Arno Erasmus

Classification of imazalil resistance in an international collection of Penicillium digitatum isolates

Abstract A total of 213 Penicillium digitatum isolates with resistance to the fungicide imazalil (IMZ) originating from green moulded citrus fruit from several countries (South Africa, USA, Uruguay, Spain, Israel, Cyprus, Chile, Australia and Argentina) were tested for their Cyp51 IMZ-resistance group (R1 to R3) using a published multiplex PCR assay. As well, the level of resistance (measured as EC50 values) was determined. Isolates from the USA showed the highest resistance group diversity (isolates belonged to R1, R2 and R3 groups) and lowest EC50 values. The isolates from the other countries were all classified into the R3 group, except for Chile, which also contained R1 isolates. There was no correlation between the level of resistance of isolates and the resistance group genotype. In general, IMZ resistance was most commonly associated (88.3%) with the R3 group. This study is the first to investigate the distribution of IMZ resistance genotypes in P. digitatum populations from a broad international scale.