Chromosome elimination in a complex hybrid of the genus Hordeum

1977 ◽  
Vol 55 (24) ◽  
pp. 3023-3033 ◽  
Author(s):  
Thomas J. Orton ◽  
William Tai
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Chromosome Elimination ◽  
Progressive Increase ◽  
Basic Chromosome Number ◽  
Chromosome Loss ◽  
Cytoplasmic Organelle ◽  
Cytological Evidence ◽  
Embryonic Tissues ◽  
Hordeum Jubatum

Hybrid embryos, derived from the cross combining a Hordeum jubatum (4x) – H. compressum (2x) amphiploid and H. vulgare (4x), were observed and found to exhibit instability of chromosome numbers that resulted in an overall loss during the first 8 days of development in embryonic tissues. This instability seemed to be manifest as a progressive increase in the variability of chromosome numbers over this developmental period. The change in the overall mean chromosome number followed no discernible pattern with the exception that counts appeared to be clustered at numbers which are exact multiples of the basic chromosome number (x = 7). For each day postpollination, however, the mean chromosome numbers were significantly lower than the expected zygotic number (with one exception), indicative of net chromosome loss. Based on the data presented and cytological evidence, possible mechanisms are proposed to account for chromosome elimination in hybrid tissues. Chromosome loss may result from an incompatible interaction of the chromosomes and spindle-timing determinants originating from each genome during development or as a consequence of the malfunctioning of a proposed cytoplasmic organelle.

Chromosome studies on African plants. 9. Chromosome numbers in Ehrharta (Poaceae: Ehrharteae)

Bothalia ◽  
1989 ◽  
Vol 19 (1) ◽  
pp. 125-132 ◽  
Author(s):  
J. J. Spies ◽  
E. J. L. Saayman ◽  
S. P. Voges ◽  
G. Davidse
Keyword(s):  
Chromosome Number ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Basic Chromosome Number ◽  
B Chromosomes ◽  
Basic Chromosome ◽  
Cytogenetic Studies ◽  
African Plants ◽  
First Time

Cytogenetic studies of 53 specimens of 14 species of the genus  Ehrharta Thunb. confirmed a basic chromosome number of 12 for the genus. Chromosome numbers for 13 species are described for the first time. The highest ploidy level yet observed in the genus (2n = lOx = 120) is reported for E. villosa var.  villosa. B chromosomes were observed in several specimens of four different species.

The mitotic chromosomes of Marsupials and their bearing on taxonomy and phylogeny.

1961 ◽  
Vol 9 (1) ◽  
pp. 38 ◽  
Author(s):  
GB Sharman
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Parallel Evolution ◽  
Mitotic Chromosomes ◽  
Cytological Evidence ◽  
Separate Genus ◽  
Y Chromosomes ◽  
Related Group ◽  
Living Species ◽  
Potorous Tridactylus

Chromosome numbers of marsupials vary between 2n = 11 B 10 @ and 2n =24. Most species have 14 or 22 chromosomes. There is no evidence that polyploidy has occurred in marsupial evolution. The Dasyuridae have 12 metacentric autosomes, a small metacentric X-chromosome and a very small Y-chromosome (20% of living species have been studied) and the chromosomes of Myrmecobius fasciatus are typically like those of other Dasyuridae. The Peramelidae (30% of species have been studied) have chromosomes like the Dasyuridae except that X- and Y-chromosomes are much larger. The occurrence of similar chromosome numbers in Dasyuridae and Peramelidae is not necessarily evidence of affinity. The chromosomes of the Phascolomidae are similar in number and morphology to those of the Peramelidae and the resemblances are, almost certainly, due to parallel evolution. The chromosomes of Phascolarctos are unlike those of any of the Phalangeridae and this genus might be just as easily grouped with the Phascolomidae. The Phalangeridae have considerable chromosomal heterogeneity but less than 20% of species have been studied. Two species of Cercaertus have 12 metacentric autosomes and small sex chromosomes like all members of the Dasyuridae. This suggests that the primitive phalangers may have retained the chromosome number and morphology of possible dasyurid ancestors but the resemblances may be due to parallel evolution of similar chromosome number and morphology in separate groups. The chromosomes have been studied in more than 50% of Macropodinae. Cytological evidence suggests that Thylogale (3 species studied), Petrogale (2 species studied), and probably Lagorchestes (1 species studied), all with 22 chromosomes, are a related group. Onychogalea unguifer, with 20 chromosomes, may be derived from this group. There is no justification for the placing of Thylogale billardierii in the genus Protemnodon. Lagostrophus fasciatus has 2n = 24 and its placement in a monotypic genus is justified. Macropus major and all species of Protentnodon, except P. bicolor, are a related group with 16 chromosomes. M. robustus is possibly included in this group. M. rufus has 20 chromosomes and should perhaps be placed in the separate genus Megaleia. P. bicolor, with 11 chromosomes in the male and 10 in the female, differs from all other species of Protemnodon and this genus, as at present constituted, may be diphyletic. The relationships of P. bicolor are unknown. Setonix brachyurus has 22, mostly metacentric, chromosomes and its affinities are at present unknown. Three species of Bettongia (Potoroinae) have 22 chromosomes which are mostly metacentric. Hypsiprymnodon moschatus has 22 chromosomes which are mostly acrocentric. Both genera are very different cytologically from Potorous tridactylus.

Chromosome numbers in some species of Trifolium

1969 ◽  
Vol 20 (5) ◽  
pp. 883 ◽  
Author(s):  
AJ Pritchard
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Basic Chromosome Number ◽  
Basic Chromosome ◽  
First Time

The chromosome numbers of 31 species of Trifolium are reported, 18 for the first time. A reduction in basic chromosome number has occurred only in the three most highly specialized subgenera, and polyploids occur mainly in one of the more primitive subgenera.

scholarly journals Fertility of Triploid Highbush Blueberry

1991 ◽  
Vol 116 (2) ◽  
pp. 336-341 ◽  
Author(s):  
N. Vorsa ◽  
James R. Ballington
Keyword(s):  
Gene Transfer ◽  
Chromosome Number ◽  
Chromosome Numbers ◽  
2N Gametes ◽  
Basic Chromosome Number ◽  
Highbush Blueberry ◽  
Pollen Stainability ◽  
Frequency Distributions ◽  
Basic Chromosome ◽  
2N Gamete

Eight highbush blueberry (V. corymbosum L.) triploids (2n = 3x = 36) were crossed with diploids (2n = 2x = 24), tetraploids (2n = 4x = 48), and hexaploids (2n = 6x = 72). No plants were recovered from 4021 3x × 2x crosses. One triploid was relatively fertile in 3x × 4x and 3x × 6x crosses, which is most likely attributable to 2n gamete production in the triploid. The lack of fertility of triploids, which do not produce 2n gametes, in crosses with diploids and tetraploids suggests that the production of gametes with numerically balanced (n = 12 or 24) chromosome numbers is extremely low. In addition, the inability to recover progeny from 3x × 2x crosses also suggests that aneuploid gametophytes and/or zygotes, including trisomics, are inviable in blueberry. Pollen stainability was also highly reduced in triploids. Frequency distributions of anaphase I pole chromosomal constitutions of three triploids were significantly different from one another. Two of the three distributions were shifted toward the basic chromosome number of 12, with one triploid having 25% poles with 12 chromosomes. However, the sterility of 3x × 2x and 2x × 3x crosses indicates that lagging chromosomes during meiotic anaphases are probably not excluded from gametes, resulting in unbalanced gametes in blueberry. Triploids can be used as a bridge to facilitate gene transfer from the diploid and tetraploid levels to the hexaploid level in blueberry.

Phylogenetics and chromosomal evolution in the Poaceae (grasses)

2004 ◽  
Vol 52 (1) ◽  
pp. 13 ◽  
Author(s):  
Khidir W. Hilu
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Chromosome Doubling ◽  
Chromosomal Evolution ◽  
Basic Chromosome Number ◽  
Basic Chromosome ◽  
Wide Range ◽  
The Family

The wide range in basic chromosome number (x = 2–18) and prevalence of polyploidy and hybridisation have resulted in contrasting views on chromosomal evolution in Poaceae. This study uses information on grass chromosome number and a consensus phylogeny to determine patterns of chromosomal evolution in the family. A chromosomal parsimony hypothesis is proposed that underscores (1) the evolution of the Joinvilleaceae/Ecdeiocoleaceae/Poaceae lineage from Restionaceae ancestors with x = 9, (2) aneuploid origin of x�=�11 in Ecdeiocoleaceae and Poaceae (Streptochaeta, Anomochlooideae), (3) reduction to x = 9, followed by chromosome doubling within Anomochlooideae to generate the x = 18 in Anomochloa, and (4) aneuploid increase from the ancestral x = 11 to x = 12 in Pharoideae and Puelioideae, and further diversification in remaining taxa (Fig. 3b). Higher basic chromosome numbers are maintained in basal taxa of all grass subfamilies, whereas smaller numbers are found in terminal species. This finding refutes the 'secondary polyploidy hypothesis', but partially supports the 'reduction hypothesis' previously proposed for chromosomal evolution in the Poaceae.

scholarly journals Chromosome numbers of selected species of Elatine L. (Elatinaceae)

2015 ◽  
Vol 84 (4) ◽  
pp. 413-417 ◽  
Author(s):  
Anna Kalinka ◽  
Gábor Sramkó ◽  
Orsolya Horváth ◽  
Attila Molnár V. ◽  
Agnieszka Popiela
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Basic Chromosome Number ◽  
Basic Chromosome ◽  
First Time

The paper reports chromosome numbers for 13 taxa of <em>Elatine</em> L., including all 11 species occurring in Europe, namely <em>E. alsinastrum</em>, <em>E. ambigua</em>, <em>E. brachysperma</em>, <em>E. brochonii</em>, <em>E. californica</em>, <em>E. campylosperma</em>, <em>E. gussonei</em>, <em>E. hexandra</em>, <em>E. hungarica</em>, <em>E. hydropiper</em>, <em>E. macropoda</em>, <em>E. orthosperma</em>, <em>E. triandra</em> originating from 17, field-collected populations. For seven of them (<em>E. ambigua</em>, <em>E. californica</em>, <em>E. campylosperma</em>, <em>E. brachysperma</em>, <em>E. brochonii</em>, <em>E. hungarica</em>, <em>E. orthosperma</em>) the chromosome numbers are reported for the first time. With these records, chromosome numbers for the whole section <em>Elatinella</em> Seub. became available. Although 2<em>n</em> = 36 was reported to be the most common and the lowest chromosome number in the genus, our data show that out of thirteen species analyzed, six had 36 chromosomes but five species had 54 chromosomes, and the lowest number of chromosomes was 18. These data further corroborates that the basic chromosome number in <em>Elatine</em> is <em>x</em> = 9.

scholarly journals Cytological Investigation of Brazilian Nightshade (Solanum seaforthianam Andr.)

2014 ◽  
Vol 15 ◽  
pp. 44-48
Author(s):  
D. Jagatheeswari
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Chromosome Complement ◽  
Basic Chromosome Number ◽  
Cytological Investigation ◽  
Ancestral Species ◽  
Basic Chromosome ◽  
Centromere Position ◽  
Solanaceae Family

Solanum genus namely Solanum seaforthianum Andr. belongs to the Solanaceae family, and comprises only dioeciously species. These plants are distributed between 29º and 40º south. All species of this genus are diploid with chromosome numbers of 2n = 24, 28 and 30. According to literature, the basic chromosome number in this genus is x = 12, 14 and 15. Solanum genus with a chromosome complement of 2n = 30 has a symmetric karyotype with a median and sub median centromere position. Because ancestral species have a symmetric karyotype, it seems that x = 12 is the initial basic chromosome number in this genus and the x = 14 and x = 15 derived from x = 12. So it seems that diploid phenomena played an important role in evolution and speciation

scholarly journals Chromosome Numbers of Rubus Species at the National Clonal Germplasm Repository

HortScience ◽  
1995 ◽  
Vol 30 (7) ◽  
pp. 1447-1452 ◽  
Author(s):  
Maxine M. Thompson
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Agricultural Research ◽  
Basic Chromosome Number ◽  
Ploidy Levels ◽  
Basic Chromosome ◽  
Rubus Species ◽  
Agricultural Research Service ◽  
The U.S ◽  
Research Service

The U.S. Dept. of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore., maintains Rubus germplasm representing worldwide diversity of the genus. Chromosome numbers were counted for 201 plants representing 124 taxa (species and varieties). There are new reports for 42 taxa, confirmation for 72 previously reported, and 10 counts for plants unidentified to species. The basic chromosome number was seven, and ploidy levels ranged from 2x to 12x.

scholarly journals Malpighiaceae: correlations between habit, fruit type and basic chromosome number

2003 ◽  
Vol 17 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Ricardo A. Lombello ◽  
Eliana R. Forni-Martins
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Basic Number ◽  
Basic Chromosome Number ◽  
Basic Chromosome ◽  
Monophyletic Origin ◽  
The Family ◽  
Number Variation ◽  
Family Based ◽  
The Relationship

The family Malpighiaceae presents species with different habits, fruit types and cytological characters. Climbers are considered the most derived habit, followed, respectively, by the shrubby and arboreal ones. The present study examines the relationship between basic chromosome numbers and the derivation of climbing habit and fruit types in Malpighiaceae. A comparison of all the chromosome number reports for Malpighiaceae showed a predominance of chromosome numbers based on x=5 or 10 in the genera of sub-family Malpighioideae, mainly represented by climbers with winged fruits, whereas non-climbing species with non-winged fruits, which predominate in sub-family Byrsonimoideae, had counts based on x=6, which is considered the less derived basic number for the family. Based on such data, confirmed by statistic assays, and on the monophyletic origin of this family, we admit the hypothesis that morphological derivation of habit and fruit is correlated with chromosome basic number variation in the family Malpighiaceae.

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