Evidence for a Hemibiotrophic Association of the Pitch Canker Pathogen Fusarium circinatum with Pinus radiata

Fusarium circinatum can be a cause of mortality in pine seedlings but it is also possible for infected seedlings to remain symptomless. The results of this study documented a biotrophic phase in symptomless Pinus radiata seedlings that can persist for at least 52 weeks. A strain of F. circinatum, transformed to express the green fluorescent protein, was observed to grow intercellularly in the root cortex, with no evidence of damage to surrounding cells. Under experimental conditions, shoot symptoms developed only following collar infection, and root deterioration was seen only in plants that first expressed aboveground symptoms. This sequence of events implies that damage to the root system was a secondary consequence of girdling. If so, root symptoms may not reliably detect seedlings infected by F. circinatum. Supplemental mineral nutrition increased the incidence of infection and symptom development in seedlings but some infected plants remained symptomless, precluding the use of this approach to detect infected seedlings. Overall, our findings suggest that the ecological activities of F. circinatum may not be limited to a necrotrophic association with pine trees. A more comprehensive understanding of the life history of this fungus may yield insights that contribute to more effective management of pitch canker.

Colloidal Hybrid Nanoparticle Insertion Reaction for Transforming Heterodimers into Heterotrimers

Three-component colloidal hybrid nanoparticles, which are central to a diverse array of applications, are typically synthesized using successive seeded growth steps, which are additive in nature and driven by surface chemistry considerations and material-specific preferences for nucleation and growth. Here, we describe a new nanoparticle insertion reaction for transforming heterodimers into heterotrimers, which is based on a supersaturation-precipitation pathway that shifts the driving force for heterotrimer formation away from surface-driven nucleation and growth. To demonstrate the concept, a Ge segment is inserted between the Au and Fe3O4 domains of Au-Fe3O4 heterodimers to form Au-Ge-Fe3O4 heterotrimers. Microscopic investigations reveal important mechanistic insights, including identification of a proposed Au-Ge-Au-Fe3O4 intermediate. The process can be modified to access the analogous addition product Ge-Au-Fe3O4, allowing tuning between two distinct heterotrimer isomers with different configurations.

The Effect of Resin and Monoterpenes on Spore Germination and Growth in Fusarium circinatum

Resin obtained from Pinus radiata and five monoterpene components of resin (limonene, α-pinene, β-pinene, camphene, and myrcene) were tested to determine their effects on mycelial growth and germination and survival of spores of Fusarium circinatum, the cause of pitch canker in pine, and F. temperatum, which is interfertile with F. circinatum but not pathogenic to pine. Averaged across all treatments, F. temperatum sustained the greatest reduction in radial growth (16.9±0.02% of control). The greatest reduction in dry weight also occurred in F. temperatum (11.7±0.01% of control), and all isolates of F. circinatum were significantly less affected (P<0.05). Spore germination rates in a saturated atmosphere of monoterpenes were relatively high for all tested isolates but, when placed in direct contact with resin, spore survival was significantly greater for F. circinatum than for F. temperatum. Our results are consistent with the hypothesis that greater tolerance of resin is one factor distinguishing F. circinatum from the nonpathogenic F. temperatum. However, differential tolerance of monoterpene components of resin is not sufficient to explain the observed variation in virulence to pine in F. circinatum.

IMA Genome-F 3: Draft genomes of Amanita jacksonii, Ceratocystis albifundus, Fusarium circinatum, Huntiella omanensis, Leptographium procerum, Rutstroemia sydowiana, and Sclerotinia echinophila

The genomes of fungi provide an important resource to resolve issues pertaining to their taxonomy, biology, and evolution. The genomes of Amanita jacksonii, Ceratocystis albifundus, a Fusarium circinatum variant, Huntiella omanensis, Leptographium procerum, Sclerotinia echinophila, and Rutstroemia sydowiana are presented in this genome announcement. These seven genomes are from a number of fungal pathogens and economically important species. The genome sizes range from 27 Mb in the case of Ceratocystis albifundus to 51.9 Mb for Rutstroemia sydowiana. The latter also encodes for a predicted 17 350 genes, more than double that of Ceratocystis albifundus. These genomes will add to the growing body of knowledge of these fungi and provide a value resource to researchers studying these fungi.

Electrocatalytic and photocatalytic hydrogen production from acidic and neutral-pH aqueous solutions using iron phosphide nanoparticles

Nanostructured transition-metal phosphides have recently emerged as Earth-abundant alternatives to platinum for catalyzing the hydrogen-evolution reaction (HER), which is central to several clean energy technologies because it produces molecular hydrogen through the electrochemical reduction of water. Iron-based catalysts are very attractive targets because iron is the most abundant and least expensive transition metal. We report herein that iron phosphide (FeP), synthesized as nanoparticles having a uniform, hollow morphology, exhibits among the highest HER activities reported to date in both acidic and neutral-pH aqueous solutions. As an electrocatalyst operating at a current density of -10 mA cm(-2), FeP nanoparticles deposited at a mass loading of ∼1 mg cm(-2) on Ti substrates exhibited overpotentials of -50 mV in 0.50 M H2SO4 and -102 mV in 1.0 M phosphate buffered saline. The FeP nanoparticles supported sustained hydrogen production with essentially quantitative faradaic yields for extended time periods under galvanostatic control. Under UV illumination in both acidic and neutral-pH solutions, FeP nanoparticles deposited on TiO2 produced H2 at rates and amounts that begin to approach those of Pt/TiO2. FeP therefore is a highly Earth-abundant material for efficiently facilitating the HER both electrocatalytically and photocatalytically.

Solution-processed phase-change VO(2) metamaterials from colloidal vanadium oxide (VO(x)) nanocrystals

We demonstrate thermally switchable VO2 metamaterials fabricated using solution-processable colloidal nanocrystals (NCs). Vanadium oxide (VOx) NCs are synthesized through a nonhydrolytic reaction and deposited from stable colloidal dispersions to form NC thin films. Rapid thermal annealing transforms the VOx NC thin films into monoclinic, nanocrystalline VO2 thin films that show a sharp, reversible metal-insulator phase transition. Introduction of precise concentrations of tungsten dopings into the colloidal VOx NCs enables the still sharp phase transition of the VO2 thin films to be tuned to lower temperatures as the doping level increases. We fabricate "smart", differentially doped, multilayered VO2 films to program the phase and therefore the metal-insulator behavior of constituent vertically structured layers with temperature. With increasing temperature, we tailored the optical response of multilayered films in the near-IR and IR regions from that of a strong light absorber, in a metal-insulator structure, to that of a Drude-like reflector, characteristic of a pure metallic structure. We demonstrate that nanocrystal-based nanoimprinting can be employed to pattern multilayered subwavelength nanostructures, such as three-dimensional VO2 nanopillar arrays, that exhibit plasmonic dipolar responses tunable with a temperature change.

Solution-based stoichiometric control over charge transport in nanocrystalline CdSe devices

Using colloidal CdSe nanowire (NW) field-effect transistors (FETs), we demonstrated the dependence of carrier transport on surface stoichiometry by chemically manipulating the atomic composition of the NW surface. A mild, room-temperature, wet-chemical process was devised to introduce cadmium, selenium, or sulfur adatoms at the surface of the NWs in completed devices. Changes in surface composition were tested for by energy dispersive spectroscopy and inductively coupled plasma-atomic emission spectroscopy and through the use of the vibrational reporter thiocyanate. We found that treatment with cadmium acetate enhances electron currents, while treatment with sodium selenide or sodium sulfide suppressed them. The efficacy of doping CdSe NWs through subsequent thermal diffusion of indium was highly dependent on the surface composition. While selenium-enriched CdSe NW FETs were characterized by little to no electron currents, when combined with indium, they yielded semimetallic devices. Sulfur-enriched, indium-doped devices also displayed dramatically enhanced electron currents, but to a lesser extent than selenium and formed FETs with desirable ION/IOFF >10(6). The atomic specificity of the electronic behavior with different surface chalcogens suggested indium was bound to chalcogens at the NW surface, indicating commonalities with and implications for indium-containing CdSe nanocrystal films. Low temperature measurements of indium-doped CdSe NW FETs showed no evidence of impurity scattering, further supporting the existence of an indium-chalcogen interaction at the surface rather than in the core of the NW.

Control of Metal Nanocrystal Size Reveals Metal-Support Interface Role for Ceria Catalysts

Interactions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions. However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts. We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals. We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, clarifying the pivotal role played by the support.

Shape-dependent plasmonic response and directed self-assembly in a new semiconductor building block, indium-doped cadmium oxide (ICO)

The influence of particle shape on plasmonic response and local electric field strength is well-documented in metallic nanoparticles. Morphologies such as rods, plates, and octahedra are readily synthesized and exhibit drastically different extinction spectra than spherical particles. Despite this fact, the influence of composition and shape on the optical properties of plasmonic semiconductor nanocrystals, in which free electrons result from heavy doping, has not been well-studied. Here, we report the first observation of plasmonic resonance in indium-doped cadmium oxide (ICO) nanocrystals, which exhibit the highest quality factors reported for semiconductor nanocrystals. Furthermore, we are able to independently control the shape and free electron concentration in ICO nanocrystals, allowing for the influence of shape on the optical response of a plasmonic semiconductor to be conclusively demonstrated. The highly uniform particles may be self-assembled into ordered single component and binary nanocrystal superlattices, and in thin films, exhibit negative permittivity in the near infrared (NIR) region, validating their use as a new class of tunable low-loss plasmonic building blocks for 3-D optical metamaterials.

Three-dimensional self-assembly of chalcopyrite copper indium diselenide nanocrystals into oriented films

CuInSe2, which is one of the highest efficiency thin-film solar cell active layer materials, has been an attractive target for nanocrystal synthesis and manipulation. Here, we report unprecedented, simultaneous control of the synthesis and self-assembly behavior of CuInSe2 nanocrystals. These nanocrystals are solution-processable, monodisperse tetragonal bipyramids that exhibit photoconductivity and self-assemble into crystallographically oriented thin films. Structural characterization indicates that these nanocrystals are tetragonal phase, as is used in high-efficiency, second-generation, thin-film solar cells. Elemental analysis indicates that approximately 1:1:2 Cu/In/Se stoichiometry can be achieved, and that the elemental composition can be adjusted from copper-rich to indium-rich with reaction time.

One fungus, one name: defining the genus Fusarium in a scientifically robust way that preserves longstanding use

In this letter, we advocate recognizing the genus Fusarium as the sole name for a group that includes virtually all Fusarium species of importance in plant pathology, mycotoxicology, medicine, and basic research. This phylogenetically guided circumscription will free scientists from any obligation to use other genus names, including teleomorphs, for species nested within this clade, and preserve the application of the name Fusarium in the way it has been used for almost a century. Due to recent changes in the International Code of Nomenclature for algae, fungi, and plants, this is an urgent matter that requires community attention. The alternative is to break the longstanding concept of Fusarium into nine or more genera, and remove important taxa such as those in the F. solani species complex from the genus, a move we believe is unnecessary. Here we present taxonomic and nomenclatural proposals that will preserve established research connections and facilitate communication within and between research communities, and at the same time support strong scientific principles and good taxonomic practice.

Designing tripodal and triangular gadolinium oxide nanoplates and self-assembled nanofibrils as potential multimodal bioimaging probes

Here, we report the shape-controlled synthesis of tripodal and triangular gadolinium oxide (Gd2O3) nanoplates. In the presence of lithium ions, the shape of the nanocrystals is readily controlled by tailoring reaction parameters such as temperature and time. We observe that the morphology transforms from an initial tripodal shape to a triangular shape with increasing reaction time or elevated temperatures. Highly uniform Gd2O3 nanoplates are self-assembled into nanofibril-like liquid-crystalline superlattices with long-range orientational and positional order. In addition, shape-directed self-assemblies are investigated by tailoring the aspect ratio of the arms of the Gd2O3 nanoplates. Due to a strong paramagnetic response, Gd2O3 nanocrystals are excellent candidates for MRI contrast agents and also can be doped with rare-earth ions to form nanophosphors, pointing to their potential in multimodal imaging. In this work, we investigate the MR relaxometry at high magnetic fields (9.4 and 14.1 T) and the optical properties including near-IR to visible upconversion luminescence and X-ray excited optical luminescence of doped Gd2O3 nanoplates. The complex shape of Gd2O3 nanoplates, coupled with their magnetic properties and their ability to phosphoresce under NIR or X-ray excitation which penetrate deep into tissue, makes these nanoplates a promising platform for multimodal imaging in biomedical applications.

Heterogeneous catalysts need not be so "heterogeneous": monodisperse Pt nanocrystals by combining shape-controlled synthesis and purification by colloidal recrystallization

Well-defined surfaces of Pt have been extensively studied for various catalytic processes. However, industrial catalysts are mostly composed of fine particles (e.g., nanocrystals), due to the desire for a high surface to volume ratio. Therefore, it is very important to explore and understand the catalytic processes both at nanoscale and on extended surfaces. In this report, a general synthetic method is described to prepare Pt nanocrystals with various morphologies. The synthesized Pt nanocrystals are further purified by exploiting the "self-cleaning" effect which results from the "colloidal recrystallization" of Pt supercrystals. The resulting high-purity nanocrystals enable the direct comparison of the reactivity of the {111} and {100} facets for important catalytic reactions. With these high-purity Pt nanocrystals, we have made several observations: Pt octahedra show higher poisoning tolerance in the electrooxidation of formic acid than Pt cubes; the oxidation of CO on Pt nanocrystals is structure insensitive when the partial pressure ratio p(O2)/p(CO) is close to or less than 0.5, while it is structure sensitive in the O(2)-rich environment; Pt octahedra have a lower activation energy than Pt cubes when catalyzing the electron transfer reaction between hexacyanoferrate (III) and thiosulfate ions. Through electrocatalysis, gas-phase-catalysis of CO oxidation, and a liquid-phase-catalysis of electron transfer reaction, we demonstrate that high quality Pt nanocrystals which have {111} and {100} facets selectively expose are ideal model materials to study catalysis at nanoscale.

Shape-controlled synthesis of Pt nanocrystals: the role of metal carbonyls

Well-controlled synthesis of nanocrystals is necessary to unambiguously correlate the structural properties of nanocrystals with the catalytic properties. The most common low-index surfaces are (111) and (100). Therefore, model materials with {111} and {100} facets are highly desirable, in order to understand the catalytic properties of (111) and (100) surfaces for various structure-sensitive reactions. We report a solution-phase synthesis using metal carbonyls as additives. This synthetic method produces highly monodisperse Pt octahedra and icosahedra as the model of Pt{111}, Pt cubes as the model of Pt{100}, respectively. Several other morphologies, such as truncated cubes, cuboctahedra, spheres, tetrapods, star-shaped octapods, multipods, and hyper-branched structure, are produced, as well. A bifunctional role of metal carbonyl in the synthesis is identified: zerovalent transition metal decomposed from metal carbonyl acts as a shape-directing agent, while CO provides the reducing power. These high-quality shape-controlled Pt nanocrystals are suitable for model catalyst studies.

Synthesis, shape control, and methanol electro-oxidation properties of Pt-Zn alloy and Pt3Zn intermetallic nanocrystals

We report the first synthesis of highly monodisperse Pt(3)Zn nanocrystals (NCs). Shape-controlled synthesis generates cubic and spherical Pt-Zn NCs. Reaction temperature is the key to incorporate Zn into Pt, even in the absence of a strong reducing agent. The Pt-Zn NCs are active toward methanol oxidation, with the spherical NCs exhibiting higher activity than the cubic NCs. The Pt-Zn alloy phase can be transformed into the Pt(3)Zn intermetallic phase, upon annealing. The intermetallic Pt(3)Zn shows better performance than the alloy phase Pt-Zn. Besides the activity toward methanol oxidation, Pt-Zn NCs show excellent poisoning tolerance. With activities comparable to the commercial Pt catalyst, enhanced poisoning tolerance and lower cost, Pt-Zn and Pt(3)Zn NCs are a promising new family of catalysts for direct methanol fuel cells.

First Report of Grass Species (Poaceae) as Naturally Occurring Hosts of the Pine Pathogen Gibberella circinata

Gibberella circinata (anamorph Fusarium circinatum) causes pitch canker in pines and is not known to have any hosts outside the Pinaceae. However, G. circinata is closely related to and interfertile with G. subglutinans, which is associated with grasses both as a pathogen and a commensal endophyte. Furthermore, studies under controlled conditions have shown that G. circinata can colonize corn (Zea mays) without inducing symptoms (4). To determine if G. circinata can also infect grasses under natural conditions, plants were collected in proximity to trees with symptoms of pitch canker in native stands of Pinus radiata (Monterey pine) on the Monterey Peninsula and P. muricata (bishop pine) at Pt. Reyes National Seashore on the California coast during July and August of 2011. Leaves and stems were rinsed in 0.1% Tween 20, immersed in 70% ethanol for 30 s followed by 1 min in 1% NaOCl, and placed on a Fusarium selective medium (FSM) (1). Single-spore subcultures of colonies growing from cultured plant material were transferred to 0.6% KCl agar and identified as G. circinata based on morphological criteria as described by Gordon et al. (2). G. circinata isolates were recovered from Holcus lanatus and Festuca arundinacea on the Monterey Peninsula and H. lanatus at Pt. Reyes National Seashore. Three isolates from each of these sources (nine total) and one known G. circinata isolate from pines (GL 17) were tested for virulence by inoculating 1-year-old, greenhouse-grown Monterey pine trees; three trees were inoculated, once for each isolate. Trees were inoculated by depositing 250 spores in a wound on the main stem by the method described by Gordon et al. (3). Two weeks later, all grass isolates had induced resinous branch cankers with lesions comparable in length (17 to 24 mm) and appearance to those caused by GL 17. Similar results were obtained when inoculations were repeated. One isolate from F. arundinacea and one from H. lanatus (collected at Pt. Reyes National Seashore) were tested and shown to be somatically compatible with tester strains for vegetative compatibility groups C6 and C1, respectively, both of which are associated with isolates previously recovered from diseased pines (2). GL 17 and one isolate each from F. arundinaceae and H. lanatus were tested for their ability to infect F. arundinaceae cv. Fawn. For each isolate, 20 14-day-old seedlings (10 pots with two plants per pot) were sprayed to runoff with an aqueous suspension of 10⁶ spores per ml. All inoculations were repeated once. Two weeks after inoculation, leaves and stems were rinsed briefly in 0.1% Tween 20, immersed for 10 s in 70% ethanol, followed by 30 s in 1% NaOCl, and cultured on FSM. All tested isolates were recovered from at least some of the inoculated plants (range 20 to 100%), from living stems and leaves, as well as from senescing tissue. These results show that grass species can be symptomless hosts for G. circinata, constituting the first documentation of any host for this pathogen outside the Pinaceae. Studies are underway to further characterize the host range of G. circinata and assess the epidemiological implications of grasses as alternate hosts for the pitch canker pathogen. References: (1) B. J. Aegerter and T. R. Gordon. For. Ecol. Manag. 235:14, 2006. (2) T. R. Gordon et al. Mycol. Res. 100:850, 1996. (3) T. R. Gordon et al. Hortscience 33:868, 1998. (4) C. L. Swett and T. R. Gordon. Phytopathology (Abstr.) 89:S126, 2009.

Nonaqueous synthesis of TiO2 nanocrystals using TiF4 to engineer morphology, oxygen vacancy concentration, and photocatalytic activity

Control over faceting in nanocrystals (NCs) is pivotal for many applications, but most notably when investigating catalytic reactions which occur on the surfaces of nanostructures. Anatase titanium dioxide (TiO(2)) is one of the most studied photocatalysts, but the shape dependence of its activity has not yet been satisfactorily investigated and many questions still remain unanswered. We report the nonaqueous surfactant-assisted synthesis of highly uniform anatase TiO(2) NCs with tailorable morphology in the 10-100 nm size regime, prepared through a seeded growth technique. Introduction of titanium(IV) fluoride (TiF(4)) preferentially exposes the {001} facet of anatase through in situ release of hydrofluoric acid (HF), allowing for the formation of uniform anatase NCs based on the truncated tetragonal bipyramidal geometry. A method is described to engineer the percentage of {001} and {101} facets through the choice of cosurfactant and titanium precursor. X-ray diffraction studies are performed in conjunction with simulation to determine an average NC dimension which correlates with results obtained using electron microscopy. In addition to altering the particle shape, the introduction of TiF(4) into the synthesis results in TiO(2) NCs that are blue in color and display a broad visible/NIR absorbance which peaks in the infrared (λ(max) ≈ 3400 nm). The blue color results from oxygen vacancies formed in the presence of fluorine, as indicated by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) studies. The surfactants on the surface of the NCs are removed through a simple ligand exchange procedure, allowing the shape dependence of photocatalytic hydrogen evolution to be studied using monodisperse TiO(2) NCs. Preliminary experiments on the photoreforming of methanol, employed as a model sacrificial agent, on platinized samples resulted in high volumes of evolved hydrogen (up to 2.1 mmol h(-1) g(-1)) under simulated solar illumination. Remarkably, the data suggest that, under our experimental conditions, the {101} facets of anatase are more active than the {001}.

First Report of Fusarium Stem and Crown Rot of Fennel in Arizona Caused by Fusarium avenaceum

In 2010 in Yuma, AZ, field-grown fennel (Foeniculum vulgare, Apiaceae) exhibited previously undescribed disease symptoms. The lower stems in contact with soil developed a brown decay and leaves on these stems became chlorotic. White mycelium and orange sporodochia were observed on affected tissues near the soil line. Diseased stems later wilted, died, and resulted in reduced quality of the fennel; these plants were not harvested. Disease distribution was patchy and prevalence was approximately 5%. Symptomatic tissues were surface sterilized in a dilute (1%) bleach solution for 3 min and tissues from the margins of the decay were placed into petri plates containing acidified corn meal agar (2 ml of 25% lactic acid/liter). Isolations consistently resulted in the recovery of a presumptive Fusarium species. Isolates were transferred to carnation leaf agar and incubated at 22°C under fluorescent lights for 10 days. Morphologies of all isolates were identical, with macroconidia being long and slender, slightly curved, with elongated, bent apical cells and notched basal cells. Conidia were borne on monophialides. Microconidia were sparse and chlamydospores were not observed. For two isolates, a portion of the translation elongation factor 1-alpha gene (TEF) was amplified with primers ef1 and ef2 (3). Based on a comparison of 668 base pairs, both isolates had the same sequence, which differed by one base pair from an accession (GQ915502.1) of Fusarium avenaceum in GenBank. The same single base pair also separated the two fennel isolates from an isolate of F. avenaceum (GL 13) previously recovered from Eustoma grandiflorum (=Lisianthus russellianus) (2). Thus, both morphological and molecular criteria support identification of the recovered fungus as F. avenaceum (Fries) Saccardo. Partial TEF sequences were deposited in GenBank (Accession Nos. JN254784, JN254785, and JN254786 for the two fennel isolates and GL 13, respectively). All isolates are archived in the Department of Plant Pathology at University of California, Davis. Pathogenicity was tested by cutting shallow slits into fennel stems, inserting one colonized agar plug into each cut, and wrapping the stems with Parafilm. Five isolates from fennel were tested on 10 stems each. Control plants were inoculated with uncolonized agar plugs. Plants were maintained at 24 to 26°C in a greenhouse. After 6 to 8 days, a brown decay developed on 70 to 90% of Fusarium-inoculated stems at the points of inoculation. Foliage later became chlorotic and F. avenaceum was recovered from all symptomatic stems. Control plants were symptomless. The experiment was completed two times and results were the same. In addition, F. avenaceum isolate GL13 from E. grandiflorum (2) was inoculated onto fennel plants with the same method. However, these inoculated plants remained symptomless. To our knowledge, this is the first report of a stem and crown rot disease of fennel caused by F. avenaceum. Apparently, the only other published account of a Fusarium disease of fennel is root rot caused by F. solani (1). The inability of the Eustoma isolate of F. avenaceum to cause disease in fennel suggests that these two crown rot pathogens may have restricted host ranges. References: (1) J. H. Gupta and V. P. Srivastava. Indian J. Mycol. Plant Pathol. 8:206, 1979. (2) S. T. Koike et al. Plant Dis. 80:1429, 1996. (3) K. O'Donnell et al. Proc. Nat. Acad. Sci. U.S.A. 95:2044, 1998.

Studies of liquid crystalline self-assembly of GdF₃ nanoplates by in-plane, out-of-plane SAXS

Directed self-assembly of colloidal nanocrystals into ordered superlattices enables the preparation of novel metamaterials with diverse functionalities. Structural control and precise characterization of these superlattices allow the interactions between individual nanocrystal building blocks and the origin of their collective properties to be understood. Here, we report the directed liquid interfacial assembly of gadolinium trifluoride (GdF(3)) nanoplates into liquid crystalline assemblies displaying long-range orientational and positional order. The macroscopic orientation of superlattices is controlled by changing the subphases upon which liquid interfacial assembly occurs. The assembled structures are characterized by a combination of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) measurements performed on a laboratory diffractometer. By doping GdF(3) nanoplates with europium (Eu(3+)), luminescent phosphorescent superlattices with controlled structure are produced and enable detailed structural and optical characterization.

Current status of the taxonomic position of Fusarium oxysporum formae specialis cubense within the Fusarium oxysporum complex

Fusarium oxysporum is an asexual fungal species that includes human and animal pathogens and a diverse range of nonpathogens. Pathogenic and nonpathogenic strains of this species can be distinguished from each other with pathogenicity tests, but not with morphological analysis or sexual compatibility studies. Substantial genetic diversity among isolates has led to the realization that F. oxysporum represents a complex of cryptic species. F. oxysporum f. sp cubense (Foc), causal agent of Fusarium wilt of banana, is one of the more than 150 plant pathogenic forms of F. oxysporum. Multi-gene phylogenetic studies of Foc revealed at least eight phylogenetic lineages, a finding that was supported by random amplified polymorphic DNAs, restriction fragment length polymorphisms and amplified fragment length polymorphisms. Most of these lineages consist of isolates in closely related vegetative compatibility groups, some of which possess opposite mating type alleles, MAT-1 and MAT-2; thus, the evolutionary history of this fungus may have included recent sexual reproduction. The ability to cause disease on all or some of the current race differential cultivars has evolved convergently in the taxon, as members of some races appear in different phylogenetic lineages. Therefore, various factors including co-evolution the plant host and horizontal gene transfer are thought to have shaped the evolutionary history of Foc. This review discusses the evolution of Foc as a model formae specialis in F. oxysporum in relation to recent research findings involving DNA-based studies.