Apomixis in diploid × triploid Tripsacum dactyloides hybrids

Genome ◽  
1991 ◽  
Vol 34 (4) ◽  
pp. 528-532 ◽  
Author(s):  
R. A. Sherman ◽  
P. W. Voigt ◽  
B. L. Burson ◽  
C. L. Dewald
Keyword(s):  
Chromosome Number ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Germ Plasm ◽  
Seed Set ◽  
Tripsacum Dactyloides ◽  
Mode Of Reproduction ◽  
Selected Subset ◽  
Diploid Level ◽  
High Level

Apomixis can hinder plant improvement if sexual or apomictic germ plasm of the appropriate ploidy level, required for effective manipulation of apomixis, is not available. To develop needed germ plasm and increase knowledge of apomixis in Tripsacum dactyloides, diploid (2n = 2x = 36) sexual plants were crossed with a highly apomictic triploid (2n = 3x = 54) accession in an attempt to transfer apomixis from a polyploid to the diploid level. The fertility of most hybrids was very low, 69% had 10% or less seed set. A selected subset of 48 hybrids, including most of the more fertile plants, was studied cytologically. The chromosome number of these hybrids ranged from 2n = 36 to 2n = 54. All but 3 of 46 of the 48 hybrids showed indications of apomictic development. Those with near-diploid chromosome numbers were primarily sexual. Highly apomictic hybrids, based on percent diplosporous ovules, had 43 or more chromosomes. Fertility of these hybrids was not related to chromosome number. Fertility of sexual to moderately apomictic plants was reduced as chromosome number increased. Apomixis in T. dactyloides is facultative. Backcrosses are needed to develop germ plasm with a high level of apomixis and near-diploid chromosome numbers.Key words: eastern gama-grass, chromosome number, fertility, mode of reproduction, germ plasm.

Cytogenetic and Pollination Studies in the Genus Verticordia DC

1991 ◽  
Vol 39 (3) ◽  
pp. 261 ◽  
Author(s):  
AP Tyagi ◽  
J Mccomb ◽  
J Considine
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Seed Set ◽  
Interspecific Crosses ◽  
Root Tips ◽  
Chromosome Counts ◽  
Flower Buds ◽  
Taxonomic Distance ◽  
Self Compatibility ◽  
High Level

Aspects of the genetic and physiological barriers to hybridisation have been assessed for the genus Verticordia which contains many species with significant potential for ornamental horticulture. The chromosome numbers of 52 species were analysed using flower buds and root tips. Previously published reports on chromosome numbers were confirmed for 21 species and new numbers reported in a further 31. Self compatibility was present in 20 species and only three species were shown to possess barriers to self pollination. Seed set occurred in two of six interspecific crosses carried out within sections. In 21 wider crosses the degree of pollen tube development was increasingly repressed with taxonomic distance. The chromosome counts also support the reclassification of the genus Verticordia into three subgenera: Chrysoma, Verticordia and Eperephes. Species within each section of a subgenus generally had the same chromosome number. Exceptions occurred in the subgenus Verticordia, sections Verticordia, Intricata and Micrantha. In species with one or two ovules, the chromosome number was also low (6, 7, 8 or 9) while species with six or more ovules had a higher chromosome number (11 or 22). There was, however, no relationship between chromosome number and chromosome size, nor between chromosome number and any observed feature which might be attributable to polyploidy or allopolyploidy. With the possible exception of V. grandis, which displayed loss of seasonality in flowering, all putative polyploids behaved developmentally as diploids and displayed a high level of male fertility.

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.

scholarly journals Chromosome Number, Ploidy Level, and Nuclear DNA Content in 23 Species of Echeveria (Crassulaceae)

Genes ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1950
Author(s):  
Guadalupe Palomino ◽  
Javier Martínez-Ramón ◽  
Verónica Cepeda-Cornejo ◽  
Miriam Ladd-Otero ◽  
Patricia Romero ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Chromosome Number ◽  
Ploidy Level ◽  
Dna Content ◽  
Chromosome Numbers ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Root Tips ◽  
Ploidy Levels ◽  
Dna Amounts

Echeveria is a polyploid genus with a wide diversity of species and morphologies. The number of species registered for Echeveria is approximately 170; many of them are native to Mexico. This genus is of special interest in cytogenetic research because it has a variety of chromosome numbers and ploidy levels. Additionally, there are no studies concerning nuclear DNA content and the extent of endopolyploidy. This work aims to investigate the cytogenetic characteristics of 23 species of Echeveria collected in 9 states of Mexico, analyzing 2n chromosome numbers, ploidy level, nuclear DNA content, and endopolyploidy levels. Chromosome numbers were obtained from root tips. DNA content was obtained from the leaf parenchyma, which was processed according to the two-step protocol with Otto solutions and propidium iodide as fluorochrome, and then analyzed by flow cytometry. From the 23 species of Echeveria analyzed, 16 species lacked previous reports of 2n chromosome numbers. The 2n chromosome numbers found and analyzed in this research for Echeveria species ranged from 24 to 270. The range of 2C nuclear DNA amounts ranged from 1.26 pg in E. catorce to 7.70 pg in E. roseiflora, while the 1C values were 616 Mbp and 753 Mbp, respectively, for the same species. However, differences in the level of endopolyploidy nuclei were found, corresponding to 4 endocycles (8C, 16C, 32C and 64C) in E. olivacea, E. catorce, E. juarezensis and E. perezcalixii. In contrast, E. longiflora presented 3 endocycles (8C, 16C and 32C) and E. roseiflora presented 2 endocycles (8C and 16C). It has been suggested that polyploidization and diploidization processes, together with the presence of endopolyploidy, allowed Echeveria species to adapt and colonize new adverse environments.

MORPHOLOGIE POLLINIQUE ET NOMBRE CHROMOSOMIQUE DANS LA SOUS-SECTION HETEROPHYLLA DU GENRE CAMPANULA

1971 ◽  
Vol 13 (4) ◽  
pp. 888-894 ◽  
Author(s):  
Alain Geslot ◽  
Jacques Medus
Keyword(s):  
Chromosome Number ◽  
Comparative Study ◽  
Linear Relationship ◽  
Frequency Distribution ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Two Factors ◽  
Pore Number

A comparative study of the palynological morphology and the chromosome numbers of 14 populations representing six species from the s.s. Heterophylla (Wit.) Fed. of the genus Campanula L. has been made. It has shown that the frequency distribution based upon the number of pores in each grain is related to the ploidy level of the species. Correspondences analysis shows the prevailing action of two factors in this phenomenon.The most important factor regarding the increased pore number is an increase of the chromosome number. Another factor still escapes interpretation. It sometimes appears without being directly dependent on the number of apertures, but it must be taken into account in the explanation of the phenomenon.The diameter of the grains seems partly to be related to polyploidy but it is independent of the number of apertures in each grain. The linear relationship between diameter and aperture number is not significant.

STUDIES ON THE CYTOLOGY OF BROMEGRASS, BROMUS INERMIS LEYSS.

1958 ◽  
Vol 38 (1) ◽  
pp. 111-117 ◽  
Author(s):  
Björn Sigurbjörnsson ◽  
Akira Mochizuki ◽  
John D. Truscott
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Somatic Chromosome ◽  
Seed Set ◽  
Bromus Inermis ◽  
Somatic Chromosome Number ◽  
Simultaneous Selection ◽  
Selection For ◽  
Type Strains ◽  
Selection Of

A population of 222 plants of 16 varieties and strains of northern and southern bromegrass was studied for somatic chromosome number. The following observations were noted: Aneuploid plants, including the chromosome numbers 54, 55, 57 and 58, were found within the species, Bromus inermis. One plant was found to have 49 chromosomes. A cytological difference was found between certain varieties of northern and southern types of bromegrass. The northern type had a significantly higher number of aneuploid plants with chromosome numbers in excess of 56, while the southern type had more aneuploid plants with fewer than 56 chromosomes. Some evidence was found suggesting that selection of northern type strains may bring about a simultaneous selection for additional chromosomes, whereas selection for southern type strains may involve a simultaneous selection for plants with missing chromosomes. Average seed set was found to be lowered in the presence of two additional chromosomes or absence of two chromosomes from the euploid complement.

scholarly journals Cytogenetics, Ploidy, and Genome Sizes of Camellia and Related Genera

HortScience ◽  
2019 ◽  
Vol 54 (7) ◽  
pp. 1124-1142 ◽  
Author(s):  
William G. Hembree ◽  
Thomas G. Ranney ◽  
Brian E. Jackson ◽  
Mark Weathington
Keyword(s):  
Flow Cytometry ◽  
Chromosome Number ◽  
Pisum Sativum ◽  
Literature Review ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Specific Information ◽  
Internal Standards ◽  
Commercially Important ◽  
Base Chromosome Number

Camellia L., the most speciose member of the diverse tea family Theaceae, has a long and complex horticultural history. Extensive cultivation and hybridization have produced thousands of varieties of Camellia, including commercially important crops such as cultivated tea, oilseed, and iconic flowering shrubs. Cytogenetics of Camellia and related genera is complicated; chromosome number and ploidy can vary widely between species, and interspecific and interploid hybridization occurs. However, specific information regarding cytogenetics of many species, cultivars, and modern hybrids is lacking. The objectives of this study were to compile a consolidated literature review of the cytogenetics of Camellia and related genera and to determine chromosome numbers, ploidy, and genome sizes of specific accessions of selected species, cultivars, and interspecific and interploid hybrids. A review of the existing literature regarding Theaceae cytogenetics is presented as a consolidated reference comprising 362 taxa. Genome sizes were determined with flow cytometry using propidium iodide as a fluorochrome and Pisum sativum ‘Ctirad' and Magnolia virginiana ‘Jim Wilson’ as internal standards. Chromosome numbers of selected taxa were determined using traditional cytology and were used to calibrate genome sizes with ploidy level. Our results confirmed a base chromosome number of x = 15 for Theeae including Camellia, x = 17 for Stewartiae, and x = 18 for Gordoniae. Surveyed camellias ranged from 2n = 2x = 30 to 2n = 8x = 120, including diploids, triploids, tetraploids, pentaploids, hexaploids, and octoploids. Previously uncharacterized taxa such as Camellia azalea, C. amplexicaulis, C. chrysanthoides, C. cordifolia, C. cucphuongensis, C. flava, C. nanyongensis, and C. trichoclada were found to be diploid. Ploidy was also newly determined for Schima argentea, S. khasiana, S. remotiserrata, and S. sinensis (all diploids). Both diploid and triploid Stewartia ovata were found, and a ploidy series was discovered for Polyspora that ranged from diploid to octoploid. Ploidy determinations were used to confirm or challenge the validity of putative interploid hybrids. Monoploid genome sizes varied among subfamily and genera, with 1Cx values ranging from 0.80 pg for Franklinia to a mean of 3.13 pg for Camellia, demonstrating differential rates of genome expansion independent of ploidy. Within Camellia, monoploid genome sizes varied among subgenera, sections, and some species (range, 2.70–3.55 pg). This study provides a consolidated and expanded knowledgebase of ploidy, genome sizes, hybridity, and reproductive pathways for specific accessions of Camellia and related genera that will enhance opportunities and strategies for future breeding and improvement within Theaceae.

scholarly journals 091 Cytogenetics of Inland Saltgrass

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 457B-457
Author(s):  
Scott Reid ◽  
Judy Harrington ◽  
Harrison Hughes
Keyword(s):  
Chromosome Number ◽  
Seed Production ◽  
Chromosome Numbers ◽  
Seed Set ◽  
Distichlis Spicata ◽  
Root Tip ◽  
Limiting Factor ◽  
Good Seed ◽  
Poor Seed

Inland saltgrass, Distichlis spicata var. stricta (Torr.) Beetle, is a native western U.S. grass that has potential in turf situations. Elite clones with outstanding potential have been selected. Poor seed production appears to be the main limiting factor for its use as turf in saline conditions. In order to better understand seed set, 40 genotypes were examined for chromosome number and morphology. Chromosome numbers of root tip metaphase spreads varied with the most common being 2n = 38. However, chromosome numbers of 39, 40, 42, and 74 were also observed. Meiotic examination of anthers revealed 19 bivalents for those with 38 chromosomes while those with 42 had 20 bivalents with 2 unpaired chromosomes. The unpaired chromosomes lagged at anaphase. Crosses among genotypes of different chromosome number have resulted in good seed set. Harvested seed are germinable and plants from these crosses are being grown for further studies.

REDUCTION OF CHROMOSOME NUMBER IN ROOT TIP CELLS OF MEDICAGO

1974 ◽  
Vol 16 (1) ◽  
pp. 219-227 ◽  
Author(s):  
R. S. Sadasivaiah ◽  
K. Lesins
Keyword(s):  
Chromosome Number ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Plant Evolution ◽  
Root Tip ◽  
Aneuploid Chromosome ◽  
Tip Cells ◽  
Root Tip Cells ◽  
In Cells

Cytological studies on progenies obtained from intercrosses between colchicine-induced octoploid (2n = 8x = 64) plants of alfalfa showed normal, haploid and aneuploid chromosome numbers in cells of the same root tip. Critical observations on cells at different divisional stages revealed the occurrence of meiosis-like mitotic divisions, resulting in a reduction of chromosome number. The frequency of cells showing reductional divisions appeared to vary with the ploidy level of the material. The possible significance of chromosome reduction in plant evolution is indicated.

scholarly journals New Contribution to the Knowledge on the Chromosome Numbers of Turkish Cerambycidae (Coleoptera)

2021 ◽  
Vol 69 (2) ◽  
pp. 93-99
Author(s):  
Yavuz Koçak ◽  
Elmas Yağmur
Keyword(s):  
Chromosome Number ◽  
Sex Determination ◽  
Chromosome Numbers ◽  
Chromosome Count ◽  
Chromosomal Number ◽  
The Poor ◽  
Karyological Data ◽  
First Time

Information on the karyotypes of Turkish species of Cerambycidae is scanty. Our study contributes to the knowledge of the karyological data (chromosomal number and mechanism of sex determination) of five Turkish longicorn beetles; karyotypes of four taxa, one endemic, are described for the first time and for the remaining one, Purpuricenus budensis (Götz, 1783), the previously published chromosome count is confirmed. The chromosome number of Purpuricenus desfontainii inhumeralis Pic, 1891 and Purpuricenus budensis (Götz, 1783) (Cerambycinae, Trachyderini) was found to be 2n = 28 (13 + Xyp); Clytus rhamni Germar, 1817 and Plagionotus floralis (Pallas, 1773) (Cerambycinae, Clytini) 2n = 20 (9 + Xyp); and the endemic Dorcadion triste phrygicum Peks, 1993 (Lamiinae, Dorcadionini) 2n = 24 (11 + Xyp). In view of the paucity of data available until now, our study is important for both to improve the poor karyological knowledge of Turkish Cerambycidae and to provide an incentive for other researchers.

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