Molecular Characterization, Fitness, and Mycotoxin Production of Fusarium asiaticum Strains Resistant to Fludioxonil.

Fludioxonil is used in seedborne disease management of various fungal pathogens, including Fusarium asiaticum, the predominant causal agent of Fusarium head blight in China. In this study, we screened resistant strains from a large number of F. asiaticum strains collected from 2012 to 2016 and found that 4 of 1,000 field strains were highly resistant to fludioxonil. The 50% effective concentration values of the resistant strains and induced mutants ranged from 80 to >400 µg/ml. Compared with field-sensitive strains, all field-collected and laboratory-induced resistant strains exhibited fitness defects in traits including mycelial growth, conidial production, pathogenicity, and sensitivity to osmotic conditions. In the presence of fludioxonil, significantly higher glycerol accumulation was found in sensitive strains but not in resistant individuals. The fludioxonil-resistant strains produced lower amounts of glycerol in liquid culture and lower amounts of trichothecene mycotoxins in rice culture and inoculated wheat spikelets than the fludioxonil-sensitive strains. Sequence analyses of the key genes of the two-component histidine kinase signaling pathway showed various amino acid substitutions in the Os1, Os4, and Os5 genes between field-sensitive and resistant strains or mutants. The results of this study suggest a potential risk of fludioxonil resistance development and a possible influence of resistance mutations on fitness parameters and toxin production in F. asiaticum.

Optical properties of Ce(3+)-Nd(3+) co-doped YAG nanoparticles for visual and near-infrared biological imaging.

Ce(3+)-Nd(3+) co-doped Y3Al5O12 (YAG) nanoparticles, an average size of 20-30 nm clusters aggregated by 8-10 nm YAG nanoparticles, were synthesized by a solvothermal method. When excited by blue irradiation source, strong and broad yellow luminescence (centered at 526 nm) from Ce(3+) as well as near-infrared (NIR) luminescence (890, 1066 and 1335 nm) of Nd(3+) was observed simultaneously. It occurred by the effective dipole-dipole energy transfer from Ce(3+) to Nd(3+). Energy transfer efficiency from Ce(3+) to Nd(3+) was also calculated to be 50%. The optical property suggests that Ce(3+)-Nd(3+) co-doped YAG nanoparticles can be used as an efficient fluorescence imaging agent for not only visual but also near-infrared imaging.

Photocatalytic activity of TiO2 films grown on different substrates.

Titanium dioxide films were prepared on glass, indium-tin oxide (ITO) glass and p-type monocrystalline silicon and studied for the photocatalytic degradation of rhodamine B in an aqueous medium. Raman, AFM, and XPS spectroscopic investigations of these films indicated that microstructure of titanium oxide films were greatly affected by the substrate materials. Rutile was confirmed to be easily formed on the surface of ITO glass, and TiO2 tended to grow as closely packed particles that were elongated strips with an average size of 20 nm, and had lovely contrast with the perfectly round particles grown on p-type monocrystalline silicon. Charge transfer between the film and silicon substrate was verified by surface photovoltage spectra. This may be the real reason why the films grown on ITO glass and silicon substrates exhibit higher photocatalytic reactivity than the film on glass substrate. Moreover, the different surface properties also seem to be responsible for the different activity.