2C Nuclear DNA Content Research Articles

Development of robust in vitro propagation protocol and cyto-genetic fidelity assessment of Siraitia grosvenorii (monk fruit)

Siraitia grosvenorii (Swingle) C. Jeffrey of the family Cucurbitaceae is a unique and precious plant of medicinal and economic importance in the international market. Due to the huge market potential and to narrow down the gap between demand and supply, an efficient in vitro propagation system using nodal explants was established. Shoot nodal segments were cultured in medium supplemented with different concentrations of 6-benzylaminopurine (BAP) and kinetin (Kn 1.0–7.5 µM). A two-stage culture is recommended for micropropagation of S. grosvenorii. The highest shoot multiplication was observed in BAP-supplemented medium (5.0 µM), whereas rooting was observed in half-strength MS medium supplemented with 8.75 µM of indole-3-butyric acid (IBA). Fully developed plantlets were acclimatized with 100 % survival in sterilized sand. These hardened 15-day-old plants were successfully established under shade net conditions in fields. In vitro raised plants were found genetically stable using molecular markers, including RAPD and ISSR. The 2C nuclear DNA content using flow cytometry was observed to be 0.73–0.76 pg. Hence, the protocol developed for in vitro propagation of S. grosvenorii is cost-effective and can be efficiently used for the industrial production of this natural sweetener and pharmaceutically important plants.

A Flow Cytometry-Based Assessment of the Genomic Size and Ploidy Level of Wild Musa Species in India.

In this paper, chromosome spreading was performed via protoplast isolation and a fast air-dry dropping method and flow cytometry were used with Raphanus sativus L. (Brassicaceae) as a standard for ploidy and genome size estimation. The results showed that genome size (2C) varied amongst Musa species, based on the ratio of G1 peak positions. The lowest genome size (2C) was found in M. balbisiana var. andamanica (1.051 ± 0.060 pg) and the highest genome size (2C) was recorded for Musa ABB.cv. Meitei-hei (1.812 ± 0.108 pg) for the section Eumusa. Among the species belonging to the section Rhodochlamys, M. rosae had the lowest 2C content of 1.194 ± 0.033 pg whereas the highest nuclear DNA content (2C) was observed in M. velutina (1.488 ± 0.203 pg). Cytogenetic analysis revealed that the chromosome number of 14 wild Musa species was 2n = 22, while 1 species-Ensete glaucum-showed a chromosome number of 2n = 18 (diploid), and for 3 species, the chromosome number was 2n = 33 (triploids). An association study based on the Pearson correlation coefficient showed 2C nuclear DNA content was significant and positively correlated with ploidy level (R = 0.9) and chromosome number (R = 0.84). The present study provides reliable information on the genome size and ploidy level of wild Musa species from the Indian region through flow cytometric analysis, which could be further utilized in taxonomic and crop improvement programs. For the first time, the nuclear DNA content of eight wild diploid and three triploid Indian species were estimated and reported. Genome size could be an effective indicator in identification of species and evolutionary studies in Musa with varying ploidy levels and morphological similarities.

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.

A Survey of Verbena xutha Lehm. (Gulf Vervain) Morphological and Cytological Characteristics

Gulf vervain (Verbena xutha) is a herbaceous perennial native to the southern United States. The species produces attractive spike inflorescences that provide a source of food for many pollinators. Besides botanical classifications, pollen morphology and cytological traits of this species have not been documented until now. Gulf vervain was found to have 2n = 42 chromosomes, with the first report of 2C nuclear DNA content of 2.95 pg. Convex-triangular pollen grains averaged 37.18 μm in diameter, with 84% stainability after cotton blue staining to estimate pollen viability. This information brings light to the genetic makeup of gulf vervain and may aid in future breeding programs.

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.

Establishment of an Efficient In Vitro Propagation of Cnidium officinale Makino and Selection of Superior Clones through Flow Cytometric Assessment of DNA Content.

Cnidium officinale is a valuable medicinal plant cultivated in Asia for its rhizomes. This study reports the in vitro regeneration of Cnidium officinale plants and the induction of rhizomes from microshoots. The rhizomatous buds of Cnidium officinale induced multiple shoots on Murashige and Skoog (MS) medium supplemented with 0.5 mg L−1 BA, which led to the regeneration of plants within four weeks of culture. After four weeks of culture, the plants were assessed for fresh weight, the number of leaves, the number of roots, and the length of roots to compare the performance of the different clones. The clones with good growth characteristics were selected with the aid of a flow cytometric analysis of 2C nuclear DNA content. The plants bearing high DNA values showed better growth characteristics. Various factors, namely, sucrose concentration (30, 50, 70, and 90 g L−1), ABA (0, 0.5, 1.0, and 2.0 mg L−1), the synergistic effects of BA (1.0 mg L−1) + NAA (0.5 mg L−1) and BA (1.0 mg L−1) + NAA (0.5 mg L−1) + ABA (1.0 mg L−1) with or without activated charcoal (1 g L−1), and light and dark incubation were tested on rhizome formation from microshoots. The results of the above experiments suggest that MS medium supplemented with 50 g L−1 sucrose, 1.0 mg L−1 ABA, and 1 g L−1 AC is good for the induction of rhizomes from the shoots of Cnidium officinale. Plantlets with rhizomes were successfully transferred to pots, and they showed 100% survival.

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.

First report on genome size and ploidy determination of five indigenous coffee species using flow cytometry and stomatal analysis

The nuclear 2C DNA content and ploidy level determination of five indigenous coffee species from India was carried out using flow cytometry and by assessing the stomatal characteristics. The nuclear DNA content (2C/pg) analyzed varied from 1.29 pg in Coffea wightiana Wall. ex Wight & Arn. to 1.48 pg in Coffea jenkinsii Hook.f. Based on the genome size, all five species were divided into two groups. The first group comprises Coffea travancorensis Wight & Arn and C. wightiana with lower genome size (2C DNA 1.29–1.30 pg), and the second group consists of Coffea bengalensis Roxb.ex Schult, Coffea khasiana (Korth.) Hook.f and C. jenkinsii with larger genome size (2C DNA 1.45–1.48 pg). The species included in the first group were inhabited in dry environmental conditions in contrast to the species included in the second group which was predominantly from mesic habitat. Among the stomatal characteristics, no significant variation in stomatal density was observed among the species, although stomatal guard cell length and stomatal chloroplast number recorded significant variation among some species. Based on flow cytometry and stomatal characteristics, all five endangered coffee species analyzed in the study were identified as diploids. The study revealed that stomatal guard cell length and stomatal chloroplast number could be fast, inexpensive, and reliable methods for determining the ploidy status of indigenous coffee species.

Assessment of Thinopyrum ponticum (Podp.) Barkworth &amp; D. R. Dewey accessions using universal rice primers and molecular cytogenetics

The aim of this study was to make morphological and molecular characterization of tall wheatgrass (Thinopyrum ponticum) accessions naturally found in Canakkale flora, Turkey. The seeds collected from 24 different locations in Canakkale vicinity were planted in the nursery field to determine thirteen morphological parameters. Twelve universal rice primers (URPs) were used to reveal genetic relationship among the accessions while ploidy analysis was done based on the nuclear DNA content of plants determined by Flow cytometer. Fluorescence in situ hybridization (FISH) method was used to determine 5S and 45S rDNA distributions on mitotic chromosomes. The agro-morphological data showed significant variation among the accessions for all parameters measured, except the number of nodes per plant. Twelve URP primers produced 73 alleles in total and 63 of those were polymorphic. The highest polymorphism information content value was obtained from URP 17R with 0.82. The first three components of Eigen values in PCA analysis explained 41.1% of total variation. The 2C nuclear DNA contents of the accessions ranged from 41.17 to 45.49 pg. All the accessions were determined as decaploid with 2n = 70 chromosomes. FISH analysis provided 18–20 interstial 5S rDNA and 12–14 terminal 45S rDNA loci. The results concluded that tall wheatgrass accessions used in this study contain a significant variation in morphological traits and PCR-based DNA polymorphism which could be used as a new genetic resource in breeding programs of tall wheatgrass and wheat improvement for intra- and intergeneric crosses.

Analysis of nuclear DNA content and ploidy levels in 3x × 4x Lilium (Lilium × elegans L.) progenies by flow cytometry

Interploidy crosses between Lilium lancifolium (3x) and Asiatic lily cultivar ‘Brunello’ (4x) were attempted for creating genetic variability and to analyse the progenies for different ploidy levels. Experimental results revealed that most of the crosses attempted were developed into fruits, confirming that male-sterile triploid lilies can be used as the female parent for crossing with a suitable male parent. Wide variation in chromosome numbers (28 to 38) was obtained in different plant progenies, indicating that aneuploidy is generated by 3x × 4x crosses. The nuclear DNA content analysis of 13 plant progenies showed that the 2C nuclear DNA content has increased (range = 32.60 pg to 41.32 pg) as compared to Lilium lancifolium, while it was found lower than the cultivar ‘Brunello. Further, morphological characterization of different plant progenies revealed significant differences among themselves, which confirmed the dependence of these traits on cultivars ploidy level. Therefore, present findings will be instrumental for development of new Lilium cultivars with high aesthetic value and utility.

First report of genome size and ploidy of the underutilized leguminous tuber crop Yam Bean (Pachyrhizus erosus and P. tuberosus) by flow cytometry

AbstractCytological understanding is an important parameter to understand the genetic architecture of yam bean. The ploidy level and genome size of two cultivated species of yam bean (Pachyrhizus erosus and P. tuberosus) were estimated using flow cytometric analysis of young leaf tissue, with propidium iodide as a fluorescent dye. Six genotypes of P. erosus and three genotypes of P. tuberosus were analysed. Rice (Oryza sativa cv. Nipponbare) and Mung bean (Vigna radiata cv Berken) were used as internal reference standards. Variation of 2C nuclear DNA content among the six P. erousus lines was 4.18%, ranging from 1.17 to 1.22 pg, whereas only 1.8% variation was observed among the three P. tuberosus lines, which ranged from 1.07 to 1.09 pg. Moreover, it was found that the nuclear DNA content of P. tuberosus was lower than that of P. erosus. The result of the flow cytometric analysis showed that all the species were diploid (2n = 2x) and coefficient of variation (CV%) of all the accessions of the two species was less than 3.5%. This is the first report of ploidy analysis and genome size estimation of the leguminous underutilized tuber crop yam bean using flow cytometry. This result will be helpful for yam bean genome sequencing and crop improvement programmes.

Molecular and Cytogenetic Study of East African Highland Banana.

East African highland bananas (EAHBs) are staple food crop in Uganda, Tanzania, Burundi, and other countries in the African Great Lakes region. Even though several morphologically different types exist, all EAHBs are triploid and display minimal genetic variation. To provide more insights into the genetic variation within EAHBs, genotyping using simple sequence repeat (SSR) markers, molecular analysis of ITS1-5.8S-ITS2 region of ribosomal DNA locus, and the analysis of chromosomal distribution of ribosomal DNA sequences were done. A total of 38 triploid EAHB accessions available in the Musa germplasm collection (International Transit Centre, Leuven, Belgium) were characterized. Six diploid accessions of Musa acuminata ssp. zebrina, ssp. banksii, and ssp. malaccensis representing putative parents of EAHBs were included in the study. Flow cytometric estimation of 2C nuclear DNA content revealed small differences (max ~6.5%) in genome size among the EAHB clones. While no differences in the number of 45S and 5S rDNA loci were found, genotyping using 19 SSR markers resulted in grouping the EAHB accessions into four clusters. The DNA sequence analysis of the internal transcribed spacer region indicated a relation of EAHB clones with M. acuminata and, surprisingly, also with M. schizocarpa. The results suggest that EAHB cultivars originated from a single hybrid clone with M. acuminata ssp. zebrina and ssp. banksii being its most probable parents. However, M. schizocarpa seems to have contributed to the formation of this group of banana.

Determination of DNA content and relative 2C genome sizes of some promising commercial varieties of sugarcane using flow cytometer

&lt;p&gt;In the present study, 2C DNA content and the genome sizes (in picograms-pg and megabase pairs-Mbp respectively) of 19 promising commercial varieties of sugarcane, the derivatives of man-made interspecific hybrids between cultivated and wild species were analyzed using flow cytometry. In this work, 2C nuclear DNA content was determined. Knowing the 2C nuclear DNA content, the unknown chromosome numbers of the varieties could be predicted. Large differences (65 % variation) in DNA content (2C) of 19 varieties were detected, ranging, from 3.80 pg to 10.96 pg, which corresponds to a genome size ranging from 3724.00 Mbp to 10740.80 Mbp due to the variation of ploidy level and are considered the most complex genomes among crop plants. However, the relationship between chromosome number and genome size was highly significant (P &amp;lt; 0.001). In the present study, internode diameter, Sugar juice content and cane yield/ha are also positively correlated with DNA content. The estimated genome sizes would also yield information critical for sugarcane breeding and genome sequencing programs. &lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;&lt;strong&gt;: &lt;/strong&gt;Genome size, Sugarcane varieties, Flow cytometry, DNA content.&lt;/p&gt;

Karyomorphology and nuclear DNA content of sixteen Ophrys L. taxa from Turkey

Karyotypes in 16 representative taxa of the Ophrys genus are compared, based on Feulgen-stained somatic metaphase chromosomes. The karyotypes of O. omegaifera subsp. israelitica, O. ulupinara, O. lycia, O. argolica subsp. lucis, O. argolica subsp. lesbis, O. climacis and O. reinholdii subsp. reinholdii are described for the first time. Karyological analyses indicate relationships among the species with respect to their asymmetry indices. All Ophrys taxa studied were diploid with 2n = 2x = 36 chromosomes. One B chromosome has been detected among the chromosomes of O. argolica subsp. lucis. All karyotypes are symmetrical, consisting of metacentric and submetacentric chromosomes. The longest chromosomes of all the investigated specimens contain a secondary constriction. It is determined that there is a correlation between the total number of chromosomes having secondary constrictions and the evolutionary development order of the taxa. Based on nuclear DNA content, analysis was carried out by flow cytometer using propodium iodide as fluorochrome, 2C nuclear DNA content of 16 Ophrys species varying between 20.80 pg (O. argolica subsp. lucis) and 23.11 pg (O. omegaifera subsp. israelitica). Karyotype asymmetry relationships are discussed according to the bidimensional scatter plots of A1–A2, CVCL–CVCI, CVCL–MCA and CVCI–MCA.

Characterization of Tulbaghia violacea (Tulbaghieae, Allioideae, Amaryllidaceae) from India: a cytogenetic and molecular approach

Tulbaghia violacea, called ‘wild garlic’, is a native of Africa, though it is widely cultivated all over the world for its medicinal and horticultural importance. Absence of the genus from Indian floras and taxonomic surveys, as well as lack of proper molecular and cytogenetic characterizations, have instigated questions regarding origin and divergence of the Indian counterpart from its African relatives. In the present study, morphotaxonomical identification of Indian T. violacea was carried out, along with its karyomorphological characterization, 2C nuclear genome content determination, and analysis of ITS sequence. Mitotic study revealed that this species possessed 2n = 2x = 12 somatic chromosomes, two of which had secondary constrictions, whereas unstable meiotic chromosomal behavior was observed in flower buds, as reported earlier. 2C nuclear DNA content of T. violacea (44.51 ± 0.06 pg) was reported for the first time using flow cytometry, as was the ITS sequence data, from India.

Intraspecific variations in cardamom (Elettaria cardamomum Maton): assessment of genomic diversity by flow cytometry, cytological studies and ISSR analysis.

Background The main goal of the work was to analyse intraspecific variation in Elettaria cardamomum Maton (cardamom) using genome size, cytological studies and molecular marker data. Nuclear DNA content and molecular marker details furnish data on genome size and genetic diversity respectively among the studied accessions and both complement each other for evolutionary and taxonomic studies.ResultsThe relative 2C genome size and total number of base pairs of cardamom was determined through flow cytometric analysis using propidium iodide staining. The nuclear DNA content was estimated in various sections of the species representing individuals from wild and cultivar genotypes following Zea mays L. CE-777 (2C = 5.43 pg) as internal reference standard. Chromosome number from growing root tip was examined following standard protocols. Twenty-six ISSR primers that generated polymorphic bands were used for genetic diversity analysis of the thirty accessions of cardamom. Estimated nuclear 2C DNA content ranged from 2.57 to 3.22 pg demonstrating 1.25-fold variation. The mean amount of 2C nuclear DNA of the cardamom was calculated as 2.87 pg which is equivalent of 2806 Mbp as the diploid genome size. The chromosome number was found to be 2n = 48. Among the thirty accessions of cardamom studied using ISSR markers, C53 (feral from Bonacaud) showed a very prominent level of genetic diversity and was lowest for C96 (Avinash-I, a released variety from Indian Institute of Spices Research, Kozhikode).ConclusionThese analyses revealed the existence of genetic variability within the studied cardamom accessions. The plant specimens also differed significantly in their genome size. However, the genetic variability parameters did not show any correlation with genome size.

The application of flow cytometry and a thioredoxin‐like nuclear gene for breeding Poa arachnifera x Poa pratensis hybrids

AbstractInterspecific hybridization between Poa arachnifera Torr. (Texas bluegrass) and Poa pratensis L. (Kentucky bluegrass) has shown to be a proven method for the development of turf‐type hybrid bluegrass cultivars for the southern United States. Unlike in P. pratensis, the use of DNA markers for molecular characterization and flow cytometry to determine nuclear DNA contents has not been extensively utilized in P. arachnifera. In this study, 2C nuclear DNA content of 19 different genotypes of P. arachnifera (both males and females) was determined to range from 8.02 to 13.24 pg/2C using flow cytometry. The DNA content of the hybrids between P. arachnifera and P. pratensis from two different pedigrees was found to be intermediate between their parents. Furthermore, the utility of the trx (thioredoxin‐like) nuclear gene in the identification of interspecific hybrids between P. arachnifera and P. pratensis was demonstrated using sequence and phylogenetic analyses. A newly discovered 851‐bp trx allele may serve as a useful marker to differentiate P. arachnifera from P. pratensis and provide insights into the evolutionary origin of P. arachnifera.

Genome Size, Leaf, Fruit and Seed Traits – Taxonomic Tools for Species Identification in the Genus Nasturtium R. Br.

Abstract Flow cytometry estimation of 2C nuclear DNA content of the examined Nasturtium species resulted in taxonomic identification of N. × sterile in eight new localities, N. microphyllum in four new localities and N. officinale in one new locality in western Poland. Scanning electron microscopy proved a few of the micromorphological traits of seeds and fruits (size and shape of cells on the fruit septum surface, their anticlinal walls; secondary sculpture on the outer periclinal walls of cells on the siliqua valve internal surface) to be of taxonomic importance.

DNA contents in Texas bluegrass (Poa arachnifera) selected in Texas and Oklahoma determined by flow cytometry

Texas bluegrass (Poa arachnifera Torr.) is a dioecious, perennial, cool-season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. Its major use has been for forage on rangelands in Texas and Oklahoma. More recently, interspecific hybrids between Texas bluegrass and Kentucky bluegrass (P. pratensis L.) have been developed and commercially released as heat tolerant turfgrass. Currently, the 2C nuclear DNA content of Texas bluegrass is unknown. Therefore, flow cytometry was performed on an assortment of male and female Texas bluegrass genotypes (n = 24) collected from fourteen locations in Texas and Oklahoma to estimate DNA content in picograms (pg). The DNA content of Texas bluegrass fell into two groups based on collection location. Plants collected from northwest Oklahoma and five other locations west of 33.75, −98.39 (latitude, longitude) ranged from 9.64 ± 0.04 to 10.07 ± 0.09 pg. Plants collected from four sites in Texas, east of 33.20, −98.16 contained a DNA content that ranged from 14.02 ± 0.04 to 14.75 ± 0.13 pg. Based on a root tip chromosome count, a male Texas bluegrass plant estimated to be 9.96 pg, appeared to contain 56 chromosomes, indicating the smaller DNA content plants may be octaploids (2n = 8x = 56). Significant differences were not detected between male and female plants based on DNA content. Knowledge of the DNA content in Texas bluegrass should be useful in a breeding program for characterizing germplasm and identifying desired DNA content levels among parental genotypes.