First Report of Phytophthora Blight of Lily Caused by Phytophthora nicotianae in China.

Lily (Lilium spp.) is an economically important cut flower in China. In August 2009, 30 to 40% of plants of lily cv. Siberia in a greenhouse for cut flower production in Yunnan, China were severely diseased. Infected plants developed water-soaked lesions and soft rot on the base of stems and leaves near the soil surface. As the disease progressed, stems bent and plants collapsed. Soft rot symptoms were observed on some bulbs and roots of severely diseased plants. Small, diseased tissue fragments (approximately 3 mm) were surface disinfected with 0.5% NaOCl and then plated to Phytophthora selective medium (10% V8 juice agar) (4). Inoculated dishes were incubated at 25°C in the dark. After 5 days, white colonies with abundant aerial mycelia developed from all plated tissue samples. The fungus had aseptate hyphae. Sporangia were papillate, both caducous and noncaducous, and the shape ranged from ovoid to spherical. The dimensions of sporangia were 30 to 62 × 21 to 46 µm. On the basis of morphological features, isolates were identified as Phytophthora nicotianae Breda de Haan. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS1/ITS4 and sequenced. BLAST analysis of the 835-bp fragment showed a 99% homology with the sequence of P. nicotianae AY833527. The nucleotide sequence has been assigned GenBank No. GU299778. PCR amplification of genomic DNAs using the P. nicotianae-specific primer pair ITS3-PNIC1 generated a 455-bp sequence (3). The result further confirmed the identity of P. nicotianae. Pathogenicity tests were conducted in the greenhouse on lily cv. Siberia grown in pots. Ten 3-month-old plantlets were inoculated by watering the wounded stem bases and soil surface with 30 ml of zoospore suspensions (105 spores per ml). Five uninoculated plantlets were used as controls. All plantlets were covered with plastic bags and incubated at room temperature (22 to 26°C) for 48 h. Inoculated plants developed initial symptoms of slight chlorosis and wilting of lower leaves. Within a 3-week period, all plants died due to soft rot of stem bases and leaves. The pathogen was reisolated from inoculated plants but not from control plants that were symptomless. P. nicotianae has been reported as the causal agent of Phytophthora blight on lily in Korea, Japan, and Hungary (1,2). To our knowledge, this is the first report of Phytophthora blight of lily in China. References: (1) J. Bakonyi et al. Plant Pathol. 50:795, 2001. (2) H. J. Jee and W. G. Kim. Plant Pathol. J. 14:452, 1998. (3) P. W. Tooley et al. Appl. Environ. Microbiol. 63:1467, 1997. (4) X. B. Zheng. Phytophthora and Its Research Technology. Beijing. China Agriculture Press, Beijing, 1997.

The microorganism community of pentachlorophenol (PCP)-degrading coupled granules.

Coupled granules are self-immobilized aggregates of microorganisms under micro aerobic conditions, which have the dissolved oxygen (DO) level of 0.6 mg.L(-1). The effects of DO concentration on pentachlorophenol (PCP) reduction and its microbial community were investigated in a coupled anaerobic and aerobic reactor. Both the diversity and the dynamicity of the Eubacteria and Archaea community, which were responsible for PCP degradation, were evaluated by means of amplification by polymerase chain reaction (PCR) and separation using the denaturing gradient gel electrophoresis (DGGE) technique. The results demonstrated a major shift in the Eubacteria and Archaea community as the mixed aerobic and anaerobic seeding sludge (1:1 by volume) developed into coupled granules and finally acclimated with PCP throughout the experiment period within 60 days. The numbers of the Eubacteria population decreased from 20, 16 to 11; Shannon diversity index decreased from 2.75, 2.53 to 2.10. In contrast, the number of the Archaea population increased from 12, 14 to 18; and Shannon diversity index increased from 1.87, 1.88 to 2.43. Phylogenetic analysis based on 16SrDNA genes showed the dominance Sphingomonas, Desulfobulbus, Proteobacteria, Actinobacterium, Methanogenic and some uncultured bacteria in the PCP-degrading coupled granules. Microorganism community construction of coupled granules was also deduced.

Direct observation of the topological spin configurations mediated by the substitution of rare-earth element Y in MnNiGa alloy.

The evolution of topological magnetic domains microscopically correlates the dynamic behavior of memory units in spintronic application. Nanometric bubbles with variation of spin configurations have been directly observed in a centrosymmetric hexagonal magnet (Mn0.5Ni0.5)65(Ga1-yYy)35 (y = 0.01) using Lorentz transmission electron microscopy. Magnetic bubbles instead of biskyrmions are generated due to the enhancement of quality factor Q caused by the substitution of rare-earth element Y. Furthermore, the bubble density and diversified spin configurations are systematically manipulated via combining the electric current with perpendicular magnetic fields. The magnetic bubble lattice at zero field is achieved after the optimized manipulation.

Oxygen defect engineering by the current effect assisted with temperature cycling in a perovskite-type La0.7Sr0.3CoO3 film.

Introducing and modulating the oxygen deficiency concentration have been received as an effective way to obtain high catalytic activity in perovskite oxides. However, it is difficult to control the oxygen vacancy in conventional oxygen defect engineering due to harsh reaction conditions at elevated temperatures and the reducing atmosphere, which make it impractical for many technological applications. Herein, we report a new approach to oxygen defect engineering based on the combination of the current effect and temperature cycling at low temperature. Our investigations revealed that the electrical conductivity of the (011)-La0.7Sr0.3CoO3/PMN-PT film changes continuously from metallicity to insulativity under repeated transport measurements below room temperature, which indicates the transformation of the Co4+ state to Co3+ in the film. Further experiments and analysis revealed that oxygen vacancies can be well regulated by the combined current effect and temperature cycling in repeated measurements, which results in a decrease of Co4+/Co3+ and thus the remarkable variation of conductive properties of the film. Our work provides a simple and highly efficient method to engineer oxygen vacancies in perovskite-type oxides and brings new opportunities in designing high-efficiency oxidation catalysts.

Polarized differential-phase laser scanning microscope.

A polarized differential-phase laser scanning microscope, which combines a polarized optical heterodyne Mach-Zehnder interferometer and a differential amplifier to scan the topographic image of a surface, is proposed. In the experiment the differential amplifier, which acts as a PM-AM converter in the experiment, converting phase modulation (PM) into amplitude modulation (AM). Then a novel, to our knowledge, phase demodulator was proposed and implemented for the differential-phase laser scanning microscope. An optical grating (1800 lp/mm) was imaged. The lateral and the depth resolutions of the imaging system were 0.5 mum and 1 nm, respectively. The detection accuracy, which was limited by the reflectivity variation of the test surface, is discussed.

Zeeman laser-scanning confocal microscopy in turbid media.

A novel Zeeman laser-scanning confocal microscope (ZLSCM) is proposed. It has the same configuration as the conventional laser-scanning confocal microscope (LSCM) in which a Zeeman laser in conjunction with a Glan-Thompson analyzer is used. In our system, the analyzer with the bandpass filter, which act simultaneously as a polarization gate and a coherence gate, enhance the collection efficiency of the weak-scattering photons and simultaneously suppress the multiple-scattering photons. The improvement in depth resolution of a ZLSCM in a scattering medium compared with that of a conventional LSCM is discussed and demonstrated experimentally.

Polarized optical coherence imaging in turbid media by use of a Zeeman laser.

A method that uses a Zeeman laser in conjunction with a Glan-Thompson analyzer to image an object in a turbid medium is proposed. A heterodyne signal is generated only when the scattering photons are partially polarized, and the spatial coherence is not seriously degraded after the signal propagates in the turbid medium. A system combining polarization discrimination with optical coherence detection to image the object in a scattering medium is successfully demonstrated. The medium is a solution of polystyrene microspheres measuring 1.072 mum in diameter suspended in distilled water contained in a 10-mm-thick quartz cuvette. The advantages of this optical system, including better selectivity of the weak partially polarized scattering photons and better imaging ability in higher-scattering media, are discussed.