Unreduced Megagametophyte Production in Lemon Occurs via Three Meiotic Mechanisms, Predominantly Second-Division Restitution

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.

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Mixed first and second division restitution in male meiosis of Hierochloë odorata (L.) Beauv (Holy Grass)

Heredity ◽

10.1038/hdy.1992.90 ◽

1992 ◽

Vol 69 (1) ◽

pp. 21-31 ◽

Cited By ~ 5

Author(s):

Colin Ferris ◽

Robert S Callow ◽

Alan J Gray

Keyword(s):

Male Meiosis ◽

Second Division Restitution ◽

Hierochloe Odorata

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UNREDUCED MEGAGAMETOPHYTE FORMATION VIA SECOND DIVISION RESTITUTION CONTRIBUTES TO TETRAPLOID PRODUCTION IN INTERPLOIDY CROSSES WITH 'ORAH' MANDARIN (CITRUSRETICULATA)

Frontiers of Agricultural Science and Engineering ◽

10.15302/j-fase-2021385 ◽

2021 ◽

Vol 0 (0) ◽

pp. 0

Keyword(s):

Second Division Restitution ◽

Interploidy Crosses

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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 ◽

10.1139/g92-001 ◽

1992 ◽

Vol 35 (1) ◽

pp. 1-7 ◽

Cited By ~ 6

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.

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

Genome ◽

10.1139/g91-150 ◽

1991 ◽

Vol 34 (6) ◽

pp. 975-982 ◽

Cited By ~ 47

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.

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