Detection and Molecular Characterization of Boscalid-Resistant Botrytis cinerea Isolates from Strawberry

Abstract Botrytis cinerea isolates (n = 122) were collected from strawberry fields located in northern Greece during a 3-year period (2008–10) and tested for their sensitivity to the succinate dehydrogenase inhibitor boscalid. Sensitivity measurements showed three distinct phenotypes consisting of isolates highly sensitive (fungicide concentration causing inhibition of germ tube growth by 50% [EC50 values] of 0.05 to 0.21 μg ml–1), moderately resistant (EC50 values of 1.37 to 7.79 μg ml–1), or highly resistant (EC50 values of >50 μg ml–1) to boscalid. Sequence analysis of the sdhB gene revealed five mutations leading to amino acid substitutions in the SdhB subunit in isolates moderately resistant and highly resistant to boscalid. Three moderately resistant isolates showed a nucleotide change from A to T at codon 230, resulting in an asparagine to isoleucine (N230I) substitution. Several moderately resistant isolates showed a nucleotide change from C to T at codon 272, resulting in a substitution from hist...