SBI-fungicides : fungicidal effectiveness and resistance in «Botrytis cinerea»

In vitro fungitoxicity tests with 14 sterol biosynthesis inhibitors (SBIs) showed that the SBIs pyrifenox, flusilazol, propiconazole, triflumizole and fenpropimorph applied at the low concentration of 1 µg ml-1 inhibited the mycelial growth of wild-type and mutant strains of Botrytis cinerea that were resistant to the benzimidazoles, to the dicarboximides and to a mixture of benzimidazole+phenylcarbamate (carbendazim+diethofencarb). The SBIs tested exhibited higher effectiveness against the wild-type and mutant strains of B. cinerea compared with some widely used botryticides, such as the dicarboximides iprodione, procymidone and chlozolinate, the aromatic hydrocarbons quintozene, chloroneb and tolclofos-methyl, and the relatively new fungicides cyprodinil and fenhexamid. Only benomyl and fludioxonil presented higher effectiveness than the SBIs. In planta pot experiments with preventive applications of the commercial products Dorado 20 EC (pyrifenox), Punch 40 EC (flusilazol), Tilt 25 EC (propiconazole), Corbel 75 EC (fenpropimorph) and Trifmine 30 EC (triflumizole) showed that lesions of cucumber seedlings by all the abovementioned strains of B. cinerea were completely inhibited at low SBI concentrations of 0.05–0.1 g a.i. l-1. After chemical mutagenesis with N-methyl-N-nitro-N-nitrosoguanidine (MNNG), only strains with low resistance (Rf 6–9, based on MIC values) to triadimefon were isolated at a mutation frequency of 3.9 10-5. Cross-resistance studies with other SBIs showed that these triadimefon-resistant strains exhibited positive cross-resistance (Rf 2–10) to the other C-14 demethylase inhibitors (DMIs), but not to the morpholine fungicides fenpropimorph or tridemorph. Study of fitness of DMI-resistant strains showed that these mutation(s) were pleiotropic, with significant adverse effects on characteristics determining phytopathogenic fitness such as rate of mycelial growth, sporulation, conidial germination and pathogenicity on cucumber seedlings. The results indicate that some SBI-fungicides are suitable for use in resistance management programmes against grey mould

Differential Effect of <i>Sdh</i>B Gene Mutations on the Sensitivity to SDHI Fungicides in <i>Botrytis cinerea</i>

Succinate dehydrogenase inhibiting (SDHI) fungicides constitute a relatively novel fungicide group used for gray mold control caused mainly by Botrytis cinerea. Shortly after registration, resistance was observed in fungal populations that correlated with several mutations in the succinate dehydrogenase complex (complex II). In the current study, 30 B. cinerea isolates possessing five different mutations at three different codons of SdhB (P225F, N230I, and H272L/R/Y) were characterized for their sensitivities to eight SDHI fungicides. The results show different sensitivities and cross-resistance patterns between structurally different SDHIs. P225F mutants were resistant in vitro to all SDHIs tested. Similarly, isolates possessing the H272L mutation were highly resistant to boscalid but showed low to moderate levels of resistance to other SDHIs. The N230I mutants were moderately resistant to boscalid, fluopyram, and fluxapyroxad and showed low resistance levels to isopyrazam, bixafen, fenfuram, benodanil, and carboxin. The H272R mutants showed moderate levels of resistance to boscalid and low resistance levels to isopyrazam, fenfuram, and carboxin but remained sensitive to fluopyram, bixafen, fluxapyroxad, and benodanil. Similarly, the H272Y showed moderate levels of resistance to boscalid and very low resistance levels to isopyrazam, bixafen, fenfuram, and carboxin but showed increased sensitivity to benodanil and fluopyram. Boscalid provided moderate to high control of H272R/Y and N230I mutants in detached fruit assays but provided little control against the H272L and P225F mutants. In contrast, fluopyram controlled H272R/Y mutants and provided moderate levels of control toward H272L, N230I, and P225F mutants. Our findings suggest that sensitivity to SDHIs may vary greatly, dependent on the point mutation in the sdhb subunit. </jats:p

Determination of Benzoylurea Insecticide Residues in Tomatoes by High-Performance Liquid Chromatography with Ultraviolet-Diode Array and Atmospheric Pressure Chemical Ionization-Mass Spectrometry Detection

Abstract A simple and sensitive method using high-performance liquid chromatography/mass spectrometry (LC/MS) was developed and validated for simultaneous determination of 5 benzoylurea insecticidesdiflubenzuron, triflumuron, teflubenzuron, lufenuron, and flufenoxuronin tomatoes. Residues were successfully separated on a C18 column by methanolwater isocratic elution. Detection was carried out by an ultraviolet diode array detector (UV-DAD) coupled with a quadrupole mass spectrometer, using atmospheric pressure chemical ionization (APCI) in negative-ion mode. The main ions were the deprotonated molecules [MH]&amp;lt;sup/&amp;gt; for triflumuron, and the anions formed by elimination of hydrofluoric acid [MHHF]&amp;lt;sup/&amp;gt; for diflubenzuron and flufenoxuron, and [M2HHF] for lufenuron and teflubenzuron. The calibration plots were linear for both detectors over the range 0.05 to 10 g/mL, and the method presented good quality parameters. The limits of detection for standard solutions were 0.0080.01 mg/L (equivalent to 0.080.1 ng injected) for both detectors, and the limits of quantification (LOQs) were approximately 10 times lower than national maximum residue levels (MRLs). Depending on the compound and the detector, the LOQ values ranged from 0.2 to 0.4 ng injected. The optimum LC-UV-DAD/APCI-MS conditions were applied to the analysis of benzoylureas in tomatoes. The obtained recoveries from fortified tomato samples (50 g), extracted with ethyl acetate and purified by solid-phase extraction on silica sorbent, were 88100 and 92.9105 for the UV-DAD and MS detectors, respectively, with precision values (relative standard deviations) of 2.911 and 3.714, respectively. The method was applied to 12 tomato samples from local markets, and diflubenzuron and lufenuron were detected in only one sample at concentrations lower than the MRLs. The results indicate that the developed LC/MS method is accurate, precise, and sensitive for quantitative and qualitative analysis at low levels of benzoylureas required by legislation.</jats:p