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Context-Dependent Fitness Trade-Offs in Penicillium expansum Isolates Resistant to Multiple Postharvest Fungicides

Summary

This research examines how apples and pears get a fungal disease called blue mold and how the fungus develops resistance to commonly used fungicides. Scientists tested fungus samples that resist different fungicides to see if this resistance makes them weaker. They found that resistant fungus strains do struggle more under stressful laboratory conditions, but remain dangerous during long-term cold storage of fruit, especially when fungicides are present.

Background

Blue mold caused by Penicillium expansum is the most significant postharvest disease affecting pome fruit globally. Multi-fungicide-resistant isolates have emerged in the U.S. Pacific Northwest, with resistance documented to thiabendazole (TBZ), pyrimethanil (PYR), and fludioxonil (FDL). The impact of these resistant isolates on decay control during long-term storage remains unknown.

Objective

This study evaluated the fitness of P. expansum isolates with different fungicide sensitivity phenotypes to determine whether fungicide resistance carries fitness penalties and how resistance affects virulence and survival during long-term cold storage of apples.

Results

On nutrient-poor media, resistant isolates showed reduced conidial germination; however, no significant differences were observed on nutrient-rich media. FDL-resistant isolates showed increased sensitivity to osmotic and oxidative stresses. Pathogenicity was not affected by sensitivity phenotype after six months of storage. Gene expression analysis revealed differential regulation of fitness-related genes, with most being up-regulated by TBZ.

Conclusion

Resistance in P. expansum carries context-dependent fitness penalties, particularly under high-stress conditions such as nutrient limitation and low temperature. However, on fruit under fungicide selection pressure, resistant isolates maintained or increased fitness. These findings suggest resistance trade-offs are environment-dependent and may not significantly impact blue mold management in commercial storage conditions.
  • Published in:Microorganisms,
  • Study Type:Experimental Laboratory Study,
  • Source: 40871349
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