Use of half-tetrad analysis to discriminate between two types of 2n egg formation in a potato haploid

Genome ◽  
1992 ◽  
Vol 35 (5) ◽  
pp. 741-745 ◽  
Author(s):  
Joanna E. Werner ◽  
David S. Douches ◽  
Rosanna Freyre
Keyword(s):  
Solanum Tuberosum L ◽  
2N Gametes ◽  
Breeding Value ◽  
Tetrad Analysis ◽  
Recombination Rates ◽  
First Division Restitution ◽  
Egg Formation ◽  
Second Division Restitution ◽  
2N Eggs ◽  
Tetraploid Progeny

The ratio of the first division restitution (FDR) to second division restitution (SDR) 2n eggs was estimated in 4182t, a haploid (2n = 2x = 24) of Solanum tuberosum L. that produces 2n eggs by the two modes. The segregation of three genes previously mapped relative to their centromeres, Pgm-2 (2.0 cM), Mdh-1 (33.5 cM), and 6-Pgdh-3 (30.1 cM) was analyzed in the tetraploid offspring of a 2x × 4x cross. Based on the segregation of the Pgm-2 locus, 39.7% of the progeny originated from FDR 2n eggs and 60.3% from SDR. Segregation patterns of the two distal loci within the FDR-derived 4x subpopulation indicated that the gene–centromere recombination rate during megasporogenesis was significantly reduced for Mdh-1 when compared with a previous estimate during microsporogenesis. In the SDR-derived 4x subpopulation, the gene–centromere recombination rates for Mdh-1 and 6-Pgdh-3 were not significantly different from previous estimates. Tetraploid progeny generated from one 2x × 4x cross where the 2x parent produces 2n gametes by two modes can be used to make an unbiased comparison of the potential breeding value of FDR and SDR gametes.Key words: potato, megasporogenesis, first division restitution, second division restitution, isozyme.

Occurrence and mechanisms of 2n egg formation in 2x potato

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 975-982 ◽  
Author(s):  
Joanna E. Werner ◽  
Stanley J. Peloquin
Keyword(s):  
Wild Species ◽  
Seed Set ◽  
2N Gametes ◽  
Origin And Evolution ◽  
First Division Restitution ◽  
Egg Formation ◽  
Second Division Restitution ◽  
2N Eggs ◽  
Haploid Species ◽  
Species Hybrids

The occurrence of 2n eggs in 381 haploids from six tetraploid parents and in 127 plants representing five diploid wild species was detected using 2x × 4x crosses. Sixty-two percent of the haploids and 24% of the wild-species plants produced 2n eggs. Twenty-six haploids and 17 species plants that gave high seed set in 2x × 4x crosses were examined cytologically to determine the frequency and mechanisms of 2n egg formation. There was significant variation in the frequency of 2n eggs among haploids (7–57%) and among species plants (4.9–57.3%). Five mechanisms of 2n egg formation were identified: synaptic variant (genetically first division restitution); delayed meiotic division (first division restitution and second division restitution); omission of the second division (the prevalent mechanism, second division restitution); irregular anaphase II (second division restitution); and failure of second cytokinesis (second division restitution). 2n eggs can be formed by more than one mechanism within a clone. The occurrence of 2n eggs in wild species and the higher frequency of 2n eggs in haploids than in wild species indicate that sexual polyploidization has been involved in the origin and evolution of polyploid series in potato. The high frequency of 2n eggs in both haploids and diploid wild species allows generation of haploid-species hybrids that produce 2n eggs. These hybrids can then be used in the 2x × 4x and 2x × 2x breeding schemes.Key words: haploids, wild species, 2n gametes, first division restitution, second division restitution.

Synaptic mutants in potato, Solanum tuberosum L. III. Effect of the Ds-1/ds-1 locus (desynapsis) on genetic recombination in male and female meiosis

Genome ◽  
1991 ◽  
Vol 34 (1) ◽  
pp. 121-130 ◽  
Author(s):  
E. Jongedijk ◽  
R. C. B. Hutten ◽  
J. M. A. S. A. van der Wolk ◽  
S. I. J. Schuurmans Stekhoven
Keyword(s):  
Genetic Recombination ◽  
Solanum Tuberosum L ◽  
2N Gametes ◽  
Potato Seed ◽  
Genetic Constitution ◽  
True Potato Seed ◽  
Female Meiosis ◽  
Recombination Rates ◽  
Male And Female ◽  
Tetraploid Progeny

By applying half-tetrad analysis to segregating tetraploid progeny that had been raised from 2x–4x and 2x–2x crosses, five marker loci (ym, y, Got-1, Got-2, and ds-1) were mapped to their respective centromeres in male and female meiosis of both normal synaptic and desynaptic (ds-1ds-1) diploid potato clones. Significant sex differences in genetic recombination for these loci did not occur in either normal plants or desynaptic mutants, which suggests that genetic exchange in both the sexes is governed by the same control system. In desynaptic mutants a severe reduction in crossing-over was observed for ym and.y (83.7 an 90.0% reduction, respectively), whereas recombination rates for Got-2 appeared to have systematically, although not significantly, increased. The ds-1 gene was concluded to substantially reduce the overall chiasma frequency and to differentially alter chiasma distribution along individual chromosomes. Based on segregation ratios in progeny from different types of testcrosses, first division restitution (FDR) and second division restitution (SDR) 2n gametes formed by normal synaptic plants were estimated to transmit on average about 82.7 and 36.1 %, respectively, of the parental heterozygosity to tetraploids. With desynapsis the average amount of heterozygosity transmitted by FDR 2n gametes amounted to 94.1%. SDR 2n gametes from desynaptic mutants are sterile as a result of aneuploidy. The ds-1 gene was demonstrated to particularly enhance the ability of FDR 2n gametes to preserve the genetic constitution of diploid parental clones with a minimum amount of reassortment. The potential value and limitations of the ds-1 gene for the production of true potato seed varieties and the experimental induction of diplosporic apomixis are discussed.Key words: Solanum, genetic markers, gene–centromere mapping, desynapsis, reduced recombination.

Gene-centromere mapping in potato by half-tetrad analysis: map distances of H1, Rx, and Ry and their possible use for ascertaining the mode of 2n-pollen formation

Genome ◽  
1992 ◽  
Vol 35 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Marinus Wagenvoort ◽  
Ewa Zimnoch-Guzowska
Keyword(s):  
Potato Virus ◽  
Potato Virus Y ◽  
Potato Virus X ◽  
2N Pollen ◽  
Tetrad Analysis ◽  
Extreme Resistance ◽  
Second Division Restitution ◽  
Pollen Formation ◽  
Tetraploid Progeny ◽  
Map Distance

Diploids from the tetraploid potato varieties 'Alcmaria' and 'Pansta' and from the tetraploid CPRO genotypes Y66-13-610 and Y66-13-636 were used in half-tetrad analyses to estimate the gene-centromere map distances of the genes Rx, Ry, and H1. Employing tetraploid progeny from 2x (second division restitution) – 4x testcrosses the gene-centromere map distance of H1, conferring resistance to pathotype Ro1 of Globodera rostochiensis, was estimated to be 16.3 centimorgans (cM). For Rχ, conferring extreme resistance to potato virus X (PVX), a map distance of 33.9 cM was estimated. The gene Ry, conferring extreme resistance to potato virus Y (PVY), was estimated to be located 14.2 cM from the centromere. Using the estimated map distance for Rx, it was attempted to determine the mode of 2n-pollen formation in four diploid interspecific hybrids, including the species Solanum tuberosum, Solanum chacoense, Solanum yungasense, and Solanum phureja, by half-tetrad analysis in tetraploid progeny from 4x-2x testcrosses. The mean frequency of 8.7% nulliplex plants for Rx was outside the range of the 95% confidence intervals, for both first division restitution and second division restitution 2n pollen.Key words: nematode resistance, potato virus X resistance, potato virus Y resistance, 2n eggs, gene-centromere mapping, Solanum.

Abnormal meiosis in alfalfa, Medicago sativa: cytology of 2N egg and 4N pollen formation

1983 ◽  
Vol 25 (2) ◽  
pp. 107-112 ◽  
Author(s):  
T. W. Pfeiffer ◽  
E. T. Bingham
Keyword(s):  
Medicago Sativa ◽  
Pollen Grain ◽  
Tetrad Analysis ◽  
Egg Formation ◽  
2N Eggs ◽  
Developmental Sequences ◽  
Clearing Technique ◽  
Medicago Sativa L ◽  
Pollen Formation ◽  
Fdr 2N Pollen

The cytological mechanism of 2n egg formation was studied in several diploid (2n = 2x = 16) and tetraploid (2n = 4x = 32) clones of cultivated alfalfa (Medicago sativa L.). The comparison of normal megasporogenesis with megasporogenesis that produced 2n eggs was made using an ovule clearing technique with methyl salicylate. Developmental sequences in the formation of n and 2n eggs were the same through anaphase II. Following anaphase II in 2n egg formation cytokinesis occurred only in the micropylar diad, not in the chalazal diad. Micropylar megaspores disintegrated leaving a functional unreduced megaspore of the second division restitution (SDR) type at the chalazal end. The two nuclei in the megaspore can fuse prior to the mitotic divisions or during the first two mitotic divisions. The SDR mechanism of 2n egg formation was confirmed in selected diploid clones by comparing half-tetrad analysis of 2n eggs with half-tetrad analysis of a known first division restitution (FDR) 2n pollen producer. During the study of 2n egg formation in tetraploid alfalfa, several diploid clones were found which produced octoploid (2n = 8x = 64) progeny from 4x-2x crosses. Pollen development in the diploids was normal through telophase II. Cytokinesis was absent, however, and the four telophase nuclei fused to produce a 4n pollen grain. The fusion of a 2n (2n = 4x = 32) egg and a 4n (4n = 4x = 32) pollen grain produced the octoploid progeny.

scholarly journals Quantitative genetics of 4x-2x hybrid populations with first-division restitution and second-division restitution 2n gametes produced by diploid parents.

Genetics ◽  
1995 ◽  
Vol 139 (4) ◽  
pp. 1797-1803
Author(s):  
J L David ◽  
P Boudec ◽  
A Gallais
Keyword(s):  
Recurrent Selection ◽  
2N Gametes ◽  
Experimental Comparison ◽  
Additive Variance ◽  
First Division Restitution ◽  
Advantages And Disadvantages ◽  
Second Division Restitution ◽  
Mean And Variance ◽  
The Mean ◽  
Genetic Value

Abstract A model is proposed to describe the genetic value of 4x-2x hybrids resulting from crosses between tetraploid genitors and diploid genitors that produce 2n gametes. The model takes into account the genetic consequences of the First Division Restitution (FDR) and Second Division Restitution (SDR) meiosis, particularly on the homozygosity level that 2n gametes contribute to 4x-2x hybrids. As genes can be identical by descent, numerous parameters are needed in the classical approach to describe the inbreeding effects on the mean and variance of 4x-2x hybrids. Using the concept of test value, the model allows a large decrease in the number of required parameters. The model gives the components of genetic variance and usual covariances between relatives using these synthetic parameters. The model is then used to study the efficiency of a recurrent breeding scheme to improve diploid genitors for their combining ability with tetraploid genitors. It appears that, in presence of dominance, ignoring the meiosis pattern will lead to an overestimation of additive variance and then of genetic advance. Some genetic considerations on the differences between FDR and SDR mechanisms lead us to suggest an experimental comparison of their respective advantages and disadvantages for the type of considered recurrent selection. An experimental crossing design is proposed to obtain estimates of the genetic parameters needed for this comparison.

Evidence for the existence of endosperm balance number in the true clovers (Trifolium spp.)

1986 ◽  
Vol 28 (4) ◽  
pp. 581-586 ◽  
Author(s):  
W. A. Parrott ◽  
R. R. Smith
Keyword(s):  
Ploidy Level ◽  
Related Species ◽  
Interspecific Hybrids ◽  
2N Gametes ◽  
Endosperm Development ◽  
Individual Species ◽  
Interspecific Crosses ◽  
Endosperm Balance Number ◽  
Endosperm Tissue ◽  
2N Eggs

The endosperm balance number (EBN) hypothesis was first advanced to explain results from interspecific crosses in Solanum and later in Impatiens. According to the EBN hypothesis, normal endosperm development following intra- or inter-specific crosses depends on having a ratio of two EBNs from the female to one EBN from the male in the endosperm tissue. EBNs may differ among related species. Successful hybrids can be obtained between species with the same EBN. The ploidy level of an individual species can be varied to modify its EBN, making it cross compatible with a species sharing its modified EBN. Interspecific crosses within Trifolium have been limited and difficult. Crosses reported in the literature, including evidence from our own study, suggest that EBN is operating in Trifolium and have been used to assign EBN numbers to some clover species. The use of 2n eggs enabled two species, differing in EBN, to be crossed. An understanding of the EBN mechanism that operates in Trifolium should make successful interspecific hybrids easier to obtain in the future.Key words: endosperm balance number, hybrids (interspecific), 2n gametes, Trifolium.

scholarly journals A Microsatellite Linkage Map of Rainbow Trout (Oncorhynchus mykiss) Characterized by Large Sex-Specific Differences in Recombination Rates

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1331-1345 ◽  
Author(s):  
Takashi Sakamoto ◽  
Roy G Danzmann ◽  
Karim Gharbi ◽  
Pamela Howard ◽  
Akiyuki Ozaki ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Linkage Map ◽  
Genetic Linkage Map ◽  
Linkage Groups ◽  
Tetrad Analysis ◽  
Recombination Rates ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Male Specific ◽  
Microsatellite Linkage

Abstract We constructed a genetic linkage map for a tetraploid derivative species, the rainbow trout (Oncorhynchus mykiss), using 191 microsatellite, 3 RAPD, 7 ESMP, and 7 allozyme markers in three backcross families. The linkage map consists of 29 linkage groups with potential arm displacements in the female map due to male-specific pseudolinkage arrangements. Synteny of duplicated microsatellite markers was used to identify and confirm some previously reported pseudolinkage arrangements based upon allozyme markers. Fifteen centromeric regions (20 chromosome arms) were identified with a half-tetrad analysis using gynogenetic diploids. Female map length is ~10 M, but this is a large underestimate as many genotyped segments remain unassigned at a LOD threshold of 3.0. Extreme differences in female:male map distances were observed (ratio F:M, 3.25:1). Females had much lower recombination rates (0.14:1) in telomeric regions than males, while recombination rates were much higher in females within regions proximal to the centromere (F:M, 10:1). Quadrivalent formations that appear almost exclusively in males are postulated to account for the observed differences.

Bilateral sexual tetraploidization in red clover

1985 ◽  
Vol 27 (1) ◽  
pp. 64-68 ◽  
Author(s):  
W. A. Parrott ◽  
R. R. Smith ◽  
M. M. Smith
Keyword(s):  
Egg Production ◽  
Trifolium Pratense ◽  
2N Gametes ◽  
Red Clover ◽  
Female Plant ◽  
2N Pollen ◽  
Sexual Polyploidization ◽  
2N Eggs ◽  
Trifolium Pratense L ◽  
Bilateral Sexual Polyploidization

Twenty-four diploid red clover (Trifolium pratense L.) plants, from the cultivars 'Arlington', 'Florex', and 'Redman', and C760, a Wisconsin synthetic, were tested for 2n egg production by crossing them with tetraploid plants. Four plants were identified and selected as 2n egg producers. These plants were then crossed with a known producer of 2n pollen in an attempt to obtain tetraploid plants through bilateral sexual polyploidization. Thirteen percent of the seed obtained in one of the 2x–2x crosses were tetraploid. The female plant produced an estimated 0.14 2n eggs per 1000 flowers in the cross. In a second experiment, bilateral sexual polyploidization was attempted, using 14 plants which had not been previously tested for 2n egg production. Two of these plants produced one and two tetraploids each, representing 2n egg frequencies of 3.33 and 5.00 2n eggs per 1000 flowers, respectively. It seems likely that it will be possible to use bilateral sexual polyploidization to tetraploidize red clover germplasm in the future.Key words: tetraploid red clover, Trifolium pratense. 2n gametes.

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