Occurrence Of Quinone Research Articles

Occurrence of Quinone Outside Inhibitor Resistance in Virginia Populations of Parastagonospora nodorum Infecting Wheat.

Stagonospora nodorum blotch (SNB) of wheat, caused by Parastagonospora nodorum, is managed using cultural practices, resistant varieties, and foliar fungicides. Frequent fungicide use can select for fungicide resistance, making certain chemistries less effective; this may in part explain the increasing severity of SNB in the mid-Atlantic United States. Quinone outside inhibitor (QoI) resistance has been documented for a diversity of fungi, but it has not been reported for P. nodorum in the United States. The objectives of this study were (i) to evaluate QoI sensitivity of P. nodorum from Virginia wheat fields, (ii) to screen P. nodorum for QoI target site mutations in the cytochrome b gene, and (iii) to develop a molecular assay to detect target site mutations associated with QoI resistance. Sensitivity of 16 isolates to pyraclostrobin and azoxystrobin was evaluated with radial growth assays, and the cytochrome b gene was sequenced. One isolate was insensitive to both fungicides and had the G143A mutation in the cytochrome b gene. For azoxystrobin, 10 isolates without target site mutations had reduced sensitivity. Additional isolates (n = 58) were sequenced. A total of seven isolates had the G143A mutation and also had reduced sensitivity to pyraclostrobin and azoxystrobin compared with a sensitive control isolate without the mutation. A pyrosequencing assay targeting G143A was developed as a rapid method to screen P. nodorum for the QoI resistance-conferring mutation. To our knowledge, this is the first report of QoI-resistant P. nodorum in the United States. Overall resistance frequency was low, but resistance management practices are needed to maintain the efficacy of fungicides for SNB control.

Occurrence and Potential Sources of Quinones Associated with PM2.5 in Guadalajara, Mexico

This study aims to establish the influence of primary emission sources and atmospheric transformation process contributing to the concentrations of quinones associated to particulate matter of less than 2.5 µm (PM2.5) in three sites within the Metropolitan Area of Guadalajara (MAG), namely Centro (CEN), Tlaquepaque (TLA) and Las Águilas (AGU). Environmental levels of quinones extracted from PM2.5 filters were analyzed using Gas Chromatography coupled to Mass Spectrometry (GC-MS). Overall, primary emissions in combination with photochemical and oxidation reactions contribute to the presence of quinones in the urban atmosphere of MAG. It was found that quinones in PM2.5 result from the contributions from direct emission sources by incomplete combustion of fossil fuels such as diesel and gasoline that relate mainly to vehicular activity intensity in the three sampling sites selected. However, this also suggests that the occurrence of quinones in MAG can be related to photochemical transformation of the parent Polycyclic Aromatic Hydrocarbons (PAHs), to chemical reactions with oxygenated species, or a combination of both routes. The higher concentration of 1,4-Chrysenequinone during the rainy season compared to the warm-dry season indicates chemical oxidation of chrysene, since the humidity could favor singlet oxygen collision with parent PAH present in the particle phase. On the contrary, 9,10-Anthraquinone/Anthracene and 1,4-Naftoquinone/Naphthalene ratios were higher during the warm-dry season compared to the rainy season, which might indicate a prevalence of the photochemical formation during the warm-dry season favored by the large solar radiation typical of the season. In addition, the estimated percentage of photochemical formation of 9,10-Phenanthrenequinone showed that the occurrence of this compound in Tlaquepaque (TLA) and Las Águilas (AGU) sites is mainly propagated by conditions of high solar radiation such as in the warm-dry season and during long periods of advection of air masses from emission to the reception areas. This was shown by the direct association between the number hourly back trajectories arriving in the TLA and AGU from Centro and other areas in MAG and the highest photochemical formation percentage.