Phytochemical and Cytogenetic Characterization of Centaurea solstitialis L. (Asteraceae) from Croatia

The cytogenetic characterization of Centaurea solstitialis L. (Asteraceae) showed a chromosome number of 2n = 16. Karyotype is composed by four pairs of metacentric, two pairs of submetacentric and two pairs of subtelocentric chromosomes. Physical mapping of two rDNA probes revealed two loci of 35S and one locus of 5S rRNA genes. Chromomycin fluorochrome banding revealed that all rDNA loci were GC rich. The genome size (2C‐value) of 1.95 pg classes this species in the group of very small genomes. Chemical composition of C. solstitialis volatile oil (VO) from Croatia, studied with gas chromatography–mass spectrometry showed dominant components as it follows: hexadecanoic acid, α‐linolenic acid, germacrene D and heptacosane. Antioxidant capacity, measured by ferric reducing power assay and 2,2‐diphenyl‐1‐picrylhydrazyl methods, as well as inhibition of acetyl‐ and butyrylcholinesterase of VO was lower comparing to a standard solutions. Volatile oil tested with disc diffusion method showed good inhibitory potential against Pseudomonas aeruginosa, Escherichia coli and all tested fungi: Candida albicans, Penicillium funiculosum and Aspergillus fumigatus. The microdilution method showed best activity against Chronobacter sakazakii and A. fumigatus.     

Antiviral and antimicrobial activities of three sesquiterpene lactones from Centaurea solstitialis L. ssp. solstitialis

Three sesquiterpene lactones (centaurepensin=chlorohyssopifolin A, chlorojanerin and 13-acetyl solstitialin A) isolated from the aerial parts of Centaurea solstitialis L. ssp. solstitialis (Asteraceae) were investigated for antimicrobial and antiviral activities. For the antimicrobial activity assessment, both standard and isolated strains of Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Candida albicans and C. parapsilosis were employed by the microdilution method. Herpes simplex type-1, a DNA virus, and Parainfluenza, an RNA virus, were employed for the determination of the antiviral activity of these three sesquiterpene lactones using Vero cell lines. Ampicilline, ofloxocine, ketoconazole, fluconazole, acyclovir and oseltamivir were used as the reference drugs. 13-Acetyl solstitialin A displayed remarkable antibacterial activity against isolated strains of E. faecalis at 1 μg/ml concentration, which was close to the effective concentrations of ampicillin. The same compound also showed significant activity against the DNA virus, being as potent as the reference compound acyclovir at maximum and minimum concentrations of 16–<0.00006 μg/ml. This is the first report showing that 13-acetyl solstitialin A possesses significant antiviral activity.     

A new Centaurea L. (Asteraceae) species from Turkey

A new Centaurea L. (Asteraceae) species from Turkey is described and illustrated. Centaurea mersinensis Uysal and Hamzao?lu exists on calcareous slopes in Pinus brutia forests of Ayd?nc?k (Mersin) in southern Anatolia. It belongs to C. sect. Phalolepis (Cass.) DC., and taxonomically its closest relative is C. lycaonica. Diagnostic morphological characters from very similar taxa are provided, and a key is provided that includes related species of sect. Phalolepis from Turkey. The geographical distribution of the new species and relatives of the same section are mapped. The chromosome number of C. mersinensis, 2n = 18, counted in root tips, is also reported and illustrated.     

Chromosome numbers of five Turkish Centaurea L. (Asteraceae) species

Abstract

We analysed the effects of patch configuration and site history on vascular plants in ancient forests of the Eastern Po Plain, documented back to 1740. Despite their reduced size, all the forests are part of Natura 2000 Network and significantly contribute to the maintenance of a threatened habitat and support biological diversity of the Continental biogeographic region. The presence of some functional ecological plant species groups was correlated with patch configuration and age. Habitat quality, in terms of suitability for forest species, was found to be important in explaining the presence of species of high conservation value, but patch age (as an indicator for habitat quality) played a major role too. For core forest species, patch area is a redundant variable in explaining species richness relative to habitat quality and patch age and the extinction of specialists seems to occur mainly in a deterministic way. Even small forest fragments can be very important for maintaining plant species diversity, at least if they are of high habitat quality and if the forest management is appropriate. However, to achieve a long term conservation, management plans should also aim at an improvement of the anthropogenic matrix surrounding forest remnants.     

Effects of the rust Puccinia jaceae var. solstitialis on Centaurea solstitialis (yellow starthistle) growth and competition

The rust fungus Puccinia jaceae var. solstitialis was introduced to California in 2003 for biological control of yellow starthistle (Centaurea solstitialis). To test its effectiveness under field conditions, we examined biomass production, chlorophyll levels, and seedhead production of yellow starthistle (YST) infected with P. jaceae. We also evaluated the effect of P. jaceae on the competitive ability of YST grown with wild oat (Avena fatua), a widespread winter annual grass commonly associated with YST infestations. Chlorophyll levels were reduced by over 50% in severely rust-infested YST leaves. P. jaceae had no effect on growth or reproductive variables in monoculture plots, but caused a modest reduction in YST performance in the competition experiment. In this study, infected plants had fewer leaves than uninfected plants and slightly reduced rosette diameters. P. jaceae also decreased YST biomass from 3.18 kg m^?2 in non-inoculated competition plots to 2.62 kg m^?2 in inoculated plots over both years of the experiment. Although not significant, there was a trend towards reduced seedhead production in the inoculated plots. These results indicate that P. jaceae may have some negative effects on YST growth, especially under conditions of interspecific competition. However, the effects of P. jaceae appear to be of minor biological significance and are unlikely to cause major declines in YST populations statewide.     

A Morphometric Study of Populations of the Centaurea jacea Complex (Asteraceae) in Belgium

Abstract: The Centaurea jacea aggregate is a polymorphic polyploid complex whose taxonomic treatment is still controversial. A numerical taxonomic approach was applied to 394 individuals of known ploidy level, from 19 populations, based on the main diagnostic characters proposed in earlier revisions. Populations from xeric grasslands were not considered. Principal Component Analysis shows that variation within the complex is continuous. UPGMA Cluster Analysis based on population means supports the recognition of three groups of populations. However, the limits between these groups are blurred to a considerable extent due to extensive within-population polymorphism. It is argued that the Belgian populations of Centaurea jacea occurring in mesic grasslands should be treated as a single species, with three subspecies. The two extremes of the morphological gradient can be referred to as C. jacea subsp. jacea and C. jacea subsp. nigra, with C. jacea subsp. pratensis occupying an intermediate position. Most populations from Belgium are tetraploid, a diploid chromosome number being found only in populations of C. jacea subsp. nigra from the Ardennes massif. On average, diploids grow at higher altitude and on more acidic soils than tetraploids. Finally, a key to the three subspecies is provided.     

入侵植物紫茎泽兰化感作用及其途径研究

紫茎泽兰广泛入侵中国西南地区,研究结果表明化感作用是其入侵的重要武器,但其化感作用的途径并不十分清楚。本研究中,我们发现紫茎泽兰可以通过多种途径对两种栽培植物大麦和玉米的生长产生化感作用,这些途径包括了叶挥发物、叶淋溶物以及根分泌物。并且在紫茎泽兰幼苗早期就可以检测到这些化感作用。然而,没有实验证据表明紫茎泽兰落叶的微生物降解物对两种测试植物具有化感作用。     

入侵植物紫茎泽兰化感作用及其途径研究

紫茎泽兰广泛入侵中国西南地区,研究结果表明化感作用是其入侵的重要武器,但其化感作用的途径并不十分清楚。本研究中,我们发现紫茎泽兰可以通过多种途径对两种栽培植物大麦和玉米的生长产生化感作用,这些途径包括了叶挥发物、叶淋溶物以及根分泌物。并且在紫茎泽兰幼苗早期就可以检测到这些化感作用。然而,没有实验证据表明紫茎泽兰落叶的微生物降解物对两种测试植物具有化感作用。     

A new species of Centaurea L. (Cardueae: Asteraceae) from Turkey

A new species of Centaurea L., C. kizildaghensis (Cardueae: Asteraceae), is described and illustrated from south Anatolia. It is restricted to the serpentine rocky slopes of Kızıl Dağ (C3 Konya–Derebucak, Çamlık), and is closely related to C. pseudokotschyi Wagenitz and C. drabifolioides Hub.-Mor., from which it differs in stem, leaf, and phyllary appendage characters. The diagnostic morphological characters are discussed. A new key is produced for Group G species for the flora of Turkey.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 61–66.     

Genetic guidelines for the conservation of the endangered polyploid Centaurea borjae (Asteraceae)

Appropriate management of species of conservation concern requires designing strategies that should include genetic information as small population size and restricted geographic range can reduce genetic variation. We used AFLPs to investigate genetic variation within and among populations of the endangered narrow endemic Centaurea borjae, and found no evidence for genetic impoverishment despite its <40 km range and potential for vegetative propagation. Genetic variation was comparable to other plants with similar life history (88 % occurring within populations) and potential clone mates were less frequent than expected. Nonetheless, populations separated by few hundred meters showed signs of significant genetic differentiation suggesting low gene flow between them. Our results suggested that the three geographically closer populations located at the center of the range might be treated as a single management unit, while the remaining ones could be considered independent units. We found evidence of fine-scale spatial genetic structure up to 80 m indicating that the collection of germplasm for ex-situ conservation should focus on individuals separated >80 m to maximize genetic variation.     

A Natural Homoploid Hybrid between Centaurea horrida and Centaurea filiformis (Asteraceae) as Revealed by Morphological and Genetic Traits

Studies over the last two decades demonstrate that hybridization has played an integral role in the evolution of several sections of the genus Centaurea. Nevertheless, natural hybridization between narrow Mediterranean endemic Centaurea species has not been documented as yet. A population of fertile Centaurea individuals exhibiting intermediate morphological traits between two Sardinian narrow endemics, C. horrida and C. filiformis, was identified at the Tavolara Islet (Sardinia, Italy). Intermediate leaf length and head width characterized this population, suggesting its hybrid origin. The putative hybrid population was structured (i.e., composed of seedlings, saplings and adult individuals) and had a relatively high levels of seed production. The number of chromosomes was identical to that of the proposed progenitors (2n?=?18). Genotyping at five microsatellite loci showed that the putative hybrid possessed several alleles in common with the proposed parental species and intermediate values of genetic differentiation, as indicated by both F _ST and R _ST, between C. horrida and C. filiformis. We therefore conclude that the studied intermediate population is of hybrid origin, and discuss possible mechanisms of its reproductive isolation from the parental species, potential re-introgression, and evolutionary implications of this hybridization.     

Secondo Contributo Alla Conoscenza Dello Sviluppo Embriologico del Genere Centaurea L. (Asteraceae). Centaurea Horrida Bad

Summary

The Author has studied the embryological development of Centaurea horrida Bad., pure pliocenic endemisms of Sardinia and has established that:

1°) the cromosomic number of the species is: 2n = 18.

2°) the genesis of microspores is of simultaneous type;

3°) The archesporium is constituted of one cell only seldom accompanied by a basal cell;

4°) the development of the female gamethophyte is of normal type;

5°) even showing cases of degenerated antipodal cells, the species has a marked tendency to the polyantipody, sometimes also characterized by a strong hypertrophy of its cells;

6°) in the species the contemporary germination of some megaspores in the same ovule is enough frequent;

7°) there are also some cases of coesistence of some gamethophytes in their different stages of development;

8°) the phenomenon of «multiple oospheres» and of «multiple synergidae» may happen;

9°) in some ovules, near the egg-apparatus, cells of two or four nuclei may be found.

For these last ascertainments (8° and 9°) the Author makes the hypothesis that it may be probably an anomalous prolification of micropylar nuclei, or asynchronous development, for delayed germination of some micropylar megaspores producing primary stages of gamethophyte.

Moreover the Author has the opportunity to bring into evidence:

10°) a case of ovular teratology represented by the extraovular development of an adult gamethophyte very similar to those previously found by the Author himself in Petasites fragrans;

11°) frequent cases of regretion of female sexuality, founding that about the 10% of the flowers examined were functionally male. The Author has fronted the possibility of the existence, in Asteraceae, also of the type of inflorescence where «flowers are all tubulated: the marginal ones neuter, the others or hermaphrodite or hermaphrodite and male».     

Genetic Differentiation among Populations of the Cave Fish Schistura Oedipus (Cypriniformes: Balitoridae)

DNA sequences were determined for portions of the mitochondrial control region and 16S rRNA genes in five populations of Schistura oedipus, a troglobitic fish from northwestern Thailand. Based on variation at seven sites out of 593 sequenced, the five populations fall into three groups, apparently isolated by altitude and distance. Nucleotide diversity within groups is on the order of 1.0×10^–3 while the extra increment of diversity among groups is on the order of 5.0×10^–3. While the groups are distinct, the level of differentiation among them is low enough to accept provisionally that the five populations represent a single species. On the basis of 16S sequence, Schistura oedipus appears to be more closely related to S. poculi than to S. reidi, a proposed sister taxon.     

Genetic Differentiation among Natural Populations of Lepilemur ruficaudatus

We studied the genetic differentiation of five populations of red-tailed sportive lemur Lepilemur ruficaudatus by means of allozyme variability and RAPD polymorphisms in order to test whether the Tsiribihina River separates the distribution areas of Lepilemur ruficaudatus and and L. edwardsi. Genetic data as well as the karyotype of a male individual clearly indicate that the Andramasay Forest in the north of Tsiribihina River is inhabited by Lepilemur ruficaudatus and not by L. edwardsi. We propose that the distribution of the two species are separated by the Manambolo River. However, the northernmost population of Lepilemur ruficaudatus inhabiting the Andramasay Forest is gentically differentiated from those that inhabit the dry forest in the south of Tsiribihina River.     

Centaurea tchihatcheffii Fischer & C.A. Meyer (Asteraceae)

Centaurea tchihatcheffii is a steppic annual possessing some unique features absent in other Centaureas. The chromosome number is 2n = 20, differing from all other annual species of Centaurea sect. Cyanus. The type locality as published is erroneous and the correct provenance is provided.