Présence en Tunisie d'isolats de Fusarium sambucinum résistants aux benzimidazoles : développement in vitro et agressivité sur tubercules de pomme de terre

Abstract

Presence in Tunisia of Fusarium sambucinum isolates resistant to benzimidazoles: in vitro growth and aggressiveness on potato tubers. The behaviour of 55 isolates of Fusarium spp. causing dry rot of the potato tubers, is studied against some enzimidazoles fungicides. Tunisian isolates of F. solani (12), F. oxysporum (23) and F. graminearum (10) are sensitive in vitro to carbendazime and benomyl at 5 mg.l-1. Their interaction with thiophanate-methyl is different; a complete inhibition of their mycelial growth is observed at doses higher than 500 mg.l-1. Tunisian isolates of F. sambucinum collected during 2002, 2003 and 2004 are resistant to these benzimidazoles showing existence of a cross-resistance. In fact, these isolates tolerated carbendazime (and benomyl) at 200 mg.l-1 and thiophanate-methyl at 1000 mg.l-1. This is the first study in Tunisia indicating emergence of this type of F. sambucinum resistance. Control isolates of F. sambucinum and those treated with carbendazime at 100 mg.l-1 showed a similar aggressiveness on potato tubers of the Spunta cultivar.

Keywords

• Dry rot
• Fusarium spp.
• benzimidazoles
• cross-resistance
• potatoes