Cytological Variation Research Articles

Epithelioid angiomyolipoma of the liver: a clinicopathologic study of 5 cases

This study aimed to study the clinicopathologic characteristics of epithelioid angiomyolipoma, a variant of angiomyolipoma (AML) in the liver; and to discuss the diagnostic challenges. Five cases of primary liver epithelioid AML were retrieved from our archives from January 2003 to October 2012. The clinicopathologic features of each case were retrospectively reviewed. All 5 patients were female, with age ranging from 36 to 70 years (median, 41 years). The size of the tumor ranged from 1.2 to 25 cm. Histologically, the tumor comprised polygonal cells with granular eosinophilic cytoplasm and accompanied by immunohistochemical expression of HMB-45 ± Melan-A. Variations in growth pattern and cytology were observed. Estrogen receptor was negative in all 5 cases. None showed cytologic atypia, coagulative necrosis, increased mitotic count, or vascular invasion. Epithelioid AML is an uncommon primary liver tumor with a female predominance. The size of the tumor can be variable. This tumor might impose diagnostic difficulty both clinically and histologically. Immunohistochemical staining with melanocytic markers is a promising means to confirm the pathologic diagnosis. A careful assessment of aggressive histologic features is recommended to stratify the risk of aggressive behavior of this tumor.

Molecular Cytological Characterization of Somatic Variation in Rice Aneuploids

Aneuploids cannot be stably preserved by sexual propagation, though they can maintain their genetic identity by asexual propagation. However, it is possible for somaclonal variation to occur during asexual propagation. Surveys taken from 2005 to 2007 showed that there were 26 lines with morphological variations from a total of 114 asexually propagated rice lines. Among these, 12 lines were detected that had either increased or decreased chromosome numbers, while the other 14 lines did not show any changes in chromosome number. Lines with increased chromosome numbers include the following four classes: (1) an extra chromosome was retained, and another normal individual chromosome was increased; (2) an extra chromosome was increased, and the normal chromosome numbers did not change; (3) an extra chromosome was lost, and another chromosome was increased; and (4) the genome was doubled. We studied 543 somatic cells from the 12 lines during mitosis and observed abnormal mitotic behaviors such as chromosome lagging, uneven distribution, and chromosome breakage at anaphase. These results show that abnormal mitotic behavior led to the somaclonal variation in chromosome number. However, cytological variation can only explain a minority of the asexual separated lines.

Diversity and endemism in deglaciated areas: ploidy, relative genome size and niche differentiation in the Galium pusillum complex (Rubiaceae) in Northern and Central Europe

Plants endemic to areas covered by ice sheets during the last glaciation represent paradigmatic examples of rapid speciation in changing environments, yet very few systems outside the harsh arctic zone have been comprehensively investigated so far. The Galium pusillum aggregate (Rubiaceae) is a challenging species complex that exhibits a marked differentiation in boreal parts of Northern Europe. As a first step towards understanding its evolutionary history in deglaciated regions, this study assesses cytological variation and ecological preferences of the northern endemics and compares the results with corresponding data for species occurring in neighbouring unglaciated parts of Central and Western Europe. DNA flow cytometry was used together with confirmatory chromosome counts to determine ploidy levels and relative genome sizes in 1158 individuals from 181 populations. A formalized analysis of habitat preferences was applied to explore niche differentiation among species and ploidy levels. The G. pusillum complex evolved at diploid and tetraploid levels in Northern Europe, in contrast to the high-polyploid evolution of most other northern endemics. A high level of eco-geographic segregation was observed between different species (particularly along gradients of soil pH and competition) which is unusual for plants in deglaciated areas and most probably contributes to maintaining species integrity. Relative monoploid DNA contents of the species from previously glaciated regions were significantly lower than those of their counterparts from mostly unglaciated Central Europe, suggesting independent evolutionary histories. The aggregate of G. pusillum in Northern Europe represents an exceptional case with a geographically vicariant and ecologically distinct diploid/tetraploid species endemic to formerly glaciated areas. The high level of interspecific differentiation substantially widens our perception of the evolutionary dynamics and speciation rates in the dramatically changing environments of Northern Europe.

Test Execution Variation in Peritoneal Lavage Cytology Could Be Related to Poor Diagnostic Accuracy and Stage Migration in Patients with Gastric Cancer

PurposePeritoneal lavage cytology is part of the routine staging workup for patients with advanced gastric cancer. However, no quality assurance study has been conducted to show variations or biases in peritoneal lavage cytology results. The aim of this study was to demonstrate a test execution variation in peritoneal lavage cytology between investigating surgeons.Materials and MethodsA prospective cohort study was designed for determination of the positive rate of peritoneal lavage cytology using a liquid-based preparation method in patients with potentially curable advanced gastric cancer (cT2~4/N0~2/M0). One hundred thirty patients were enrolled and underwent laparotomy, peritoneal lavage cytology, and standard gastrectomy, which were performed by 3 investigating surgeons. Data were analyzed using the chi-square test and a logistic regression model.ResultsThe overall positive peritoneal cytology rate was 10.0%. Subgroup positive rates were 5.3% in pT1 cancer, 2.0% in pT2/3 cancer, 11.1% in pT4a cancer, and 71.4% in pT4b cancer. In univariate analysis, positive peritoneal cytology showed significant correlation with pT stage, lymphatic invasion, vascular invasion, ascites, and the investigating surgeon. We found the positive rate to be 2.1% for surgeon A, 10.2% for surgeon B, and 20.6% for surgeon C (P=0.024). Multivariate analysis identified pT stage, ascites, and the investigating surgeon to be significant risk factors for positive peritoneal cytology.ConclusionsThe peritoneal lavage cytology results were significantly affected by the investigating surgeon, providing strong evidence of test execution variation that could be related to poor diagnostic accuracy and stage migration in patients with advanced gastric cancer.

Systematics of the hypervariable <i>Moraea tripetala</i> complex (Iridaceae: Iridoideae) of the southern African winter rainfall zone

Field and laboratory research has shown that the Moraea tripetala complex of western South Africa, traditionally treated as a single species, sometimes with two additional varieties, has a pattern of morphological and cytological variation too complex to be accommodated in a single species. Variation in floral structure, especially the shape of the inner tepals, degree of union of the filaments, anther length and pollen colour form coherent patterns closely correlated with morphology of the corm tunics, mode of vegetative reproduction, and in some instances capsule and seed shape and size. The morphological patterns also correlate with geography, flowering time and sometimes habitat. It is especially significant that different variants of the complex may co-occur, each with overlapping or separate flowering times, a situation that conflicts with a single species taxonomy. We propose recognizing nine species and three additional subspecies for plants currently assigned to M. tripetala. M. grandis, from the western Karoo, has virtually free filaments and leaves often ± plane distally; closely allied M. amabilis, also with ± free filaments and often hairy leaves, is centred in the western Karoo and Olifants River Valley. Its range overlaps that of M. cuspidata, which has narrowly channelled, smooth leaves, linear inner tepals spreading distally and filaments united for up to 1.5 mm. M. decipiens from the Piketberg, M. hainebachiana, a local endemic of coastal limestone fynbos in the Saldanha District, M. ogamana from seasonally wet lowlands, and early flowering M. mutila constitute the remaining species of the complex in the southwestern Western Cape. M. helmei, a local endemic of middle elevations in the Kamiesberg, Namaqualand, has small flowers with short, tricuspidate inner tepals. All but M. amabilis and M. mutila are new species. We divide M. tripetala sensu stricto into three subspecies: widespread subsp. tripetala, subsp. violacea from the interior Cape flora region, and late-flowering subsp. jacquiniana from the Cape Peninsula and surrounding mountains.

Chromosome and genome size variation inLuzula(Juncaceae), a genus with holocentric chromosomes

The present study examines chromosome and genome size evolution in Luzula (woodrush; Juncaceae), a monocot genus with holocentric chromosomes. Detailed karyotypes and genome size estimates were obtained for seven Luzula spp., and these were combined with additional data from the literature to enable a comprehensive cytological analysis of the genus. So that the direction of karyotype and genome size changes could be determined, the cytological data were superimposed onto a phylogenetic tree based on the trnL-F and internal transcribed spacer (ITS) DNA regions. Overall, Luzula shows considerable cytological variation both in terms of chromosome number (2n = 6–66) and genome size (15-fold variation; 2C = 0.56–8.51 pg; 547.7–8322.8 Mb). In addition, there is considerable diversity in the genomic mechanisms responsible, with the range of karyotypes arising via agmatoploidy (chromosome fission), symploidy (chromosome fusion) and/or polyploidy accompanied, in some cases, by the amplification or elimination of DNA. Viewed in an evolutionary framework, no broad trend in karyotype or genome evolution was apparent across the genus; instead, different mechanisms of karyotype evolution appear to be operating in different clades. It is clear that Luzula exhibits considerable genomic flexibility and tolerance to large, genome-scale changes.

Investigating Phenotypic Variability inColletotrichum lindemuthianumPopulations

Colletotrichum lindemuthianum, causal agent of anthracnose in the common bean, has wide genetic variability. Differential bean cultivars and morphological and physiological characteristics were used to analyze 74 isolates of C. lindemuthianum collected in two counties in the state of Minas Gerais, Brazil. Six different races were found, with a predominance of race 65 at both locations. Isolates were classified according to their sensitivities to the fungicide thiophanate-methyl, normally used in the control of common bean anthracnose. In all, ≈10% of isolates were resistant to the fungicide in vitro. Characteristics such as indexes of mycelia growth rate, colony diameter, sporulation capacity, and percentage of germination demonstrated the high genetic variability of C. lindemuthianum. We also observed variation in conidial cytology. The conidia of most isolates showed septa formation after germination, in contrast to septa absence, previously reported in the literature. Sexual and asexual reproduction were evaluated for mechanisms that may contribute in the generation of variability in C. lindemuthianum. Conidial anastomosis tubes were commonly found, indicating that asexual reproduction can help increase variability in this species. Information from this study confirmed high variability in C. lindemuthianum and will guide future studies in basic knowledge and applied technologies.

Assessment of karyotypical variation among 16 populations of Thymus daenensis Celak and Thymus kotschyanus Boiss. species in Iran

In order to study the cytological variation between Iranian native Thymus, karyotypes of two taxa (16 populations) from different geographic origins were presented. The ploidy level was different in populations belonging to T. kotschyanus (2x and 4x), but the same level was found (2x) in T. daenensis populations. According to intrachromosomal asymmetry, T. daenensis (10534) had the most asymmetrical and evolutionary karyotype and T. kotschyanus (10513) had the most symmetrical karyotype in all of the populations. While based on interchromosomal asymmetry, among diploid populations, T. daenensis (10535) and among tetraploid populations, only T. kotschyanus (10515) had the most asymmetrical karyotype. In terms of the Stebbins’ system, the karyotype were of populations seizes 1A classes. The results of analysis of variance revealed significant differences between the populations based on all karyotypic characteristics (P<%1). The results of cluster analysis showed that populations of each species T. daenensis and T. kotschyanus have been grouped in separate cluster. The results seemed to provide enough genetic evidence to identify the species and useful data to clarify the interspecific relationships. Detailed karyotype analysis allows us to group the different populations and to specify their relationships. Key words: Chromosome, karyotype, ploidy, principal components analysis, Thyme.

Morphological variation in populations of the Poa orinosa complex (Poaceae: Poeae) in northeastern China

We conducted a detailed study of the morphological and cytological variation in seven populations of the Poa orinosa complex along an ecological gradient in northeastern China. Three of the populations were at different elevations in wooded habitats; three were in habitats dominated by grasses other than Poa; and one was in a shrub–steppe habitat. Plants from two of the wooded sites were diploid; those from the third wooded site were primarily octoploid. Plants from two of the grassy sites were tetraploid; those from the third grassy site were hexaploid. The seventh population, located in a shrub–steppe habitat, was diploid. Twenty-four morphological characters were scored on specimens from each site. Plants from the three wooded sites and the lowest grassy site differed from those from the other three sites in having longer culms, internodes and sheaths. The similarity of the tetraploid plants to the diploid plants suggested that they may be autotetraploids. Similarly, the morphological similarity of the octoploid population to the two diploid populations suggested that it too may be an autopolyploid. The morphological distinction of the hexaploid population suggests that it has incorporated a genome not present in the other populations.

English

In order to study the morphological and cytological variation among Iranian nativeIrises, first,&nbsp;morphological traits were analyzed in order to clarify taxonomic relationships among taxa and validity of diagnostic characters. Floral and vegetative characters were measured in 54 plant samples belonging to five species during peak of the flowering season in 2008. Analysis of variance showed significant differences. Result of analysis shows&nbsp;that the most variation coefficient belongs to leaf width. Correlation of coefficients defined between the date of the first blooming of the flowers and the date of the least blooming of the flowers, flowers surface and diameter had the positive and significant correlation. Factor analysis showed that only three factors define almost near to 92% variance among characters. Secondly, in cytological variation each species showed different karyotypic formula such as&nbsp;2n = 2sm+ 14st+4t for&nbsp;Iris meda, 2n = 8m + 16sm + 20st with one pair of terminal satellite chromosomes for&nbsp;Iris caspica, 2n = 26m + 18sm for&nbsp;Iris spuria, 2n= 14m + 12sm + 8st with one pair of terminal satellite chromosomes for&nbsp;Iris pseudacorousand 2n= 8m + 20sm + 20st for&nbsp;Iris germanica. This is the first karyotypic report in&nbsp;I. caspica,&nbsp;I. spuria&nbsp;and&nbsp;I. meda&nbsp;species in Iran.&nbsp;The results seemed to provide enough genetic evidence to identify each species and useful data to clarify the interspecific relationships among Iranian native&nbsp;Iris&nbsp;species. &nbsp; Key words:&nbsp;Iris, karyotype, Iranian native, chromosome analysis, genome.

Karyotype variability in species of the genus Zephyranthes Herb. (Amaryllidaceae–Hippeastreae)

In this work, the cytotaxonomic implications of the chromosomal characterization of cultivated and native Zephyranthes species described in northeastern Brazil were studied. All individuals had karyotype formed by a set of metacentric chromosomes, in addition to submetacentric and acrocentric chromosomes. In Zephyranthes robusta, 2n = 12 was observed and karyotype with formula 4M + 2SM in somatic cells, representing the most symmetric karyotype among the investigated species. Z. sylvatica showed three different chromosome complement numbers: 2n = 12 with formula 1M + 5SM, 2n = 12 + 1B with 1M + 5SM + (1B), and 2n = 18 formed by cracks. The cultivated species Z. rosea Lindl. presented 2n = 24 with 4M + 7SM + 1A, however Z. grandiflora Lindl. showed the same chromosome number with 2M + 5SM + 5A. Zephyranthes aff. rosea Lindl. presented 2n = 25 with one small metacentric forming a crack in the fourth metacentric pair. Z. brachyandra has 2n = 24 + (1B) and formula 4M + 3SM + 5A + (1B). Z. candida Herb. presented 2n = 38 and karyotype formula 9M + 10SM. In Habranthus itaobinus numerical variation was observed, with the majority of populations showing a chromosome complement composed of 2n = 44 + 1B with 5M + 12SM + 5A + (1B), or 2n = 44 + 3B in a single population. Mechanisms involved in the formation of these karyotypes from chromosomal imbalance data are discussed. Taken together, data from this study only partially confirm previous counts for epithets and further enhance the cytological variability data previously reported for the genus.

Epilithic algae from caves of the Krakowsko-Częstochowska Upland (Southern Poland)

This paper describes the first study of algae assemblages in 20 caves in the Krakowsko-Częstochowska Upland (Southern Poland), in the period between 2005-2006. The investigations showed mostly on epilithic algae and their subaeric habitats (rock faces within caves and walls at cave entrances). The morphological and cytological variability of algae were studied in fresh samples, in cultures grown on agar plates and in SPURR preparations. A total of 43 algae species was identified, mostly epilithic species and tolerant of low light intensities. The largest group was formed by representatives of the division &lt;em&gt;Chlorophyta&lt;/em&gt; (24 species), and then the division &lt;em&gt;Chrysophyta&lt;/em&gt; (&lt;em&gt;Heterokontophyta&lt;/em&gt;) - 17 species, with 9 species belonging to the class &lt;em&gt;Bacillariophyceae&lt;/em&gt;, 7 species - Xanthophyceae and 1 species representing the class &lt;em&gt;Eustigmatophyceae&lt;/em&gt;. &lt;em&gt;Dinophyta&lt;/em&gt; (2 species) constituted the last and the smallest group. Among the collected algae, the following species deserve special attention: &lt;em&gt;Thelesphaera alpina&lt;/em&gt;, &lt;em&gt;Bracteacoccus minor&lt;/em&gt;, &lt;em&gt;Trachychloron simplex&lt;/em&gt;, &lt;em&gt;Tetracystis intermedia&lt;/em&gt; and &lt;em&gt;T. cf. isobilateralis&lt;/em&gt;. The last species was not earlier found in Europe. Identification of species was greatly aided by examination of cell ultrastructure, which provided an array of further features, increasing chances of correct species identification. Furthermore, the studies focused that algae, although usually remaining under dominance of cyanobacteria, excellently differentiate this special area and even enrich it.

Morphological variations in populations of Urginea indica Kunth.Liliaceae

An attempt has been made to enquire into the morphological variations which leads to evolutionary divergence of populations of Urginea indica Kunth. In particular, there were considerable morphological variations within the species. The thirty two cytotypes showed distinct morphological differences in shape, size and colour of bulb and leaf, the length of inflorescence and flower colour. The morphological complexity is accompanied by high degree of cytological variations. Preliminary measurements of reproductive, characters have shown that no noteworthyresults may be obtained in this characters except pedicel length but the vegetative character deviated significantly. Flowering and blooming time varied that also played a role in isolation of these populations. These morphological differences have a genetic basis and would be worthy in recognizing them as a separate sub specific taxon.

Morphological and cytological diversity of regenerants derived from half-anther cultures of anthurium

Anthurium anther culture was successfully established using half-anthers as explants. Explants were cultured on Winarto–Teixeira basal medium (WT-1) containing 0.01 mg/l α-naphthalene acetic acid (NAA), 0.5 mg/l thidiazuron (TDZ), and 1.0 mg/l 6-benzylaminopurine (BAP), or on New Winarto–Teixeira basal medium (NWT-3) supplemented with 0.02 mg/l NAA, 1.5 mg/l TDZ, and 0.75 mg/l BAP for callus initiation. Regenerated calli produced multiple shoots on WT-1, which were then rooted in NWT-3 supplemented with 1% activated charcoal. Plantlets were acclimatized ex vitro using a mixture of burned rice husk, rice husk, and bamboo peat (1:1:1, v/v/v) as the potting medium. There was considerable morphological and cytological diversity of regenerants derived from anther culture, which are described in detail in this study. The callus cluster color ranged from green to light green and had a high regeneration capacity (7.3 and 4.8 shoots/callus cluster), light reddish-yellow callus showed moderate regeneration (2.6 shoots/callus cluster), while reddish-yellow callus had the lowest regeneration capacity (1.5 shoots/callus cluster). Morphological variations clearly observed in regenerants derived from this technique included alterations in plant size, peduncle length, spathe position compared to leaves, the type and number of buds, spathe and spadix color, and spadix length. There were also cytological variations in both in vitro and ex vitro regenerants of anther culture with 23–29% haploids, 5–10% aneuploids, 56–69% diploids, and 3–4% triploids. The results strengthen other studies in which the development of anther cultures, especially via callus formation, resulted in morphological and cytological alterations. These variations have been discussed to great length in this paper.

Morphologic diversity of plasma cell neoplasms

To investigate the architectural and cytological variations of plasma cell neoplasms, and discuss the diagnosis and differential diagnosis. Histological and immunohistochemical examinations were used to study the morphologic and immunophenotypic features of 46 cases of plasma cell neoplasms. 40 out of 46 cases were diffuse growth pattern. 3 cases had a nestlike architecture that can mimic neuroendocrine tumors and 3 cases had a prominent fibrous sclerosis background. Amyloid deposition, calcification or ossification and angiomatoid areas can be prominent and may obscure the neoplastic plasma cells. Cytologically, 30 cases were composed of relatively mature plasma cells and can be recognized without too much difficulty. Tumor cells resembled immunoblasts in 6 cases and small lymphocytes in 4 cases. In another 2 cases tumor cells were easily confused with Signet-ring cells or clear cells. Tumor cells were composed of anaplastic cells, histocytoid cells and spindle cells in each one case, respectively. Lastly, tumor cells can be polymorphous which composed of multilobated, monocytoid or multinucleated cells in one case. 93.1% (27/29) cases expressed CD79a while only 5.1% (2/39) cases expressed CD20.87.1% (27/31) cases expressed CD38 and 83.3% (25/30) cases expressed CD138, 96.8% (30/31) cases expressed MUM-1. Light chain restrictions were detected in 38 cases, that 27 cases expressed lambda and 11 for kappa. Except for the common architecture and cytology in plasma cell tumor, unusual morphology may appear. Thus, pay attention to distinguish from lymphoma such as small lymphocytic lymphoma and anaplastic large cell lymphoma, pooly differentiated carcinoma, clear cell carcinoma or Signet-ring cell carcinoma, sarcoma, etc. And immunohistochemistry is essential in the diagonosis.

Morphological and cytological studies of diploid and colchicine-induced tetraploid lines of crape myrtle ( Lagerstroemia indica L.)

The tips of cotyledon-stage seedlings of three crape myrtle cultivars (“Zi Wei”, “Hong Wei” and “Yin Wei”) were treated with colchicine. Various concentrations of colchicine and different treatment durations were tested. Seedlings of “Zi Wei” treated with 0.5% colchicine for 72 h and seedlings of “Yin Wei” treated with colchicine (0.2% for 96 h, 0.5% for 48 h and 0.8% for 72 h) demonstrated high rates of mutation; “Hong Wei” showed a slightly lower rate. The highest rate of morphological variation was 54.17% and this was achieved when tips were treated with 0.5% colchicine for 72 h. Putative tetraploid plants were identified with morphological and cytological variations, such as larger and thicker leaves, darker green coloration, larger stomata, lower density of stomata across the lower leaf epidermis and increased numbers of chloroplasts per stomata guard cell. Flow cytometric analysis demonstrated that the nuclear DNA content of 15 of these putative tetraploids (of which 7 were “Zi Wei”, 5 were “Yin Wei”, and 3 were “Hong Wei”) was indeed doubled relative to that of control diploid plants. The chromosome number of the tetraploid plants was 2 n = 4 x = 96, while that of the control diploid plants was 2 n = 2 x = 48. Ornamental characteristics were also enhanced in the tetraploid plants, with increased diameter of the individual flowers and greater basal length of the petals and claws. Pollen diameter and the size of capsules and seeds were also significantly greater than those of diploid plants.

Morphologically Cryptic Species Within Downingia yina (Campanulaceae)

The Downingia yina species complex (Campanulaceae), centered in northern California and southern Oregon, currently contains three morphologically distinguished species: D. yina, D. elegans, and D. bacigalupii. This complex of species is notable for high levels of morphological and cytological variation, with chromosome counts of n = 6, 8, 10, and 12. Molecular evidence suggests three main clades within this complex, corresponding more with cytological variation than with morphological variation. Additionally, the molecular evidence suggests a phylogeographic pattern associated with the Cascade Ranges, where members of the clade characterized by chromosome counts of n = 6, 8, and 10 are distributed primarily to the west of the Cascades while members of the clade characterized by chromosome counts of n = 12 are distributed primarily to the east. A third clade characterized by n = 10 is localized in the Lake of the Woods region of southern Oregon. Evidence from morphological, cytological, interfertility, and molecular data was used to re-examine the delimitation of species within this complex. Downingia elegans and D. bacigalupii are maintained, while D. yina is split into three morphologically cryptic species (D. yina, D. willamettensis, D. pulcherrima) that do not form a clade.

Karyotype differentiation in three species of Tripogandra Raf. (Commelinaceae) with different ploidy levels

Most species of the genus Tripogandra (Commelinaceae) are taxonomically poorly circumscribed, in spite of having a relatively stable basic number x = 8. Aiming to estimate the cytological variation among Tripogandra species carrying this base number, several structural karyotypic characters were investigated in the diploid T. glandulosa, the hexaploid T. serrulata, and the octoploid T. diuretica. A careful evaluation of chromosome size and morphology did not reveal clear chromosome homeologies among karyotypes. The mean chromosome size was strongly reduced in the octoploid species, but not in the hexaploid species. They also differed largely in the CMA+ banding pattern and in the number of 5S and 45S rDNA sites per monoploid chromosome complement. All three species showed proximal DAPI + heterochromatin, although in T. serrulata this kind of heterochromatin was only visible after FISH. Further, the meiosis in T. serrulata was highly irregular, suggesting that this species has a hybrid origin. The data indicate that, in spite of the conservation of the base number, these species are karyologically quite different from each other.

Molecular, morphological, and cytological analysis of diverseBrachypodium distachyoninbred lines

Brachypodium distachyon (brachypodium) is a small grass with the biological and genomic attributes necessary to serve as a model system for all grasses including small grains and grasses being developed as energy crops (e.g., switchgrass and Miscanthus). To add natural variation to the toolkit available to plant biologists using brachypodium as a model system, it is imperative to establish extensive, well-characterized germplasm collections. The objectives of this study were to collect brachypodium accessions from throughout Turkey and then characterize the molecular (nuclear and organelle genome), morphological, and cytological variation within the collection. We collected 164 lines from 45 diverse geographic regions of Turkey and created 146 inbred lines. The majority of this material (116 of 146 inbred lines) was diploid. The similarity matrix for the diploid lines based on AFLP analysis indicated extensive diversity, with genetic distances ranging from 0.05 to 0.78. Organelle genome diversity, on the other hand, was low both among and within the lines used in this study. The geographic distribution of genotypes was not significantly correlated with either nuclear or organelle genome variation for the genotypes studied. Phenotypic characterization of the lines showed extensive variation in flowering time (7-22 weeks), seed production (4-193 seeds/plant), and biomass (15-77 g). Chromosome morphology of the collected brachypodium accessions varied from submetacentric to metacentric, except for chromosome 5, which was acrocentric. The diverse brachypodium lines developed in this study will allow experimental approaches dependent upon natural variation to be applied to this new model grass. These results will also help efforts to have a better understanding of complex large genomes (i.e., wheat, barley, and switchgrass).

Intraspecific Chromosome Number Variation: a Neglected Threat to the Conservation of Rare Plants

The effectiveness of rare plant conservation will increase when life history, demographic, and genetic data are considered simultaneously. Inbreeding depression is a widely recognized genetic concern in rare plant conservation, and the mixing of genetically diverse populations in restoration efforts is a common remedy. Nevertheless, if populations with unrecognized intraspecific chromosome variation are crossed, progeny fitness losses will range from partial to complete sterility, and reintroductions and population augmentation of rare plants may fail. To assess the current state of cytological knowledge of threatened and endangered plants in the continental United States, we searched available resources for chromosome counts. We also reviewed recovery plans to discern whether recovery criteria potentially place listed species at risk by requiring reintroductions or population augmentation in the absence of cytological information. Over half the plants lacked a chromosome count, and when a taxon did have a count it generally originated from a sampling intensity too limited to detect intraspecific chromosome variation. Despite limited past cytological sampling, we found 11 plants with documented intraspecific cytological variation, while 8 others were ambiguous for intraspecific chromosome variation. Nevertheless, only one recovery plan addressed the chromosome differences. Inadequate within-species cytological characterization, incomplete sampling among listed taxa, and the prevalence of interspecific and intraspecific chromosome variation in listed genera, suggests that other rare plants are likely to have intraspecific chromosome variation. Nearly 90% of all recovery plans called for reintroductions or population augmentation as part of recovery criteria despite the dearth of cytological knowledge. We recommend screening rare plants for intraspecific chromosome variation before reintroductions or population augmentation projects are undertaken to safeguard against inadvertent mixtures of incompatible cytotypes.