Long-Term Monitoring for Resistance of Botryotinia fuckeliana to Anilinopyrimidine, Phenylpyrrole, and Hydroxyanilide Fungicides in Switzerland

Abstract

In Switzerland, the use of phenylpyrrole, anilinopyrimidine, and hydroxyanilide fungicides for control of Botryotinia fuckeliana, causal agent of gray mold in grapes, has been restricted to one treatment per fungicide class per year as part of an anti-resistance strategy. Resistance development in B. fuckeliana was monitored from 1995 to 2001 for the anilinopyrimidine cyprodinil and the phenylpyrrole fludioxonil and from 1997 to 2001 for the hydroxyanilide fenhexamid in experimental vineyards in Richterswil and Stäfa, Switzerland. In total, over 2,400 field isolates were tested. In 1996, the first case of field resistance to anilinopyrimidines was encountered in Richterswil. Efficacy of the anilinopyrimidine cyprodinil decreased significantly, and 54% of the isolates were resistant to anilinopyrimidines. During 7 years of monitoring, one field isolate was found that showed a slightly decreased sensitivity to the phenylpyrrole fludioxonil. Resistance to the hydroxyanilide fenhexamid was not found in 1997 and 1998. From 1999 to 2001, the level of fenhexamid-resistant isolates increased to 100% in Stäfa. The analysis of monitoring and efficacy data showed that subpopulations of B. fuckeliana resistant to cyprodinil and fenhexamid have increased significantly; however, the efficacy of a mixture of fludioxonil and cyprodinil and of fenhexamid alone was still effective. The objective of this study was to initiate long-term monitoring in order to establish an early resistance-detection system as a tool to assess the effectiveness of the anti-resistance strategy used in Switzerland.

Phenotypic Analyses of Fenhexamid Resistant Botrytis cinerea Mutants

“…Fenhexamid, a hydroxanilide derivative, is one of the newly developed fungicides that exhibit strong inhibitory activity against B. cinerea, owing to its ability to inhibit 3-ketoreductase in the C4-demethylation enzyme complex during ergosterol biosynthesis (Rosslenbroich et al 2000;Debieu et al 2001). Fenhexamid is used in many European countries and is considered to be an effective fungicide against B. cinerea due to its unique mode of action (Rosslenbroich et al 2000;Debieu et al 2001;Baroffio et al 2003). However, B. cinerea wild types exhibiting resistance to fenhexamid were detected shortly after its introduction (Leroux et al 2002;Baroffio et al 2003).…”

Resistance to Botryticides

“…Any shift of B. cinerea toward fluazinam in vineyards has still not revealed. In 1999, firstly in Switzerland, a botryticide with novel botryticidial action was registered, the fenhexamid (Baroffio et al, 2003). Early investigations on the fenhexamid mode of action suggested that it has different mechanism from than of all other botryticides (Rosslenbroich & Stuebler, 2000).…”

“…Different levels of dicarboximides-resistance variously accompanied by resistance to phenylpyrrole fungicides and reduced tolerance to high osmotic pressure point to polymorphism of Daf1 and with time become evident that there are at least five classes of responsible alleles (Hilber et al, 1995;Faretra & Pollastro, 1991;Faretra & Pollastro, 1993a, 1993bVignutelli et al, 2002;Baroffio et al, 2003). Recent studies suggested that an amino acid substitution of serine for isoleucine in the second unit of tandem amino acid repeats on 86 codon of BcOS1p gene is responsible for dicarboximides resistance in the field (Oshima et al, 2002).…”

“…In 1999 botryticide with a high preventive activity against B. cinerea, fenhexamide, was introduced into vineyards (Baroffio et al, 2003). Owing to its novel mode of action, differing from all other botryticides it was presumed that resistance to fenhexamid will not occur easily.…”

“…High risk of resistance was already evident in the first laboratory investigations. The baseline sensitivity of B. cinerea towards fenhexamide was recorded in 1992 and afterwards resistant strains of B. cinerea were detected in French and Swiss vineyards but so far loss of the fungicide's effectiveness has never been observed Suty et al, 1997;Baroffio et al, 2003). In France were high level fenhexamidresistant strains collected even before use of fenhexamid.…”