Diploid Cytotypes Research Articles

Ploidy-Dependent Effects of Light Stress on the Mode of Reproduction in the Ranunculus auricomus Complex (Ranunculaceae).

Polyploidy in angiosperms is an influential factor to trigger apomixis, the reproduction of asexual seeds. Apomixis is usually facultative, which means that both sexual and apomictic seeds can be formed by the same plant. Environmental abiotic stress, e.g. light stress, can change the frequency of apomixis. Previous work suggested effects of stress treatments on meiosis and megasporogenesis. We hypothesized that polyploidy would alter the stress response and hence reproductive phenotypes of different cytotypes. The main aims of this research were to explore with prolonged photoperiods, whether polyploidy alters proportions of sexual ovule and sexual seed formation under light stress conditions. We used three facultative apomictic, pseudogamous cytotypes of the Ranunculus auricomus complex (diploid, tetraploid, and hexaploid). Stress treatments were applied by extended light periods (16.5 h) and control (10 h) in climate growth chambers. Proportions of apomeiotic vs. meiotic development in the ovule were evaluated with clearing methods, and mode of seed formation was examined by single seed flow cytometric seed screening (ssFCSS). We further studied pollen stainability to understand effects of pollen quality on seed formation. Results revealed that under extended photoperiod, all cytotypes produced significantly more sexual ovules than in the control, with strongest effects on diploids. The stress treatment affected neither the frequency of seed set nor the proportion of sexual seeds nor pollen quality. Successful seed formation appears to be dependent on balanced maternal: paternal genome contributions. Diploid cytotypes had mostly sexual seed formation, while polyploid cytotypes formed predominantly apomictic seeds. Pollen quality was in hexaploids better than in diploids and tetraploids. These findings confirm our hypothesis that megasporogenesis is triggered by light stress treatments. Comparisons of cytotypes support the hypothesis that ovule development in polyploid plants is less sensitive to prolonged photoperiods and responds to a lesser extent with sexual ovule formation. Polyploids may better buffer environmental stress, which releases the potential for aposporous ovule development from somatic cells, and may facilitate the establishment of apomictic seed formation.

Epigenetic consequences of interploidal hybridisation in synthetic and natural interspecific potato hybrids.

Interploidal hybridisation can generate changes in plant chromosome numbers, which might exert effects additional to the expected due to genome merger per se (that is genetic, epigenetic and phenotypic novelties). Wild potatoes are suitable to address this question in an evolutionary context. To this end, we performed genetic (AFLP and single sequence repeart (SSR)), epigenetic (MSAP), and cytological comparisons in: (1) natural populations of the diploid cytotype of the hybrid taxonomic species Solanum×rechei (2n=2×, 3×) and its parental species, the triploid cytotype of Solanum microdontum (2n=2×, 3×) and Solanum kurtzianum (2n=2×); and (2) newly synthesised intraploidal (2××2×) and interploidal (3××2×) S.microdontum×S.kurtzianum hybrids. Aneuploidy was detected in S.×rechei and the synthetic interploidal progeny; this phenomenon might have originated the significantly higher number of methylation changes observed in the interploidal vs the intraploidal hybrids. The wide epigenetic variability induced by interploidal hybridisation is consistent with the novel epigenetic pattern established in S.×rechei compared to its parental species in nature. These results suggest that aneuploid potato lineages can persist throughout the short term, and possibly medium term, and that differences in parental ploidy resulting in aneuploidy are an additional source of epigenetic variation.

Autopolyploid lineage shows climatic niche expansion but not divergence in Arabidopsis arenosa.

Successful establishment of neopolyploids, and therefore polyploid speciation, is thought to be contingent on environmental niche shifts from their progenitors. We explore this niche shift hypothesis in the obligate outcrosser Arabidopsis arenosa complex, which includes diploid and recently formed autotetraploid populations. To characterize the climatic niches for both cytotypes in Arabidopsis arenosa, we first gathered climatic data from localities with known ploidy types. We then estimated the climatic niches for diploids and autotetraploids and calculated niche overlap. Using this niche overlap statistic, we tested for niche equivalency and similarity. We explored differences in niches by estimating and comparing niche optimum and breadth and then calculated indices of niche expansion and unfilling. Climatic niche overlap between diploids and autotetraploids is substantial. Although the two niche models are not significantly divergent, they are not identical as they differ in both optimum and breadth along two environmental gradients. Autotetraploids fill nearly the entire niche space of diploids and have expanded into novel environments. We find climatic niche expansion but not divergence, together with a moderate change in the niche optimum, in the autotetraploid lineage of Arabidopsis arenosa. These results indicate that the climatic niche shift hypothesis alone cannot explain the coexistence of tetraploid and diploid cytotypes.

Chromosomal variability in Brazilian species of Anthurium Schott (Araceae): Heterochromatin, polyploidy, and B chromosomes.

The genus Anthurium has a Neotropical distribution, with karyotype predominance of x = 15, although some species show disploidy or polyploid variations. The karyotypes of seven species and different populations of Anthurium were analyzed using fluorochrome CMA and DAPI staining. The karyotypes were composed of meta- and submetacentric chromosomes, with numbers varying from 2n = 30 to 2n = 60. Supernumerary euchromatic chromosomes were observed in A. affine, and supernumerary heterochromatic chromosomes were observed in A. gladiifolium and A. petrophilum. Polyploidy was recurrent in the Anthurium species analyzed, with records of 2n = 30 and 60 in different A. pentaphyllum populations. Fluorochrome staining revealed different CMA+ banding distributions between diploid and polyploid cytotypes of A. pentaphyllum, suggesting structural alteration events. Anthurium petrophilum, on the other hand, showed a more consistent banding profile, with 10 to 12 proximal CMA bands in the three populations analyzed. DAPI+/CMA0 regions occurred exclusively in populations of A. gracile and A. pentaphyllum. The heterochromatic fraction in Anthurium was found to be quantitatively variable among species and populations, which may be related with adaptive aspects, different environmental conditions, or phylogenetic position.

New wild diploids in Paspalum notatum Flügge (Poaceae): potential accessions for use in breeding.

Abstract Paspalum notatum is a polymorphic species with two accepted varieties, according to the ploidy level. The ploidy level is closely related to the reproductive mode of this species. Usually, diploid cytotypes have sexual reproduction, and tetraploid cytotypes have an apomictic reproduction. Apomixis limits genetic recombination, hindering the development of new cultivars. The identification of sexual plants represents many possibilities in breeding programs. This study aimed to analyze the chromosome number in P. notatum accessions under agronomic evaluation. Ploidy level was determined in 25 accessions. Two ploidy levels were detected, resulting in 21 tetraploid and four diploid accessions. The four diploid accessions originate from Argentina and Uruguay, in a region close to the origin of Pensacola, which is a diploid sexual cultivar of P. notatum. These new diploid accessions may be useful in the development of breeding programs of Paspalum species.

Euchromatic Supernumerary Chromosomal Segments-Remnants of Ongoing Karyotype Restructuring in the Prospero autumnale Complex?

Supernumerary chromosomal segments (SCSs) represent additional chromosomal material that, unlike B chromosomes, is attached to the standard chromosome complement. The Prospero autumnale complex (Hyacinthaceae) is polymorphic for euchromatic large terminal SCSs located on the short arm of chromosome 1 in diploid cytotypes AA and B7B7, and tetraploid AAB7B7 and B6B6B7B7, in addition to on the short arm of chromosome 4 in polyploid B7B7B7B7 and B7B7B7B7B7B7 cytotypes. The genomic composition and evolutionary relationships among these SCSs have been assessed using fluorescence in situ hybridisation (FISH) with 5S and 35S ribosomal DNAs (rDNAs), satellite DNA PaB6, and a vertebrate-type telomeric repeat TTAGGG. Neither of the rDNA repeats were detected in SCSs, but most contained PaB6 and telomeric repeats, although these never spanned whole SCSs. Genomic in situ hybridisation (GISH) using A, B6, and B7 diploid genomic parental DNAs as probes revealed the consistently higher genomic affinity of SCSs in diploid hybrid B6B7 and allopolyploids AAB7B7 and B6B6B7B7 to genomic DNA of the B7 diploid cytotype. GISH results suggest a possible early origin of SCSs, especially that on chromosome 1, as by-products of the extensive genome restructuring within a putative ancestral P. autumnale B7 genome, predating the complex diversification at the diploid level and perhaps linked to B-chromosome evolution.

Male Meiosis and Chromosomal Status in the Genus <i>Lactuca</i> L. from Western Himalayas (India)

Chromosome counts including analyses of male meiosis and pollen fertility have been made on 36 accessions of 10 Lactuca species collected from the western Himalayas. L. orientalis (2n=18) and L. undulata (2n=18) have been counted chromosomally for the first time from India and the counts in other species confirmed previous counts. The study also adds the existence of intraspecific diploid cytotype for L. orientalis. B-chromosomes have been reported for the first time in the accession of L. hastata. Cytomixis has been detected in some accessions of L. dolicophylla, L. macrorhiza and L. scariola. Consequent to cytomixis, the accessions were depicted some pollen sterility. Based on compiled chromosomal information it is apparent that dysploidy in conjugation with polyploidy seems to play an important role in the evolution of genus the Lactuca seems to be polybasic (x=5, 8, 9, 17), and x=8 and x=9 seem to be the most common and favored base numbers.

Multiple Origins and Nested Cycles of Hybridization Result in High Tetraploid Diversity in the Monocot Prospero.

Polyploidy is a major driving force in angiosperm evolution, but our understanding of establishment and early diversification processes following allo- vs. auto-polyploidy is limited. An excellent system to address such questions is the monocot plant Prospero autumnale, as it comprises several genomically and chromosomally distinct diploid cytotypes and their auto- and allotetraploid derivatives. To infer origins and evolutionary trajectories of the tetraploids, we use genome size data, in situ hybridization with parental genomic DNAs and specific probes (satDNA, rDNAs), as well as molecular-phylogenetic analyses. Thus, we demonstrate that an astounding range of allotetraploid lineages has been formed recurrently by chromosomal re-patterning, interactions of chromosomally variable parental genomes and nested cycles of extensive hybridization, whereas autotetraploids have originated at least twice and are cytologically stable. During the recurrent formation and establishment across wide geographic areas hybridization in some populations could have inhibited lineage diversification and nascent speciation of such a hybrid swarm. However, cytotypes that became fixed in populations enhanced the potential for species diversification, possibly exploiting the extended allelic base, and fixed heterozygosity that polyploidy confers. The time required for polyploid cytotype fixation may in part reflect the lag phase reported for polyploids between their formation and species diversification.

B chromosomes and fertility in a native population of Hymenachne amplexicaulis (Poaceae: Panicoideae: Paspaleae)

Fertility is a measure of reproductive success, defined as the capacity of an individual to reproduce and generate offspring, and has been identified as an important trait correlating to the invasive ability of a species. Hymenachne amplexicaulis (Rudge) Nees is a grass native to South America of high bromatological quality, making it a species with good forage potential. In the places where it was introduced it is now considered an invasive weed due to its dominance over native vegetation. In this work, individuals of H. amplexicaulis were analyzed from a native population in its southernmost native range, situated on Yacyretá reservoir dam. All individuals show a diploid cytotype with two B chromosomes (2n = 2x = 20 + 2B). This is the first chromosome count recording B chromosomes for the genus, and a new cytotype for the species. The karyotype was found to be symmetrical and unimodal, composed by 20 metacentric chromosomes and two small B chromosomes. Pollen viability was tested at 90.6%, seed set production of population reaches 18.65%, and the viable seeds presented a germination power of 41%. The reproductive performance is less than expected with respect to the mean amount of spikelets that a single inflorescence possesses and notwithstanding optimal conditions of supply and availability of viable pollen for fecundation. Germination test indicate good seed quality and viability in native range. In H. amplexicaulis effective fertility is lower than its potential fertility, but it is not an indicator of absence of invasive threat. Reproductive performance of B host plants indicates sufficient invasive potential.

Differential content of secondary metabolites in diploid and tetraploid cytotypes of Siegesbeckia orientalis L.

Siegesbeckia orientalis L. is an annual herb widely distributed throughout the world and has many medicinal properties. In Chinese traditional system, it is popularly known as Xi-Xian and used for its anti-inflammatory properties. In the present study, two cytotypes (diploid and tetraploid) have been investigated for their secondary metabolites. The different plant parts have been explored in terms of total phenolics, total flavonoids, DPPH radical scavenging acitivity and total antioxidant capacity. Out of different plant parts, leaves have the maximum amount of secondary metabolites and antioxidant potential. HPTLC technique has been applied to quantify six marker compounds in the two cytotypes. Tetraploid cytotype has been compared with diploid cytotype, which shows that tetraploid has the maximum amount of studied secondary metabolites with high antioxidant potential.

ELEMENTAL ANALYSIS AND BIOLOGICAL STUDIES OF PHYSALIS ANGULATA L. USING WAVE LENGTH-DISPERSIVE X-RAY FLUORESCENCE TECHNIQUE, WAVELENGTH DISPERSION X-RAY FLUORESCENCE, FROM RAJASTHAN

Physalis angulata L. is an important medicinal plant, commonly known by different names such as mullaca, wintercherry, camapu, cutleaf, andreferred as “pilu,” by local tribal people of Rajasthan. This plant species is distributed from temperate to tropical region of the world. Traditionally, ithas anticancerous, antimycobacterial, and anticoagulant properties. The juice is used in the treatment of earache, jaundice, fever, gonorrhea bladderdiseases, etc., cytological exploration of the species from Rajasthan revels the existence of two cytotypes diploid (2n=12) and tetraploid (2n=24). Thisstudy is undertaken to identify the total mineral content of both the cytotypes from different plant parts, i.e., fruit, leaf, stem, and roots by wavelength dispersion X-ray fluorescence technique which is a simple method, recognized as a nondestructive technique to determine the elements from the raw plant material without any chemical treatment and helps to ascertain the nutritional role. The analysis of mineral content led to the identification and concentration analysis of twenty-seven elements in diploid cytotype and twenty-five in tetraploid cytotype. The percentage value of potassium (5.52%); iron (0.50%) and selenium (0.0042%) is reported to be higher in diploid cytotype and the amount of calcium (2.15%); magnesium (0.75%) and zinc (0.0075%) are higher in tetraploid cytotype. The amount of most of the minerals is higher in tetraploid cytotype as compared to the diploid cytotype. This information is very helpful in standardization of herbal products as this plant species is widely used for its medicinal benefits.

Cytomorphological variations and new reports of B-chromosomes in the genus Plantago (Plantaginaceae) from the Northwest Himalaya

The genus Plantago is known with more than 200 species, used extensively all over the world as a promising source of functional foods and for various remedies. The present cytological study covers 24 populations of 5 species of the genus Plantago and intraspecific cytomorphological diversity in P. depressa from the Northwest Himalaya. Out of these, P. himalaica (n=12) is a first euploid report for the world. The B-chromosomes have been reported for the first time in 3 species, P. lanceolata (n=6+0−1B), P. major (n=6+0−1B), and diploid (n=6+0−1B) and tetraploid (n=12+0−1B) cytotypes of P. depressa. Beside this, intraspecific cytomorphological variations are also reported in P. depressa with three different cytotypes (2x, 4x, 6x). The detailed meiotic course of all the populations reveals the meiotic anomalies in the form of cytomixis, un-oriented bivalents, chromosome stickiness, laggards and chromatin bridges. The effect of these abnormalities on size and viability of the pollen grains is also discussed. The presence of B-chromosomes is found to be related with the reduction in the meiotic anomalies. Dendrogram constructed for the quantitative morphological features between the three intraspecific cytotypes of P. depressa, depicts the close relationship of diploid cytotype to the tetraploid one, rather than the hexaploid populations.

English

Lygeum spartum represents a natural barrier in the Algerian high plateaus against the advance of sand and the desertification. The plant is of interest due to its tolerance to environmental stress. There are two levels of ploidy in this species; the diploid cytotype 2n = 16 which is confined in the locality of Ain Benkhllil and the polyploid cytotype 2n = 40 which thrives in semi-arid climates and has a large ecologic plasticity. The The aim of this study was the evaluation of the phenolic compounds and flavonoids in both cytotypes. The antioxidant activity was also measured with results showing differences in the level of phenolic compounds; thus, these compounds could serve as biomarkers to distinguish the two cytotypes. Key words: Lygeum spartum L, total phenols, flavonoids, 2,2-diphenylpicrylhydrazyl (DPPH), lipid peroxidation.

No confirmation for previously suggested presence of diploid cytotypes of Sesleria (Poaceae) on the Balkan Peninsula

AbstractThe species-rich grass genus

Cytomorphological diversity of Ageratum Species from North-West India.

Ageratum belongs to tribe Eupatoriae of family Asteraceae. In the present study floristic forays revealed the prevalence of two species of the genus in North India namely, A. conyzoides and A. houstonianum. Two morphovariants were observed in both the species. The plants were found to differ on the basis of leaf shape and flower colour. Further, analysis of male meiosis revealed the presence of three cytotypes of A. conyzoides and two cytotypes of A. houstonianum. The specimens of A. conyzoides with purple flowers were found to have chromosome count of n=10 (diploid cytotype, 2x) and rarely plants with chromosome count of 2n=30 (triploid cytotype, 3x) were also observed. This is the first report of 3x plants of A. conyzoides from wild. The white flowered plants were found to be tetraploid with n=20. In the specimens of A. houstonianum, the diploid number n=10 was found in white flowered plants while tetraploid number n=20 was found in purple flowered plants. The meiotic course varies from normal to abnormal in some populations of both the species.

Diploid Ruppia cirrhosa populations from a southern Mediterranean shallow system

This paper focuses on the morphology and karyology of representative Ruppia populations from a southern Mediterranean shallow system. The cosmopolitan genus Ruppia L. generally inhabits shallow waters such as coastal lagoons and brackish habitats. Ruppia species are characterised by a simplified morphology and high intraspecific phenotypic plasticity. The chromosome number of Sicilian Ruppia populations is reported here for the first time. The analysed populations showed morphological and reproductive characters of Ruppia cirrhosa (Petagna) Grande but a diploid cytotype (2n=20). A low fruit production was also observed, suggesting that vegetative reproduction is the main reproductive strategy adopted by the plant. This study did not resolve conclusively the taxonomic identity of these Ruppia populations and it also raises some open questions, needing further investigations.

CMA band variability and physical mapping of 5S and 45S rDNA sites in Brazilian Cactaceae: Pereskioideae and Opuntioideae

Representatives of the Cactaceae subfamilies Pereskioideae and Opuntioideae from northeastern Brazil were studied using banding with the fluorochromes, CMA3 and DAPI, as well as with fluorescent in situ hybridization using 45S and 5S rDNA probes to identify the distributions of their heterochromatin and rDNA sites. Pereskia aculeata, P. bahiensis, P. grandifolia (Pereskioideae), Brasilopuntia brasiliensis, Tacinga funalis, and T. palmadora showed 2n = 22, while Opuntia dillenii showed 2n = 44, and O. ficus-indica 2n = 88. The karyotypes of all of the species were symmetric, with average chromosome lengths varying from 1.94 µm in O. dillenii to 3.17 µm in P. aculeata. One pair of terminal CMA+ bands corresponding to NORs occurred in all of the diploid cytotypes (except O. ficus-indica, which has two pairs of terminal CMA+ bands) as well as in O. dillenii (tetraploid). CMA+ bands were also observed in the interstitial region of the long arm of a chromosome pair in B. brasiliensis, while a number of variable proximal bands were observed on three chromosome pairs in O. dillenii and on most of the chromosomes of O. ficus-indica. The 45S rDNA sites corresponded to the terminal CMA+ bands, while the 5S rDNA sites were located in the interstitial regions of the long arms of the chromosome pairs of P. aculeata, P. bahiensis, P. grandifolia, and B. brasiliensis. Our data, and earlier publications, suggest that the subfamily Opuntioideae can be characterized as having proximal/interstitial CMA+ heterochromatin in at least one chromosome pair (except in Tacinga). The absence of proximal heterochromatic bands, however, appears to be a synapomorphy of the basal lineages of Cactaceae (subfamily Pereskioideae + Maihuenioideae), suggesting that karyotypes with heterochromatin restricted to the terminal region of a chromosome pair (45S rDNA) represent a plesiomorphic character of the family.

Karyotype studies on eight populations ofPlantago albicansL. from Algeria

AbstractA karyological study of eight populations of Plantago albicans L. (Plantaginaceae) collected from the central high-plain steppe in the province of Djelfa in Algeria was undertaken for the first time. Chromosome numbers were determined as 2n = 2x = 10 for populations growing at medium altitudes (600–900 m) and 2n = 4x = 20 for those growing at higher altitudes (1000–1300 m) of arid bioclimates. Intermediate chromosome numbers 2n = 6, 8, 9, 12, 14, 15, 17 and 18 were found in individuals of the studied populations and were probably aneuploid forms. The analysis of the karyotype asymmetry indices showed that the diploid cytotype (2n = 2x = 10) is characterized by ancestral chromosomes that are symmetrical, large and homogeneous, while the tetraploid cytotype (2n = 4x = 20) is more evolved with asymmetric, small and heterogeneous chromosomes. Based on our findings, it can be suggested that environmental factors and geographical location might have an effect on the genetic structure and evolution of P....

Structural polymorphisms and distinct genomic composition suggest recurrent origin and ongoing evolution of B chromosomes in the Prospero autumnale complex (Hyacinthaceae).

Summary Supernumerary B chromosomes (Bs) are genomic parasitic components, originating from the A complement via chromosomal rearrangements, which follow their own evolutionary trajectories. They often contain repetitive DNAs, some shared with regular chromosomes and some newly evolved. Genomic composition, origin and evolution of Bs have been analysed in the chromosomally variable Prospero autumnale complex.Two rDNAs and a satellite DNA (PaB6) from regular chromosomes were mapped to Bs of 26 plants from three diploid cytotypes, their hybrids and polyploid derivatives. In homoploid diploid hybrids, genomic in situ hybridization (GISH) allowed B painting with the parental DNAs.Bs were structurally variable and highly enriched in 5S rDNA and satDNA PaB6, and rarely in 35S rDNA. Eleven combinations of rDNA and PaB6 localization were observed. The quantities of PaB6 in Bs and regular chromosomes were not correlated, suggesting amplification mechanisms other than recombination. PaB6 and 5S rDNA amounts increased with increasing ploidy level. GISH revealed two independent origins of Bs.The structural variation, repeat content, repeat‐type fluctuations and differing genomic affinities of Bs in different cytotypes suggest that they represent young proto‐B chromosomes. Bs in P. autumnale probably form recurrently as by‐products of the extensive genome restructuring within this chromosomally variable species complex.

Identification of new cytotypes of Valeriana jatamansi Jones, 1970 (Valerianaceae) from North-Western Himalayan region of India.

Valeriana jatamansi, a medicinally important species of the family Valerianaceae, has been cytologically studied in different geographical areas of North-Western Himalayan region of India. The tetraploid cytotype with chromosome numbers 2n=32 is in conformity with the earlier reports of the species from different parts of the world. An octoploid cytotype (2n=64) makes a new addition for the species on a worldwide basis, whereas the diploid cytotype (2n=16) is new to India have been reported for the first time in India. These cytotypes (2n=16, 32, 64) show significant variations with respect to morphology as well as geographical distribution in the Western Indian Himalayas. Further, anomalous populations have been marked with meiotic abnormalities in the form of cytomixis, chromosomal stickiness, unoriented bivalents, formation of laggards and bridges resulting in abnormal microsporogenesis, and production of heterogeneous-sized fertile pollen grains along with reduced pollen fertility.