Effects Of Flusilazole On Growth And Virulence Of Sclerotinia Sclerotiorum

The ascomycete fungus Sclerotinia sclerotiorum(Lib.)de Bary is a necrotrophic plant pathogen capable of infecting a variety of crops and vegetables,and the control of S.sclerotiorum is still dominated by fungicides.The fungicide flusilazole has not been registered for control of S.sclerotiorum in China.In this study,sensitivity of S.sclerotiorum to flusilazole,control efficiency and hormetic effects of flusilazole on virulence of S.sclerotiorum were assessed.Baseline sensitivity of S.sclerotiorum to flusilazole was established by determining the effective concentration for 50% inhibition(EC50)of 150 isolates.The mean EC50 value was 0.1237 ?g/mL with a range from 0.0227 to 0.3436 ?g/mL.The preventive efficacy of flusilazole was significantly higher than that of carbendazim.Flusilazole at 0.03,0.06 and 0.12 ?g/mL in potato dextrose agar(PDA)significantly reduced the cell membrane permeability of mycelia,changed mycelial morphology and thickened mycelial cell wall.Mycelia grown on PDA amended with flusilazole at concentrations from 0.005 to 0.16 ?g/mL were more virulent than the non-treated control,and the maximum percent stimulation on virulence was 19.81% for isolate HN-24.Flusilazole sprayed at low doses enhanced virulence of S.sclerotiorum.Flusilazole sprayed at concentrations from 0.002 to 2 ?g/mL on potted rapeseed plants increased virulence by 8.28% to 10.72% for isolate HN-24.The stimulatory effects on virulence could be observed at 12 h post inoculation,therefore indicating a direct stimulation mechanism.Growning on PDA amended with flusilazole could not significantly changed tolerance of S.sclerotiorum to H2O2.Flusilazole preconditioning significantly enhanced tolerance of S.sclerotiorum to flusilazole and other fungicides with the same mode of action,and reduced tolerance to fungicides with different mode of action.Flusilazole preconditioning reduced the growth of S.sclerotiorum on PDA without fungicide.