Cytogenetics of Lathyrus palustris, a natural autohexaploid

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 827-831 ◽  
Author(s):  
H. I. T. Khawaja ◽  
J. R. Ellis ◽  
J. Sybenga
Keyword(s):  
Pollen Fertility ◽  
Seed Set ◽  
Somatic Metaphase ◽  
Perennial Plant ◽  
Ring Bivalents ◽  
Multivalent Formation ◽  
I Cells ◽  
Pairing Initiation ◽  
Haploid Complement ◽  
Metaphase I

American as well as British forms of the perennial plant Lathyrus palustris have 2n = 42 chromosomes with one group of 6 long submetacentric chromosomes, two groups of 6 medium-long subacrocentric chromosomes, three groups of 6 medium-long to medium-short submetacentric to subacrocentric chromosomes, and one group of 6 medium-short metacentric chromosomes. One haploid complement measures 45.8 μm at somatic metaphase. At meiotic first metaphase both forms show extensive multivalent formation. In 50 metaphase I cells of one plant of the British form there were 51 ring hexavalents, 80 chain and open-branched hexavalents of various forms, 2 quinquivalents, 41 ring quadrivalents, 58 chain quadrivalents, 20 branched quadrivalents of various forms, 1 trivalent, 128 ring bivalents, 280 open bivalents, and 9 univalents. It is concluded that L. palustris is most likely a natural autohexaploid with frequent multivalent pairing, many points of pairing initiation, several partner exchanges per multivalent, and many interstitial chiasmata. It may well be the first fully documented true natural autohexaploid reported. Pollen fertility was 56.2% and seed set 37%, apparently sufficient for a perennial plant species.Key words: Lathyrus, natural, autohexaploid, meiosis, multivalents.

Interlocked bivalents in reconstructed metaphase I cells of bread wheat

1985 ◽  
Vol 75 (1) ◽  
pp. 85-92
Author(s):  
J.S. Heslop-Harrison ◽  
M.D. Bennett
Keyword(s):  
Triticum Aestivum ◽  
Light Microscopy ◽  
Bread Wheat ◽  
Chromosome Pairing ◽  
Light Microscope ◽  
Serial Sections ◽  
Ring Bivalents ◽  
Mother Cells ◽  
I Cells ◽  
Metaphase I

Complete reconstructions of all the bivalents were made from electron micrographs of serial sections through six pollen mother cells at metaphase I of meiosis in Triticum aestivum (hexaploid bread wheat). At least two of these metaphases contained interlocked pairs of bivalents. In one, two ring bivalents were interlocked, while in another a rod bivalent ran through the centre of a ring bivalent. Two other groups of bivalents were too closely appressed to allow separation into individual bivalents and may have contained interlocks. Meiosis in other anthers of the same plants examined by light microscopy was considered normal. The frequency of interlocking found was much higher than reported from light-microscope spreads. Not all interlocks in metaphase I cells need adversely affect meiosis, but knowledge of their regularity and form may facilitate understanding the processes of chromosome pairing.

Cytogenetics of a hybrid and amphiploid between Hordeum pubiflorum and Secale africanum

1985 ◽  
Vol 27 (1) ◽  
pp. 1-5 ◽  
Author(s):  
George Fedak
Keyword(s):  
Chiasma Frequency ◽  
Seed Set ◽  
Embryo Rescue ◽  
Low Frequency ◽  
Intergeneric Hybrid ◽  
Secale Africanum ◽  
Ring Bivalents ◽  
Metaphase I

A low frequency (0.86) of rod bivalents was observed at metaphase I of meiosis in the F1 hybrid between Hordeum pubiflorum 2x and Secale africanum 2x. Seeds were obtained from colchicine-doubled sectors on the hybrid. An average of 2.49′ + 12.77″ per cell characterized meiosis in the amphiploid. The univalent and bivalent frequencies among Hordeum and Secale chromosomes were approximately equal, although there was a higher proportion of ring bivalents formed by the Hordeum chromosomes. Over 90% of the pollen was stainable, but only 40% seed set was obtained on the amphiploid. Although the seeds were badly shrivelled, some were viable.Key words: intergeneric hybrid, chiasma frequency, embryo rescue, Hordeum–Secale.

scholarly journals Inheritance of fertility restoration of A4 cytoplasm in pearl millet [Pennisetum glaucum (L.) R. Br.]

2020 ◽  
Vol 80 (01) ◽  
Author(s):  
J. Jorben ◽  
S. P. Singh ◽  
C. Tara Satyavathi ◽  
S. Mukesh Sankar ◽  
Jayant S. Bhat ◽  
...  
Keyword(s):  
Pearl Millet ◽  
Pollen Fertility ◽  
Seed Set ◽  
Pennisetum Glaucum ◽  
Fertility Restoration ◽  
Duplicate Genes ◽  
New Delhi ◽  
Regional Centre ◽  
Fertility Restorers ◽  
Mode Of Inheritance

Present investigation was carried out to study the mode of inheritance of fertility restoration for A4 cytoplasm using pollen fertility and seed set per cent as criterion in determining the fertile and sterile plants. Two CMS lines of A4 cytoplasm were crossed with two fertility restorers generating four F1 crosses, namely, ICMA 99111 x PPMI 1003, ICMA 99111 x PPMI 1087, ICMA 03999 x PPMI 1003 and ICMA 03999 x PPMI 1087, their F2s and backcross generations. All the F1s were completely fertile indicating complete fertility restoration. F2s and backcross generations were evaluated at IARI, New Delhi and IARI Regional Centre, Dharwad during summer 2017 and χ 2 test was applied to test the significance. At both the locations, all the F2 segregating populations fit well into a Mendelian ratio of 15:1 indicating digenic duplicate dominance of fertility restoring genes with χ 2 value of 0.82, 2.90, 0.04, 3.97, 4.86, 4.98, 0.02, 1.26, 3.15, 4.98, 3.15 and 0.02. The F2 hypothesis was verified with the observed frequency of segregating plants fitting well into 3:1 ration with χ 2 value of 5.45, 1.93, 4.93, 0.60, 2.83, 0.44, 4.94, 2.77, 3.33, 0.13, 4.08 and 1.51. It is further confirmation of the findings that fertility restoration is indeed governed by two duplicate genes. Association between pollen fertility and seed set per cent was significant and positive.

CYTOLOGICAL STUDIES OF THE DEVELOPMENT OF METAPHASE I IN HYBRIDS BETWEEN TRITICUM TIMOPHEEVI ZHUK. AND T. DURUM DESF.

1961 ◽  
Vol 39 (1) ◽  
pp. 81-108 ◽  
Author(s):  
E. B. Wagenaar
Keyword(s):  
Late Stage ◽  
Developmental Stages ◽  
Progressive Increase ◽  
Cell Populations ◽  
Equatorial Plate ◽  
Triticum Timopheevi ◽  
Late Stages ◽  
I Cells ◽  
Metaphase I

In two hybrids between Triticum timopheevi Zhuk. and T. durum Desf., which have irregular meioses, metaphase I was subdivided into four developmental stages, early, medium, late, and very late. This subdivision was based on the presence in the anthers of other stages that occurred together with metaphase I. It was then discovered that in metaphase I cell populations there was a progressive increase of univalents from the early and medium stages to the very late stage. This phenomenon can be explained on the assumption that metaphase I is of shorter duration in the less irregular cells which pass into anaphase I earlier than the more irregular cells. As a consequence of this developmental phenomenon at metaphase I, the anaphase I and telophase I cells in the late anthers contained fewer lagging chromosomes than the anaphase I and telophase I cells in the very late anthers. Despite these numerical differences, the degrees of lagging were remarkably similar in both stages; approximately 70% of these univalents lagged at late and very late stages in both hybrids.During metaphase I many univalents of the irregular cells moved towards the equatorial plate, became oriented, and lagged at anaphase I and telophase I. It was found that the univalents of the least irregular cells accumulated somewhat faster at the plates than those of the more irregular cells.Considering the relationships between all of the available data, the hypothesis is advanced that when a certain number of univalents have accumulated at the equatorial plate a state of equilibrium is established and anaphase I is initiated. On the basis of this hypothesis an explanation of the trends observed at metaphase I is given.

Cytogenetics of decaploid Agropyron elongatum (Elytrigia elongata) (2n = 70). I. Frequency of decavalent formation

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 811-817 ◽  
Author(s):  
Mikio Muramatsu
Keyword(s):  
High Frequency ◽  
Chromosome Association ◽  
Agropyron Elongatum ◽  
Homologous Chromosomes ◽  
Ring Shape ◽  
Meiotic Configuration ◽  
Multivalent Formation ◽  
A Cell ◽  
Chromosome Associations ◽  
Metaphase I

The multivalents that appeared in the decaploid strain of Agropyron elongatum (2n = 10x = 70), a relative of wheat, ranged from trivalent to decavalent. Few univalents occurred. The metaphase I chromosome association in 12 cells where all configurations could clearly be identified averaged 0.42 ring X + 0.17 chain X + 0.42 ring VIII + 0.17 branched VIII + 0.25 chain VIII + 0.17 chain VII + 1.17 ring VI + 0.33 branched VI + 0.5 chain VI + 1.67 ring IV + 0.42 branched IV + 0.58 chain IV + 0.08 branched III + 0.17 chain III + 12.58 ring II + 3.75 open II + 0.25 I. The occurrence of decavalents, up to two in one cell, and of a cell with five multivalents, each of which involved more than five chromosomes, and many multivalents of ring shape indicated that the strain is autodecaploid.The chromosome associations of each cell can be interpreted as seven groups of 10 homologous chromosomes. The high frequency of bivalents indicated a tendency toward reduced multivalent formation, for which an explanation is suggested.Key words: Agropyron elongatum, meiotic configuration, decaploid, multivalent.

Relationship in annual spceies of Medicago. III. The complex M. littoralis Rhode-M. truncatula Gaertn

1967 ◽  
Vol 15 (1) ◽  
pp. 35 ◽  
Author(s):  
JP Simon ◽  
AJ Millington
Keyword(s):  
Interspecific Hybrids ◽  
Seed Set ◽  
Chromosomal Rearrangements ◽  
Chromosome Translocation ◽  
Pollen Sterility ◽  
Multivalent Formation ◽  
Structural Differences ◽  
Intraspecific Hybrids ◽  
Adult Plants ◽  
Cytological Behaviour

A programme of interspecific hybridization, involving species from subsections Pachyspirae, Leptospirae, and Rotatae of section Spirocarpos, resulted in only one successful combination out of the 20 attempted. Viable hybrids were obtained with ease in crosses between different accessions of M. littoralis and M. truncatula. The morphology, fertility, and cytological behaviour of interspecific hybrids involving seven strains of M. truncatula and three strains of M. littoralis was compared with intraspecific hybrids of each species. With the exception of those with N.2829, which was differentiated from the other strains by one chromosome translocation, intraspecific hybrids of M. truncatula were fully fertile. Considerable pollen sterility and reduced seed set were observed in intraspecific crosses of M. littoralis, but there was no evidence of chromosomal rearrangements. The morphology of the hybrids between M. littoralis and M. truncatula was intermediate between the parents. Chlorophyll deficiency in seedlings and adult plants, dwarfism, and other morphological irregularities were observed in F2 plants. In some FT1s failure of pairing, multivalent formation at metaphase I, and other irregularities at meiosis indicated chromosome rearrangements. Up to three independent translocations and one inversion in the hybrid combinations and pronounced sterility were observed in both FT1s and FT2s. The pollen sterility of the hybrids could be explained in several instances by structural differences, but these do not account completely for the results obtained. Inheritance studies of three possible strain markers indicated simple monohybrid segregation in most intraspecific crosses, but in the interspecific and partially fertile intraspecific crosses, ratios were disturbed and phenotypes abnormal. The agronomic implications of these studies are discussed.

Male Sterility in Sorghum bicolor (L.) Moench Induced by Low Night Temperature. II. Genotypic Differences in Sensitivity

1979 ◽  
Vol 6 (2) ◽  
pp. 143 ◽  
Author(s):  
IR Brooking
Keyword(s):  
Low Temperature ◽  
Pollen Fertility ◽  
Seed Set ◽  
Genotypic Differences ◽  
Night Temperature ◽  
Progressive Reduction ◽  
Treatment Regimes ◽  
Controlled Environments ◽  
Sorghum Bicolor L ◽  
Quantitative Response

Three genotypes of sorghum grown in controlled environments were compared for low temperature sensitivity during the leptotene stage of microsporogenesis. Treatment regimes imposed during this period were 21°C day and 14,11, 8 or 5°C night. A known sensitive hybrid (CK60 × Tx415) showed progressive reduction in pollen proline level, percentage starched pollen, and seed set with decreasing night temperature, indicating that sterility induction was a quantitative response to night temperature. The line 606, deveIoped at high altitudes in Mexico, was fertile under all treatment regimes. The hybrid CK60 × 606 was intermediate in response for pollen fertility, but pollen fertility was still sufficient to enable near complete seed set in all treatments. Factors considered important in breeding grain sorghums with low-temperature-tolerant microsporogenesis are discussed.

Spontaneous structural rearrangements in Solanum phureja Juz. et Buk. 2. Meiotic behaviour and identification of interchange chromosomes using primary trisomics

Genome ◽  
1995 ◽  
Vol 38 (1) ◽  
pp. 140-147
Author(s):  
M. Wagenvoort
Keyword(s):  
Pollen Mother Cell ◽  
Mother Cell ◽  
Solanum Phureja ◽  
Chromosome Identification ◽  
Structural Rearrangements ◽  
Primary Trisomics ◽  
Interchange Heterozygote ◽  
Mother Cells ◽  
I Cells ◽  
Metaphase I

Meiosis was studied in two diploid (2n = 2x = 24) siblings of Solanum phureja Juz. et Buk. and in 11 disomic and 2 trisomic descendants. The diploid siblings carry the same heterozygous interchange and either one or two inversions. The frequency of quadrivalents at diakinesis/metaphase I in these clones was 0.56 and 0.62 per pollen mother cell. In two plants from the first inbred generation (I1) this frequency was about the same but in some other I1 plants and a full sib the frequency was substantially lower, varying from 0.00 to 0.16. Most quadrivalents, 78–83%, were rings. A variety of quadrivalent configurations at diakinesis and metaphase I was observed, giving rise to balanced and unbalanced gametes. The absence of ring quadrivalents in trisomic descendants of one of the siblings implied that tertiary trisomics or primaries being homozygous for the interchange were present in the I1 generation. Regular chromosome distribution (12–12) at anaphase I occurred in 46.5 and 73.2% of the pollen mother cells studied in the two original clones. Irregularities, such as 11–13 distribution, lagging chromosomes, and a bridge and fragment, were detected on average in 2.7, 3.3, and 32.5%, respectively, of the anaphase I cells analysed. In hybrids from crosses between 6 primary trisomics as females with the interchange heterozygote, the involvement in the interchange of chromosomes 3 and 12 was clearly demonstrated.Key words: Solanum phureja, interchange heterozygote, chromosome identification, interchange trisomic, meiosis.

Metaphase I pairing of deficient chromosomes and genetic mapping of deficiency breakpoints in common wheat

Genome ◽  
1991 ◽  
Vol 34 (4) ◽  
pp. 553-560 ◽  
Author(s):  
C. A. Curtis ◽  
A. J. Lukaszewski ◽  
M. Chrzastek
Keyword(s):  
Triticum Aestivum ◽  
Genetic Mapping ◽  
Chromosome Pairing ◽  
Triticum Aestivum L ◽  
Genetic Distances ◽  
Homologous Chromosomes ◽  
Transmission Rates ◽  
Chromosome 5B ◽  
Pairing Initiation ◽  
Metaphase I

Metaphase I pairing of deficient chromosomes was analyzed in a set of 'Chinese Spring' (CS) wheat (Triticum aestivum L. em. Thell.) plants with varying lengths of deficiencies in the long arm of chromosome 4A (6, 8, 11, 17, 23, 34, 36, 39, and 50% missing), the long arm of chromosome 5B (49% missing), and the long arm of chromosome 2B (33% missing). Pairing in homologous chromosomes between deficient and complete arms was greatly reduced even by small differences in arm length. In deficiency homozygotes and in an isochromosome derived from a deficient 4AL arm, pairing of the two deficient arms was high and approached that of two complete arms. In plants where deficient and complete arms competed for pairing partners, pairing was exclusively between arms of the same length. These results suggest that in wheat, pairing initiation sites are distributed throughout at least the distal halves of the arms and that the alignment of telomeres may be critical for pairing success. Genetic mapping of the deficiency breakpoints was confounded by misdivision of unpaired chromosomes and abnormal transmission rates. Genetic distances between centromeres and breakpoints appeared to be proportional to metaphase I pairing frequencies.Key words: bread wheat, deficiency, chromosome pairing competition, mapping, telomere, pairing initiation.

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