flumorph and dimethomorph

Topics: Antifungal Agents; Chemistry Techniques, Synthetic; Cucumis sativus; Drug Resistance; Imidazoles; Morpholines; Oomycetes; Plant Diseases; Pyrimidines; Sulfonamides; Triticum; Zea mays

To determine the residues of flumorph and dimethomorph in vegetables, a method was established with improved QuEChERS-gas chromatography coupled to mass spectrometry (GC-MS). With acetonitrile as the extraction solvent, the samples were pretreated with the improved QuEChERS method including extraction, salting-out and purification processes. Then all the sample extracts were analyzed with GC-MS in selected-ion monitoring (SIM) mode, and quantified by matrix-matched standard solution in external standard method. Under electron ionization conditions, the analysis was carried out with a capillary column (DB-5 MS, 30 mx 0. 25 mm x 0. 25 μm) at a flow rate of 1. 1 mL/min. The quantitation was performed to detect ions of m/z 285, 371, 165 for flumorph and m/z 301, 387, 165 for dimethomorph. Good linearity was obtained in the range of 10-1 000 μg/kg for both pesticides with correlation coefficients greater than 0. 999. The recovery experiments were carried out by spiking blank samples of ginger, tomato, carrot, spinach, cabbage and tremella at the three levels of 10, 20 and 100 μg/kg. For both pesticides in different matrices, the limits of detection (S/N=3) were in the range of 0. 67-2. 42 μg/kg. The average recoveries of flumorph and dimethomorph ranged from 71% to 116% with the relative standard deviations (RSDs) in the range of 1. 8%- 14. 7%. Meanwhile, the pyrolysis mechanism and matrix effect for the determination of flumorph and dimethomorph in vegetables were investigated in this study. The method is simple, rapid and accurate, and can be used for the routine analysis of flumorph and dimethomorph in vegetables.

Topics: Food Analysis; Gas Chromatography-Mass Spectrometry; Morpholines; Pesticide Residues; Vegetables

The oomycete fungicide flumorph is a recently introduced carboxylic acid amide (CAA) fungicide. In order to evaluate the risk of developing field resistance to flumorph, the authors compared it with dimethomorph and azoxystrobin with respect to the ease of obtaining resistant isolates to these fungicides, the level of resistance and their fitness in the laboratory.. Mutants with a high level of resistance to azoxystrobin were isolated readily by adaptation and UV irradiation, and their fitness was as good as that of the parent isolates. Attempts to generate mutants of Pseudoperonospora cubensis (Burk. & MA Curtis) Rostovsev resistant to flumorph and dimethomorph by sporangia adaptation on fungicide-treated leaves were unsuccessful. However, moderately resistant mutants were isolated using UV mutagenesis, but their resistance level [maximum resistance factor (MRF) < 100] was much lower than that of the azoxystrobin-resistant mutant (MRF = 733). With the exception of stability of resistance, all mutants showed low pathogenicity and sporulation compared with wild-type isolates and azoxystrobin-resistant mutants. There is cross-resistance between flumorph and dimethomorph, suggesting that they have the same resistance mechanism.. The above results suggest that the resistance risk of flumorph may be similar to that of dimethomorph but lower than that of azoxystrobin and can be classified as moderate. Thus, it can be managed by appropriate product use strategies.

Topics: Cucumis sativus; Drug Resistance, Fungal; Fungicides, Industrial; Methacrylates; Morpholines; Mutation; Oomycetes; Plant Leaves; Pyrimidines; Selection, Genetic; Strobilurins; Ultraviolet Rays