IDENTIFICATION OF BENZIMIDAZOLE RESISTANCE IN CLADOBOTRYUM DENDROIDESUSING A PCR-BASED METHOD

Cladobotryum dendroides, causal agent of cobweb disease of Agaricus bi sporus, has become increasingly resistant to methylbenzimidazole carba mate (MBC) fungicides following the extensive use of MBC in cultivated mushroom production in Ireland. Of 38 isolates of C. dendroides obtai ned from Irish mushroom units, 34 were resistant to carbendazim. Prime rs based on conserved regions of the beta-tubulin gene were used to am plify and sequence a portion of the beta-tubulin gene in C. dendroides . A point mutation was detected at codon 50 in isolates resistant to b enzimidazole fungicides, causing an amino acid substitution from tyros ine to cyst eine. Species-specific PCR primers were designed to amplif y the region of the beta-tubulin gene containing this substitution. Th e point mutation removed an Ace I restriction site in the beta-tubulin gene sequence of resistant isolates. Digestion of the PCR product wit h Ace I thus provides a rapid diagnostic test to differentiate sensiti ve and resistant isolates of this fungus. EMBL accession number: Y1225 6.