Failure of chromosome pairing in a probable Desmodium intortum × D. sandwicense hybrid

1968 ◽  
Vol 16 (3) ◽  
pp. 545
Author(s):  
JB Hacker
Keyword(s):  
Chromosome Pairing ◽  
Seed Set ◽  
Tetraploid Plant ◽  
Putative Hybrid ◽  
Pollen Stainability ◽  
Single Flower ◽  
Hybrid Derivative ◽  
Number Of Cells

Failure of chromosome pairing was noted in some plants in the progeny of a putative hybrid derivative of Desmodium intortum and D. sandwicense. Pairing failure resulted in abnormal tetrad formation, the number of cells in each tetrad ranging from one to eight. Pollen stainability was poor but varied considerably, even within a single flower. Seed set in asynaptics was poor or nil. A sample of 30 seedlings derived from a single asynaptic parent was entirely euploid; a single tetraploid plant probably occurred following the fusion of two restitution nuclei.

Induced tetraploidy and trisomic production of Helianthus annuus L.

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 647-651 ◽  
Author(s):  
C. C. Jan ◽  
J. M. Chandler ◽  
S. A. Wagner
Keyword(s):  
Helianthus Annuus ◽  
Chromosome Pairing ◽  
Chromosome Pair ◽  
Seed Set ◽  
Chromosome Doubling ◽  
Meiotic Chromosome ◽  
Pollen Grains ◽  
Inbred Lines ◽  
Pollen Stainability ◽  
Normal Seed

Seedlings of the Helianthus annuus inbred lines P21 and HA89 were treated with colchicine to study chromosome doubling. Frequency of tetraploids, meiotic chromosome pairing, pollen stainability, and fertility were examined. Five-hour colchicines treatments at 0.15%, pH 5.4, with 2% dimethyl sulfoxide resulted in tetraploid sectors on 42% of P21 and 11% of HA89 plants. Tetraploids had larger disk florets and larger pollen grains. Otherwise, tetraploid plants were morphologically similar to their diploid progenitors. Tetraploidy in P21 was not stable, with plants having 2n = 4x = 65 to 70 chromosomes. Tetraploid plants of HA89 had reduced vigor and did not produce seed. At diakinesis, tetraploid P21 plants had an average of 0.85 univalents, 21.12 open bivalents, 6.66 closed bivalents, 0.21 trivalents, and 2.74 quadrivalents per cell. The number of chiasma per chromosome pair in P21 was reduced from 1.50 for diploid to 1.32 for tetraploid plants. Pollen stainability in tetraploid P21 was less than 50% and the plants produced an average of eight seeds per sibbed head, about 1% of normal seed set. Reciprocal crosses of diploid and tetraploid P21 produced four triploid plants. Backcrossing triploids to P21 produced 137 plants with 2n = 34 to 47 + t. Thirty-one of these plants were trisomies having 2n = 35.Key words: Helianthus annuus, tetraploids, triploids, trisomies.

Chromosome pairing and fertility in Spartina × caespitosa

1970 ◽  
Vol 48 (1) ◽  
pp. 183-188 ◽  
Author(s):  
C. J. Marchant
Keyword(s):  
Chromosome Pairing ◽  
Seed Set ◽  
Meiotic Pairing ◽  
Pollen Stainability ◽  
Breeding Behavior ◽  
High Pollen ◽  
Hybrid Nature ◽  
In The Wild

A detailed study of meiosis and breeding behavior of Spartina × caespitosa (A. A. Eaton) Fern, and a comparison with S. patens (Ait.) Muhl. and S. pectinata Link, its putative parents, has revealed regular meiotic pairing, relatively high pollen stainability, and a low seed set in the hybrid when intercrossed with other clones of S. × caespitosa or with S. patens and S. pectinata. S. × caespitosa quite frequently occurs and persists under competition amidst juxtaposed clones of rhizomatous S. patens and S. pectinata but there is little evidence of an F2 generation in the wild and it maintains a very localized distribution. Many characteristics of S. × caespitosa are closely similar to those of a species and features of hybrid nature are not easy to define.

scholarly journals Meiotic Chromosome Behavior and Capsule Setting in Doritaenopsis Hybrids

2008 ◽  
Vol 133 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Pablo Bolaños-Villegas ◽  
Shih-Wen Chin ◽  
Fure-Chyi Chen
Keyword(s):  
Cell Division ◽  
Pollen Mother Cell ◽  
Chromosome Pairing ◽  
Chromosomal Aberrations ◽  
High Frequency ◽  
Mother Cell ◽  
Seed Set ◽  
Pollen Viability ◽  
High Pollen ◽  
Mother Cells

The development of new cultivars in Doritaenopsis Guillaum. & Lami orchids is often hindered by factors such as low seed count in hybrids. Cytological study may offer the ability to develop new hybrids by revealing cultivars with good chromosome pairing and high pollen viability, which are somewhat difficult to obtain under current breeding programs. Cross pollination, pollen viability, and chromosomal behavior during meiosis were analyzed to reveal the relation between seed fertility and capsule set in Doritaenopsis hybrids. The number of mature capsules harvested and their relative seed content were used as indices of crossing availability. The results of meiosis were evaluated according to pollen viability detected by fluorescein diacetate and quantification of sporad types by acid fuchsin staining. Chromosome number and pairing at meiosis were observed in root tips or in samples of pollen mother cells. A positive relation was found among high seed set, high frequency of viable tetrads, high degree of chromosome pairing, and low frequency of chromosomal aberrations such as inversions and translocations. On the basis of these factors, three types of hybrids could be distinguished. In type one hybrids, chromosomes paired as bivalents, pollen mother cells divided into tetrads, and capsule setting occurred after pollination of pollen acceptors. In type two hybrids, chromosomes remained mainly as univalents that developed into micromeiocytes, pollen mother cell division was disrupted, and seed recovery was low after pollination. Type three hybrids showed chromosomes paired mostly as multivalents, chromosome bridges, pollen mother cell division with massive failure, and little fertility. In Doritaenopsis orchids, high pollen viability and high fertility depends on a high frequency of normal tetrads, and low seed set in cross-pollination is predicted with micronuclei in the end products of meiosis. The occurrence of chromosomal aberrations may suggest a process of genome differentiation that could compromise breeding efforts if not taken into consideration.

CHROMOSOME PAIRING IN POA ANNUA L.

1973 ◽  
Vol 15 (3) ◽  
pp. 549-551 ◽  
Author(s):  
W. M. Ellis ◽  
B. T. O. Lee ◽  
D. M. Calder
Keyword(s):  
Chromosome Pairing ◽  
Breeding System ◽  
Tetraploid Plant ◽  
Poa Annua ◽  
Diploid Population ◽  
Bivalent Formation

Cytological studies carried out on six tetraploid and one diploid population and a synthesized tetraploid plant have shown regular bivalent formation at meiosis. This regularity appears to be genetically controlled in this species. Plants from all the populations behave as diploids. The implications of this regular disomic chromosome pairing on recombination, variation and the breeding system of P. annua are considered.

The swift parrot Lathamus discolor (Psittacidae), social bees (Apidae), and native insects as pollinators of Eucalyptus globulus ssp. globulus (Myrtaceae)

2004 ◽  
Vol 52 (3) ◽  
pp. 371 ◽  
Author(s):  
A. B. Hingston ◽  
B. M. Potts ◽  
P. B. McQuillan
Keyword(s):  
Eucalyptus Globulus ◽  
Seed Set ◽  
Bombus Terrestris ◽  
Pollination Services ◽  
Social Bees ◽  
Single Flower ◽  
Fitness Benefits ◽  
The Cost ◽  
Effective Pollinator ◽  
Better Than

It has been argued that the production of sufficient nectar to attract bird pollinators would evolve if the fitness benefits accruing from pollination services by birds, compared with insects, outweighed the cost of increased allocation of photosynthate to nectar. This hypothesis implies that the pollination services provided by birds must be considerably better than those provided by insects with which the plant has evolved. Consistent with this, we found that the endangered native swift parrot Lathamus discolor (Shaw) was a very effective pollinator of the native tree Eucalyptus globulus Labill. in Tasmania, facilitating an average of 76% of the maximum possible seed set for open-pollinated flowers in just one visit to a flower, whereas single flower visits by native insects did not facilitate any seed production. Flowers visited once by either species of introduced social bees, the honeybee Apis mellifera L. or the bumblebee Bombus terrestris (L.), produced less than 7% of the maximum possible seed set for open-pollinated flowers. Hence, easily managed social bees appear to be poor substitutes for bird pollinators in commercial seed orchards of this tree. We propose three possible reasons why this largely bird-pollinated tree has not evolved characters that deter insects from removing nectar.

Meiotic behaviour of induced autotetraploids in Triticum L.

Genome ◽  
1990 ◽  
Vol 33 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Yang Yen ◽  
Gordon Kimber
Keyword(s):  
Chromosome Pairing ◽  
Seed Set ◽  
Chromosome Association ◽  
Meiotic Behaviour ◽  
Meiotic Analysis

Colchicine-induced autotetraploids of Triticum speltoides, T. longissimum, T. sharonense, T. bicorne, T. uniaristatum, T. monococcum, and T. tauschii were all morphologically similar to but larger than their diploid forms. Seed set was lower than in the diploids except for the autotetraploid T. speltoides. Meiotic analysis showed fewer quadrivalents and more bivalents than would be expected in all of these autotetraploids. Arm-pair switch, indicated by complex trivalents and quadrivalents, was found and involved 0.1% of total chromosomes in T. umbellulatum, 0.5% in T. longissimum, 0.7% in both T. sharonense and T. tauschii, 6.3% in T. bicorne, and 15.3% in T. uniaristatum.Key words: meiosis, chromosome association, arm-pair switch, chromosome pairing, bivalentization.

Synaptic mutants in hexaploid oats (Avena sativa L.)

Genome ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 1-7 ◽  
Author(s):  
H. W. Rines ◽  
S. S. Johnson
Keyword(s):  
Chromosome Pairing ◽  
Sodium Azide ◽  
Avena Sativa ◽  
Seed Set ◽  
Single Gene ◽  
Inheritance Pattern ◽  
Late Prophase ◽  
Homologous Chromosomes ◽  
Breeding Station ◽  
Meiotic Synapsis

Three meiotic synapsis-deficient mutants of oats (Avena sativa L.) were analyzed to determine their inheritance pattern, detailed chromosomal behavior, and location to chromosome. These highly sterile mutants, one in the cultivar 'Stout' and two in 'Noble', had been recovered from progeny of sodium azide mutagenized populations. Each segregated as a single gene recessive. The only synapsis-deficient variants previously described in hexaploid oats have been nullisomics or ditelosomics. Mutant 'Stout 1212' was classified as asynaptic due to deficiencies in chromosome pairing at all meiotic stages. Mutants 'Noble 1362' and 'Noble 1911' were classified as desynaptic since their homologous chromosomes were paired in early meiosis but they disassociated prematurely in late prophase I. Using a partial monosomic series from the Welsh Plant Breeding Station, mutant 1212 was mapped to monosome XII and is probably a mutation in Syn-5, a gene previously defined only by its nulli effect. Mutants 1362 and 1911 were mapped to monosome IV and are probably mutations in Syn-1, a gene also previously defined only by its nulli effect. Seed set on the synaptic mutant plants in the field was less than 0.2% of that on fertile sibs and likely resulted from pollination by surrounding fertile plants. This seed may serve as a source of unique aneuploid stocks in oats.Key words: meiotic mutants, gene mapping, monosomics, nullisomics, oat cytogenetics.

scholarly journals Fertility Changes in Inbred Families of Self-incompatible Chrysanthemums (Dendranthema grandiflora)

2000 ◽  
Vol 125 (5) ◽  
pp. 619-625 ◽  
Author(s):  
Neil O. Anderson ◽  
Peter D. Ascher
Keyword(s):  
Seed Production ◽  
Recombinant Inbred ◽  
Seed Set ◽  
Hybrid Seed Production ◽  
Pollen Stainability ◽  
Breeding Programs ◽  
Self Compatibility ◽  
Rapid Generation ◽  
Gain Loss ◽  
Inbred Populations

Chrysanthemum [Dendranthema ×grandiflora Tzvelv. (syn. Chrysanthemum ×morifolium Ramat.)] breeding programs have been selecting for reduced expression of self-incompatibility (via pseudo-self-compatibility) to create inbred families with selected genotypes to serve as parents for F1 hybrid chrysanthemum seed production. However, it is not known to what extent inbreeding is affecting fertility in this outcrossing, heterozygous species. The objective of this research was to assess male/female fertility changes (gain/loss) in successive inbred generations of chrysanthemums. Pseudo-self-compatible chrysanthemum parents (n = 41 inbred, noninbred, and recombinant inbred) were chosen for fertility analyses. As many as three generations of inbreds (I1, I2, and I3) from self-pollinations were created using rapid generation cycling. Female and male fertility levels of the parents and all derived inbred populations were assessed using outcross seed set and pollen stainability, respectively. Average seed set ranges were 0.3% to 96.1% (inbred parents), 24.5% to 38.5% (noninbred parents), and 0.9% to 85.1% (recombinant inbred parents); these began decreasing in the I1 and continued to decline steadily into the I3. Statistically significant (P < 0.05) decreases in seed set occurred in n = 23 (56.1%) inbred families; the remaining inbred families had similar or higher fertility than the parents. Pollen stainability was >50% for the parents, but began declining in some inbred families as inbreeding progressed. Fertility reductions were attributed to inbreeding depression. Lack of significant fertility losses in other inbred families demonstrates the opportunity of selection of fertile inbred parents for use in hybrid seed production.

Chromosome pairing in Solanum commersonii- S. tuberosum sexual hybrids detected by commersonii-specific RAPDs and cytological analysis

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 218-224 ◽  
Author(s):  
Amalia Barone ◽  
Angela Sebastiano ◽  
Domenico Carputo
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Recombination ◽  
Recombination Event ◽  
The Other ◽  
Homoeologous Pairing ◽  
Cytological Analysis ◽  
Pollen Stainability ◽  
Solanum Commersonii ◽  
Molecular Studies ◽  
High Production

BC1 pentaploid to near-pentaploid Solanum commersonii-S. tuberosum genotypes obtained from 3x × 4x crosses have been used for cytological and molecular studies on chromosome pairing and meiotic recombination. Microsporogenesis analysis at diakinesis revealed that chromosomes had a tendency to pair as bivalents, though multivalents were also observed in many cells. Meiosis resulted in a high production of tetrads and pollen stainability was high, ranging from 34.5% to 92.1%. DNA from S. commersonii and S. tuberosum was amplified with 87 decameric primers, resulting in the identification of 26 S. commersonii-specific RAPDs. The analysis of these RAPDs in BC1 genotypes showed that a number of commersonii-specific markers was present in all BC1 genotypes. On the other hand, markers which were missing in one or more of the BC1 genotypes suggested that in some cases homoeologous pairing occurred. Two linked markers were transmitted together in all of the BC1 genotypes except two. This provided evidence that a recombination event between these markers occurred during megasporogenesis of their triploid parents. The possibility of demonstrating other recombination events is discussed.Key words: triploid, pentaploid, microsporogenesis, gene flow, recombination.

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