CYTOLOGICAL STUDIES IN ALFALFA POLYPLOIDS

1954 ◽  
Vol 32 (4) ◽  
pp. 531-542 ◽  
Author(s):  
J. M. Armstrong
Keyword(s):  
Chiasma Frequency ◽  
Diploid Species ◽  
Low Frequency ◽  
Morphological Characters ◽  
Tetraploid Species ◽  
Meiotic Behavior ◽  
Meiotic Irregularities ◽  
Medicago Sativa L ◽  
Partial Homology ◽  
Quadrivalent Frequency

Normal tetraploid alfalfa, Medicago sativa L., is characterized by meiotic irregularities consisting of a low percentage of univalents, trivalents, and quadrivalents. While these irregularities might suggest an autoploid origin, their frequency is too low to be conclusive. Cytological studies of the induced octoploid and of the hexaploid, obtained from crossing tetraploid and octoploid, indicate that the two genomes in the tetraploid are only partially homologous. The partial homology is established by the meiotic behavior in the hexaploid in which a low univalent frequency indicates fairly complete pairing between the A and B genomes. The comparatively low frequency of quadrivalents in the octoploid indicates a correspondingly low chiasma frequency at pachytene. Nevertheless this quadrivalent frequency in the octoploid is more than three times as high as in the tetraploid which suggests a lack of complete homology between the two genomes. The theory is advanced that tetraploid species of Medicago originated from crosses between a series of diploid species fairly similar cytologically but differing in well marked, morphological characters. This affords an explanation for the inheritance of some characters in a disomic and others in a tetrasomic manner. Cytological and genetic evidence thus points to tetraploid alfalfa as originating as an alloploid from closely related diploid species.

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.

A new diploid species belonging to the Odontophrynus americanus species group (Anura: Odontophrynidae) from the Espinhaço range, Brazil

Zootaxa ◽  
2017 ◽  
Vol 4329 (4) ◽  
pp. 327 ◽  
Author(s):  
PEDRO CARVALHO ROCHA ◽  
LETÍCIA MOREIRA FERRAZ DE SENA ◽  
TIAGO LEITE PEZZUTI ◽  
FELIPE SÁ FORTES LEITE ◽  
MARTA SVARTMAN ◽  
...  
Keyword(s):  
Diploid Species ◽  
Morphological Characters ◽  
Dominant Frequency ◽  
Species Group ◽  
The Body ◽  
Advertisement Call ◽  
Campo Rupestre ◽  
Tetraploid Species ◽  
Espinhaço Range ◽  
Low Contrast

The Odontophrynus americanus species group is a complex of diploid and tetraploid species hardly distinguished by morphological characters. It currently consists of three allopatric diploid species (i.e. O. cordobae, O. lavillai, and O. maisuma) and one widely distributed tetraploid species (i.e. O. americanus). We herein describe a new diploid allopatric species from campo rupestre, a typical phytophysiognomy of the Espinhaço Range, Brazil. The new species is distinguishable by the diploid complement of 2n = 2x = 22 chromosomes, small to medium-sized dorsal dark brown blotches with low contrast on a light brown background, light mid-dorsal stripe absent or greatly interrupted in most specimens with yellowish coloration as the background of both head and flanks of the body, advertisement call with dominant frequency of 840–1080 Hz, pulse rate of 90.5–106.7 pulses/s, and small tadpoles (TL = 24.30–35.69 mm). 

scholarly journals Chromosome number and microsporogenesis in Paspalum maritimum (caespitosa group; gramineae)

2000 ◽  
Vol 43 (3) ◽  
pp. 301-305 ◽  
Author(s):  
Eleniza de Victor Adamowski ◽  
Maria Suely Pagliarini ◽  
Luiz Alberto Rocha Batista
Keyword(s):  
Chromosome Number ◽  
Pollen Fertility ◽  
Low Frequency ◽  
Economic Importance ◽  
Meiotic Behavior ◽  
First Report ◽  
Meiotic Irregularities ◽  
Low Rate

Despite of economic importance of the genus Paspalum, little or no cytologic information is available for many species. This is the first report about chromosome number and meiotic behavior for P. maritimum. The three accessions collected in Amapá State (North Region of Brazil) were tetraploid (2n=4x=40) with the chromosomes associating predominantly as bivalents. The low frequency of multivalents suggested that they were segmental allotetraploids. All accessions showed a low rate of meiotic irregularities, and as a consequence the pollen fertility was high. The results suggested that these accessions presented potential for use in a hybridization program.

CHROMOSOME ASSOCIATIONS AT PACHYTENE AND METAPHASE IN MEDICAGO SATIVA

1971 ◽  
Vol 13 (4) ◽  
pp. 697-702 ◽  
Author(s):  
K. C. Armstrong
Keyword(s):  
Medicago Sativa ◽  
Chiasma Frequency ◽  
General Tendency ◽  
Chromosome Associations ◽  
Medicago Sativa L ◽  
Quadrivalent Frequency ◽  
Metaphase I

Chromosome associations were analyzed at pachytene and metaphase I from six plants of Medicago sativa L. (2n = 4x = 32). Quadrivalent frequency at pachytene ranged from 0.89 to 2.93. These values are considerably below theoretical expectations for an autotetraploid. The chromosome associations at metaphase I did not entirely reflect differences in quadrivalent frequency at pachytene, although there was a general tendency for plants with higher quadrivalent frequencies at pachytene to have a higher trivalent and univalent frequency at metaphase I. However, there were obvious differences in the amount and kind of pachytene quadrivalent dissociation that occurred, which are probably a result of small differences in chiasma frequency and distribution.

THE SIGNIFICANCE OF CHROMOSOME ASSOCIATION IN AN ADVANCED POPULATION OF TETRAPLOID RYE

1976 ◽  
Vol 18 (4) ◽  
pp. 601-609 ◽  
Author(s):  
M. Gul Hossain
Keyword(s):  
Chiasma Frequency ◽  
Random Mating ◽  
Inbred Lines ◽  
Chromosome Association ◽  
Meiotic Behavior ◽  
Association Pattern ◽  
Mating Population ◽  
Secale Cereale L ◽  
Quadrivalent Frequency ◽  
Positive Correlations

Chromosome pairing was studied in a population of tetraploid spring rye (Secale cereale L.) 20 years after the chromosomes were doubled. Cytogenetically the population was heterogeneous as revealed by significant differences between plants for chiasma frequency, the proportions of regular MI cells and regular quartets. Compared to early C generations meiotic behavior in the population improved by an increase in quadrivalent frequency, mainly at the expense of trivalents and univalents. However, quadrivalent frequency failed to correlate with all other meiotic features; instead bivalent frequency had significant positive correlations with the features of meiotic regularity including chiasma frequency. Furthermore, the average quadrivalent frequency in the population was considerably less than that of inbred lines. These facts led to the conclusion that disomic association dominated the chromosome association pattern in this random mating population, whereas in inbred materials the chromosome association pattern is predominantly tetrasomic. This was further proved by a test against the theoretically expected chromosome association pattern in a true autotetaploid.

Comparative Analysis of Genetic and Morphological Variation within the Platanthera hyperborea Complex (Orchidaceae)

2020 ◽  
Vol 45 (4) ◽  
pp. 767-778
Author(s):  
Eranga Wettewa ◽  
Nick Bailey ◽  
Lisa E. Wallace
Keyword(s):  
North America ◽  
Diploid Species ◽  
Morphological Characters ◽  
Evolutionary Patterns ◽  
Founding Population ◽  
Multiple Origins ◽  
Geographic Structure ◽  
Species Complexes ◽  
Nuclear Its ◽  
Cryptic Taxa

Abstract—Species complexes present considerable problems for a working taxonomy due to the presence of intraspecific variation, hybridization, polyploidy, and phenotypic plasticity. Understanding evolutionary patterns using molecular markers can allow for a more thorough assessment of evolutionary lineages than traditional morphological markers. In this study, we evaluated genetic diversity and phylogenetic patterns among taxa of the Platanthera hyperborea (Orchidaceae) complex, which includes diploid (Platanthera aquilonis) and polyploid (Platanthera hyperborea, P. huronensis, and P. convallariifolia) taxa spanning North America, Greenland, Iceland, and Asia. We found that three floral morphological characters overlap among the polyploid taxa, but the diploid species has smaller flowers. DNA sequence variation in a plastid (rpL16 intron) and a nuclear (ITS) marker indicated that at least three diploid species have contributed to the genomes of the polyploid taxa, suggesting all are of allopolyploid origin. Platanthera convallariifolia is most like P. dilatata and P. stricta, whereas P. huronensis and P. hyperborea appear to have originated from crosses of P. dilatata and P. aquilonis. Platanthera huronensis, which is found across North America, has multiple origins and reciprocal maternal parentage from the diploid species. By contrast, P. hyperborea, restricted to Greenland and Iceland, appears to have originated from a small founding population of hybrids in which P. dilatata was the maternal parent. Geographic structure was found among polyploid forms in North America. The area of Manitoba, Canada appears to be a contact zone among geographically diverse forms from eastern and western North America. Given the geographic and genetic variation found, we recommend continued recognition of four green-flowered species within this complex, but caution that there may be additional cryptic taxa within North America.

scholarly journals Interploid Hybridizations in Ornamental Cherries Using Prunus maackii

2012 ◽  
Vol 30 (2) ◽  
pp. 89-92
Author(s):  
Margaret Pooler ◽  
Hongmei Ma ◽  
David Kidwell-Slak
Keyword(s):  
United States ◽  
Tissue Culture ◽  
Cold Hardiness ◽  
Diploid Species ◽  
Pest Resistance ◽  
The United States ◽  
Tetraploid Species ◽  
Genetic Base ◽  
Flowering Cherry ◽  
New Cultivars

The United States National Arboretum has an ongoing flowering cherry (Prunus) breeding program aimed at broadening the genetic base of cultivated ornamental cherries by developing new cultivars with disease and pest resistance, tolerance to environmental stresses, and superior ornamental characteristics. Interploid crosses, specifically 2X × 4X, in ornamental Prunus would be beneficial in breeding because they could allow introgression of traits not available in the diploid germplasm (pest resistance, cold hardiness), and could result in the creation of seedless triploids that would not set nuisance fruit and possibly have extended bloom durations. This report documents successful hybridization of P. maackii (Manchurian or Amur cherry), a tetraploid species, with P. campanulata, P. ‘Umineko’, and P. maximowiczii, all diploid species. Chromosomes of one of these resulting triploid hybrids were successfully doubled using oryzalin in tissue culture to create a hexaploid plant.

Cytological identification of some trisomics of Russian wildrye (Psathyrostachys juncea)

Genome ◽  
1995 ◽  
Vol 38 (6) ◽  
pp. 1271-1278 ◽  
Author(s):  
Jun-Zhi Wei ◽  
W. F. Campbell ◽  
G. J. Scoles ◽  
A. E. Slinkard ◽  
R. Ruey-Chyi Wang
Keyword(s):  
Crop Improvement ◽  
Diploid Species ◽  
Pollen Grains ◽  
Morphological Characters ◽  
Cereal Crop ◽  
Banding Patterns ◽  
C Banding ◽  
Psathyrostachys Juncea ◽  
Double Deletion ◽  
Russian Wildrye

Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski (2n = 2x = 14; NsNs), is an important forage grass and a potential source of germplasm for cereal crop improvement. Because of genetic heterogeneity as a result of its self-incompatibility, it is difficult to identify trisomics of this diploid species based on morphological characters alone. Putative trisomies (2n = 2x + 1 = 15), derived from open pollination of a triploid plant by pollen grains of diploid plants, were characterized by Giemsa C-banding. Based on both karyotypic criteria and C-banding patterns, four of the seven possible primary trisomics, a double-deletion trisomic, and two tertiary trisomics were identified.Key words: Russian wildrye, Psathyrostachys juncea, trisomic, C-banding, karyotype.

Two closely related Tulipa species with different ploidy levels show distinct germination rates

2020 ◽  
Vol 30 (1) ◽  
pp. 45-48
Author(s):  
Giovanni Astuti ◽  
Sandro Pratesi ◽  
Lorenzo Peruzzi ◽  
Angelino Carta
Keyword(s):  
Ploidy Level ◽  
Comparative Studies ◽  
Diploid Species ◽  
Tetraploid Species ◽  
Natural Conditions ◽  
Ploidy Levels ◽  
Final Length ◽  
Diploid Ancestor

AbstractIn the tetraploid Tulipa sylvestris we found larger and heavier seeds that germinated around 28 days earlier than those of the diploid ancestor Tulipa pumila. The faster germination of the tetraploid species is linked to the faster growth of embryos, which reached their final length much earlier than the embryos of the diploid species. In conclusion, we argue a cautionary approach when dealing with comparative studies on ploidy level and germination to avoid misinterpretation of results when set against the natural conditions.

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