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.

THE SIGNIFICANCE OF MEIOTIC CHROMOSOME PAIRING IN TETRAPLOID (2n = 28) BROMUS PUMPELLIANUS SCRIBN. SSP. DICKSONII

1972 ◽  
Vol 14 (4) ◽  
pp. 763-771 ◽  
Author(s):  
K. C. Armstrong
Keyword(s):  
Chromosome Pairing ◽  
High Frequency ◽  
Chiasma Frequency ◽  
Karyotype Analysis ◽  
Meiotic Chromosome ◽  
Low Frequency ◽  
Meiotic Chromosome Pairing ◽  
Ring Bivalents ◽  
Bivalent Formation

Bivalent formation was predominant at meiosis in B. pumpellianus ssp. dicksonii. The average in 15 plants ranged from 11.38 to 13.77 bivalents per cell. The high chiasma frequency (23.41-26.74) was a reflection of the high frequency of ring bivalents (9.48-12.42). A low frequency of quadrivalents occurred (0.06-1.22). A karyotype of this species was presented from both a highly contracted and moderately contracted cell and the differences between these two were noted. Four satellites were found, two large and two minute. There were 3-5 submedian and 5-7 median chromosomes depending on the cell studied. In addition two subterminal chromosomes were present. The meiotic and karyotype analysis suggest a deviation from an autotetraploid behaviour, but the presence of quadrivalents and similarities between pairs in the karyotype suggested closely related genomes. Alternatively it was considered that the quadrivalents could be due to translocation heterozygotes. The implications of these results were discussed in relation to the reported meiotic events in the octoploids, B. inermis and B. pumpellianus.

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.

Plant-level fecundity and andromonoecy in three common (Melaleuca styphelioides, M. thymifolia, M. nodosa) and one rare (M. deanei) Melaleuca (Myrtaceae) species of the Sydney region

2014 ◽  
Vol 62 (4) ◽  
pp. 276 ◽  
Author(s):  
Alison Hewitt ◽  
Paul Holford ◽  
Adrian Renshaw ◽  
Anthony Haigh ◽  
E. Charles Morris
Keyword(s):  
Reproductive Performance ◽  
Fruit Set ◽  
Seed Set ◽  
Low Frequency ◽  
Common Species ◽  
Flowering Plants ◽  
Breeding Systems ◽  
Small Populations ◽  
Small Field ◽  
Plant Level

This paper reports plant-level measures of reproductive performance from large and small field populations of the vulnerable species Melaleuca deanei F.Meull. compared with three common species within the genus: Melaleuca nodosa (Sol. ex Gaertn.) Sm., Melaleuca thymifolia Sm. and Melaleuca styphelioides Sm. Measures reported include average seed numbers per capsule and per plant; average fruit loads per plant; the proportion of buds that become flowers and thence fruits (fruit set); the number of ovules per flower and seed : ovule ratios (seed set); and floral morphologies. Results indicate that when M. deanei flowers, bud to flower ratios and flower to fruit ratios are not reduced compared with the congeners or between large and small populations. Seed loads per plant held by fruiting plants were comparable between the species and between large and small populations of M. deanei. Seed to ovule ratios were in the order of 5–9% in M. nodosa; 5–7% in M. styphelioides; 7–10% in M. deanei; and 12–15% in M. thymifolia. Larval herbivory of ovules was recorded in M. nodosa and pre-dispersal seed predation noted in M. thymifolia. Andromonoecy was recorded in two of the species at rates of 0.9–3.1% (M. deanei) and 2.9–7% (M. thymifolia). Results suggest that seed production within smaller populations of M. deanei is poor because of a low frequency of flowering and a low proportion of flowering plants per population, rather than plant-level pollination, fruit- or seed-set barriers. Further study is needed to determine the triggers to flowering, the breeding systems, the extent of clonality and the germination and establishment requirements in these species.

Evidence of nonchiasmate bonds at metaphase I in inbred rye

1984 ◽  
Vol 26 (4) ◽  
pp. 409-414 ◽  
Author(s):  
M. C. Cermeño ◽  
J. Orellana ◽  
J. R. Lacadena
Keyword(s):  
Secale Cereale ◽  
Chiasma Frequency ◽  
Meiotic Pairing ◽  
Secale Cereale L ◽  
Chromosome 1R ◽  
Metaphase I

The loss of bound chromosome arms through early, middle, and late metaphase I has been analyzed in a plant of inbred rye (Secale cereale L.) heterozygous for a terminal heterochromatic C-band of the long arm of chromosome 1R. From the increase in the number of univalent pairs due to bound arm loss, and from the comparison between the frequencies of bound arms at metaphase I and recombinant chromosomes at anaphase I, it is concluded that some of the chromosome bonds appearing at metaphase I are actually nonchiasmate associations that can be considered as remnants of prophase pairing. Conclusions concerning recombination obtained solely from the analysis of chiasma frequency measured as bound arms may be invalid.Key words: inbred rye, C-heterochromatin, meiotic pairing, nonchiasmate bonds.

Analysis of synaptonemal complexes and chromosome pairing at metaphase I in the diploid intergeneric hybrid Lolium multiflorum × Festuca drymeja

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 465-471 ◽  
Author(s):  
Hum M. Thomas ◽  
W. G. Morgan
Keyword(s):  
Chromosome Pairing ◽  
Complex Analysis ◽  
Lolium Multiflorum ◽  
Intergeneric Hybrid ◽  
Chiasma Formation ◽  
Genotypic Effect ◽  
Synaptonemal Complexes ◽  
Dna Values ◽  
Synaptonemal Complex Analysis ◽  
Metaphase I

The synaptonemal complexes in the diploid hybrid Lolium multiflorum × Festuca drymeja were examined by the surface spreading technique, and chromosome pairing at metaphase I was analysed. Synaptonemal complex analysis revealed "illegitimate" pairing, including multivalents and foldback pairing. At metaphase I, most chiasmata were between chromosomes of the same genome, and again multivalents were found. It was concluded that most synaptonemal complexes resulted in chiasma formation. The effects of the large differences in DNA values of the two species and the possible genotypic effect of F. drymeja on chromosome pairing are discussed.Key words: Lolium-Festuca, synaptonemal complexes, nonhomologous pairing, DNA values.

Genome constitution of the Australian hexaploid grass Elymus scabrus (Poaceae: Triticeae)

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 147-151 ◽  
Author(s):  
J. Torabinejad ◽  
R. J. Mueller
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Genome Constitution ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Thinopyrum Bessarabicum ◽  
Mother Cells ◽  
Metaphase I

Eight intergeneric hybrid plants were obtained between Elymus scabrus (2n = 6x = 42, SSYY??) and Australopyrum pectinatum ssp. retrofractum (2n = 2x = 14, WW). The hybrids were vegetatively vigorous but reproductively sterile. Examination of pollen mother cells at metaphase I revealed an average of 16.63 I, 5.29 II, 0.19 III, and 0.05 IV per cell for the eight hybrids. The average chiasma frequency of 6.77 per cell in the above hybrids strongly supports the presence of a W genome from A. pectinatum ssp. retrofractum in E. scabrus. Meiotic pairing data of some other interspecific hybrids suggest the existence of the SY genomes in E. scabrus. Therefore, the genome constitution of E. scabrus should be written as SSYYWW. Two other hybrid plants resulted from Elymus yezoensis (2n = 4x = 28, SSYY) crosses with A. pectinatum ssp. pectinatum (2n = 2x = 14, WW). Both were weak and sterile. An average of 0.45 bivalents per cell were observed at metaphase I. This clearly indicates a lack of pairing between W genome of Australopyrum and S or Y genomes of E. yezoensis. In addition, six hybrid plants of E. scabrus with Psathyrostachys juncea (2n = 2x = 14, NN) and one with Thinopyrum bessarabicum (2n = 2x = 14, JJ) were also obtained. The average bivalents per cell formed in both combinations were 2.84 and 0.70, respectively. The results of the latter two combinations showed that there is no N or J genome in E. scabrus.Key words: wide hybridization, chromosome pairing, genome analysis, Australopyrum, Elymus.

A study on genomic relationships of Agropyron trachycaulum with Elymus scabriglumis, E. innovatus, and Hordeum procerum

Genome ◽  
1988 ◽  
Vol 30 (4) ◽  
pp. 525-528 ◽  
Author(s):  
P. K. Gupta ◽  
H. S. Balyan ◽  
George Fedak
Keyword(s):  
Chiasma Frequency ◽  
Embryo Rescue ◽  
Intergeneric Hybrids ◽  
Genomic Constitution ◽  
Rescue Technique ◽  
Genomic Relationships ◽  
Chromosome Associations ◽  
Synthetic Hybrids ◽  
The Mean ◽  
Agropyron Trachycaulum

Synthetic hybrids of Agropyron trachycaulum (2n = 4x = 28) with Elymus scabriglumis (2n = 6x = 42), E. innovatus (2n = 4x = 28), and Hordeum procerum (2n = 6x = 42) were produced through the embryo rescue technique, at relative frequencies of 7.1, 4.2, and 1.8%, respectively, of pollinated florets. The mean chromosome associations in two hybrids with E. scabriglumis was 11.71II + 1.47III + 0.15IV (mean chiasma frequency = 22.75), in one hybrid with H. procerum was 7.27II + 0.63III + 0.09IV (mean chiasma frequency = 10.20) and in a hybrid with E. innovatus was 2.8II (2.19 chiasma frequency). The data suggested two common genomes (S and H) with E. scabriglumis, one common genome (H) with H. procerum, and no common genome with E. innovatus. The evidence obtained suggested a SSHHYY genomic constitution for E. scabriglumis and two genomes different from SH for E. innovatus. The evidence also suggested that in H. procerum there may not be two related genomes present (derived from H. jubatum) as speculated in some earlier studies.Key words: intergeneric hybrids, Agropyron, Elymus, Hordeum, chromosome pairing.

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.

CHIASMA FREQUENCY IN SPECIES AND SPECIES HYBRIDS OF AVENA

1934 ◽  
Vol 11 (3) ◽  
pp. 347-361 ◽  
Author(s):  
Jane D. Spier
Keyword(s):  
Chiasma Frequency ◽  
Diploid Species ◽  
Low Frequency ◽  
Chiasma Formation ◽  
Maximum Effect ◽  
Triploid Hybrid ◽  
Significant Difference ◽  
Close Relationship ◽  
Pentaploid Hybrid ◽  
Species Hybrids

(i) Chiasma frequency at metaphase has been studied in the following species and species hybrids: A. strigosa Schreb.; A. brevis Roth; A. Wiestii Steud.; A. barbata Pott; A. abyssinica Hochst. (2 strains); A. sterilis L. (2 strains); A. sativa L. var. Radnorshire Sprig; a triploid hybrid, A. barbata × A. strigosa; a pentaploid hybrid, A. abyssinica "naine" × A. sterilis maxima; and a hexaploid hybrid, A. sterilis (white) × A. sativa var. Radnorshire Sprig.(ii) The various factors that may affect chiasma frequency are discussed and it is concluded that there may be some parallelism between closeness of relationship and similarity in chiasma formation, as genetical control is one factor affecting the process. The results are examined in the light of this conclusion.(iii) The homogeneity of species in respect to proportion of bivalents with zero, one, two, three, or four chiasmata is tested by means of χ2. The test indicates no significant difference between the closely related diploid species, A. brevis and A. strigosa, but both differ significantly from the less closely related A. Wiestii. The differences between the tetraploid species are of questionable significance, those between the hexaploids, insignificant. It is suggested that the lack of significant differences among these last-mentioned forms may be due to a multiplication, in the polyploid, of genes favoring high chiasma frequency. In this way a maximum effect might be brought about, and inter-specific differences with respect to this character would consequently be lacking.(iv) High chiasma frequency in the hybrid might be regarded as strong evidence of homology, and consequently of relationship between parental forms. The triploid hybrid, A. barbata × A. strigosa shows a high chiasma frequency at metaphase, a condition consistent with the close relationship of the parental forms. The pentaploid hybrid, as might be expected, has a low chiasma frequency. The chiasma frequency of the hexaploid hybrid, A. sterilis × A. sativa var. Radnorshire Sprig does not differ significantly from that of its low-frequency parent, A. sterilis. Cytological observations in this hybrid, therefore, reveal only a slight degree of non-homology between parental chromosomes. It is noted that there are certain characters of A. sativa var. Radnorshire Sprig that suggest affinity with A. byzantina, a species commonly associated with A. sterilis in relationship schemes.

Transfer of leaf rust and stem rust resistance genes from Triticum triaristatum to durum and bread wheats and their molecular cytogenetic localization

Genome ◽  
1994 ◽  
Vol 37 (3) ◽  
pp. 410-418 ◽  
Author(s):  
D. Bai ◽  
G. J. Scoles ◽  
D. R. Knott
Keyword(s):  
Leaf Rust ◽  
Stem Rust ◽  
Rust Resistance ◽  
Seed Set ◽  
Wide Spectrum ◽  
Embryo Rescue ◽  
Addition Line ◽  
Addition Lines ◽  
The Cross ◽  
Disomic Addition Lines

Six accessions of Triticum triaristatum (Willd) Godr. &Gren. (syn. Aegilops triaristata) (6x, UUMMUnUn), having good resistance to both leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm) races and stem rust (P. graminis f.sp. tritici Eriks. &Henn.) races, were successfully crossed with both susceptible durum wheats (T. turgidum var. durum L., 2n = 28, AABB) and bread wheats (T. aestivum, 2n = 42, AABBDD). In some crosses, embryo rescue was necessary. The T. triaristatum resistance was expressed in all F1 hybrids. Backcrossing of the F1 hybrids to their wheat parents to produce BC1F1 plants was more difficult (seed set 0–7.14%) than to produce F1 hybrids (seed set 12.50–78.33%). The low female fertility of the F1 hybrids was due to low chromosome pairing. Only gametes with complete or nearly complete genomes from the F1 hybrids were viable. In BC2F4 populations from the cross MP/Ata2//2*MP, monosomic or disomic addition lines (2n = 21 II + 1 I or 22 II) with resistance to leaf rust race 15 (IT 1) were selected. In BC2F2 populations from the crosses CS/Ata4//2*MP and MP/Ata4//2*MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 or stem rust race 15B-1 (both IT 1) were selected. Rust tests and cytology on the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the added T. triaristatum chromosomes. The homoeologous groups of the T. triaristatum chromosomes in the addition lines from the crosses MP/Ata2//2*MP, CS/Ata4//2*MP, and MP/Ata4//2*MP were determined to be 5, 2, and 7, respectively, through the detecting of RFLPs among genomes using a set of homoeologous group specific wheat cDNA probes. The addition lines with resistance to leaf rust race 15 from the crosses MP/Ata2//2*MP and CS/Ata4//2*MP were resistant to another nine races of leaf rust and the addition line with resistance to stem rust race 15B-1 from the cross MP/Ata4//2*MP was resistant to another nine races of stem rust as were their T. triaristatum parents. Since such genes provide resistance against a wide spectrum of rust races they should be very valuable in wheat breeding for rust resistance.Key words: Triticum triaristatum, rust resistance, addition line, molecular cytogenetics.

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