Genome Size Variation in Sesamum indicum L. Germplasm from Niger.

Sesamum indicum L. (Pedaliaceae) is one of the most economically important oil crops in the world, thanks to the high oil content of its seeds and its nutritional value. It is cultivated all over the world, mainly in Asia and Africa. Well adapted to arid environments, sesame offers a good opportunity as an alternative subsistence crop for farmers in Africa, particularly Niger, to cope with climate change. For the first time, the variation in genome size among 75 accessions of the Nigerien germplasm was studied. The sample was collected throughout Niger, revealing various morphological, biochemical and phenological traits. For comparison, an additional accession from Thailand was evaluated as an available Asian representative. In the Niger sample, the 2C DNA value ranged from 0.77 to 1 pg (753 to 978 Mbp), with an average of 0.85 ± 0.037 pg (831 Mbp). Statistical analysis showed a significant difference in 2C DNA values among 58 pairs of Niger accessions (p-value < 0.05). This significant variation indicates the likely genetic diversity of sesame germplasm, offering valuable insights into its possible potential for climate-resilient agriculture. Our results therefore raise a fundamental question: is intraspecific variability in the genome size of Nigerien sesame correlated with specific morphological and physiological traits?

The global distribution of angiosperm genome size is shaped by climate.

Angiosperms, which inhabit diverse environments across all continents, exhibit significant variation in genome sizes, making them an excellent model system for examining hypotheses about the global distribution of genome size. These include the previously proposed large genome constraint, mutational hazard, polyploidy-mediated, and climate-mediated hypotheses. We compiled the largest genome size dataset to date, encompassing 16 017 (> 5% of known) angiosperm species, and analyzed genome size distribution using a comprehensive geographic distribution dataset for all angiosperms. We observed that angiosperms with large range sizes generally had small genomes, supporting the large genome constraint hypothesis. Climate was shown to exert a strong influence on genome size distribution along the global latitudinal gradient, while the frequency of polyploidy and the type of growth form had negligible effects. In contrast to the unimodal patterns along the global latitudinal gradient shown by plant size traits and polyploid proportions, the increase in angiosperm genome size from the equator to 40-50°N/S is probably mediated by different (mostly climatic) mechanisms than the decrease in genome sizes observed from 40 to 50°N northward. Our analysis suggests that the global distribution of genome sizes in angiosperms is mainly shaped by climatically mediated purifying selection, genetic drift, relaxed selection, and environmental filtering.

Taxonomy and distribution of Taraxacum sect. Erythrosperma (Asteraceae) in Poland.

The dandelions from Taraxacumsect.Erythrosperma are taxonomically well distinguished and ecologically restricted to warm and sunlit habitats of steppes, dry and sandy grasslands, and distributed in temperate regions of Europe and Central Asia, with some being introduced to North America. Despite the long tradition of botanical research, the taxonomy and distribution of dandelions of T.sect.Erythrosperma is still underexplored in central Europe. In this paper, by combining traditional taxonomic studies supported by micromorphological, molecular and flow cytometry analyses as well as potential distribution modelling we shed light on taxonomical and phylogenetical relationships between members of T.sect.Erythrosperma in Poland. We also provide an identification key, species-checklist, detailed descriptions of morphology and occupated habitats as well as distribution maps for 14 Polish erythrosperms (T.bellicum, T.brachyglossum, T.cristatum, T.danubium, T.disseminatum, T.dissimile, T.lacistophyllum, T.parnassicum, T.plumbeum, T.proximum, T.sandomiriense, T.scanicum, T.tenuilobum, T.tortilobum). Finally, conservation assessments performed using the IUCN method and threat categories for all the examined species are proposed.

Genome size, chromosome number variation and its correlation with stomatal characters for assessment of ploidy levels in a core subset of mulberry (Morus spp.) germplasm.

The large size of the germplasm collection along with scanty information on their cytological and genome constitution have hindered well-planned breeding schemes in mulberry. To address the issue, a study was undertaken to investigate the variability in DNA content and genome size, chromosome number, ploidy and its relation with important stomatal characteristics among 162 mulberry germplasm collection. These germplasm comprise a core subset of 150 collections along with a representative collection of different mulberry species including the wild. Among the germplasm belonging to 16 species, we identified 122 diploids (2n = 28), 4 aneuploids (2n = 30), 13 triploids (2n = 42), 15 tetraploids (2n = 56), 7 hexaploids (2n = 84) and 1 dodecosaploid (2n = 308) based on the chromosome count. Most of the cultivated mulberries are found to be diploids. The mean nuclear 2C DNA content estimated by Flow cytometry, varied from 0.723 ± 0.006 pg (M. australis, 2n = 2x) to 7.732 pg (M. nigra, 2n = 22x). The 2C DNA content positively correlated with the ploidy status and stomatal length (r = 0.814, p < 0.001). Based on the 1Cx value, the study also suggests that the majority of the polyploid species have experienced genome downsizing in relation to their diploid progenitors. This study provides the most essential information on chromosome number, ploidy and DNA content to facilitate the utilization of a core subset of germplasm in the mulberry breeding program.

Ploidy Status, Nuclear DNA Content and Start Codon Targeted (SCoT) Genetic Homogeneity Assessment in Digitalis purpurea L., Regenerated In Vitro.

Digitalis purpurea L. is a therapeutically important plant that synthesizes important cardiotonics such as digitoxin and digoxin. The present work reports a detailed and efficient propagation protocol for D. purpurea by optimizing various PGR concentrations in Murashige and Skoog (MS) medium. The genetic homogeneity of in vitro regenerants was assessed by the flow cytometric method (FCM) and Start Codon Targeted (SCoT) marker technique. Firstly, the seeds inoculated in full MS medium added with 0.5 mg/L GA3 produced seedlings. Different parts such as hypocotyl, nodes, leaves and apical shoots were used as explants. The compact calli were obtained on BAP alone or in combinations with 2, 4-D/NAA. The hypocotyl-derived callus induced somatic embryos which proliferated and germinated best in 0.75 mg/L BAP-fortified MS medium. Scanning electron microscopic (SEM) images confirmed the presence of various developmental stages of somatic embryos. Shoot regeneration was obtained in which BAP at 1.0 mg/L and 2.0 mg/L BAP + 0.5 mg/L 2,4-D proved to be the best treatments of PGRs in inducing direct and indirect shoot buds. The regenerated shoots showed the highest rooting percentage (87.5%) with 24.7 ± 1.9 numbers of roots/shoot in 1.0 mg/L IBA augmented medium. The rooted plantlets were acclimatized in a greenhouse at a survival rate of 85-90%. The genome size and the 2C nuclear DNA content of field-grown, somatic embryo-regenerated and organogenic-derived plants were estimated and noted to be 3.1, 3.2 and 3.0 picogram (pg), respectively; there is no alteration in ploidy status and the DNA content, validating genetic uniformity. Six SCoT primers unveiled 94.3%-95.13% monomorphic bands across all the plant samples analyzed, further indicating genetic stability among in vitro clones and mother plants. This study describes for the first time successful induction of somatic embryos from hypocotyl callus; and flow cytometry and SCoT marker confirmed the genetic homogeneity of regenerated plants.

Estimation of Nuclear DNA Content in Some Aegilops Species: Best Analyzed Using Flow Cytometry.

The genera Triticum and Aegilops have been considered as the main gene pool of wheat due to their features, such as tolerance of all types of abiotic and biotic stresses. This study was conducted to evaluate the cytogenetic analyses in 115 native and wild populations from eleven Aegilops species using their nuclear DNA quantification. Mean 2C nuclear DNA contents of different ploidy levels in the wild wheat of Turkey and Iran were measured using the flow cytometry technique. The obtained results showed that the mean nuclear DNA content in diploid species varied from 10.09 pg/2C (Ae. umbellulata) to 10.95 pg/2C (Ae. speltoides var. ligustica) in Turkey. In Iranian diploids, the mean nuclear DNA content varied from 10.20 pg/2C (Ae. taushii) to 11.56 pg/2C (Ae. speltoides var. ligustica). This index in the tetraploid species of Turkey varied from 18.09 pg/2C (Ae. cylindrica) to 21.65 pg/2C (Ae. triaristata), and in Iranian species, it was from 18.61 pg/2C (Ae. cylindrica) to 21.75 pg/2C (Ae. columnaris). On the other hand, in the hexaploid species of Turkey, this index varied from 31.59 pg/2C (Ae. crassa) to 31.81 pg/2C (Ae. cylindrica); in the Iranian species, it varied from 32.58 pg/2C (Ae. cylindrica) to 33.97 pg/2C (Ae. crassa). There was a significant difference in the DNA content of Turkey and Iran diploid as well as tetraploid species; however, in hexaploid species, the difference was not significant. It was concluded that the variation in intraspecific genome size was very low in diploid and tetraploid populations; this means that the low variation is not dependent on geographic and climatic parameters. On the other hand, the interspecific variation is significant at the diploid and tetraploid populations. It is generally very difficult to distinguish Aegilops species from each other in natural conditions; meanwhile, in this study, all species could be, easily, quickly and unambiguously, distinguished and separated using the FCM technique.

Combining genome size and pollen morphology data to study species relationships in the genus Daucus (Apiaceae).

BACKGROUND: The genus Daucus (Apiaceae) comprises about 40 wild species and the cultivated carrot, a crop of great economic and nutritional importance. The rich genetic diversity of wild Daucus species makes them a valuable gene pool for carrot improvement breeding programs. Therefore, it is essential to have good knowledge of the genome structure and relationships among wild Daucus species. To broaden such knowledge, in this research, the nuclear DNA content for 14 Daucus accessions and four closely related species was estimated by flow cytometry and their pollen morphology was analyzed by light and scanning electron microscopy (SEM). RESULTS: The flow cytometric analysis showed a 3.2-fold variation in the mean 2C values among Daucus taxa, ranging from 0.999 (D. carota subsp. sativus) to 3.228 pg (D. littoralis). Among the outgroup species, the mean 2C values were 1.775-2.882 pg. The pollen grains of Daucus were tricolporate, mainly prolate or perprolate (rarely) in shape, and mainly medium or small (rarely) in size (21.19-40.38 µm), whereas the outgroup species had tricolporate, perprolate-shaped, and medium-sized (26.01-49.86 µm) pollen grains. In the studied taxa, SEM analysis revealed that exine ornamentation was striate, rugulate, perforate, or the ornamentation pattern was mixed. At the time of shedding, all pollen grains were three-celled, as evidenced by DAPI staining. We also found high positive correlations between the length of the polar axis (P) and the length of the equatorial diameter (E) of pollen grains, as well as between P and P/E. However, when comparing cytogenetic information with palynological data, no significant correlations were observed. CONCLUSIONS: This study complements the information on the nuclear DNA content in Daucus and provides comprehensive knowledge of the pollen morphology of its taxa. These findings may be important in elucidating the taxonomic relationships among Daucus species and can help in the correct identification of gene bank accessions. In a broader view, they could also be meaningful for the interpretation of evolutionary trends in the genus.

Biotechnology of the Tree Fern Cyathea smithii (J.D. Hooker; Soft Tree Fern, Katote) II Cell Suspension Culture: Focusing on Structure and Physiology in the Presence of 2,4-D and BAP.

The aim of our research was to describe the structure and growth potential of a cell suspension of the tree fern Cyathea smithii. Experiments were performed on an established cell suspension with ½ MS medium supplemented with 9.05 µM 2,4-D + 0.88 µM BAP. In the experiments, attention was paid to the microscopic description of cell suspension, evaluation of cell growth dependent on the initial mass of cells and organic carbon source in the medium, the length of the passage, the content of one selected flavonoid in the post-culture medium, nuclear DNA content, ethylene production, and the antimicrobial value of the extract. For a better understanding of the cell changes that occurred during the culture of the suspension, the following structures of the cell were observed: nucleus, lipid bodies, tannin deposits, starch grains, cell walls, primary lamina, and the filaments of metabolites released into the medium. The nuclear DNA content (acriflavine-Feulgen staining) of cell aggregates distinctly indicated a lack of changes in the sporophytic origin of the cultured cell suspension. The physiological activity of the suspension was found to be high because of kinetics, intensive production of ethylene, and quercetin production. The microbiological studies suggested that the cell suspension possessed a bactericidal character against microaerobic Gram-positive bacteria. A sample of the cell suspension showed bacteriostatic activity against aerobic bacteria.

Chromosome Number and Genome Size Evolution in Brasolia and Sobralia (Sobralieae, Orchidaceae).

Despite the clear circumscription of tribe Sobralieae (Orchidaceae), its internal relationships are still dubious. The recently delimited genus Brasolia, based on previous Sobralia species, is now assumed to be paraphyletic, with a third genus, Elleanthus, nested in it. The morphology of these three genera is significantly different, indicating the necessity of new data for a better genera delimitation. Though morphology and molecular data are available, cytogenetics data for Sobralieae is restricted to two Sobralia and one Elleanthus species. Aiming to evaluate the potential of cytogenetic data for Brasolia-Elleanthus-Sobralia genera delimitation, we present chromosome number and genome size data for 21 and 20 species, respectively, and used such data to infer the pattern of karyotype evolution in these genera. The analysis allowed us to infer x = 24 as the base chromosome number and genome size of average 1C-value of 5.0 pg for the common ancestor of Brasolia-Elleanthus-Sobralia. The recurrent descending dysploidy in Sobralieae and the punctual genome upsize suggest a recent diversification in Sobralieae but did not allow differing between Brasolia and Sobralia. However, the basal position of tribe Sobralieae in the subfamily Epidendroideae makes this tribe of interest to further studies clarifying the internal delimitation and pattern of karyotype evolution.

Plant material selection, collection, preservation, and storage for nuclear DNA content estimation.

In theory, any plant tissue providing intact nuclei in sufficient quantity is suitable for nuclear DNA content estimation using flow cytometry (FCM). While this certainly opens a wide variety of possible applications of FCM, especially when compared to classical karyological techniques restricted to tissues with active cell division, tissue selection and quality may directly affect the precision (and sometimes even reliability) of FCM measurements. It is usually convenient to first consider the goals of the study to either aim for the highest possible accuracy of estimates (e.g., for inferring genome size, detecting homoploid intraspecific genome size variation, aneuploidy, among others), or to decide that histograms of reasonable resolution provide sufficient information (e.g., ploidy level screening within a single model species). Here, a set of best practices guidelines for selecting the optimal plant tissue for FCM analysis, sampling of material, and material preservation and storage are provided. In addition, factors potentially compromising the quality of FCM estimates of nuclear DNA content and data interpretation are discussed.

Genome Size, Chromosome Number and Morphological Data Reveal Unexpected Infraspecific Variability in Festuca (Poaceae).

Polyploidy has played an important evolutionary role in the genus Festuca (Poaceae), and several ploidy levels (ranging from 2n = 2x = 14 to 2n = 12x = 84) have been detected to date. This study aimed to estimate the genome size and ploidy level of two subspecies belonging to the F. yvesii polyploid complex by flow cytometry and chromosome counting. The phenotypic variation of the cytotypes was also explored, based on herbarium material. The genome size of F. yvesii subsp. lagascae has been estimated for the first time. Nuclear 2C DNA content of F. yvesii subsp. summilusitana ranged from 21.44 to 31.91 pg, while that of F. yvesii subsp. lagascae was from 13.60 to 22.31 pg. We report the highest ploidy level detected for Festuca (2n = 14x = 98) and previously unknown cytotypes. A positive correlation between holoploid genome size and chromosome number counts shown herein was confirmed. The morphometric approach showed a slight trend towards an increase in the size of some organs consistent with the variation in the ploidy level. Differences in characters were usually significant only among the most extreme cytotypes of each subspecies, but, even in this case, the high overlapping ranges prevent their distinction.

Genome Size Covaries More Positively with Propagule Size than Adult Size: New Insights into an Old Problem.

The body size and (or) complexity of organisms is not uniformly related to the amount of genetic material (DNA) contained in each of their cell nuclei ('genome size'). This surprising mismatch between the physical structure of organisms and their underlying genetic information appears to relate to variable accumulation of repetitive DNA sequences, but why this variation has evolved is little understood. Here, I show that genome size correlates more positively with egg size than adult size in crustaceans. I explain this and comparable patterns observed in other kinds of animals and plants as resulting from genome size relating strongly to cell size in most organisms, which should also apply to single-celled eggs and other reproductive propagules with relatively few cells that are pivotal first steps in their lives. However, since body size results from growth in cell size or number or both, it relates to genome size in diverse ways. Relationships between genome size and body size should be especially weak in large organisms whose size relates more to cell multiplication than to cell enlargement, as is generally observed. The ubiquitous single-cell 'bottleneck' of life cycles may affect both genome size and composition, and via both informational (genotypic) and non-informational (nucleotypic) effects, many other properties of multicellular organisms (e.g., rates of growth and metabolism) that have both theoretical and practical significance.

Genome Size Diversity in Rare, Endangered, and Protected Orchids in Poland.

Orchidaceae is one of the largest and the most widespread plant families with many species threatened with extinction. However, only about 1.5% of orchids' genome sizes have been known so far. The aim of this study was to estimate the genome size of 15 species and one infraspecific taxon of endangered and protected orchids growing wild in Poland to assess their variability and develop additional criterion useful in orchid species identification and characterization. Flow cytometric genome size estimation revealed that investigated orchid species possessed intermediate, large, and very large genomes. The smallest 2C DNA content possessed Liparis loeselii (14.15 pg), while the largest Cypripedium calceolus (82.10 pg). It was confirmed that the genome size is characteristic to the subfamily. Additionally, for four species Epipactis albensis, Ophrys insectifera, Orchis mascula, Orchis militaris and one infraspecific taxon, Epipactis purpurata f. chlorophylla the 2C DNA content has been estimated for the first time. Genome size estimation by flow cytometry proved to be a useful auxiliary method for quick orchid species identification and characterization.

Is the evolution of carnivory connected with genome size reduction?

PREMISE: As repeatedly shown, the remarkable variation in the genome size of angiosperms can be shaped by extrinsic selective pressures, including nutrient availability. Carnivory has evolved independently in 10 angiosperm clades, but all carnivorous plants share a common affinity to nutrient-poor habitats. As such, carnivory and genome reduction could be responses to the same environmental pressure. Indeed, the smallest genomes among flowering plants are found in the carnivorous family Lentibulariaceae, where a unique mutation in cytochrome c oxidase (COX) is suspected to promote genome miniaturization. Despite these hypotheses, a phylogenetically informed test of genome size and nutrient availability across carnivorous clades has so far been missing. METHODS: Using linear mixed models, we compared genome sizes of 127 carnivorous plants from 7 diverse angiosperm clades with 1072 of their noncarnivorous relatives. We also tested whether genome size in Lentibulariaceae reflects the presence of the COX mutation. RESULTS: The genome sizes of carnivorous plants do not differ significantly from those of their noncarnivorous relatives. Based on available data, no significant association between the COX mutation and genome miniaturization could be confirmed, not even when considering polyploidy. CONCLUSIONS: Carnivory alone does not seem to significantly affect genome size decrease. Plausibly, it might actually counterbalance the effect of nutrient limitation on genome size evolution. The role of the COX mutation in genome miniaturization needs to be evaluated by analysis of a broader data set because current knowledge of its presence across Lentibulariaceae covers less than 10% of the species diversity in this family.

Evaluation of genome size and quantitative features of the dolipore septum as taxonomic predictors for the Serendipita 'williamsii' species complex.

Despite multiple taxonomic revisions, several uncertainties at the genus and species level remain to be resolved within the Serendipitaceae family (Sebacinales). This volatile classification is attributed to the limited number of available axenic cultures and the scarcity of useful morphological traits. In the current study, we attempted to discover alternative taxonomic markers not relying on DNA sequences to differentiate among the closely related members of our Congolese Serendipita isolate collection and the reference strains S. indica (syn. Piriformospora indica) and S. williamsii (syn. P. williamsii). We demonstrated that nuclear distribution across hyphal cells and genome size (determined by flow cytometry) did not have enough resolving power, but quantitative and qualitative variations in the ultrastructure of the dolipore septa investigated by transmission electron microscopy did provide useful markers. Multivariate analysis revealed that subtle differences in ultrastructural characteristics of the parenthesome and the attached endoplasmic reticulum are most relevant when studying this fungal group. Moreover, the observed clustering pattern showed that there might be more diversity amongst the Congolese isolates within the S. 'williamsii' species complex than previously anticipated based on molecular data. Altogether, our results provide novel perspectives on the use of integrative approaches to support sebacinoid and Serendipitaceae taxonomy.

Cytogenetic and pollen identification of genus Gagnepainia (Zingiberaceae) in Thailand.

Gagnepainia godefroyi K. Schumann, 1904 and G. harmandii K. Schumann, 1904 belong to the genus Gagnepainia K. Schumann, 1904 of the Ginger family. They have the potential to be developed as medicinal and attractive ornamental plants. To date, the knowledge on the cytological and reproductive aspects of Gagnepainia have not been publicly available. Therefore, the aims of this research are to investigate the cytogenetic and pollen characters of Gagnepainia species using light, fluorescence, and scanning electron microscopes. The regular meiotic figures of 15 bivalents are found in both species and presented for the first time. These evidences indicate that Gagnepainia is diploid and contains 2n = 2x = 30 with basic number of x = 15. The mean nuclear DNA contents range from 1.986 pg in Gagnepainia sp., 2.090 pg in G. godefroyi to 2.195 pg in G. harmandii. Pollens of all species are monad, inaperturate, prolate with bilateral symmetry, and thick wall with fossulate exine sculpturing. The pollen size of G. harmandii (74.506 ± 5.075 µm, 56.082 ± 6.459 µm) is significantly larger than that of G. godefroyi (59.968 ± 3.484 µm, 45.439 ± 2.870 µm). Both 2C DNA content and pollen size are the effective characteristics for species discrimination. The reproductive evidence of high meiotic stability and normal pollen production indicate that both Gagnepainia species have high fertility and seed productivity, which are in accordance with the broad distribution. The present study provides good cytogenetic and pollen characters not only for plant identification, but also plant fertility assessment through plant genetic resource management and improvement of Gagnepainia.

One Major Challenge of Sequencing Large Plant Genomes Is to Know How Big They Really Are.

Any project seeking to deliver a plant or animal reference genome sequence must address the question as to the completeness of the assembly. Given the complexity introduced particularly by the presence of sequence redundancy, a problem which is especially acute in polyploid genomes, this question is not an easy one to answer. One approach is to use the sequence data, along with the appropriate computational tools, the other is to compare the estimate of genome size with an experimentally measured mass of nuclear DNA. The latter requires a reference standard in order to provide a robust relationship between the two independent measurements of genome size. Here, the proposal is to choose the human male leucocyte genome for this standard: its 1C DNA amount (the amount of DNA contained within unreplicated haploid chromosome set) of 3.50 pg is equivalent to a genome length of 3.423 Gbp, a size which is just 5% longer than predicted by the most current human genome assembly. Adopting this standard, this paper assesses the completeness of the reference genome assemblies of the leading cereal crops species wheat, barley and rye.

In vitro culture responses, callus growth and organogenetic potential of brinjal (Solanum melongena L.) to He-Ne laser irradiation.

The present investigation was designed to analyze the influence of Helium-Neon (He-Ne 632.8nm) laser irradiation on defense enzymes, proline content and in vitro responses of callus induction, shoot initiation and on plantlet regeneration potential of brinjal. The seeds of Mattu Gulla (Solanum melongena L.) were irradiated with 20, 25 and 30J/cm2 of He-Ne laser followed by surface sterilization and sprouted on Murashige and Skoog medium without plant growth regulators. The activity of defense enzymes, proline content and the organogenetic potential of hypocotyl, leaf and shoot tip explants were determined from thirty day old seedlings. During seed germination, most of the seedlings showed normal two cotyledons whereas small number of seedlings showed tricotyledonous at 20J/cm2 treatment and no other morphological abnormalities were observed during further growth and development. There was no substantial variation was noted in both ß-1,3-glucanase and chitinase activity as well as proline content which proves the He-Ne laser irradiation does not causes any stresses for the plant. The in vitro culture of hypocotyl, leaf and shoot tip explants from laser irradiated seedlings showed differential responses as compared to un-irradiated control. The laser induced enhancement of callus induction, growth rate of callus tissues and shoot tip, percentage of responses of shoot and root initiation, days to shoot and root initiation, shoots formed per callus, number of roots per shoots, length of roots and nuclear DNA content of in vitro raised plants were evaluated. Among the tested laser doses (20, 25 and 30J/cm2), 25J/cm2 showed significant biostimulatory effect over un-irradiated control seedlings. The present observations reveal and endorsed our earlier reports with substantial enhancement of in vitro and ex vitro by He-Ne laser irradiation.

Ploidy and domestication are associated with genome size variation in Palms.

PREMISE OF THE STUDY: The genome size of a species (C-value) is associated with growth, development and adaptation to environmental changes. Angiosperm C-values range 1200-fold and frequently vary within species, although little is known about the impacts of domestication on genome size. Genome size variation among related species of palms is of evolutionary significance because changes characterize clades and may be associated with polyploidy, transposon amplifications, deletions, or rearrangements. Further knowledge of genome size will provide crucial information needed for planning of whole genome sequencing and accurate annotations. We studied the genome size of Cocos nucifera and its variation among cultivars, and compared it to values for related palms from the Attaleinae subtribe. METHODS: Flow cytometric analysis of isolated nuclei from young palm leaves was used to estimate genome sizes of 23 coconut cultivars (Talls, Dwarfs, and hybrids) worldwide and 17 Cocoseae species. Ancestral genome size was reconstructed on a maximum likelihood phylogeny of Attaleinae from seven WRKY loci. KEY RESULTS: The coconut genome is large-averaging 5.966 pg-and shows intraspecific variation associated with domestication. Variation among Tall coconuts was significantly greater than among Dwarfs. Attaleinae genomes showed moderate size variation across genera, except polyploids Jubaeopsis caffra, Voanioala gerardii, Beccariophoenix alfredii, and Allagoptera caudescens, which had larger genomes. CONCLUSIONS: Our results contribute to the understanding of the relationship between domestication and genome size in long-lived tree crops and provide a basis for whole-genome sequencing of the coconut and other domesticated plants. Polyploidy evolved independently in two clades within Attaleinae.

Flow cytometry and K-mer analysis estimates of the genome sizes of Bemisia tabaci B and Q (Hemiptera: Aleyrodidae).

The genome sizes of the B- and Q-types of the whitefly Bemisia tabaci (Gennnadius) were estimated using flow cytometry (Drosophila melanogaster as the DNA reference standard and propidium iodide (PI) as the fluorochrome) and k-mer analysis. For flow cytometry, the mean nuclear DNA content was 0.686 pg for B-type males, 1.392 pg for B-type females, 0.680 pg for Q-type males, and 1.306 pg for Q-type females. Based on the relationship between DNA content and genome size (1 pg DNA = 980 Mbp), the haploid genome size of B. tabaci ranged from 640 to 682 Mbp. For k-mer analysis, genome size of B-type by two methods were consistent highly, but the k-mer depth distribution graph of Q-type was not enough perfect and the genome size was estimated about 60 M larger than its flow cytometry result. These results corroborate previous reports of genome size based on karyotype analysis and chromosome counting. However, these estimates differ from previous flow cytometry estimates, probably because of differences in the DNA reference standard and dyeing time, which were superior in the current study. For Q-type genome size difference by two method, some discussion were also stated, and all these results represent a useful foundation for B. tabaci genomics research.