THREE MECHANISMS OF 2n POLLEN FORMATION IN DIPLOID POTATOES

Three mechanisms of 2n pollen formation observed in diploid hybrids between Solatium tuberosum Group Phureja (2x) and haploids of S. tuberosum Group Tuberosum (4x) are termed parallel spindles (ps), premature cytokinesis 1 (pc 1) and premature cytokinesis 2 (pc 2). A II spindles are parallel to each other in many cells of clones producing 2n pollen by ps. A single cleavage furrow follows and forms a dyad which generates two 2n microspores. The other two mechanisms, pc 1 and pc 2, produce 2n pollen by omission of the second meiotic division. Premature cytokinesis 1 (pc 1) involves asynchronized movement of bivalents to and from the M I plate and falling apart of chromatids at T I. A cleavage furrow follows the first meiotic division, no second division occurs and products of meiosis are dyads. Premature cytokinesis 2 (pc 2) exhibits no abnormalities at the first meiotic division. However, cytokinesis occurs prematurely at P II, no second division occurs, and only dyads are formed. Genetic data suggested that these three mechanisms may be controlled by single loci, and are inherited independently as simple recessives.

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2n pollen formation via parallel spindles in the potato cultivar sebago

American Potato Journal ◽

10.1007/bf02854460 ◽

1980 ◽

Vol 57 (9) ◽

pp. 449-455 ◽

Cited By ~ 6

Author(s):

E. W. Souter ◽

J. C. Dawe ◽

S. J. Peloquin

Keyword(s):

Potato Cultivar ◽

2N Pollen ◽

Parallel Spindles ◽

Pollen Formation

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Second meiotic division restitution (SDR) 2n pollen formation in diploid and hexaploid species of Asparagus

Genetic Resources and Crop Evolution ◽

10.1007/bf00051417 ◽

1994 ◽

Vol 41 (1) ◽

pp. 1-7 ◽

Cited By ~ 12

Author(s):

E. L. Camadro

Keyword(s):

Meiotic Division ◽

2N Pollen ◽

Hexaploid Species ◽

Pollen Formation

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Cytological basis of 2n pollen formation in a wide range of 2x, 4x, and 6x taxa from tuber-bearing Solanum species

Genome ◽

10.1139/g93-002 ◽

1993 ◽

Vol 36 (1) ◽

pp. 8-13 ◽

Cited By ~ 17

Author(s):

Kazuo Watanabe ◽

Stanley J. Peloquin

Keyword(s):

South America ◽

Solanum Species ◽

2N Pollen ◽

Parallel Spindles ◽

Wide Range ◽

Pollen Formation

Cytological mechanisms of 2n pollen formation were investigated in microsporogenesis and sporad development in 2x, 4x, and 6x taxa of tuber-bearing Solanum species that were originally collected from Mexico, and Central and South America. Parallel spindles and tripoles were seen at anaphase II in the majority of genotypes observed. The occurrence of parallel spindles and tripoles were well correlated with the occurrence of dyads and triads at the sporad stage. Further, the frequency of 2n pollen predicted by frequencies of parallel spindles and tripoles and by frequencies of dyads and triads were also well correlated with observed 2n pollen frequencies. Premature cytokinesis at telophase I to prophase II was seen only in 2x and 4x species from series Conicibaccata. The frequency of premature cytokinesis corresponded well with the frequency of dyads leading to 2n pollen formation. It was concluded that the major mechanisms of 2n pollen formation in tuber-bearing Solanum species is parallel spindles.Key words: cytological mechanisms, parallel spindles, ploidy series, tuber-bearing Solanum species, 2n pollen.

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2n GAMETES IN DIPLOID SOLANUM: FREQUENCY AND TYPES OF SPINDLE ABNORMALITIES

Canadian Journal of Genetics and Cytology ◽

10.1139/g82-032 ◽

1982 ◽

Vol 24 (3) ◽

pp. 301-314 ◽

Cited By ~ 31

Author(s):

R. E. Veilleux ◽

N. A. McHale ◽

F. I. Lauer

Keyword(s):

Cross Sections ◽

Meiotic Division ◽

2N Gametes ◽

Anatomical Study ◽

Solanum Phureja ◽

Spindle Orientation ◽

Pollen Production ◽

2N Pollen ◽

Genetic Theory ◽

Parallel Spindles

Cytological disturbances resulting in 2n pollen were examined in four clones of diploid (2x = 24) Solanum phureja Juz. and Buk.; two (148-17 and 127-14) were variable and two (154-1 and B2-11) were consistently high in 2n pollen production. Three types of abnormal spindle orientation were observed at the second meiotic division: fused, tripolar, and parallel spindles (fs, tps, and ps, respectively). All four genotypes had fs. Three had tps, and ps was least frequent, occuring in two genotypes only. Cross-sections of buds revealed that all three abnormalities can occur in adjacent cells of a locule. In all genotypes, fs predominated at high levels of expression of 2n gametes. At lower levels of expression (i.e. less than 60%, which occurred only in 148-17 and 127-14), however, the frequencies of tps and ps increased. In general, there was little evidence for localization of dyads (resulting from fs or ps) or tetrads (resulting from normal divisions) within cross sections of locules, but 52.4% of all tetrads which occurred in a single locule of genotype 127-14 were found in 25% of the locular area. Cross-sections of buds revealed variation in frequency of 2n gametes among anthers (61.7 vs. 5.6% in 148-17) and between locules of an anther (73.1 vs. 90.0% in B2-11). Implications of the anatomical study were applied to current genetic theory regarding the development of 2n gametes in potato species.

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Environmental induction of high frequency 2n pollen formation in diploid Solanum

Canadian Journal of Genetics and Cytology ◽

10.1139/g83-091 ◽

1983 ◽

Vol 25 (6) ◽

pp. 609-615 ◽

Cited By ~ 39

Author(s):

N. A. McHale

Keyword(s):

High Frequency ◽

The Other ◽

Similar Response ◽

2N Pollen ◽

Flowering Period ◽

Field Site ◽

Phenotypic Stability ◽

Mean Frequency ◽

Environmental Induction ◽

Pollen Formation

Ten genotypes of Solanum phureja Juz. and Buk. producing 2n pollen via fused (FS) and tripolar (TPS) spindles at the second meiotic division were grown in 2 consecutive years at a cool field site (E1, 8–22 °C) and in a warm greenhouse (E2, 14–40 °C) to examine environmental effects on mean frequency and phenotypic stability of 2n pollen production. Overall frequencies of big pollen (BP) and dyad formation were substantially higher in E1 in both years. The stable standard (154-1) gave almost complete expressions of dyads in E1, with no bud below 99%. Four other genotypes (413, 414, 416, 417) gave a similar response in E1, producing mean dyad frequencies between 93 and 99%, with no bud below 80%. The other four genotypes (420, 424, 427, 429) and the variable standard (127–14) produced higher dyad frequencies in E1 versus E2, but their phenotypes remained variable in E1, showing disparities up to 79% between buds of a single collection. The fidelity of stable and variable phenotypes in E1 was examined by scoring dyad frequencies in putatively stable (413, 414, 415, 416) versus variable (420, 424, 427, 127–14) genotypes at four dates spanning the flowering period in this environment. The four stable genotypes showed consistent expression of high dyad frequency (86–99%) at all four dates. In contrast, dyad frequencies of the variable genotypes were substantially lower and more variable between and within collections.

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Effects of 2n-pollen formation by first meiotic division restitution with and without crossover on eight quantitative traits in 4x-2x potato progenies

Theoretical and Applied Genetics ◽

10.1007/s001220051197 ◽

1999 ◽

Vol 98 (8) ◽

pp. 1311-1319 ◽

Cited By ~ 10

Author(s):

J. A. Buso ◽

F. J. B. Reifschneider ◽

L. S. Boiteux ◽

S. J. Peloquin

Keyword(s):

Meiotic Division ◽

Quantitative Traits ◽

2N Pollen ◽

Pollen Formation

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Cytology of 2n Pollen Formation in Diploid Crested Wheatgrass, Agropyron cristatum

Crop Science ◽

10.2135/cropsci1992.0011183x003200060011x ◽

1992 ◽

Vol 32 (6) ◽

pp. 1361-1365 ◽

Cited By ~ 7

Author(s):

Ian M. Ray ◽

Mary K. Tokach

Keyword(s):

Agropyron Cristatum ◽

2N Pollen ◽

Crested Wheatgrass ◽

Pollen Formation

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CYTOLOGY OF 2n POLLEN FORMATION IN DIPLOID ALFALFA, MEDICAGO SATIVA

Canadian Journal of Genetics and Cytology ◽

10.1139/g79-057 ◽

1979 ◽

Vol 21 (4) ◽

pp. 525-530 ◽

Cited By ~ 52

Author(s):

Nicholi Vorsa ◽

E. T. Bingham

Keyword(s):

Medicago Sativa ◽

Seed Set ◽

Pollen Grains ◽

Genetic Constitution ◽

2N Pollen ◽

Diploid Parent ◽

2N Gamete ◽

Medicago Sativa L ◽

Pollen Formation ◽

Mother Cells

Four diploid (2x) clones of alfalfa, Medicago sativa L., which produced good seed set when used as male parents in 4x-2x crosses were selected for study. The 2x clones descended from 2x haploids of cultivated 4x alfalfa. Fertility in the 4x-2x cross was due to the production of pollen with the unreduced chromosome number (2n pollen) from the 2x parent. The cytological mechanism of 2n pollen formation was found to be disorientation of spindles at metaphase II in up to 38% of the pollen mother cells. Thus, both n and 2n pollen were produced by all four diploids examined. Normal spindles at metaphase II were oriented such that they defined the poles of a tetrahedron and resulted in normal tetrads in a tetrahedral arrangement. Disoriented spindles were basically parallel to each other and resulted in formation of dyads and occasionally a triad. Dyads developed into two 2n pollen grains; triads developed into one 2n and two n pollen grains. Since both n and 2n pollen grains are produced by the diploids, they can be maintained as diploids or they can be used as male parents in crosses to tetraploids. The genetic constitution of 2n pollen resulting from parallel spindles is similar to that expected after first division restitution of meiosis and much of the heterozygosity of the diploid parent is conserved in the gametes. The 2n gamete mechanism has potential application in germplasm transfer and in maximizing heterozygosity in tetraploid hybrids.

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