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Pandey Thesis4.67 MB
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Thesis
PHENOTYPIC AND MOLECULAR CHARACTERIZATION OF FUNGICIDE SENSITIVITY IN SEVERAL PENICILLIUM SPECIES CAUSING BLUE MOLD OF POME FRUITS IN THE PACIFIC NORTHWEST
Washington State University
Master of Science (MS), Washington State University
12/2024
DOI:
https://doi.org/10.7273/000007205
Abstract
Blue mold, caused by Penicillium spp., poses a substantial threat to apples and pears during storage, resulting in about 50% fruit loss in the Pacific Northwest (PNW). The primary approach to managing blue mold is through postharvest applications of four fungicides, i.e., thiabendazole (TBZ), difenoconazole (DIF), pyrimethanil (PYR), and fludioxonil (FDL). Between 2016 and 2018, a total of 162 Penicillium isolates were collected from decayed apples and pears from multiple packinghouses in the states of Washington and Oregon. These isolates included 31 P. expansum isolates and 131 isolates of 13 other Penicillium species referred to as non-expansum isolates. In vitro conidial germination and mycelial growth inhibition assessments were conducted to establish EC50 values of 162 Penicillium isolates to TBZ, DIF, PYR, and FDL. The results revealed a high in vitro tolerance of several non-expansum isolates compared to P. expansum isolates. Overall, the EC50 values were particularly high (>500 μg/ml) for TBZ and FDL in non-
expansum species including P. solitum, P. roqueforti, P. commune, P. paneum, P. crustosum and P. palitans, moderate (>10 μg/ml) for PYR, and low (<2 μg/ml) for DIF. Reduced sensitivity to multiple postharvest fungicides was observed for several Penicillium spp. The recommended label rates of TBZ, PYR, and FDL proved ineffective in inhibiting blue mold decay from at least six Penicillium species on detached apples after five months of storage at 1.5°C. Sequencing of the β-tubulin gene revealed mutations at codon 167 (F167Y) in 16TBZ-resistant isolates of six Penicillium species. Additionally, concurrent mutations were found at codons 198 and 240 in P. roqueforti and P. paneum isolates with high EC50 values. Sequencing of the CYP51, MDL1, NIKA and OS1 genes, known to confer resistance to DIF, PYR, and FDL in other fungi, identified several mutations that were not consistently linked to in vitro sensitivity and will necessitate further investigation. The high in vitro tolerance and the control failure observed on fruit highlight the potential risk posed by several “non-expansum” Penicillium species to pome fruit packers.
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Details
- Title
- PHENOTYPIC AND MOLECULAR CHARACTERIZATION OF FUNGICIDE SENSITIVITY IN SEVERAL PENICILLIUM SPECIES CAUSING BLUE MOLD OF POME FRUITS IN THE PACIFIC NORTHWEST
- Creators
- Madan Pandey
- Contributors
- Achour Amiri (Chair)Chakradhar Mattupalli (Committee Member)Gary Grove (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Plant Pathology
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 109
- Identifiers
- 99901195340101842
- Language
- English
- Resource Type
- Thesis