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.

scholarly journals Mitotic and meiotic studies on two species of Ocimum (Lamiaceae) and their F1 hybrids

2017 ◽  
Vol 23 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Johnson Ademola Idowu ◽  
Matthew Oziegbe
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Interspecific Variation ◽  
F1 Hybrids ◽  
Root Tips ◽  
Flower Buds ◽  
Ploidy Levels ◽  
Ocimum Species ◽  
Karyotype Formula ◽  
Standard Techniques

AbstractOcimum L. species are important aromatic and medicinal plants. Many researchers have observed complexity in their chromosome numbers and ploidy levels. We studied the somatic and germline chromosomal features and behaviour of Ocimum basilicum L., two variants of O. canum Sims (‘c1’ and ‘c2’) and their F1hybrids. Chromosomes from root tips and flower buds were investigated using standard techniques; karyograms were formed and analysed. A chromosome number of 2n = 4x = 52 was observed in O. basilicum and O. canum ‘c1’ and their F1hybrid. One of the variants, O. canum ‘c2’ had a chromosome number of 2n = 2x = 24 and its intraspecific hybrid O. canum ‘c2’ × O. canum ‘c1’ had a chromosome number of 2n = 38. These Ocimum species and their F1hybrids showed different karyotype formula, but their chromosomes were mostly metacentric (174) and submetacentric (36) with few subtelocentric (8). Based on pairing configuration, O. basilicum is an allotetraploid plant, O. canum ‘c1’ is an autotetraploid plant and the O. canum ‘c1’ is a diploid. The F1 hybrids showed higher frequency of meiotic abnormalities than the parents. The study showed intraspecific and interspecific variation in chromosome numbers and pairing patterns, but the chromosomes of the Ocimum species were similar in their centromeric positions.

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.

Chromosome numbers of 15 North American bumble bee species (Hymenoptera, Apidae, Bombini)

1983 ◽  
Vol 25 (1) ◽  
pp. 26-29
Author(s):  
Robin E. Owen
Keyword(s):  
Chromosome Number ◽  
North American ◽  
Chromosome Numbers ◽  
Bumble Bees ◽  
Bumble Bee ◽  
Morphological Divergence ◽  
Chromosome Counts ◽  
Monophyletic Origin ◽  
The Social

Chromosome counts were obtained for 14 Bombus Latr. species (the social bumble bees) belonging to four subgenera and for one Psithyrus Lep. species (the social parasitic bumble bees). In Bombus the haploid numbers were consistent within each subgenus and there was variation between subgenera; the subgenera Bombus s.s. and Pyrobombus have n = 18, while Separatobombus and Cullumanobombus have n = 19. Thus considerable morphological divergence between subgenera is often, but not always, paralleled by divergence in chromosome number. Psithyrus ashtoni has n = 25, higher than all Bombus species yet examined. This provides support for the monophyletic origin of Psithyrus, but the high n is not expected if eusociality selects for increase in chromosome number.

The chromosome numbers of five North American and European leech species

1987 ◽  
Vol 65 (3) ◽  
pp. 681-684 ◽  
Author(s):  
Ronald W. Davies ◽  
R. N. Singhal
Keyword(s):  
Chromosome Number ◽  
North American ◽  
Chromosome Numbers ◽  
Chromosome Evolution ◽  
Chromosome Counts ◽  
Prophase I ◽  
Metaphase I

Chromosome counts were obtained for four glossiphoniid species belonging to three genera (Glossiphonia, Theromyzon, Placobdella) and for one erpobdellid species (Dina lineata) of freshwater leeches. Theromyzon rude, which has a Palaearctic distribution, had seven bivalents at prophase I and metaphase I, while the Holarctic T. tessulatum had eight bivalents, giving diploid chromosome numbers of 14 and 16, respectively. Placobdella papillifera from Alberta had a chromosome number of 2n = 24 and Glossiphonia complanata from Alberta and England had chromosome counts of 2n = 28. At prophase I and metaphase I nine bivalents occurred in the majority of the nuclei of Dina lineata. These findings are discussed in relation to the chromosome evolution and phylogenetic schemes proposed by previous authors.

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.

scholarly journals Chromosome Number and Meiotic Behavior of Cultivated Chia, Salvia hispanica (Lamiaceae)

HortScience ◽  
1990 ◽  
Vol 25 (12) ◽  
pp. 1646-1647 ◽  
Author(s):  
A. Estilai ◽  
A. Hashemi ◽  
K. Truman
Keyword(s):  
Chromosome Number ◽  
Species Identification ◽  
Southern California ◽  
Herbarium Specimens ◽  
Meiotic Behavior ◽  
Root Tips ◽  
Chromosome Counts ◽  
Salvia Hispanica ◽  
Meiotic Analyses ◽  
Metaphase I

Edible chia seeds, purchased from the local markets in Guatemala, Mexico, and southern California, were used for species identification, chromosome counts, karyotype construction, and meiotic analyses. Plants raised from those seeds had ovate leaves, dense racemose inflorescences, pale-blue flowers, and were identified from herbarium specimens as Salvia hispanica L. Mitotic analyses of root tips from 50 plants showed 2n = 12—the lowest chromosome number in the genus. Chromosomes were small, ranging from 2 to 3.5 pm. One pair of chromosomes was metacentric (with the long arm: short arm ratio, r = 1.5), four pairs were submetacentric (r = 2.6 to 3.6), and one pair was telocentric (r = 12). Meiosis was regular and six bivalents were observed at metaphase I. Ring and rod bivalents averaged 1.53 ± 1.05 and 4.47 ± 1.05, respectively;

scholarly journals Cytological Analysis of a Clethra alnifolia `Hokie Pink' × C. pringlei Hybrid

HortScience ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 339-342
Author(s):  
Sandra M. Reed
Keyword(s):  
Chromosome Number ◽  
Cold Hardiness ◽  
Male Gamete ◽  
Cytological Analysis ◽  
Root Tips ◽  
Chromosome Counts ◽  
Pollen Mother Cells ◽  
Size And Shape ◽  
Mother Cells ◽  
Deciduous Shrub

Clethra alnifolia L., a native deciduous shrub cultivated as an ornamental, was recently hybridized with C. pringlei S. Wats. The purpose of this hybridization was to combine the cold hardiness and adaptability of C. alnifolia with the ornamental foliage of C. pringlei. While most of the C. alnifolia × C. pringlei hybrids more closely resembled C. alnifolia than the paternal species, a `Hokie Pink' × C. pringlei hybrid (NA71586) with foliage that flushes red like C. pringlei was recovered. The objectives of this study were to analyze cytologically the F1 and produce a F2 population from NA71586. Chromosome counts from root tips cells indicated that NA71586 has 32 chromosomes. Since the chromosome number of C. alnifolia is 2n = 32 and that of C. pringlei was found to be 2n = 16, NA71586 appears to have developed following fertilization of a C. alnifolia egg with an unreduced male gamete from C. pringlei. Both `Hokie Pink' and C. pringlei exhibited primarily bivalent pairing in pollen mother cells (PMCs). Over half of the PMCs from NA71586 contained 16 bivalents, indicating substantial homology within the C. alnifolia genome. It was theorized that C. alnifolia is either an autotetraploid that exhibits bivalent pairing or a segmental allotetraploid produced from hybridization of species with similar genomes. More than 700 F2 progeny were obtained from self-pollination of NA71586. Although many of the F2 progeny resembled NA71586, variation in foliage color, size and shape was apparent in the population.

CYTOLOGICAL STUDIES IN THE GENUS ERIGERON

1960 ◽  
Vol 38 (3) ◽  
pp. 381-386 ◽  
Author(s):  
F. H. Montgomery ◽  
Shung-Jun Yang
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Large Area ◽  
Chromosome Counts

The literature relating to the chromosome numbers in the genus Erigeron has been reviewed, and all reported numbers are given. The chromosome number for E. breweri var. porphyreticus (Jones) Cronquist, 2n = 18; E. divergens var. cinereus A. Gray, 2n = 27; E. glabellus var. glabellus Cronquist, 2n = 36; E. glabellus var. pubescens (Hook.) Cronquist, 2n = 36; E. hyssopifolius Michx., 2n = 18; E. quercifolia Lam., 2n = 36; E. simplex Greene, 2n = 27; E. strigosus var. beyrichii (Fisch. & Mey.) A. Gray, 2n = 27; and E. vernus T. & G., 2n = 18 are new determinations. Different numbers from those previously reported have been found for E. pulchellus Michx., 2n = 27, and E. strigosus (Muhl.) Willd., 2n = 36. Chromosome counts over a large area of their distribution have been made for E. annuus (L.) Pers., E. pulchellus Michx., E. philadelphicus L., and E. strigosus (Muhl.) Willd.

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 Improved Method of Enzyme Digestion for Root Tip Cytology

HortScience ◽  
2017 ◽  
Vol 52 (7) ◽  
pp. 1029-1032 ◽  
Author(s):  
Jason D. Lattier ◽  
Hsuan Chen ◽  
Ryan N. Contreras
Keyword(s):  
Chromosome Numbers ◽  
Enzyme Digestion ◽  
Root Tip ◽  
Root Tips ◽  
Chromosome Counts ◽  
Ploidy Levels ◽  
Long Duration ◽  
Wide Range ◽  
Plant Sciences ◽  
Breeding And Genetics

Chromosome numbers are an important botanical character for multiple fields of plant sciences, from plant breeding and genetics to systematics and taxonomy. Accurate chromosome counts in root tips of woody plants are often limited by their small, friable roots with numerous, small chromosomes. Current hydrolysis and enzyme digestion techniques require handling of roots before the root squash. However, optimum chromosome spread occurs when the cell walls have degraded past the point of easy handling. Here, we present a new enzyme digestion protocol that is fast, efficient, and flexible. This protocol reduces handling of the roots allowing for long-duration enzyme digestion. Digestions are performed on a microscope slide, eliminating the need for handling digested cells with forceps or pipettes. To illustrate the flexibility of this method across woody plant taxa, we performed chromosome counts on five angiosperms and one gymnosperm. Ploidy levels included diploids, triploids, and tetraploids with chromosome numbers ranging from 2n = 16 to 2n = 80. The range of holoploid 2C genome sizes spanned 1.54–24.71 pg. This protocol will provide a useful technique for plant cytologists working with taxa that exhibit a wide range of genome size and ploidy levels.

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