Date of Award

5-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Committee Member

Dr. Guido Schnabel

Committee Member

Dr. Paula Agudelo

Committee Member

Dr. Julia Kerrigan

Abstract

Reduced-risk fungicides are a major component of modern IPM programs, but their site-specific mode of action makes them vulnerable to resistance development. Assessing the resistance risk of a fungicide is critical to establishment of sustainable use protocols for the practitioner. Several controlled laboratory studies indicate that fungicide-induced mutagenesis may be an underappreciated trait in resistance risk assessment. In the brown rot fungus Monilinia fructicola, microsatellite instability and transposon movement resulted after prolonged exposure to the fungicide azoxystrobin in vitro. In this study, azoxystrobin or propiconazole fungicides were applied weekly to nectarine trees for two years between bloom and harvest, and fungal isolates were investigated for phenotypic and genotypic changes. Results showed no evidence of fungicide-induced microsatellite instability or reduction of sensitivity to fungicides used in the study or to unrelated chemical classes, indicating that fungicide-induced mutagenesis may not occur in field populations as readily as it does in vitro. Further research examining larger portions of the genome may be necessary to ascertain the significance of fungicide-induced mutagenesis to fungicide resistance risk assessment.

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