Cloning of the CYP51 gene from the eyespot pathogen Tapesia yallundae indicates that resistance to the DMI fungicide prochloraz is not related to sequence changes in the gene encoding the target site enzyme

Resistance to sterol 14 alpha -demethylase inhibitor (DMI) fungicides has b een correlated with mutations in the CYP51 gene encoding the target enzyme eburicol 14 alpha -demethylase. CYP51 was isolated from the eyespot pathoge n Tapesia yallundae revealing a predicted 526-amino acid product exhibiting homology to other fungal CYP51s. CYP51 was sequenced from four field isola tes sensitive or resistant to the DMI fungicide prochloraz and partially se quenced from two further isolates and eight progeny from a cross between pr ochloraz-sensitive and resistant parents. Two alleles of the gene were dete cted termed CYP51-1 and CYP51-2. No correlation was found between sequence change and fungicide sensitivity. Therefore prochloraz resistance involved a mechanism other than mutation in the target site gene. (C) 2001 Federatio n of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.