commonly observed in data sets used for quantitative trait locus (QTL) mapping. In this study, a multipoint method of maximum likelihood (ML) was newly developed to estimate the positions and effects of the segregation distortion loci (SDLs) in two F2 populations of rice (Oryza sativa L.), i.e. Taichung65/Bhadua (TB; japonica–indica cross) and CPSLO17/W207-2 (CW; japonica–japonica). Of the four parents, W207-2 and Bhadua were found to be spikelet semi-sterile and stably inherited through selfing, and spikelet fertility segregated in the two populations. Therefore, recombination frequencies were recalculated after mapping the SDLs by using the multipoint method, and the molecular linkage maps of the two F2 populations were constructed to detect QTLs underlying spikelet fertility. As a result, five SDLs in the TB population were mapped on chromosomes 1, 3, 8 and 9, respectively. Two major QTLs underlying spikelet fertility, namely qSS-6a and qSS-8a, were detected on chromosomes 6 and 8, respectively. In the CW population, a total of 12 SDLs were detected on all 12 chromosomes except 1, 5, 7 and 11. Three QTLs underlying spikelet sterility, namely qSS-2, qSS-6b and qSS-8b on chromosomes 2, 6 and 8, were determined on the whole genome scale. Interestingly, both qSS-6a and qSS-6b, detected in the two F2 populations respectively, were located on a similar position as the S5 gene on chromosome 6; while qSS-8a and qSS-8b were also simultaneously detected on similar positions of the short arm of chromosome 8 in the two populations, which should be a new sterility gene showing the same type of zygotic selection.

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Five Gametophytic Mutations Affecting Pollen Development and Pollen Tube Growth in Arabidopsis thaliana

Genetics ◽

10.1093/genetics/158.4.1773 ◽

2001 ◽

Vol 158 (4) ◽

pp. 1773-1783 ◽

Cited By ~ 1

Author(s):

Antonia Procissi ◽

Solveig de Laissardière ◽

Madina Férault ◽

Daniel Vezon ◽

Georges Pelletier ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Pollen Tube ◽

Pollen Tube Growth ◽

Pollen Development ◽

Male Gametophyte ◽

Pollen Grains ◽

Segregation Ratio ◽

Variable Number ◽

Tube Growth ◽

Mutant Lines

Abstract Mutant analysis represents one of the most reliable approaches to identifying genes involved in plant development. The screening of the Versailles collection of Arabidopsis thaliana T-DNA insertion transformants has allowed us to isolate different mutations affecting male gametophytic functions and viability. Among several mutated lines, five have been extensively studied at the genetic, molecular, and cytological levels. For each mutant, several generations of selfing and outcrossing have been carried out, leading to the conclusion that all these mutations are tagged and affect only the male gametophyte. However, only one out of the five mutations is completely penetrant. A variable number of T-DNA copies has integrated in the mutant lines, although all segregate at one mutated locus. Two mutants could be defined as “early mutants”: the mutated genes are presumably expressed during pollen grain maturation and their alteration leads to the production of nonfunctional pollen grains. Two other mutants could be defined as “late mutant” since their pollen is able to germinate but pollen tube growth is highly disturbed. Screening for segregation ratio distortions followed by thorough genetic analysis proved to be a powerful tool for identifying gametophytic mutations of all phases of pollen development.

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An impact of environment on segregation ratio of qualitative traits in maize

Genetika ◽

10.2298/gensr0802145v ◽

2008 ◽

Vol 40 (2) ◽

pp. 145-156 ◽

Cited By ~ 4

Author(s):

Jelena Vancetovic

Keyword(s):

Plant Species ◽

Segregation Distortion ◽

Significant Influence ◽

Environmental Influence ◽

Segregation Ratio ◽

Preferential Pairing ◽

Qualitative Traits

The significant influence of environment was found on the segregation ratio in a dyhibrid inheritance in maize. Two possible causes are proposed for this segregation distortion: 1) environmental influence (selection) prior forming the gametes or/and 2) different preferential pairing in different environments. Further studies, however, on other self or cross-pollinated plant species, and with different traits are needed to better understand this phenomena.

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Laboratory Exercise on the Segregation of Flower Color and Related Genes Using Velvet Flower (Salpiglossis sinuata Ruiz et Pavon)

HortTechnology ◽

10.21273/horttech.9.4.589 ◽

1999 ◽

Vol 9 (4) ◽

pp. 589-593

Author(s):

Chiwon W. Lee

Keyword(s):

Phenotypic Expression ◽

Pollen Grains ◽

Flower Color ◽

Segregation Ratio ◽

Crop Breeding ◽

Horticultural Crop ◽

Flower Opening ◽

Laboratory Exercise ◽

Demonstration Plant ◽

Corolla Color

Velvet flower (Salpiglossis sinuata, Solanaceae) can be used as an excellent demonstration plant for horticultural crop breeding classes. Salpiglossis produces large trumpetlike flowers exhibiting an assortment of corolla colors and pigmentation patterns. The pistil is large (3 to 4 cm or 1.2 to 1.6 inches long) with a sticky stigmatal tip and flowers can be easily emasculated prior to anthesis. The large pollen grains are shed in tetrads which can be separated and placed on the stigmatal surface. It takes eight to nine weeks from seeding to blooming, with a prolific flowering cycle that comes in flushes. Numerous seeds (about 750 per capsule) are obtained in three weeks after self- or cross-pollination. The influences of three genes that control flower color and pigmentation pattern can be conveniently demonstrated with their dominant and recessive alleles. The R gene controls flower color with red (RR or Rr) being dominant over yellow (rr). The D gene controls the density of pigmentation with solid (DD or Dd) color being dominant over dilute (dd) color. Corolla color striping is controlled by the St gene with striped (stst) being recessive to nonstriped (StSt or Stst) pattern. By using diploid lines of genotypes RRDD (red, solid), RRdd (red, dilute), or rrdd (yellow, dilute) and their crosses, students can easily observe a dominant phenotypic expression in the F1 hybrid and the digenic 9:3:3:1 segregation ratio in the F2 progeny. Another gene (C) that controls flower opening can also be used to show its influence on cleistogamous (closed, selfpollinated, CC or Cc) versus normal chasmogamous (open-pollinated, cc) corolla development. In addition, the induction and use of polyploid (4x) plants in plant breeding can also be demonstrated using this species.

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Analysis of Segregation Ratio Distortion and Linkage Mapping in Two Switchgrass F1 Populations: Lowland-lowland and Lowland-upland Using Genotyping by Sequencing Data

10.21203/rs.2.15334/v1 ◽

2019 ◽

Author(s):

Rasyidah Razar ◽

Katrien Devos ◽

Ali Missaoui

Keyword(s):

Genetic Diversity ◽

Segregation Distortion ◽

Biomass Yield ◽

Genotyping By Sequencing ◽

Segregation Ratio ◽

Genetic Maps ◽

Linkage Maps ◽

Sequencing Data ◽

Target Number ◽

High Genetic Diversity

Abstract Background: Switchgrass is an emerging bioenergy crop due to its perennial nature, high biomass yield, and ability to grow in marginal land. The high genetic diversity in switchgrass germplasm can be exploited to capture favorable traits that increase the range of adaptation and biomass yield. Genetic diversity can be explored using single nucleotide polymorphisms (SNPs) that next-generation sequencing has made possible for high-throughput genotyping. We used genotyping-by-sequencing (GBS) of genomic fragments resulting from two methylation sensitive restriction enzymes: PstI and MspI . Two bi-parental F1 populations were developed from crosses between lowland B6 and lowland AP13 (AB population), and lowland B6 with upland VS16 genotypes (BV population), with a target number of 298 progenies in each population. Pseudo-testcross strategy was adopted to perform linkage analysis in these populations that are segregating for winter dormancy using single dose markers (SDA): heterozygous in one parent and homozygous in the other parent. We compared the amount of polymorphisms between the two crosses and examined the pattern of segregation distortion based on the SNPs data generated. Results: Two genetic maps were generated for each population, with 2772 markers in AB and 3766 markers in BV. The higher number of markers in the BV population was expected for since the parents originated from different ecotypes and verified to have the highest genetic distance. More segregation distortion was observed in markers located in the telomeric regions where more genes reside. More markers from the AB population exhibited segregation distortion compared to the BV, and the proportion of heterozygous alleles were significantly higher than homozygous alleles in AB population. The linkage maps showed strong collinearity with P. virgatum V5.1 reference genome with a very minimal number of markers originating from different chromosomes. Conclusion: Understanding the extent of segregation distortion in switchgrass crosses is important for the correct inclusion of markers based on their segregation ratio when constructing a linkage map. Switchgrass linkage maps should be a useful resource to dissect beneficial biomass traits linked to SNP markers.

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Mapping Quantitative Trait Loci Using Distorted Markers

International Journal of Plant Genomics ◽

10.1155/2009/410825 ◽

2009 ◽

Vol 2009 ◽

pp. 1-11 ◽

Cited By ~ 40

Author(s):

Shizhong Xu ◽

Zhiqiu Hu

Keyword(s):

Qtl Mapping ◽

Segregation Distortion ◽

Quantitative Trait ◽

Expectation Maximization Algorithm ◽

Real Life ◽

Segregation Ratio ◽

Joint Analysis ◽

Mendelian Segregation ◽

Real Life Data ◽

Trait Locus

Quantitative trait locus (QTL) mapping is usually performed using markers that follow a Mendelian segregation ratio. We developed a new method of QTL mapping that can use markers with segregation distortion (non-Mendelian markers). An EM (expectation-maximization) algorithm is used to estimate QTL and SDL (segregation distortion loci) parameters. The joint analysis of QTL and SDL is particularly useful for selective genotyping. Application of the joint analysis is demonstrated using a real life data from a wheat QTL mapping experiment.

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ON THE MODELS OF SEGREGATION DISTORTION IN DROSOPHILA MELANOGASTER

Genetics ◽

10.1093/genetics/93.2.423 ◽

1979 ◽

Vol 93 (2) ◽

pp. 423-435

Author(s):

Diana W Martin ◽

Yuichiro Hiraizumi

Keyword(s):

Drosophila Melanogaster ◽

Segregation Distortion ◽

Regulatory Protein ◽

Segregation Ratio ◽

Major Elements ◽

Necessary Condition ◽

Slight Reduction ◽

Mendelian Segregation ◽

Multiple Alleles ◽

Actual Observation

ABSTRACT The Segregation Distorter system of Drosophila melanogaster consists of two major elements, Sd and Rsp. There are two allelic alternatives of Rsp—sensitive (Rsp8) and insensitive (Rspi); a chromosome carrying Rspi is not distorted. According to the model proposed by HARTL (1973), these two elements interact to cause segregation distortion. For a sperm to complete the maturation process, it is assumed that the Rsp locus has to be complexed with the product of the Sd locus. This product is assumed to be a multimetric regulatory protein. Three kinds of regulatory multimers may be distinguished: Sd+/Sd+, which is assumed to complex with both Rsp8 and Rspi; Sd+/Sd heteromultimers, which complex preferentially with Rspi; and Sd/Sd hmomultimers, which complex with neither Rsp8 nor Rspi. Most of the regulatory protein in the Sd+/Sd heterozygous male is assumed to be the Sd+/Sd heteromultimer. ——Some modifications of HARTL'S model were made by GANETZEY (1977). Rather than the binding of a product of Sd at the Rsp locus being a necessary condition for normal spermigenesis, this binding causes sperm dysfunction. It is assumed that the product of Sd complexes more readily with Rsp8 than with Rspi and that the amount of Sd product is limited with respect to the number of binding sites available. No function is ascribed to the Sd+ locus. In order to explain reduced male fertility of some genotypes, GANETZKY further assumes that the Sd product, when not competed for by an Rsp8 locus, can bind to an Rspi locus.——Two consequences of these models were criticically examined: according to these models (1) an Sd Rsp8/Sd+ RspS male should not show any segregation distortion, and (2) an Sd Rsps/Sd Rsp8 male should show much reduced fertility, if not complete sterility.—The results of the present study bear on these two points. (1) Rsp8 locus seems to consist of multiple alleles, each having a different degree of ability to interact with the product of the Sd locus. An Sd Rsp8/Sd+RspS male shows a certain degree of segregation distortion when the two RspS alleles are different, but it shows a normal Mendelian segregation ratio when the Rsp8 alleles are homozygous. The first prediction of the models is supported by actual observation when the two Rsps alleles are the same. (2) There is a suggestion of slight reduction in fertility, but generally Sd Rsp8/Sd Rsp8 males are quite fertile. Thus, the second prediction is not supported by actual observation. The mechanism of segregation distortion is still open for future studies.

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Meiosis leads to pervasive segregation distortion and copy-number variation in accessory chromosomes of the wheat pathogen Zymoseptoria tritici

10.1101/214882 ◽

2017 ◽

Cited By ~ 1

Author(s):

Simone Fouché ◽

Clémence Plissonneau ◽

Bruce A. McDonald ◽

Daniel Croll

Keyword(s):

Segregation Distortion ◽

High Throughput Screening ◽

Sequence Similarity ◽

Chromosomal Rearrangements ◽

Screening Method ◽

Segregation Ratio ◽

Zymoseptoria Tritici ◽

Repeat Content ◽

Number Variation ◽

Accessory Chromosomes

AbstractMeiosis is one of the most conserved molecular processes in eukaryotes. The fidelity of pairing and segregation of homologous chromosomes has a major impact on the proper transmission of genetic information. Aberrant chromosomal transmission can have major phenotypic consequences, yet the mechanisms are poorly understood. Fungi are excellent models to investigate processes of chromosomal transmission, because many species have highly polymorphic genomes that include accessory chromosomes. Inheritance of accessory chromosomes is often unstable and chromosomal losses have little impact on fitness. We analyzed chromosomal inheritance in 477 progeny coming from two crosses of the fungal wheat pathogen Zymoseptoria tritici. For this, we developed a high-throughput screening method based on restriction site associated DNA sequencing (RAD-seq) that generated dense coverage of genetic markers along each chromosome. We identified rare instances of chromosomal duplications (disomy) in core chromosomes. Accessory chromosomes showed high overall frequencies of disomy. Chromosomal rearrangements were found exclusively on accessory chromosomes and were more frequent than disomy. Accessory chromosomes present in only one of the parents in an analyzed cross were inherited at significantly higher rates than the expected 1:1 segregation ratio. Both the chromosome and the parental background had significant impacts on the rates of disomy, losses, rearrangements and segregation distortion. We found that chromosomes with higher sequence similarity and lower repeat content were inherited more faithfully. The large number of rearranged progeny chromosomes identified in this species will enable detailed analyses of the mechanisms underlying chromosomal rearrangement.

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Selection of T-DNA-Tagged Male and Female Gametophytic Mutants by Segregation Distortion in Arabidopsis

Genetics ◽

10.1093/genetics/149.2.621 ◽

1998 ◽

Vol 149 (2) ◽

pp. 621-631 ◽

Cited By ~ 6

Author(s):

Ross Howden ◽

Soon Ki Park ◽

James M Moore ◽

James Orme ◽

Ueli Grossniklaus ◽

...

Keyword(s):

Insertional Mutagenesis ◽

Generative Cell ◽

Embryo Sac ◽

Pollen Grains ◽

Segregation Ratio ◽

Dapi Staining ◽

Genetic Transmission ◽

Segregation Ratios ◽

Ratio Distortion ◽

Mutant Phenotypes

Abstract As a strategy for the identification of T-DNA-tagged gametophytic mutants, we have used T-DNA insertional mutagenesis based on screening for distorted segregation ratios by antibiotic selection. Screening of ~1000 transgenic Arabidopsis families led to the isolation of eight lines showing reproducible segregation ratios of ~1:1, suggesting that these lines are putative gametophytic mutants caused by T-DNA insertion at a single locus. Genetic analysis of T-DNA transmission through reciprocal backcrosses with wild type showed severe reductions in genetic transmission of the T-DNA through the male and/or female gametes. Direct evidence for mutant phenotypes in these lines was investigated by DAPI staining of mature pollen grains and by the analysis of seed set and embryo sac morphology in cleared ovules. One line, termed limpet pollen, showed a novel pollen phenotype in that the generative cell failed to migrate inward after pollen mitosis I, such that the generative or sperm cells remained against the pollen wall. Two other lines, andarta and tistrya, were defective in female transmission and showed an early arrest of embryo sac development with the viable megaspore not initiating the nuclear division cycles. These data demonstrate the efficacy of a segregation ratio distortion strategy for the identification of T-DNA-tagged gametophytic mutants in Arabidopsis.

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