Patterns of cross-resistance to fungicides in Botryotinia fuckeliana (Botrytis cinerea) isolates from French vineyards

Field strains of Botryotinia fuckeliana were isolated from diseased grape b erries which were collected at the harvest, between 1993 and 1997, from Fre nch vineyards located in Alsace, Armagnac, Bordeaux, Champagne and Loire Va lley. According to the inhibitory effects of fungicides towards spore germi nation, germ-tube elongation and mycelial growth, several phenotypes could be characterized. Thus, two types of benzimidazole (e.g. carbendazim, thiab endazole)-resistant strains were detected; negative cross-resistance toward s diethofencarb, diphenylamine and dicloran was found only in one type. Mos t dicarboximide (e.g. iprodione, procymidone, vinclozolin)-resistant strain s were also weakly resistant to aromatic hydrocarbon fungicides (e.g. chlor oneb, dicloran, tolclofosmethyl) but remained sensitive to phenylpyrroles ( e.g. fenpiclonil, fludioxonil). However, in some other dicarboximide-resist ant strains, resistance was observed either as being restricted to dicarbox imides or as extending weakly to phenylpyrroles. Towards anilinopyrimidines (e.g. cyprodinil, mepanipyrim, pyrimethanil), three resistant phenotypes h ave been identified. In the most resistant one, resistance was restricted t o anilinopyrimidines, whereas in the others, resistance extended to various other groups of fungicides including dicarboximides, phenylpyrroles, stero l biosynthesis inhibitors (e.g. tolfanate, prochloraz, tebuconazole) and th e hydroxyanilide derivative, fenhexamid. According to the pattern of cross- resistance, two phenotypes were characterized within these multifungicide-r esistant strains. In vitro tests conducted with fenpropimorph, fenpropidin and spiroxamine, revealed the existence of strains highly susceptible to th ese sterol Delta(14)- reduction inhibitors. This property was correlated wi th a decreased sensitivity towards fenhexamid. (C) 2000 Elsevier Science Lt d. All rights reserved.