Nuclear DNA content (2C) is reported for all genera of the Cycadales, using flow cytometry with propidium iodide. Nuclear DNA content ranges from 24 to 64 pg in cycads. This implies that the largest ...genome contains roughly 40 × 10(9) more base pairs than the smallest genome. The narrow range in nuclear DNA content within a genus is remarkable for such an old group. Furthermore, 42 of the 58 plants measured, covering five genera, have 18 chromosomes. They vary from 36.1 to 64.7 pg, covering the whole range of genome sizes (excluding the genome of Cycas). Hence, their does not seem to be a correlation between genome size and the number of chromosomes.
Zonneveld (Pl Syst Evol 281:217-245, 2009) proposed an infrageneric classification of Tulipa (Liliaceae) based on the nuclear content determined by flow cytometry and available morphological data. ...The nomenclatural consequences of this are discussed here, involving the typification of generic and infrageneric names. Additional notes on some species are given. Four subgenera are distinguished, of which two are new; ten sections are proposed, four new; three new combinations are made, and seven lectotypes are designated. Tulipa praecox Ten. is a later homonym of T. praecox Cav. (Descripción de las plantas. 2: 448, 625, 1803); its correct name is Tulipa agenensis DC. Tulipa lemmersii Zonn., A. Peterse, J. de Groot is validated here by giving the type citation.
Nuclear genome size, as measured by flow cytometry with propidium iodide, was used to investigate the relationships within the genus Eucomis L'Hér. (Hyacinthaceae). Most species of Eucomis have the ...same basic chromosome number, x = 15. However, the somatic DNA 2C-value (2C) is shown to range from 21 to 31 pg for the diploids. The largest genome contains roughly 10¹⁰ more base pairs than the smallest. Genome sizes are evaluated here in combination with available morphological and geographical data. Therefore, the taxonomy proposed here is not based on genome size alone. The genus Eucomis, as here determined, has 12 species. These can be divided into two groups: mainly dwarf diploid species and large-sized, tetraploid species. A small diploid plant, Eucomis (autumnalis subsp.) amaryllidifolia, is restored to species status, as a diploid subspecies seems incongruent with an allotetraploid Eucomis autumnalis. Moreover, as a diploid it is separated reproductively from the allotetraploid E. autumnalis. A new diploid species that has the lowest C value, E. grimshawii, is described here. On the basis of DNA content and other morphological characters, possible parents are suggested for all tetraploid species. Nuclear DNA content as measured by using flow cytometry may conveniently be used to produce systematic data. It is applicable even in dormant bulbs or sterile plants for the monitoring of the trade in bulbous species.
Nuclear genome size, as measured by flow cytometry with propidium iodide, was used to investigate the relationships within the genus
Gagea
(Liliaceae), mainly from the Netherlands. The basic ...chromosome number for
Gagea
is x = 12. The inferred ploidy in the Dutch and German accessions varies from diploid to decaploid. Consequently there is a large range of genome sizes (DNA 2C-values) from 14.9 to 75.1 pg. Genome sizes are evaluated here in combination with the results of morphological observations. Five species and the hybrid
G.
×
megapolitana
are reported. Apart from 14 diploid
G. villosa
, six plants of
G. villosa
with an inferred tetraploidy were found. For the 186 Dutch accessions investigated 85 turned out to be the largely sterile
G. pratensis
(inferred to be pentaploid). Inferred tetraploid and hexaploid
G. pratensis
were found in 30 and 20 localities, respectively. In one locality an inferred decaploid (10×) plant was found that could represent a doubled pentaploid
G. pratensis
. An inferred decaploid
G. pratensis
was never reported before. The genome size of
Gagea
×
megapolitana
from Germany fitted with its origin as a cross between the two hexaploids
G. pratensis
and
G. lutea
.
Gagea spathacea
from the Netherlands was inferred to be nonaploid as was recorded from plants across Europe. The aim of the study was to use flow cytometry as a tool to elucidate the taxonomic position of the Dutch
Gagea
.
Somaclonal variation of some 124 specially selected cultivars of Hosta Tratt. (Hostaceae) was investigated. Nuclear DNA contents (2C‐value) were measured by flow cytometry of leaves and roots of L1, ...L2 and L3 layers derived from apical meristems. These values were then converted to inferred ploidies by comparing the measured 2C‐values and ploidy with those of the parent plant. During tissue‐culture propagation, on occasion diploid (L1‐L2‐L3 = 2‐2‐2) hostas give rise to polyploids, such as fully tetraploids (4‐4‐4), and periclinal chimeras, such as partial tetraploids (4‐2‐2). Continual propagation can result in partial tetraploids becoming full tetraploids. Nuclear DNA of some diploids increased with incomplete chromosome sets resulting in fully aneuploids, such as hostas with a DNA ploidy of L1‐L2‐L3 = 2.5‐2.5‐2.5 and 3.7‐3.7‐3.7, and even in aneuploid periclinal chimeras, such as L1‐L2‐L3 = 2.5‐2‐2 and 3.8‐2‐2. The polyploidy of L1, irrespective of the ploidy of L2 and L3, is found to mainly determine the thickness of leaves. Also the higher the ploidy of L1, the wider and more intense in color is the leaf margin. The measurements of Hosta cultivars and their lineages of sports show that chromosome losses or gains are an important source of new cultivars. The complexity of chromosomal distribution in lineages of several Hosta cultivars is discussed.
The white-flowered Tulipa kolbintsevii (Liliaceae), section Biflores, occurs in SE Kazakhstan, Dzjungarian Ala-Tau, Taskora valley. So far only T. aff. altaica and T. brachystemon (sect. ...Kolpakowskianae) both with yellow flowers, flushed greenish-violet or red on the outside, were known to be present there. It differs in that it is not only the easternmost species of the section Biflores, and has different placement of hairs on the tepals, but also has the lowest genome size of the species in this section with 2C = 48 pg. The other 14 species have 51.5-59.4 pg. Flow cytometry supported morphological differences. This method is useful for identification of dormant bulbs or sterile plants and is therefore important for monitoring of the trade in bulbous species.
Ploidy distributions in L1, L2, and L3 apical or meristematic layers of 56 different plants (79 accessions) from vegetative and sexual progeny of the triploid Hosta ‘Sum and Substance’ were ...determined. Nuclear DNA contents (2C) of each apical layer were measured by flow cytometry with propidium iodide, and inferred ploidies are calculated. During tissue culture, the triploid (L1–L2–L3 = 3–3–3) Hosta ‘Sum and Substance’ exhibited chromosome losses resulting in somaclonal variants such as DNA aneuploids (e.g., 2.7–2.7–2.7) and aneuploidy chimeras (e.g., 3–2.7–2.7). Most interestingly, some chimeras exhibited even an increase in genome size as in plants with 3.5–3–3 configuration. Hybrids of H. ‘Sum and Substance’ show only losses of nuclear DNA compared with the original triploid. This gives rise to fully aneuploid plants and no chimeras. The measurements of Hosta ‘Sum and Substance’ lineages of sports and hybrids indicate that chromosome losses or gains are an important source of new cultivars. The complexity of chromosomal distribution in derivatives from the triploid Hosta ‘Sum and Substance’ is discussed.
Genome size (C-values) and pollen viability staining were applied as new criteria to investigate the species of the genus Helleborus Linnaeus (Ranunculaceae). All species have the same chromosome ...number (2n = 32). However, the nuclear DNA content, as measured by flow cytometry with propidium iodide, could be demonstrated to range between 19 pg to 35.7 pg. The different genome sizes of the species coincided to a large extent with earlier determined section boundaries based on morphology. Flow cytometry can be a convenient method to discriminate between some species.
To investigate the origin of cultivated trumpet daffodils the genome size (2C-value) of more than 100 old and new cultivars were measured. A large number of concolored yellow tetraploid cultivars ...with large coronas seem to be derived from a doubling of chromosomes of a hybrid of the two species N. hispanicus Gouan and N. pseudonarcissus L. This can also still be recognized by the presence of a black spot at the top of the anthers in about 15 % of the tetraploid cultivars. Assuming N. pseudonarcissus as one of the parents of the allotetraploid cultivars, species of trumpet daffodils of section Pseudonarcissi investigated earlier were compared. Doubling of the nuclear DNA content of 23.8 pg of N. pseudonarcissus falls short of the values found for the trumpet daffodils. Species of trumpet daffodils of section Pseudonarcissi with a complementing higher amount of nuclear DNA like N. hispanicus with 25.8 pg, N. poeticus L. with 26 pg and the hexaploid N. pseudonarcissus ssp. bicolor (L.) Baker with 67.7 pg (Zonneveld,2008) and other species were evaluated. N. hispanicus with 25.8 pg clearly differs from N. pseudonarcissus with 23.8 pg and is accepted here also as a species. The nuclear DNA content of N. bujei (Fern. Casas) Fern. Casas with 30 pg fits with the (ancient) hybrid origin for N. bujei between N. longispathus Pugsley (36 pg) and N. hispanicus Gouan (25.8 pg). The tetraploids with white tepals and yellow corona’s can be obtained by crossing a diploid N. pseudonarcissus with the hexaploid and bicolored N. pseudonarcissus ssp. bicolor (L.) Baker.
A unique combination of chloroplast and ploidy chimeras is found in some Hosta Tratt. (Hostaceae) cultivars. The absence of endopolyploidy in the above—ground parts made it possible to study the fate ...of the apical or germ layers in all organs. Moreover, we would like to address the question of the number of apical cell layers in Hosta also to explain breeding results. Nuclear DNA content in twelve different organs of Hosta was determined by flow cytometric analysis of four chimeric cultivars with a 4-2-2 or 2-2-4 composition. The margin of the leaf, derived from the L1, can be determined separately and has a 4C amount of DNA in 4-2-2 ploidy chimeras but a 2C amount of DNA in 2-2-4 chimeras. The presence of three layers in Hosta was deduced from comparisons of the percentage of 4C nuclei in (2)-2-4 and (4)-2-2 chimeras. If Hosta organs derive only from two layers the percentage of 4C cells in the different ploidy chimeras should add up to 100%, but they do not. The absence of nuclei with a 2C amount of DNA in the roots of 2-2-4 plants shows that only the L3 participates in adventitious root formation. Gametes and consequently seedlings are mainly derived from the L2. The often found correlation between the color of the centre of the leaf and the color of the seedlings is the consequence of the way these cultivars originate. The presence of three apical layers is visualized in the tricolored leaves of Hosta cultivars like 'Striptease'. The nuclear DNA amounts show unequivocally, that in all the above ground parts of Hosta the three apical layers L1, L2 and L3 are present. However, only the L3 participates in adventitious root formation.
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