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

1979 ◽  
Vol 21 (4) ◽  
pp. 525-530 ◽  
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.

Desynapsis and spindle abnormalities leading to 2n pollen formation in Vaccinium darrowi

Genome ◽  
1999 ◽  
Vol 42 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Luping Qu ◽  
Nicholi Vorsa
Keyword(s):  
Chromosome Complement ◽  
2N Gametes ◽  
Complete Separation ◽  
Genetic Constitution ◽  
2N Pollen ◽  
Spindle Formation ◽  
Vaccinium Darrowi ◽  
Pollen Formation ◽  
High Level ◽  
Mother Cells

Cytological investigation revealed desynapsis in microsporogenesis of a wild diploid clone of Vaccinium darrowi. Expression of desynapsis appears variable among the pollen mother cells (PMCs). In the PMCs expressing desynapsis, all or most chromosomes appeared to be completely desynapsed before anaphase I (AI) since bivalents were rare at this stage. In some PMCs complete separation of chromatids was also observed before AI. Consequently, one or both meiotic divisions were lacking, which in turn suggests either a lack of spindle formation or function. Lack of spindle function was hypothesized from the observation that in PMCs with only separated chromatids (daughter chromosomes) before AI or anaphase II (AII), their subsequent movement to anaphase poles was not observed. Thus, spindle formation or function appears to be dependent on paired homologues (bivalents) or minimally joined sister chromatids (univalents) being present. Omission of meiosis II could lead to formation of fertile 2n pollen (~5%), since a balanced chromosome complement would be expected with an equational division of the entire chromosome complement at AI. The genetic constitution of the 2n gamete would be equivalent to first division restitution (FDR) origin. If chiasmata are lacking then recombination would be absent, and 100% transmission of parental heterozygosity would be expected with FDR 2n gametes. Because desynapsis may arise from the lack of effective chiasmata between the paired homologues, a high level of parental heterozygosity is expected to be retained in the 2n gametes. The potential usage of the 2n gametes in blueberry breeding was discussed.Key words: desynapsis, spindle abnormality, 2n pollen, blueberry.

THE INHERITANCE OF 2n POLLEN FORMATION IN DIPLOID ALFALFA MEDICAGO SATIVA

1982 ◽  
Vol 24 (3) ◽  
pp. 315-323 ◽  
Author(s):  
T. J. McCoy
Keyword(s):  
Medicago Sativa ◽  
High Frequency ◽  
Seed Set ◽  
Single Gene ◽  
Recessive Gene ◽  
2N Pollen ◽  
Good Seed ◽  
Ploidy Levels ◽  
Pollen Formation ◽  
Diploid Level

The inheritance of 2n pollen formation was studied in two diploid clones of alfalfa, Medicago sativa L. The two clones consistently produced a high frequency of 2n pollen, and they also porduced good seed set when used as males in 4x-2x crosses due to the functioning of 2n(2x) pollen. For the inheritance study the two clones were crossed with diploid clones of cultivated alfalfa at the diploid level (CADL), and with several clones of diploid M. falcata. In segregating families, plants that produced a high frequency of 2n pollen were identified by good seed set when used as males in 4x-2x crosses, and/or by bimodal pollen sizes. Plants that produced 4% or more 2n pollen generally produced greater than one seed per pollination in 4x-2x crosses, and these plants were considered 2n pollen producers. Analysis of self, F1, F2 and backcross (BC) families indicated 2n pollen formation was controlled by a single recessive gene, designated rp (restitution pollen). An allelism test indicated 2n pollen formation was controlled by the same recessive gene in both clones. Although there was considerable variation in the frequency of 2n pollen in rp/rp plants grown in different environments, all rp/rp plants consistently produced a significant frequency of 2n pollen (greater than 4%). Simple genetic control of 2n pollen formation has important implications in the evolution of the genus Medicago. In addition, 2n pollen formation controlled by a single gene may have potential application in the breeding of highly heterozygous tetraploids and in the efficient transfer of germplasm across ploidy levels.

SELECTION FOR SEED SET IN NONINBRED AND PARTLY INBRED POPULATIONS OF ALFALFA

1977 ◽  
Vol 57 (3) ◽  
pp. 873-881 ◽  
Author(s):  
R. MICHAUD ◽  
T. H. BUSBICE
Keyword(s):  
Medicago Sativa ◽  
Seed Set ◽  
Exponential Model ◽  
Seed Setting ◽  
Medicago Sativa L ◽  
Selection For ◽  
Inbred Populations ◽  
The Relationship ◽  
Advanced Generation ◽  
Coefficient Of Inbreeding

Alfalfa (Medicago sativa L.) is a highly heterozygous cross-pollinating species, and most breeding efforts have been conducted on noninbred populations. The purpose of this study was to determine whether greater breeding progress could be made by selecting within partly inbred populations rather than within noninbred ones. One hundred and twenty F1 (noninbred) and 120 S1 (partly inbred) plants that were issued from crossing and selfing four alfalfa clones were evaluated for self-fertility. The most self-fertile 10% of the plants from each family were selected in each population. The selected plants within each level of inbreeding were intercrossed to produce an advanced generation in which the effectiveness of the selection was evaluated. Selection increased both self- and cross-fertility in the advanced generation. Selection was more effective at the F1 level than at the S1 level. Fertility was reduced drastically by inbreeding. The average self-fertility of the S1’s was only about 7% of the cross-fertility of their parental clones. An exponential model was proposed to describe the relationship between seed setting and the coefficient of inbreeding in the developing zygote. This model explained 95% of the variation among 11 unselected populations having differing levels of inbreeding.

RAPD polymorphism in the prebreeding material for cultivation of synthetic variations of lucerne (Medicago sativa L.)

2013 ◽  
Vol 8 (1) ◽  
pp. 38-47 ◽  
Author(s):  
Lidia Skuza ◽  
Stanisława Rogalska ◽  
Stanisław Dyba ◽  
Jan Bocianowski
Keyword(s):  
Medicago Sativa ◽  
Genetic Similarity ◽  
Seed Set ◽  
Inbred Lines ◽  
Specific Yield ◽  
Group Method ◽  
Green Mass ◽  
Molecular Image ◽  
Synthetic Population ◽  
Medicago Sativa L

AbstractGenetic diversity between synthetic cultivars (Syn5, Syn7), inbred lines (D3, D5, E1/2, G1/1, G1/2) and ecotypes (E16, E51, E182, E231) of lucerne (Medicago sativa L.) was studied using the RAPD-PCR method. The plants differed in the efficiency of seed set and in the yield of green mass. The ecotypes E182 and E231 and the synthetic population Syn5 showed the highest fertility. Additionally, Syn5 also showed the highest efficiency of seed set and the yield of green mass. Among the inbred lines, D3 was characterised by the highest yield of green mass and E1/2 by the highest fertility. An optimal combination of yield and biomass was observed for the synthetic population Syn5, obtained by crossing the lines D3, D5 and G1/1, as demonstrated using comparative analysis. A total of 338 polymorphic products were generated using 20 arbitrary primers. Cluster analysis using the Unweighted-Pair Group Method with Arithmetic Mean (UPGMA) in the Molecular image Gel Doc™ XR (Bio-Rad) software based on the Dice’s coefficient of genetic similarity showed a division of the studied forms into two groups based on genetic similarity. The ecotype E16 formed one of the groups whereas all of the other ecotypes observed in this study clustered into the second group. A high level of polymorphism among the studied lucerne forms was detected indicating an interesting gene pool awaiting future exploration. Analysis of variance also supported a high diversity among the studied forms. This study provides insightful information into the heterosis effect of synthetic populations or hybrids of F1 lucerine by providing correlations between the genetic background of the inbred lines and their ability to produce a specific yield.

Anther culture of a 2n pollen producing clone of Solanum phureja Juz. &Buk.

1985 ◽  
Vol 27 (5) ◽  
pp. 559-564 ◽  
Author(s):  
R. E. Veilleux ◽  
J. Booze-Daniels ◽  
E. Pehu
Keyword(s):  
Anther Culture ◽  
Polyacrylamide Gel Electrophoresis ◽  
Pollen Grains ◽  
Unreduced Gametes ◽  
Solanum Phureja ◽  
2N Pollen ◽  
Regenerated Plants ◽  
Series Of Experiments ◽  
Pollen Formation ◽  
First And Second Generation

In a series of experiments, a total of 95 plants were regenerated from culture of 1416 anthers of a single genotype (PP5) of Solanum phureja that expressed a variable frequency of 2n pollen by the genetic equivalent of first division restitution. The regenerated plants included 29 monoploids (2n = x = 12), 58 diploids (2n = 2x = 24) and 8 tetraploids (2n = 4x = 48). Monoploids carrying the potential for 2n pollen formation are central to the development of a breeding scheme to construct highly heterozygous diplandroids. Segregation of tuber flesh color and tuber protein bands revealed by polyacrylamide gel electrophoresis in first and second generation anther-derived diploid plants provided evidence for both embryogenesis of 2n pollen as well as doubling of monoploid genomes as sources of anther-derived diploids. Because of variation for the same genetic markers in anther-derived tetraploids, sources other than embryogenesis of doubly restituted (4n) pollen grains were implied. An enhanced response to anther culture was noted in some anther-derived dihaploids.Key words: unreduced gametes, potato, anther culture, diplandroid, monoploid.

Effect of phalaris (Phalaris aquatica L.) and lucerne (Medicago sativa L.) density on seed yield and regeneration of subterranean clover (Trifolium subterraneum L.)

2000 ◽  
Vol 51 (2) ◽  
pp. 267 ◽  
Author(s):  
B. S. Dear ◽  
P. S. Cocks ◽  
A. D. Swan ◽  
E. C. Wolfe ◽  
L. M. Ayre
Keyword(s):  
Medicago Sativa ◽  
Seed Yield ◽  
Seed Bank ◽  
Seed Set ◽  
Basal Area ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Phalaris Aquatica ◽  
Medicago Sativa L ◽  
Clover Seed

A mixture of 3 subterranean clover (Trifolium subterraneum L.) cultivars (cvv. Goulburn, Seaton Park, and Dalkeith) was grown with 5–40 plants/m2 of phalaris (Phalaris aquatica L.) or lucerne (Medicago sativa L.) for 3 years at Wagga Wagga, NSW (147°21´E, 35°03´S). Clover seed yield was assessed each year, the number of regenerating clover seedlings was counted, herbage yield of clover and the perennials was measured, and the change in perennial density recorded. The influence of perennials on water availability in spring and light during clover seed set was also examined. The impact of perennial density on clover was assessed using regression analyses. In each of the 3 years, subterranean clover seed yield was negatively related to perennial density, but phalaris suppressed clover seed yield more than equivalent densities of lucerne in 2 of the years. Clover seed yield was positively related (R2 = 0.30–0.85) to clover biomass in spring in all 3 years (except for subterranean clover in phalaris in 1994) and to the proportion of total photosynthetically active radiation reaching the clover canopy beneath the perennial (R2 = 0.33–0.83) in 2 of the 3 years. There was a positive relationship between clover seedling regeneration in autumn and size of the summer seed bank in both years in lucerne (R2 = 0.40–0.76) and in 1 year in phalaris (R2 = 0.76) and a negative association between perennial density and clover seedling regeneration. The rate at which the surface profile (0–37 cm) dried in spring was independent of phalaris and lucerne density over the 3 years and did not differ from that of pure clover. The late season clover cultivar, Goulburn, constituted between 57% and 79% of the seed bank following seed set, substantially more than the earlier flowering cultivars, Seaton Park and Dalkeith. Neither perennial density nor species changed the relative competitiveness of the 3 cultivars. The high seed yield of Goulburn and the lack of a perennial-induced change in surface soil water in spring suggest that growing perennials in association with subterranean clover does not increase the level of moisture stress during clover seed set. The good performance of Goulburn is attributed to superior competitive ability for light in late spring. The basal area occupied by lucerne and phalaris increased with perennial density in each of the first 2 years. However, in the third year, phalaris basal area was similar at all densities. The findings suggest that sowing low densities of lucerne should assist in promoting seed yield and regeneration of subterranean clover. Management of phalaris, which has the capacity to substantially increase plant size at low densities, may require additional strategies such as more frequent grazing in spring.

CYTOGENETICS OF 6X-AMPHIPLOID × AVENA SATIVA L. F1 HYBRIDS

1971 ◽  
Vol 13 (2) ◽  
pp. 292-297 ◽  
Author(s):  
R. A. Forsberg ◽  
S. Wang
Keyword(s):  
Avena Sativa ◽  
Seed Set ◽  
Pollen Grains ◽  
F1 Hybrids ◽  
Root Tip ◽  
Ploidy Levels ◽  
Sperm Nuclei ◽  
Mother Cells ◽  
Tip Cells ◽  
Root Tip Cells

Avena abyssinica (2n=28) × A. strigosa (2n=14) 6x amphiploids were crossed with 13 different A. sativa (2n=42) varieties or selections. There was considerable variation in chromosome number within and among F1 plants. The mode was 40 in root tip cells and 41 in pollen mother cells (PMC's). The number of univalents in PMC's ranged from 10 to 27 with a mean of 18.9. The average number of bivalents was 7.1, ranging from 2 to 13. Multiple associations were common. Only 10.8% of the pollen grains contained normally developed nuclei, i.e. one vegetative and two elongated sperm nuclei. Forty of 41 F1 plants were completely self-sterile and only one seed was obtained from 16,950 florets. Seed set in backcross pollinations with A. sativa was 1.25%, providing some opportunity for perpetuation of desirable genes from lower ploidy levels.

scholarly journals Studia nad kariologią i rozwojem pyłku kilku odmian Medicago saliva L. Cz. I [Studies on karyology and pollen development in several varieties of Medicago sativa L. Part I]

2015 ◽  
Vol 24 (2) ◽  
pp. 319-341
Author(s):  
K. Bijok ◽  
E. Adamkiewicz ◽  
L. Grygorczyk
Keyword(s):  
Medicago Sativa ◽  
Meiotic Division ◽  
Pollen Development ◽  
Pollen Grains ◽  
Mature Pollen ◽  
Meiotic Stage ◽  
Medicago Saliva ◽  
Medicago Sativa L

At the stage of diakinensis and metaphase of the first meiotic division, conjugating chromosomes in the form of bivalents were always observed. At the pre-meiotic stage some of .the mother pollen cells underwent degeneration (in 'Australian' var. 17% in 'Warminska' 20%, in 'Kleszczewska' 23%, in 'Grimma' 30% and in 'Miechowska' 40%). In the degenerating mother pollen cells no meiotic division were observed. In the surviving mother pollen cells, meiotic division were found to be normal. The mature pollen grains were trinucleate.

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