Identification and characterization of benzimidazole resistance in Monilinia fructicola from stone fruit orchards in California

• Published in: Applied and Environmental Microbiology Vol. 69; no. 12; pp. 7145 - 7152
• Main Authors: Ma, Z.H, Yoshimura, M.A, Michailides, T.J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.12.2003
• Subjects: Ascomycota - drug effects; Ascomycota - genetics; Ascomycota - growth & development; benomyl; Benomyl - pharmacology; benzimidazole fungicides; Benzimidazoles - pharmacology; Biological and medical sciences; California; DNA, Fungal - analysis; Drug Resistance, Fungal - genetics; Flowers - microbiology; fruit diseases; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; fungicide residues; Fungicides, Industrial - pharmacology; Microbiology; microsatellite repeats; Molecular Sequence Data; Monilinia fructicola; mutants; mutation; nucleotide sequences; orchards; Plant Diseases - microbiology; Plant Microbiology; polymerase chain reaction; Polymerase Chain Reaction - methods; Prunus; Prunus - microbiology; Sequence Analysis, DNA; stone fruits; structural genes; Thiophanate - pharmacology; thiophanate-methyl; tubulin; Tubulin - genetics; California; Fungi; Resistance; Plant pathogen; Benzimidazole; Pesticides; Stone fruit; Ascomycetes; Identification; Monilinia fructicola; Fungicide; Thallophyta
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.69.12.7145-7152.2003

Low and high levels of resistance to the benzimidazole fungicides benomyl and thiophanate-methyl were observed in field isolates of Monilinia fructicola, which is the causative agent of brown rot of stone fruit. Isolates that had low levels of resistance (hereafter referred to as LR isolates) and high levels of resistance (hereafter referred to as HR isolates) were also cold and heat sensitive, respectively. Results from microsatellite DNA fingerprints showed that genetic identities among the populations of sensitive (S), LR, and HR isolates were very high (>0.96). Analysis of DNA sequences of the beta-tubulin gene showed that the LR isolates had a point mutation at codon 6, causing a replacement of the amino acid histidine by tyrosine. Codon 198, which encodes a glutamic acid in S and LR isolates, was converted to a codon for alanine in HR isolates. Based on these point mutations in the beta-tubulin gene, allele-specific PCR assays were developed for rapid detection of benzimidazole-resistant isolates of M. fructicola from stone fruit.