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Biodiversity has been confronted with anthropogenic threats and several natural threats such as biological invasions. The success of these invasions involves phytotoxic products released by invasive plants that can exhibit allelopathic effects on target species. Thus, aqueous extracts from different parts of the Mediterranean yellow star-thistle [Centaurea solstitialis subsp. schouwii (DC.) Gugler], were tested for their allelopathic effects on seed germination and seedling growth of Sulla coronaria (L.). Bioassays were conducted in vitro to test the effects of the aqueous extracts of shoot, basal and root parts of C. solstitialis subsp. schouwii at two different concentrations (50 g·L−1 and 10 g·L−1). The concentrations of total polyphenols, flavonoids, and tannins of the extracts were also evaluated. Our results showed inhibitory effects on the germination and seedling growth of S. coronaria seedlings, particularly with the extract form the basal part, reaching 84%. This study confirms the linear relationships between the allelopathic effects of C. solstitialis subsp. schouwii and the polyphenol and flavonoid contents. However, further experiments are needed under field conditions to confirm the results obtained under laboratory conditions.

Background: The antioxidant activity and the total phenolic and flavonoid contents of the derived extracts (chloroform, ethyl acetate and n-butanol) of the 70% hydroalcoholic extract of the aerial parts of Centaurea solstitialis growing in Algeria was assessed. The active extracts were selected for phytochemical investigations. Methods: The antioxidant capabilities of the extracts were assessed using 1, 1-diphenyl-2- picrylhydrazyl radical (DPPH•) scavenging and Cupric Ion Reducing Antioxidant Capacity (CUPRAC) assays. Butylhydroxyanisole (BHA), butylhydroxytoluene (BHT) and α –tocopherol were used as positive controls. The total phenolic content and total flavonoid content of the extracts were determined as gallic acid equivalents and quercetin equivalents, respectively. Chromatographic methods were used to isolate the secondary metabolites and spectrometric and spectroscopic methods were used to determine their chemical structures. Results: The ethyl acetate extract exhibited the highest antioxidant activities followed by the n-butanol extract. The highest phenolic and flavonoid contents were found in the n-butanol extract. Phytochemical study of the ethyl acetate and n-butanol extracts led to the isolation of an undescribed guaianolide named 3-(4-hydroxybenzoyl)-cynaratriol and a known sesquiterpene lactone along with three known flavonoid glycosides. Their structures were established by spectral analyzes mainly high resolution electrospray ionisation mass spectrometry (HR-ESIMS) and 1D and 2D nuclear magnetic resonance experiments. Conclusion: The extracts of aerial parts of C. solstitialis showed significant antioxidant activities. An undescribed sesquiterpene lactone and four known secondary metabolites were isolated from the most active extracts.

Ramularia ranunculicola sp. nov. (Mycosphaerellaceae) is described from Iran on Ranunculus muricatus and compared with other species reported on Ranunculus spp. Ramularia carletonii on Lactuca tuberosa and R. nagornyi on Centaurea solstitialis are newly reported from Iran, and Picris strigosa is a new host for R. picridis (= R. inaequalis s. lat.).

PREMISE OF THE STUDY: Seed-level trade-offs of heterocarpic species remain poorly understood. We propose that seedlings emerging from seeds with apermanent pappus (dispersing seeds) are stronger competitors than those emerging from seeds without a pappus (nondispersing seeds) because dispersingseeds are larger and germinate faster than nondispersing seeds in Centaurea solstitialis .METHODS: We conducted a competition experiment with both seed morphs, in which we recorded emergence rate and proportion, estimated seed dispersalby wind (anemochory) and by mammals (exozoochory), and measured size and abundance of seed morphs.KEY RESULTS: We found that seedlings from pappus seeds had greater competitive abilities than those from non-pappus seeds. Similarly, pappus seedlingsemerged at much faster rates and larger proportions than non-pappus seedlings. Pappus seeds were larger, were more numerous, and displayed improvedexozoochory compared to non-pappus seeds. Anemochory was poor for both seed morphs.CONCLUSIONS: We found support for our hypothesis, raising in turn the possibility that competition and colonization are positively associated in seedmorphs of heterocarpic species with enhanced exozoochory of larger seeds. These fi ndings are not consistent with those from heterocarpic species withenhanced anemochory of smaller seeds or slower-germinating seeds. Our results additionally suggest that pappus and non-pappus seeds of C. solstitialisdisplay a task-division strategy in which pappus morphs colonize and preempt unoccupied sites through improved dispersal and fast and large emergenceof seedlings with increased competitive abilities, whereas non-pappus morphs promote site persistence through delayed germination and dormancy.This strategy may contribute to the success of C. solstitialis in highly variable environments. Fil: Miguel, María Florencia. Universidad Nacional de la Pampa. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Lortie, Christopher J.. University of York; Reino Unido Fil: Callaway, Ragan M.. University of Montana; Estados Unidos Fil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Allelopathy, the release of chemicals byplants that inhibit the germination and growth ofcompeting species, can be an important trait forinvasive success. However, little is known aboutpotential biogeographical differences in allelopathydue to divergent regional eco-evolutionary histories.To test this, we examined the allelochemical potentialof the highly invasive species Centaurea solstitialisfrom six world regions including native (Spain,Turkey) and non-native ranges (Argentina, Chile, California and Australia). Seeds from several populationsin each region were collected and grown undercommon garden conditions. Allelopathic potential andchemical composition of three leaf extract concentrationsof C. solstitialis from each region: 0.25%, 0.5%0.75% (w/v-1) were assessed on the phytometerLactuca sativa. The main allelochemicals present inthe leaf-surface extract were sesquiterpene lactonesthat varied in major constitutive compounds acrossregions. These leaf extracts had strong inhibitoryeffects on L. sativa seed germination and net growth.Summed across regions, the 0.25% concentrationsuppressed germination by 72% and radicle elongationby 66%, relative to the controls. At the 0.5% concentration, no seeds germinated when exposed toextracts from the non-native ranges of Argentina andChile, whereas germination and radicle growth werereduced by 98% and 89%, respectively, in theremaining regions, relative to controls. Germinationand seedling growth were completely inhibited at the0.75% concentration extract for all regions. Some nonnativeregions were characterized by relatively lowerconcentrations of allelochemicals, suggesting thatthere is biogeographical variation in allelopathicexpression. These findings imply that rapid selectionon the biochemical signatures of an exotic invasiveplant species can be highly region-specific across theworld. Fil: Irimia, Ramona E.. Universidad de Coimbra; Portugal Fil: Lopes, Susana M. M.. Universidad de Coimbra; Portugal Fil: Sotes, Gastón. Universidad de Tarapaca.; Chile. Universidad de Chile; Chile Fil: Cavieres, Lohengrin A.. Universidad de Chile; Chile. Universidad de Concepción. Facultad de Ciencias Naturales y Oceanografía; Chile Fil: Eren, Ozkan. Adnan Menderes Universitesi; Turquía Fil: Lortie, Christopher J.. York University; Canadá Fil: French, Kristine. University Of Wollongong. School Of Earth And Enviromental Sciences; Australia Fil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Confluencia. Instituto de Ciencias de la Tierra y Ambientales de la Pampa. Grupo Vinculado Fundacion Centro de Salud E Investigaciones Medicas | Universidad Nacional de la Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de la Pampa. Grupo Vinculado Fundacion Centro de Salud E Investigaciones Medicas.; Argentina Fil: Rosche, Christoph. University of Montana; Estados Unidos. Martin Luther University Halle Wittenberg; Alemania Fil: Callaway, Ragan M.. University of Montana; Estados Unidos Fil: Pinho e Melo, Teresa M. V. D.. Universidad de Coimbra; Portugal Fil: Montesinos, Daniel. Universidad de Coimbra; Portugal. James Cook University; Australia

Phoma exigua Desm. (teleomorph Didymella exigua (Niessl) Sacc.) was isolated from wilted Centaurea solstitialis L. (yellow starthistle) plants displaying necrosis of the crown that were found near Krasnodar, Russia. The fungus was identified using morphological and cultural characteristics (1,2) and confirmed by sequencing the complete internal transcribed spacer region of the nuclear rDNA (GenBank Accession No. AY089978). P. exigua is a relatively common soilborne fungus that is weakly pathogenic on a diverse range of primarily dicotyledonous plants throughout the world (1). To our knowledge, it has never been reported previously on members of the genus Centaurea. Yellow starthistle is native to eastern Europe and the Mediterranean Region, and is now a noxious weed in North America for which P. exigua is being investigated as a potential biological control agent. Repeated pathogenicity studies (N = 30) resulted in a mortality of 80 and 93% within 7 days when 1-week-old seedlings were transplanted in soil infested with P. exigua-colonized wheat seed at rates of 6.7 and 10% (vol/vol), respectively. Symptoms of the seedlings included necrosis of the stem and wilting of the seedling. Pycnidia were observed in the roots of dead seedlings. The isolate of P. exigua has been deposited as a dried specimen at the U.S. National Fungus Collections, Beltsville, MD (BPI 841766) and as a living culture at the CBS collection in Utrecht, Netherlands (CBS 110211). References: (1) G. Morgan-Jones and K. B. Burch. Mycotaxon 32:477, 1988. (2) H. A. Van Der Aa et al. Persoonia 17:435, 2000.

Centaurea solstitialis L. (yellow starthistle [YST]), family Asteraceae, an invasive weed in California and the western United States is targeted for biological control. During the spring of 2004, an epidemic of dying YST plants was found near Kozani, Greece (40°22′07″N, 21°52′35″E, 634 m elevation). Rosettes of YST had small, brown leaf spots on most of the lower leaves. In many cases, these spots coalesced and resulted in necrosis of many of the leaves and death of the rosette. Along the roadside where the disease was found, >100 of the YST plants showed disease symptoms. Diseased plants were collected, air dried, and sent to the quarantine facility of the Foreign Disease-Weed Science Research Unit (FDWSRU), USDA, ARS, Fort Detrick, MD. Diseased leaves were surface disinfested and placed on moist filter paper in petri dishes. Conidiophores and conidia were observed after 48 h. The fungal isolate, DB04-011, was isolated from these diseased leaves. Pathogenicity tests were performed by spray inoculating the foliage of 20 4-week-old YST rosettes with an aqueous suspension of 1 × 106 conidia per ml. Conidia were harvested from 2-week-old cultures grown on modified potato carrot agar (MPCA). Inoculated plants were placed in an environmental chamber at 23°C with 8 h of daily light and continuous dew for 48 h. Inoculated and control plants were moved to a 20°C greenhouse bench and watered twice per day. After 7 days, leaf spots were observed first on lower leaves. After 10–12 days, all inoculated plants showed typical symptoms of the disease. No symptoms developed on control plants. The pathogen, DB04-011, was consistently isolated from symptomatic leaves of all inoculated plants. Disease symptoms were scattered, amphigenous leaf spots in circular to subcircular spots that were 0.2 to 7 mm in diameter and brownish with distinct dark green margins. Intraepidermal stromata, 14 to 77 μm in diameter and pale yellow to brown, were formed within the spots. Conidiophores that arose from the stromata were straight, subcylindrical, simple, 70 to 95 × 2.8 to 4 μm, hyaline, smooth, and continuous or septate with conidial scars that were somewhat thickened, colorless, and refractive. Primary conidia were subcylindrical, slightly obclavate or fusiform, ovoid, 21 to 49 × 5 to 7.5 μm, 0 to 5 septate, hyaline, smooth, had a relatively rounded apex, and the hilum was slightly thickened. Conidial dimensions on MPCA were 11.2 to 39.2 × 4.2 to 7 μm (average 25.5 × 5.5 μm). Koch's postulates were repeated two more times with 20 and 16 plants. On the basis of fungal morphology, the organism was identified as a Cercosporella sp., (1,2; U. Braun and N. Ale-Agha, personal communication). To our knowledge, this is the first report of this genus of fungus parasitizing YST. Results of host range tests will establish if this isolate of Cercosporella has potential as a biological control agent of YST in the United States. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 844247). Live cultures are being maintained at FDWSRU and European Biological Control Laboratoryt (EBCL), Greece. References: (1) U. Braun. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 1. IHW-Verlage, Eching-by-Munich, 1995. (2) U. Braun. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 2. IHW-Verlage, 1998.

Yellow starthistle (Centaurea solstitialis) is an annual invasive weed in the United States with Mediterranean origins. The expense of chemical control and the vast area of invasion make this weed an appropriate target for classical biological control. Observations of a field site in southern France revealed small orange galls on the leaves of yellow starthistle seedlings caused by the fungus Synchytrium solstitiale. Inoculation of yellow starthistle seedlings with a suspension of zoospores released from infected tissue resulted in infection. Ten days after inoculation, typical orange galls appeared on the exposed tissue. Preliminary host range testing showed up to 100% infection of C. solstitialis seedlings from both France and the United States and infection of Carthamus tinctorius, Centaurea americana, C. diffusa, C. rothrockii, C. squarrosa, and Helianthus annuus seedlings. No symptoms were observed on seedlings of Centaurea calcitrapa, C. maculosa, C. sulfurea, Cirsium californica, C. occidentale, Cynera cardunculus, and Taraxacum officinale. Zoospores were released in a pH range between 4.45 and 8.25 and optimally at temperatures between 5 and 15°C. Infection of yellow starthistle seedlings occurred after a minimum 1-h exposure to a zoospore suspension at 20°C.

Centaurea solstitialis L. (yellow starthistle), family Asteraceae, an invasive weed in California and the western United States, is targeted for biological control. In the summer of 2003, an epidemic of unknown etiology on dying C. solstitialis plants was observed near Kozani, Greece (40°22′07″N, 21°52′35″E, elevation, 634 m). Plants had necrotic light brown leaf spots on the lower leaves and the decurrent leaf bases along the stems. Often, necrotic lesions extended along the stems to the capitula. Virtually all plants in a solid stand of C. solstitialis (approximately 0.5 ha) showed disease symptoms. Diseased plants were collected, air dried, and sent to the quarantine facility of the Foreign Disease-Weed Science Research Unit (FDWSRU), USDA/ARS, Fort Detrick, MD. On the basis of culture growth (45-cm diameter after 2 weeks at 25°C on malt extract agar), fungal morphology (1), and comparison with 21 internal transcribed spacer sequences in GenBank, the putative causal organism was identified as Cladosporium herbarum (Pers.:Fr.) Link. (teleomorph = Davidiella tassiana (De Not.) Crous & U. Braun). Sixteen C. solstitialis plants in the rosette stage and 16 plants in the bolted stage were inoculated with an aqueous suspension of spores (106 conidia ml-1) and placed in an environmentally controlled chamber at 25°C with 8 h of dew and 12 h of light daily. Plants in the rosette stage were resistant, but the fungus was very aggressive on bolted plants. Within 4 to 6 days of inoculation, necrosis developed on leaves and stems and then spread up the stems to the capitula, often resulting in plant death. The fungus also infected developing flowers. Cladosporium herbarum was reisolated from each of the 16 bolted C. solstitialis plants in two separate tests at the FDWSRU and from all bolted inoculated plants at the European Biological Control Laboratory (EBCL) in Greece. In the greenhouse at the EBCL, the pathogen readily spread to (and was isolated from) another 10 noninoculated C. solstitialis plants in close vicinity to the inoculated C. solstitialis plants. Results of host range tests will establish if this isolate of Cladosporium herbarum has the potential as a biological control agent of C. solstitialis in the United States and does not pose a threat to other Centaurea spp. used in horticulture. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 863446). Live cultures are being maintained at the FDWSRU and EBCL, Greece. To our knowledge, this is the first report of a disease caused by Cladosporium herbarum on C. solstitialis. Reference: (1) M. H. M. Ho et al. Mycotaxon 72:115, 1999.

Yellow starthistle (YST), Centaurea solstitialis L., is a weedy plant that is widely distributed in the Krasnodar Region of Russia. It is also an aggressive invasive weed in the western United States and a target of biological control efforts. In the summer of 2006, several hundred diseased plants were found near Taman, Russia. Symptoms of the disease were yellow, water-soaked leaf spots. Diseased leaves were collected, air dried, and sent to the Russian State Collection of Phytopathogenic Organisms at the All Russia Institute of Phytopathology (ARIP). The fungus isolated from the diseased leaves conformed to Periconia igniaria E.W. Mason & M.B. Ellis (teleomorph Didymosphaeria igniaria C. Booth) (1). Colonies of the fungus grew rapidly on potato glucose nutrition medium with aerial mycelium from fluffy to pressed and colorless at the beginning and darkening to black with age. The medium side of the colonies gradually became violet purple to wine colored. Conidiophores had aerial mycelia as much as 550 μm long and 9 to 13 μm wide tapering to 6 to 10 μm. Conidiophores were dark with short, swollen branched stipes. Conidia, formed in short twisted chains, were spherical, dark brown, 7 to 9 μm in diameter, and covered by 1 μm long spines. Yellow starthistle plants were grown in growth chambers with day/night air temperatures of 26 to 28/20 to 22°C, 60 to 70% relative air humidity, and 10,000 lx light for 16 h. Fifteen plants in the rosette stage were spray inoculated with an aqueous suspension of P. igniaria conidia at 5 × 106 conidia/ml and 5 ml per plant. Disease on leaves was observed on all plants 3 to 4 weeks after inoculation when the plants started to bolt. When the plants reached flowering stage, diffused yellow spots were observed on stems and inflorescences and all flowers died. Diseased leaves were surface disinfested and put on potato saccharose nutrition medium. P. igniaria was reisolated from 3 to 5 leaves of each plant and from flowers and stems that developed from 10 inoculated rosettes. Flowers of 10 YST plants were also inoculated with P. igniaria isolated from the previously inoculated plants. Disease developed in the flowers of all inoculated plants, and the symptoms were identical to those observed when rosettes were inoculated and disease followed bolting and flowering. No symptoms developed on four noninoculated plants included in each test. Internal transcribed spacer (ITS) sequences of the fungus were obtained and compared with sequences from GenBank. An uncultured soil fungus and three isolates of P. macrospinosa Lefebvre & Aar.G. Johnson produced the best homology (96%). No sequences for P. igniaria were available for comparison, but the description of P. macrospinosa (conidia 18 to 32 μm in diameter with 2.5 to 6 μm long spines) is clearly different than our isolate. ITS sequences for our isolate have been deposited in GenBank (Accession No. EU367468) and a voucher specimen has been deposited with the U.S. National Fungus Collection (BPI 878355). To our knowledge, this is the first report of P. igniaria causing disease on YST. Live cultures are being maintained at the Russian State Collection of Phytopathogenic Organisms in ARIP. Reference: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, UK, 1971.

The rust fungus Puccinia jaceae var. solstitialis is the first pathogen released for biological control of yellow starthistle (Centaurea solstitialis). From 2004 to 2006, the pathogen was released at 176 sites in 40 counties throughout the state of California. Release sites were evaluated 1 to 3 months and 1, 2, and, in some cases, 3 years after releases to monitor for reemergence. At 1 to 3 months after inoculation, 58 to 93% of sites had rust infection, depending on the year. After 1, 2, and 3 years, the percentages declined to 19 to 21, 9 to 10, and 3% respectively. Spread was detected at 19% of the sites with rust infection, with an average distance of 21 m (±13.3 standard error). The greatest spread occurred at a site in Sonoma County. At this site, the rust spread to over 37 acres 1 year after it was released and has remained in this area for three seasons. Reemergence 1 and 2 years after inoculations was more likely in Northern (above 40°N) compared with Southern California (below 36°N). In general, reemergence was more likely at lower elevations when release sites were within 150 km of the coast. Overall, the rust has not demonstrated a strong record of persistence based on these observations.

Yellow starthistle (Centaurea solstitialis L) (YST) is an invasive weed native to the Mediterranean region with a geographical centre of diversity in Turkey. It is widely established in Chile, Australia, and western North America. It arrived in California as a contaminant in alfalfa seed in 1859 and, by 2002, had infested >7.7 million hectares in the U.S.A. Biological control of YST using capitula feeding weevils, picture wing flies and a foliar rust pathogen has been ongoing in the western U.S.A. for more than three decades with limited success. Modelling and field research suggest natural enemies that kill whole plants and/or reduce seed production of survivors are good candidates for successful biological control. A candidate species with some of these attributes is the rosette weevil Ceratapion basicorne (Illiger). In the present study, a model of the rosette weevil is added to an extant system model of YST and its capitula feeding natural enemies and, in a GIS context, is used to assess YST control in the Palearctic region and the weevil's potential impact on YST in western U.S.A. The results obtained suggest densities of mature YST plants in western U.S.A. would be reduced by 70–80% in many areas.

Summary Arbuscular mycorrhizal (AM) fungi can exert a powerful influence on the outcome of plant–plant competition. Since some exotic plants interact differently with soil biota such as AM fungi in their new range, range-based shifts in AM responsiveness could shift competitive interactions between exotic and resident plants, although this remains poorly studied. We explored whether genotypes of the annual exotic Centaurea solstitialis (yellow starthistle), collected from populations across the native and non-native ranges, differed in responsiveness to AM fungi in the introduced range and whether range-based differences in mycorrhizal responsiveness affected how strongly C. solstitialis tolerated competition with the North American native bunchgrass, Stipa pulchra. Grown alone, C. solstitialis from both ranges derived only weak benefits from AM fungi. However, association with AM fungi was costly to plants when grown in competition with S. pulchra. The magnitude of the suppressive effect of AM fungi was greater for genotypes from native versus introduced populations. Synthesis. Many exotic invasive species are known to associate weakly with AM fungi, which may be beneficial in disturbed habitats where competition for resources is low. Our results indicate that reduced mycorrhizal associations may also benefit invaders in a competitive environment. Centaurea solstitialis were more strongly suppressed by established S. pulchra plants in the presence versus absence of AM fungi, but exotic genotypes were less suppressed than native genotypes. This suggests that AM fungi may contribute to invasion resistance in established native communities, but range-based shifts in the way exotic genotypes respond to AM fungal partners may counter such biotic resistance.

In this study, calcium oxalate (CaOx) crystals in the tissues and organs of 18 species that belong to tribe Cardueae (Asteraceae), Arctium minus, Silybum marianum, Cirsium vulgare, Cirsium creticum, Cirsium arvense, Carduus nutans, Carduus candicans, Carduus pycnocephalus, Tyrimnus leucographus, Jurinea consanguinea, Centaurea diffusa, Centaurea solstitialis, Centaurea iberica, Centaurea salonitana, Centaurea cyanus, Carthamus lanatus, Carthamus dentatus and Xeranthemum annuum , were investigated, and their morphologies and distribution were determined using a light microscope. Two morphological types of crystals, styloids and prismatics, were the most found crystals in the species examined. Raphides were only observed in the stem cortex and pith parenchyma cells of Silybum marianum, while druses were only viewed in the stem pith cells of Carduus pycnocephalus. Styloids were observed (if present) in the leaf, corolla, anther, filament, and style tissues. Prismatic crystals were seen almost in all the ovaries of the species investigated, except for Xeranthemum annuum. Prismatics, styloids, raphides, and druses were present in the stems of the species. It is considered that crystal formation within the cell is under genetic control. Thus the type, and presence or absence of crystals may be represented as a taxonomic character. In conclusion, it is suggested that the shape and location of CaOx crystals in the Cardueae constitute a diagnostic character and they may have taxonomic significance in this tribe.

A host choice experiment was carried out to determine the host range of some potential biological control agents of yellow starthistle (Centaurea solstitialis), a Mediterranean plant which has become a serious rangeland weed in western USA. This paper describes the results of that experiment and discusses its taxonomic implications. The experiment confirmed the extreme host specificity of some species. However, two reputedly polyphagous species, Acanthiophilus helianthi (Rossi) and Urophora quadrifasciata (Meigen), attacked a narrower range of hosts than expected. The results of this and similar host choice experiments are discussed and it is concluded that this sort of anomaly can be caused by the existence of host races, unrecognized sibling species, or by varieties of plants naturally resistant to attack. These complex patterns of host relationship highlight the need to interpret host catalogue data cautiously, as they oversimplify complex biological systems. The identity of one species reared in the experiment, Terellia luteola (Wiedemann), is discussed; a key is presented for its separation from other Terellia species, and it is removed from synonymy with T. colon (Meigen).

Invasive plants may leave enemies behind when they colonize a new habitat, allowing selection to favor increased investment in growth and/or reproduction over defensive traits. Previous studies have identified reduced diversity of potential bacterial pathogens and evolutionary increases in growth and reproduction in invading populations of yellow starthistle (Centaurea solstitialis). This study leverages a recently developed high-throughput assay of immune function to test for evidence of a trade-off between increased growth and defense against bacterial pathogens in yellow starthistle's invasion of California (USA). Seven bacterial strains were cultured from infected leaf tissue in the native range. Healthy leaf tissue from five native European collections and six invading collections were exposed to these native bacterial strains. A standardized assay of peroxidase activity was used measure the oxidative burst immune response to pathogen recognition by the leaf. Immune responses were compared to plant growth within and between ranges to assess evidence for a trade-off. Plant genotypes from the native range demonstrated a higher immune response to bacterial strains than did invading genotypes, consistent with a trade-off with plant growth across regions. The same trade-off was also apparent across genotypes from the native range, but not across genotypes from the invaded range. Our results provide evidence that increased growth in a highly invasive plant species may come at a cost to immune function, consistent with the hypothesis that escape from enemies can provide opportunities for shifts in resource allocation that favor the proliferation of non-native species.

Centaurea solstitialis L. (yellow starthistle, Asteraceae) is a Eurasian native plant introduced as an exotic into North and South America, and Australia, where it is regarded as a noxious invasive. Changes in ploidy level have been found to be responsible for numerous plant biological invasions, as they are involved in trait shifts critical to invasive success, like increased growth rate and biomass, longer life-span, or polycarpy. C. solstitialis had been reported to be diploid (2nD2x D16 chromosomes), however, actual data are scarce and sometimes contradictory. We determined for the first time the absolute nuclear DNA content by flow cytometry and estimated ploidy level in 52 natural populations of C. solstitialis across its native and non-native ranges, around the world. All the C. solstitialis populations screened were found to be homogeneously diploid (average 2C value of 1.72 pg, SD D 0.06 pg), with no significant variation in DNA content between invasive and non-invasive genotypes. We did not find any meaningful difference among the extensive number of native and non-native C. solstitialis populations sampled around the globe, indicating that thespecies invasive success is not due to changes in genome size or ploidy level. Fil: Irimia, Ramona Elena. Universidad de Coimbra; Portugal. Stejarul Research Centre for Biological Sciences; Rumania Fil: Montesinos, Daniel. Universidad de Coimbra; Portugal Fil: Eren, Ozkan. Adnan Menderes Üniversitesi; Turquía Fil: Lortie, Christopher J.. University of York; Reino Unido Fil: French, Kristine. University Of Wollongong; Australia Fil: Cavieres, Lohengrin A.. Universidad de Concepción; Chile. Instituto de Ecología y Biodiversidad; Chile Fil: Sotes, Gastón J.. Universidad de Concepción; Chile. Instituto de Ecología y Biodiversidad; Chile Fil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Jorge, Andreia. Universidad de Coimbra; Portugal Fil: Loureiro, João. Universidad de Coimbra; Portugal

Herbivore damage often deters pollinator visitation and many invasive plants in North America are pollinator-dependent. This has important implications for the biological control of invasive plants because it means that agents that deter pollinators may have a larger than expected impact on the plant. Yet interactions between pollinators and biocontrol agents are rarely evaluated. Centaurea solstitialis, one of the most problematic invasive species in California, is dependent on pollinators for reproduction. I factorially manipulated infection by a biocontrol pathogen and pollen supplementation to test for (1) pollen limitation in C. solstitialis, (2) whether infection increased pollen limitation, and (3) whether this varied across a soil moisture gradient. Plants growing on north-facing slopes where soil moisture was higher experienced mild pollen limitation in the absence of the pathogen and more pronounced pollen limitation when they were infected. Plants on drier south-facing slopes did not suffer from pollen limitation but instead appeared to suffer from resource limitation. Pathogen infection directly reduced seed set in C. solstitialis by 67–72 %. On north-facing slopes, infection had an additional, indirect effect by increasing the degree of pollen limitation plants experienced. The trait that mediates this indirect pathogen–pollinator interaction is the number of inflorescences plants produced: infected plants made fewer inflorescences which led to greater pollen limitation. Although in the present study this outcome is dependent on abiotic factors that vary over small spatial scales, exploiting other invasive plants’ dependence on pollinators by selecting agents that deter visitation may enhance agent impact.

Dittrichia graveolens is a rapidly spreading invasive plant in California. While populations are observed primarily in disturbed areas, there is concern it may expand into adjacent undisturbed areas, particularly grasslands and riparian corridors. In a field experiment conducted in two successive years, we compared plant growth and phenological development of fall, winter, and spring sown seeds. Plants establish equally well in disturbed upland sites in both above and below average precipitation years but the absence of late spring rainfall negatively affected total plant biomass. In a greenhouse experiment, we compared growth in four light environments (100, 50, 27 and 9 % available light). Total plant growth decreased exponentially with decreasing light. This suggests that D. graveolens is not competitive in low light environments, such as woodlands and riparian forests. All plants flowered in early- to mid-September, coinciding with flowering in field grown plants, suggesting that photoperiod is the primary signal for reproductive growth. Using a minirhizotron system, we measured root growth over time in D. graveolens and three common California annual grassland species, two non-natives, Centaurea solstitialis and Bromus hordeaceus, and the native forb Holocarpha virgata. Root growth of D. graveolens began later in the season than the other species, reaching depths >1 m by late May. Roots of C. solstitialis and H. virgata reached >1 m earlier in the season. The temporal difference in root growth suggests that D. graveolens may be less competitive for soil moisture with other early season annuals than other deep-rooted broadleaf species found in grasslands.

A 2-yr (2014-2015) field study in eastern Washington State quantified the effect of environmental factors on the overwintered Eustenopus villosus (Boheman) and Larinus curtus (Hochhut) adults in relation to phenology of Centaurea solstitialis L. (Asteraceae: Cardueae), the feeding and breeding host for these two weevil biocontrol agents. We recorded in the study area: ambient and soil temperatures, soil moisture, percent cover and developmental stage of C. solstitialis, and presence of adults of each weevil species. Sampling took place from early May to mid-August. Weevil activity for both species in both years was segregated into three phases: 1 - a pre-appearance phase in which neither species was detected, 2 - appearance and increase in frequency, and 3 - decrease in frequency. Eustenopus villosus increase in frequency was most strongly associated with warming temperatures both years. Larinus curtus increase in frequency in 2014 was most associated with increasing C. solstitialis cover and in 2015 with warming temperatures and drying soils. In both years, both weevil species' decline in frequency was likely due to the advancing C. solstitialis phenology. This pattern indicates that the appearance and increase in frequency of the overwintered E. villosus and L. curtus adults was likely a function of warming temperatures. Both species' decline in frequency was likely a function of the weevils completing their life cycle in synchrony with the phenological advancement of C. solstitialis and decline of abundant breeding and foraging sites (buds and flowers).

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.

Ceratapion basicorne is a weevil native to Europe and western Asia that is being evaluated as a prospective classical biological control agent of Centaurea solstitialis (yellow starthistle) in the United States. Choice oviposition experiments were conducted under laboratory conditions to help assess host-plant specificity of the insect. Mean oviposition rates were highest on C. solstitialis (66% of eggs, on a per replicate basis) followed by Centaurea cyanus (bachelor's button 22%), Centaurea melitensis (6%), Centaurea americana (1%), Saussurea americana (3%) and Carthamus tinctorius (safflower 2%). Adult feeding damage followed a similar pattern; however, there was less oviposition relative to the amount of adult feeding on each of the non-target species than on the target host plant, C. solstitialis. Thirteen safflower varieties were tested, and oviposition occurred on eight of them, at low rates. Adult feeding occurred on all safflower varieties tested, although at rates much lower than on yel...

Many invasive plants are attacked by more than one biocontrol agent. Attack by multiple enemies may give rise to indirect interactions, the nature of which may be influenced by the abiotic environment. We conducted a field experiment to determine (1) whether indirect interactions arose between Centaurea solstitialis, a foliar pathogen and three insect seed predators and (2) how the outcome was influenced by soil type (serpentine and non-serpentine). Because serpentine soils support high numbers of endemic species they are a priority for conservation. They also have very low calcium concentrations and Ca++ regulates plants’ ability to defend against pathogen infection. C. solstitialis growing on serpentine soil may therefore be more vulnerable to the pathogen and this may in turn affect the plant’s subsequent interactions with seed predators. We found that pathogen infection had a direct, negative impact on plant performance but its impact was not greater on serpentine plants. When attacked by the seed predators, inflorescences produced more viable seed when they were on plants infected with the pathogen than when they were on uninfected plants and the data suggest that this reflects reductions in larval seed-feeding. On the non-serpentine soil, the pathogen’s direct, negative impact was entirely canceled out by its indirect, positive effect via reduced seed predation. On the serpentine soil, plants attacked by the pathogen and the insect seed predators produced half as many seeds than plants attacked only by the seed predators. Our results demonstrate that biocontrol agent interactions may be modified by the plant and by the abiotic environment in a way that fundamentally alters their net impact on the weed.

Understanding the differences between weedy and non-weedy plant populations is important because they may provide clues to genetic factors that create invasive species, as well as important insights into local adaptation. We studied weedy, non-native (California and Argentina) and non-weedy, native populations (Republic of Georgia and Turkey) of Centaurea solstitialis in a common garden setting. Specimens grown from non-native seed stock were generally taller, had longer leaves with more surface area, and flowered earlier than plants grown from native seed stock. Plants from California tended to be much taller, on average, than plants from any other country, and plants from the Republic of Georgia tended to bolt much later than plants from other countries. When we compared neutral genetic variation at microsatellite or simple sequence repeat markers using AMOVA to quantitative morphological variation, we found that quantitative variation was much more likely to be partitioned among regions than genetic variation. We also evaluated F ST values against Q ST (F ST/Q ST analysis) and found evidence for possible selection on plant height and leaf length in the non-native regions. Our results suggest that local adaptation may play a role in the success of C. solstitialis as an invasive weed. Fil: Eriksen, Renée L.. University of Massachusetts-Boston; Estados Unidos Fil: Desronvil, Theodora. University of Massachusetts-Boston; Estados Unidos Fil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Kesseli, Rick. University of Massachusetts-Boston; Estados Unidos

SummaryIn this study, honeys samples of different origin: pine (Pinus pinea); tufted vetch (Vicia cacca); locust (Robinia pseudoacacia); garden vetch (Vicia sativa); cedar (Cedrus spp.); yellow starthistle (Centaurea solstitialis); cotton (Gosspium hirsutum); trefoil (Trifolium spp.); cornflower (Centaurea cyanus) obtained from different locations in Turkey were investigated. Mineral contents of honeys were determined by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Whilst the Sodium contents of the honeys varied between 168.11 ppm and 729.94 ppm, and phosphorus concentrations varied from 462.38 ppm to 845.65 ppm, magnesium was found at the highest concentrations in our samples.

Centaurea solstitialis (yellow starthistle, Asteraceae) is an invasive annual weed in the western USA that is native to the Mediterranean Region and is a target for classical biological control. Aceria solstitialis is an eriophyid mite that has been found exclusively in association with Ce. solstitialis in Italy, Greece, Turkey and Bulgaria. The mite feeds on leaf tissue and damages bolting plants, causing stunting, witch's broom and incomplete flower development. Field experiments and laboratory no-choice and two-way choice experiments were conducted to assess host plant specificity of the mite in Bulgaria. Mites showed the highest degree of host specificity in the field and lowest in the no-choice experiments. In the field, highest densities of mites occurred on Ce. solstitialis and Ce. cyanus (bachelor's button), and either no mites or trace numbers occurred on the other test plants: Ce. diffusa (diffuse knapweed), Carthamus tinctorius (safflower) and Cynara scolymus (artichoke). In no-choice experiments, mites persisted for 60 days on Ce. diffusa, Ce. cyanus, Ce. solstitialis, Ca. tinctorius and Cy. scolymus, whereas in two-way choice experiments mites persisted on 25% of Cy. scolymus plants for 60 days and did not persist on Ca. tinctorius beyond 40 days. The eight other species of plants that were tested in the laboratory were less suitable for the mite. These results suggest that although A. solstitialis can persist on some nontarget plants for as long as 60 days in the laboratory, it appears to be much more specific under natural conditions, and warrants further evaluation as a prospective biological control agent.

Yellow starthistle (YST, Centaurea solstitialis) is a major weed pest of the western United States. Synchytrium solstitiale, a pathogen of YST, caused significant damage to symptomatic (versus asymptomatic) plants in a field study in France. Before it was evaluated as a candidate for biological control of YST in the United States, protocols for pathogen maintenance under greenhouse conditions were developed. Maintenance, increase, and host range determination protocols involved incubation at 10/15°C (night/day) with an 8-h photoperiod either of potted or exhumed (i.e., roots of 4-week-old plants grown in flasks of water) plants inoculated with galled leaf tissue, or potted plants in which inoculum was wrapped within healthy leaves by a plastic wrap. The leaf-wrap protocol, used during the host range determination, always resulted in disease of YST. Several safflower (Carthamus tinctorius) cultivars and other plants related to YST became diseased following this protocol, thus raising concern about host specificity. Development of disease on nontarget species precludes proposal of S. solstitiale for biological control of YST at this time.

7p., il., fotografías color, mapas [EN] New habitats, new menaces: Centaurea x kleinii (C. moncktonii x C. solstitialis), a new hybrid species between two alien weeds.- Anthropic alteration of habitat opens the door to the cohabitation of imported species that in their native range would never coexist. Centaurea solstitialis and Centaurea moncktonii are two invasive species whose natural distributions in Eurasia do not overlap. After introduction in North America, invasive spread led to overlapping distributions. Although the environmental requirements differ between the two species, the close proximity of diverse habitats (within pollinator range) has resulted in several cases of natural hybridization between the two. The result of the cross between these two distantly related species is a sterile perennial. Many of its characteristics are intermediate between its parents, but morphologically it is closer to Centaurea moncktonii (probably the maternal parent, and itself of hybrid origin). The plant could possibly become an invasive weed through clonal reproduction. The apparent maternal parent, which the hybrid may more closely resemble physiologically as well as morphologically, is a wellknown creeping weed in alpine pastures throughout Europe. [ES] Nuevos hábitats, nuevas amenazas: Centaurea x kleinii (C. moncktonii x C. solstitialis), nueva especie híbrida entre dos malas hierbas invasoras.- La alteración antrópica del hábitat da paso a la cohabitación de especies importadas que nunca coexistirían en su ámbito natural. Centaurea solstitialis y Centaurea moncktonii son dos especies invasoras cuyas distribuciones en Eurasia apenas se solapan. Después de su introducción en Norteamérica, la expansión invasiva condujo a distribuciones superpuestas. Aunque los requerimientos ambientales de las dos especies son distintos, la proximidad de hábitats diversos (dentro del alcance de los polinizadores) ha dado lugar a varios casos de hibridación natural entre ambas. El cruce resultante entre dos especies lejanamente emparentadas es una planta perenne estéril. Muchos de los caracteres del híbrido son intermedios entre sus especies parentales, pero morfológicamente es más parecida a Centaurea moncktonii (probablemente la especie materna y a su vez ya de origen híbrido). La nueva especie podría convertirse en una mala hierba invasora gracias a su reproducción vegetativa. La que suponemos especie materna, a la cual el híbrido se acerca morfológicamente y puede que fisiológicamente, es una mala hierba rastrera bien conocida de las praderas alpinas en toda Europa.

Six insect biocontrol agents have been introduced, with limited success, for managing the invasive plant yellow starthistle ( Centaurea solstitialis ). In 2003, a recently introduced fungal rust agent, Puccinia jaceae var. solstitialis , was approved for release in California. The presence of the rust in this multi-species complex was evaluated for its effect on performance of the two most common insect biocontrol agents for yellow starthistle, Chaetorellia succinea and Eustenopus villosus . To accomplish this, yellow starthistle was planted in 1 m 2 plots in monocultures at three densities and in a competition replacement series with wild oat ( Avena fatua ) in both 2006 and 2007. Twenty seedheads were dissected from each plot to evaluate the effect of P. jaceae on seedhead maturation and insect attack rate. In the replacement series experiment in 2007 and in 2006 and 2007 combined, P. jaceae caused a 35% and 20% increase, respectively, in the proportion of mature seedheads compared to total seedheads. However, there were no significant differences in the density experiment in either year or in the replacement series experiment in 2006. Although P. jaceae appeared to have a slight effect on yellow starthistle seedhead maturation, there was no effect of the rust on seedhead attack rates of either insect biological control, regardless of the experiment or year. These results indicate that P. jaceae does not interact significantly with the insect biological control agents for yellow starthistle.

In a 2-year field study, we quantified lateral root growth patterns and soil water depletion dynamics in the invasive annual Centaurea solstitialis and two native perennials, Elymus glaucus and Grindelia camporum. Centaurea solstitialis produced lateral roots most actively from early April to mid-June, during the late rosette to spiny seedhead stage while both root growth and water depletion were completed before flowering. In the wet year, roots were evenly distributed throughout the soil profile to 180 cm deep. Lack of deep soil moisture recharge in the second year restricted root distribution to shallow soil depths (< 60 cm). In contrast to C. solstitialis, living roots of the native perennials persisted throughout the year. Elymus glaucus roots were most abundant (47% of total roots) in the upper soil profile (≤ 60 cm) in the wet year, but most abundant (55%) in the lower profile (≥ 150 cm) in the dry year. However, the distribution of G. camporum roots was comparable between the 2 years. This indicates that in years with little to no deep soil moisture recharge, C. solstitialis roots are distributed in the shallow soil profile similar to annual grasses, whereas in wet ter years it is similar to deep-rooted perennial species. We also show that C. solstitialis impacts grassland communities by depleting soil moisture during the short period of lateral root growth from the late rosette to the spiny stage. Therefore, control of C. solstitialis early in the season is critical during native plant restoration where success depends upon available soil moisture.

Molecular analyses can play a primary role in the process of host specificity evaluation at species and population levels. Here we present an example of their application with a promising candidate biological control agent for yellow starthistle, Centaurea solstitialis L. Although it is highly host specific, Ceratapion basicorne (Coleoptera: Apionidae) can develop on safflower in laboratory tests. A field experiment was conducted to further evaluate host plant specificity; however, it was not possible to rear all larvae to the adult stage, which was necessary for species determination. Therefore molecular genetic methods were used to identify immature specimens. A 731 bp fragment of mtDNA cytochrome C oxidase I gene (COI) was sequenced from 41 individuals of C. basicorne and four congeners: Ceratapion orientale , Ceratapion onopordi , Ceratapion penetrans and Ceratapion scalptum . Intraspecific variability ranged from 0.0% to 0.2%, and interspecific divergences ranged from 1.7% to 17.6%. All larvae that were sequenced from the field study, clearly matched one of the five species, enabling us to unambiguously identify them. Use of molecular genetics to identify larvae should also help the process of foreign exploration, enabling the identification of field-collected larvae, which often provide more reliable host plant associations than field collected adults.

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 microditution 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 tactones using Vero cell tines. 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 mu g/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

The larvae of about 20 phytophagous species exploit heads of Centaurea solstitialis in the Mediterranean region. Host ranges, life histories and distribution of the more important species of the C. solstitialis fauna are described and their value for biological control of C. solstitialis is discussed. According to the available field data 5 species are strictly monophagous, 8 species breed only in hosts of the genus Centaurea, 3 species attack Centaurea and another genus in the subtribe Centaureini and the remaining species are associated with a broader range of Cynareae genera. Average percentages of attacked C. solstitialis heads, average larval numbers/100 heads and “species packing” are low in southern France and northeastern Spain and distinctly higher in southern Italy and the northern Balkans. They reach maximal values in northern Greece. Here, the degree of “species packing” exceeds that in any other Cynareae insect-host system so far studied. “Species packing”, percentages of attacked heads and abundance of phytophagous larvae within the heads are highly intercorrelated. Within the guild of phytophagous insects associated with C. solstitialis heads the tephritid Urophora sirunaseva Hg. and the weevil Bangasternus orientalis Cap. exhibit particularly promising characteristics for the biological control of C. solstitialis in California. Zusammenfassung Phytophage Insekten in Blutenkopfen von Centaurea solstitialis L. Etwa 20 Phytophagenarten beuten im Larvenstadium Blutenkopfe von Centaurea solstitialis im Mittelmeergebiet aus. Verbreitung, Wirtskreis und Biologie der wichtigeren Arten werden im Hinblick auf ihre Eignung zur biologischen Bekampfung von C. solstitialis beschrieben. Nach den heute vorliegenden Freilanddaten sind 5 Arten strikt monophag, 8 Arten befallen neben C. solstitialis noch weitere Centaurea-Arten, 3 Arten befallen neben Centaurea noch Vertreter anderer Gattungen der Untertribus Centaureini, und die restlichen Arten besitzen ein Wirtsspektrum, das mehrere Untertriben der Cynareae umfast. Die mittleren Befallsraten von C.-solstitialis-Kopfen, die Zahl von Phytophagenlarven pro 100 Kopfe und die ”Artendichte„ (Zahl von Phytophagenarten pro 100 Kopfe) zeigen sehr niedere Werte in Sudfrankreich und Nordost-Spanien, mittlere bis hohe Werte in Suditalien und der nordlichen Balkanhalbinsel und ausgesprochen hohe Werte in Nordgriechenland. Hier liegt mit einer mittleren Artendichte von 9,5 Phytophagenarten/100 Kopfe (Maximum 12) eine Artenkonzentration vor, die bislang nirgendwo in der Tribus der Cynareae (Distel- und Flockenblumengruppe) beobachtet wurde. Artendichte, Befallsgrad von C.-solstitialis-Kopfen und Abundanz der Phytophagenlarven sind hochgradig miteinander korreliert. Innerhalb des Phytophagenkomplexes in C.-solstitialis-Kopfen weisen besonders die Bohrfliege Urophora sirunaseva und der Russelkafer Bangasternus orientalis Eigenschaften auf, die einen Einsatz dieser Arten zur biologischen Bekampfung von C. solstitialis in Nordamerika nahelegen.

Larinus curtus Hochhuth (Coleoptera: Curculionidae) was first introduced into the western United States from Greece for the biological control of yellow starthistle (YST), Centaurea solstitialis L., in 1992. The discovery of L. curtus adults in the open flowerheads of safflower (SF), Carthamus tinctorius L., near Lewiston, Idaho in 2007 suggested this weevil might be expanding its host range to include a non-target crop species closely related to YST. In 2008 field plots near the 2007 observation site, 92 L. curtus adults fed in open SF flowerheads (pollen feeding and minor feeding on corolla tubes). No eggs were found in the ovarioles of 19 pollen-feeding females. No eggs, larvae, or evidence of larval feeding were detected in 39 tagged SF capitula, and no adults emerged from approximately 7,135 post-flowering SF capitula. These collective results are not indicative of an expanding developmental host-range of L. curtus. Also, they are consistent with pre-release host-specificity test results.

Entire yellow starthistle, Centaurea solstitialis L. (Asteraceae), plants were harvested from three southeastern Washington sites in September 2004 for seed head dissections to assess intra-plant patterns in the spatial distribution of the introduced false peacock fly, Chaetorellia succinea (Costa), and peacock fly, Chaetorellia australis Hering (Diptera: Tephritidae). Thirty plants were partitioned into three height classes and collected at each site, spanning the longitudinal range of yellow starthistle in Washington. Seed head canopies were stratified into three vertical sections and individual heads were dissected to determine bioagent occupation. Logistic regression analysis using a binary logit model was performed on data collected from each of the three sites separately due to varying site effects. Explanatory variables included plant height, plant width, plant canopy stratum (apical, mid, basal), and presence of other bioagents within a head. ‘Other bioagents’ detected include the yellow ...

The gall fly, Urophora sirunaseva, is one of six insect species released as classical biological control agents to control the invasive weed, yellow starthistle. Two study sites were established in Northern California to evaluate the per capita impact of galls on seed production. Evaluations during two years at each site used small cloth bags placed over developing seedheads to contain developing seeds and insects. Larger seedheads produced more seed but also supported more galls. Within-seedhead gall densities as high as 15 were detected. The impact of a single gall was estimated to reduce seed number by between 2.1–2.9 seeds per gall. A regression model was developed that estimated percentage seed loss as a function of seedhead size and number of galls. Individual galls were estimated to cause a 5–11% decrease in seed production compared to ungalled seedheads. The impact of the gall fly was greatest in smaller seedheads at both sites. Gall densities did not reach levels needed to exert significant control of seed production. Seed production in non-galled seedheads was not affected by the presence of galls in seedheads elsewhere on the plant. Gall flies were more likely to attack plants already supporting galls. Two generations of the fly were detected at both sites. The occurrence of overwintering larvae began in mid- to late-July depending on site. By early-August, all new galls held only overwintering larvae. Follow-up samples at one location eight years later showed the gall fly still present but at less than half of the population level observed earlier.

We studied the life history, geographic distribution, behavior, and ecology of Larinus filiformis Petri (Coleoptera: Curculionidae) in its native range to determine whether it is worthy of further evaluation as a classical biological control agent of yellow starthistle, Centaurea solstitialis (Asteraceae: Cardueae). Larinus filiformis occurs in Armenia, Azerbaijan, Turkey, and Bulgaria and has been reared only from C. solstitialis. At field sites in central and eastern Turkey, adults were well synchronized with the plant, being active from mid-May to late July and ovipositing in capitula (flowerheads) of C. solstitialis from mid-June to mid-July. Larvae destroy all the seeds in a capitulum. The insect is univoltine in Turkey, and adults hibernate from mid-September to mid-May. In the spring, before adults begin ovipositing, they feed on the immature flower buds of C. solstitialis, causing them to die. The weevil destroyed 25-75% of capitula at natural field sites, depending on the sample date. Preliminary host specificity experiments on adult feeding indicate that the weevil seems to be restricted to a relatively small number of plants within the Cardueae. Approximately 57% of larvae or pupae collected late in the summer were parasitized by hymenopterans [Bracon urinator, B. tshitsherini (Braconidae) and Exeristes roborator (Ichneumonidae), Aprostocetus sp. (Eulophidae), and unidentified species of Eurytomidae and Ormyridae]. This weevil may be a better choice than the other capitula insects already established in the United States, particularly in colder parts of the plant's range.

Since the introduction of Puccinia jaceae var. solstitialis into California in 2003, multiple urediniospore generations have been observed, along with teliospores and pycnia, on yellow starthistle ( Centaurea solstitialis ). A field and laboratory study of urediniospore viability was conducted to determine the potential of using infected plant material for redistribution of inoculum into new areas. To better understand the life history of P. j. solstitialis , urediniospore viability was measured during the summer and fall when the host plant is usually senescent. Latent period (time from inoculation to pustule eruption) after field and laboratory inoculations was measured in order to determine the potential number of urediniospore generations that occur per year. Viability of urediniospores stored in the laboratory gradually declined over a period of 10 weeks; spore hydration increased germination. Based on the results obtained in this study, introductions of harvested infected plant material would have to be done quickly to offset losses in urediniospore viability. Urediniospore viability in the field decreased exponentially 86% near the coast and 97% in the Central Valley three weeks after production, and was negligible (0–0.2%) thereafter. Latent period ranged from four to five weeks at cool winter temperatures to two to three weeks at warm summer temperatures in both the laboratory and field. Results of this study suggest that urediniospores are not likely to remain viable through the summer and fall dry season. Teliospores, therefore, serve as the inoculum source when YST seedlings germinate in the winter. Approximately six urediniospore generations can be expected to occur each year in central-northern California under suitable conditions for disease.

During exploration for new biological control agents of yellow starthistle, Centaurea solstitialis L. (Asteraceae: Cardueae), in eastern Turkey, we observed four species of broad-nosed weevils (subfamily Entiminae) that are newly associated with this plant: Epiphanops persicus (Chevrolat), Eusomomorphus oligops Daniel, Altonomus modestus (Khnzorian), and Araxia cristofaroi sp. n. Host plants of these species are recorded for the first time. Adults of E. persicus feed on young spines of C. solstitialis capitula (flower heads), whereas A. modestus and A. cristofaroi feed on leaves of C. solstitialis rosettes. Large numbers of E. oligops adults were observed feeding on leaves of both C. solstitialis and Russian knapweed, Acroptilon repens (L.). The genus Araxia Khnzorian is transferred from tribe Brachyderini Schoenherr to the tribe Sciaphilini Sharp, and it is redescribed. Female genitalia of this genus were studied and described for the first time. The new species, Araxia cristofaroi sp. n., is described, illustrated, and compared with the only other known Araxia species: A. mucronata Khnzorian. A taxonomic key discriminating the two Araxia species was developed. The new species differs by having claws that are almost equal in length, thinner and longer protibiae, wider antennal scape, more slender rostrum, and shorter body length. A. mucronata is newly recorded for Turkish fauna.

Hyperspectral remote-sensed data were obtained via a Compact Airborne Spectrographic Imager-II (CASI-II) and used to estimate leaf-area index (LAI) and aboveground biomass of a highly invasive weed species, yellow starthistle (YST). In parallel, 34 ground-based field plots were used to measure aboveground biomass and LAI to develop and validate hyperspectral-based models for estimating these measures remotely. Derivatives of individual hyperspectral bands improved the correlations between imaged data and actual on-site measurements. Six derivative-based normalized difference vegetation indices (DNDVI) were developed; three of them were superior to the commonly used normalized difference vegetation index (NDVI) in estimating aboveground biomass of YST, but did not improve estimates of LAI. The locally integrated derivatives-based vegetation indices (LDVI) from adjacent bands within three different spectral regions (the blue, red, and green reflectance ranges) were used to enhance absorption characteristics. Three LDVIs outperformed NDVI in estimating LAI, but not biomass. Multiple regression models were developed to improve the estimation of LAI and aboveground biomass of YST, and explained 75% and 53% of the variance in biomass and LAI, respectively, based on validation assessments with actual ground measurements.

Many members of the tribe Cardueae are invasive weeds, including yellow starthistle (Centaurea solstitialis L.), one of the most important weeds in the Western United States. We examined the root crowns and stems of yellow starthistle and related plants growing in five countries (Armenia, Republic of Georgia, Greece, Russia, and Turkey) where yellow starthistle is native. In its native range, the root crowns and lower stems of yellow starthistle are frequently attacked by the internal feeding larvae of apionid weevils. We present illustrations and a key to the adults of the six apionid species that we reared from yellow starthistle and its relatives: Ceratapion basicorne (Illiger), C. carduorum (Kirby), C. gibbirostre (Gyllenhal), C. onopodri (Kirby), C. orientale (Gerstaecker), and C. penetrans (Germar). The only apionid we reared from yellow starthistle was C. basicorne. In Turkey, where we collected most intensively, 58% of the yellow starthistle at 20 sites had larvae of this weevil, and at sites where C. basicorne was present, there were an average of 1.8 immatures per yellow starthistle plant. This apionid is currently being further researched for its potential as a biological control agent for yellow starthistle.

There is much discussion as to why a plant becomes invasive in a new location but is not problematic in its native range. One example is yellow starthistle, which originates in Eurasia and is considered a noxious weed in the United States. We grew yellow starthistle originating from native and introduced regions in a common environment to test whether differences in growth would be observed. In growth chamber studies, seedlings originating from the invasive range were larger than seedlings from the native range after 2 wk. Seed starch content is an important component of initial seedling growth. The starch content of seeds from introduced populations was higher than that of seeds from native populations. Regression analysis showed a relationship between the amount of starch in the seeds and the weight of yellow starthistle seedlings after 2 wk growth. There was no difference in chromosome number, except in accessions originating from Sicily and Sardinia. Field studies conducted in France and Russia revealed that rosettes and mature plants grown under natural conditions were larger when grown from seeds originating from the invasive range than from seeds originating from the native range. The number of capitula per plant and stem diameters were not significant among all populations, but differences were noted. The F1 progeny of plants originating from U.S. seed, but grown and pollinated in France, showed no differences in seedling growth, mature plant characteristics, and seed starch content from the plants grown from field-collected U.S. seed. The changes in seed starch resource allocation and its relation to plant growth is useful in understanding factors that contribute to yellow starthistle's invasibility.

Ceratapion basicorne (Coleoptera: Apionidae) is a weevil native to Europe and western Asia that is being evaluated as a prospective classical biological control agent of Centaurea solstitialis (yellow starthistle) in the United States. Host plant speciWcity of the insect was evaluated in no-choice oviposition experiments. Feeding on leaf tissue by adult females was highly correlated to oviposition rate, both of which occurred primarily on plants in the tribe Cardueae, and especially those in the monophyletic subtribe Centaureinae. The highest rates of larval development occurred on Ce. solstitialis and Centaurea cyanus (bachelor’s button, garden cornXower), and there was signiWcant development on Centaurea melitensis (Napa starthistle, tocalote), Cnicus benedictus (blessed thistle), Carthamus tinctorius (saZower), and Crupina vulgaris (common crupina). All the plants that supported some larval development are within a monophyletic clade within the Centaureinae. No native North American plants appear to be at risk of signiWcant damage by this insect. Additional testing of saZower and bachelor’s button under choice conditions should complement these results to help determine the degree to which these plants are at risk.

Phytotoxicity bioassays and pot experiments using activated carbon both suggest that Centaurea solstitialis (yellow star-thistle) does not rely on phytotoxic root exudates for invasion of California grasslands. Pot experiments in which five native species were grown in the presence/absence of C. solstitialis and in the presence/absence of activated carbon (fully crossed design) showed that C. solstitialis competitively suppressed native species, but did not inhibit them through allelochemicals. In separate experiments examining the role of root exudates in invasion success, treatment with crude root exudates and chloroform-extracted root exudates from C. solstitialis reduced growth of the model plant Arabidopsis thaliana. However, high concentrations of the exudates (50%, v/v or 500 μg mL-1) were required to inhibit A. thaliana growth and did not result in A. thaliana mortality, suggesting the presence of only a weak growth inhibitor. Moreover, high concentrations of C. solstitialis crude root exudates did not affect the growth of five native grass species often displaced by C. solstitialis invasions in California grasslands. Finally, root exudates collected from C. solstitialis had weaker effects on a native California root parasite, Triphysaria versicolor, than root exudates collected from Zea mays, a species not renowned for its competitive or invasive capabilities. Our results suggest that, while C. solstitialis might possibly "be persuaded to yield a product that is toxic to one species or another" (Population biology of plants, Academic, 1977), we find no evidence that allelopathic root exudates play a role in the competitive success of this invasive. Fil: Qin, Bo. Colorado State University; Estados Unidos Fil: Lau, Jennifer A.. University of California; Estados Unidos Fil: Kopshever, Joseph. University of California; Estados Unidos Fil: Callaway, Ragan M.. University of Montana; Estados Unidos Fil: McGray, Heather. University of California; Estados Unidos Fil: Perry, Laura G.. Colorado State University; Estados Unidos Fil: Weir, Tiffany L.. Colorado State University; Estados Unidos Fil: Paschke, Mark W.. Colorado State University; Estados Unidos Fil: Hierro, Jose Luis. University of Montana; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Yoder, John. University of California; Estados Unidos Fil: Vivanco, Jorge M.. Colorado State University; Estados Unidos Fil: Strauss, Sharon. University of California; Estados Unidos

Plant chemical defenses can be qualitative (toxins) to face generalist herbivores and quantitative (digestibility reducers) to specialists. Trichomes can produce chemicals, but also acts as a quantitative defense and in water loss. The shifting defense hypothesis (SDH) poses that invasive plants reduce the production of qualitative defenses against specialist herbivores because those are frequently absent in invaded regions, while increasing defenses against generalist herbivores. Chemical and physical leaf surface defensive traits could give information about direct plant–herbivore interaction in native and non-native regions. We studied leaf surface morphology and epicuticular chemistry of the invasive C. solstitialis in plants from native and non-native regions. Across regions, the main chemical components were sesquiterpene lactones, similar densities of sessile glandular trichomes and a variable number of large multicellular trichomes. Exotic plants face different sets of challenges in the new regions. In accordance with SDH, plants from non-native regions presented higher total sesquiterpene lactones concentrations (qualitative defense). Trichome density was possibly associated to differences in local climatic conditions. Sesquiterpene lactones are likely to play an important role on the invasion success of Centaurea. Leaf surface components provide meaningful information that should be consider in future studies to unravel the mechanisms involved in plant invasions. Fil: Sotes, Gastón J.. Universidad de Chile; Chile. Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas, Departamento de Botánica; Chile Fil: Cavieres, Lohengrin Alexis. Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas, Departamento de Botánica; Chile. Universidad de Chile; Chile Fil: Montesinos, Daniel. Universidad de Coimbra; Portugal Fil: Pereira Coutinho, António Xavier. Universidad de Coimbra; Portugal Fil: Peláez, Walter José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Martins Lopes, Susana Margarida. Universidad de Coimbra; Portugal Fil: Vasconcelos Dias de Pinho e Melo, Teresa Margarida. Universidad de Coimbra; Portugal

A laboratory colony of Ceratapion basicorne (Illiger) was established from adults reared from infested plants of yellow starthistle, Centaurea solstitialis L. (Asteraceae), that were collected in eastern Turkey. Newly emerged adults fed on yellow starthistle foliage and mated, but females did not oviposit. The feeding rate of females decreased to almost zero by 16 d after emergence, whereas males continued to feed for at least 26 d. Dispersal activity was initially high but decreased to low levels in 2–3 wk. After 6 wk, most adults were hiding inside tightly curled dry leaves and in the crevices of crumpled paper towel. Insects were held in a cold dark incubator (5°C) for at least 3 mo to terminate reproductive diapause. Females began ovipositing 4.4 d after being placed on yellow starthistle leaves at 19°C. The oviposition period lasted a mean of 20.6 d, and lifetime fecundity was 34.5 eggs. Daily fecundity was high during the first 14 d of oviposition (1.8 eggs/d) and declined to low levels (0....

Plant invasions pose a serious threat to native ecosystem structure and function. However, little is known about the potential role that rhizosphere soil microbial communities play in facilitating or resisting the spread of invasive species into native plant communities. The objective of this study was to compare the microbial communities of invasive and native plant rhizospheres in serpentine soils. We compared rhizosphere microbial communities, of two invasive species, Centaurea solstitialis (yellow starthistle) and Aegilops triuncialis (barb goatgrass), with those of five native species that may be competitively affected by these invasive species in the field (Lotus wrangelianus, Hemizonia congesta, Holocarpha virgata, Plantago erecta, and Lasthenia californica). Phospholipid fatty acid analysis (PLFA) was used to compare the rhizosphere microbial communities of invasive and native plants. Correspondence analyses (CA) of PLFA data indicated that despite yearly variation, both starthistle and goatgrass appear to change microbial communities in areas they invade, and that invaded and native microbial communities significantly differ. Additionally, rhizosphere microbial communities in newly invaded areas are more similar to the original native soil communities than are microbial communities in areas that have been invaded for several years. Compared to native plant rhizospheres, starthistle and goatgrass rhizospheres have higher levels of PLFA biomarkers for sulfate reducing bacteria, and goatgrass rhizospheres have higher fatty acid diversity and higher levels of biomarkers for sulfur-oxidizing bacteria, and arbuscular mycorrhizal fungi. Changes in soil microbial community composition induced by plant invasion may affect native plant fitness and/or ecosystem function.

Ceratapion basicorne (Coleoptera: Apionidae) is a prospective biological control agent of yellow starthistle (Centaurea solstitialis, Asteraceae: Cardueae), which is an important invasive alien weed in the western United States. Previous studies have shown that it is possible for this insect to oviposit on and complete development on saZower (Carthamus tinctorius) under no-choice laboratory conditions; however, it has never been reported as a pest of saZower. Field experiments were conducted at three sites in eastern Turkey during 3 years to evaluate the risk of attack on saZower by this insect in its native range. At two sites where C. basicorne was the only apionid observed, no saZower plants were attacked despite high attack rates on yellow starthistle test plants (48–98% of plants infested). At a third site, where C. basicorne and three other species in the same genus; C. scalptum, C. orientale, and C. onopordi were present, 8–26% of saZower plants were infested, but none of the insects reared from saZower during 3 years were C. basicorne. Other authors have reported rearing C. basicorne from Weld-collected plants of only Ce. solstitialis, Ce. cyanus, Ce. depressa, and Cnicus benedictus. Our results indicate that C. basicorne does not attack saZower under Weld conditions and that its introduction would not pose a risk to this crop. Published by Elsevier Inc.