Imazalil resistance linked to a unique insertion sequence in the PdCYP51 promoter region of Penicillium digitatum

• Published in: Postharvest biology and technology 2007-04, Vol.44 (1), p.9-18
• Main Authors: Ghosoph, Jennifer M., Schmidt, Leigh S., Margosan, Dennis A., Smilanick, Joseph L.
• Format: Article
• Language: English
• Subjects: 14α-Demethylase CYP51 gene; Biological and medical sciences; Citrus; citrus fruits; citrus green mold; Demethylation inhibitors (DMIs); Food industries; food microbiology; Fruit and vegetable industries; fruit diseases; fruit quality; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; Fungal plant pathogens; Fungicide resistance; Imazalil; microbial detection; microbial genetics; molecular sequence data; Penicillium digitatum; Phytopathology. Animal pests. Plant and forest protection; postharvest diseases; promoter regions; strain differences; transposons
• ISSN: 0925-5214; 1873-2356
• DOI: 10.1016/j.postharvbio.2006.11.008

Two mechanisms of resistance to the fungicide imazalil (IMZ) existed among California strains of Penicillium digitatum, cause of citrus green mold. Sensitive (S; n = 50) strains did not grow on IMZ above 0.1 μg mL −1, while those resistant (R; n = 59) grew ≥0.5 mg L −1. After amplification of the promoter region of the CYP51 gene, fragments 250, 450, and 750 bp in size were generated. All S strains had a 250 bp product, while among R strains, 47 had a 450 bp product and 12 had a 750 bp product. The 450 bp unit was common among R strains, while the 750 bp unit, reported previously by others, was not. The promoter region of all was identical; variations occurred in the region's transcriptional enhancer unit. S strains with a 250 bp product and R strains with a 750 bp product had one and five copies, respectively, of a 126 bp transcriptional enhancer unit. R strains with a 450 bp product had a unique 199 bp insert within the 126 bp transcriptional enhancer unit with no known sequence correlations (GenBank). Both types of R strains exhibited significantly elevated expression, approximately 10-fold, of the target site CYP51 gene, indicating its overexpression was the mechanism of resistance.