Peel Diffusion and Antifungal Efficacy of Different Fungicides in Pear Fruit: Structure-Diffusion-Activity Relationships

Abstract

Fungal pathogens can invade not only the fruit peel but also the outer part of the fruit mesocarp, limiting the efficacy of fungicides. In this study, the relationships between fungicide structure, diffusion capacity and in vivo efficacy were evaluated for the first time. The diffusion capacity from pear peel to mesocarp of 11 antifungal compounds, including p-aminobenzoic acid, carbendazim, difenoconazole, dipicolinic acid, flusilazole, gentamicin, kojic acid, prochloraz, quinolinic acid, thiophanate methyl and thiram was screened. The obtained results indicated that size and especially polarity were negatively correlated with the diffusion capacity. Although some antifungal compounds, such as prochloraz and carbendazim, were completely degraded after a few days in peel and mesocarp, other compounds, such as p-aminobenzoic acid and kojic acid, showed high stability. When applying the antifungal compounds at the EC50 concentrations, it was observed that the compounds with high diffusion capacity showed higher in vivo antifungal activity against Alternaria alternata than compounds with low diffusion capacity. In contrast, there was no relationship between stability and in vivo efficacy. Collectively, the obtained results indicated that the diffusion capacity plays an important role in the efficacy of fungicides for the control of pear fruit diseases.

Dipicolinic acid enhances kiwifruit resistance to Botrytis cinerea by promoting phenolics accumulation

“…Considering that DPA‐caused effects were only detected for a few days, DPA must show preventive efficacy only when the pathogen attacks the fruits just after DPA treatment, but it may not protect the fruits for long periods. Previous reports indicated that DPA shows relatively high stability in plant tissues, with approximately 50% degradation in pear skin after 5 days 36 and no obvious degradation in pear trunk after 20 days 23 …”

“…36 Fungicides typically show low diffusion capacities and remain in the fruit skin, allowing the advancement of the pathogens throughout fruit internal phases. 36 This could explain why strong antifungal compounds, such as prochloraz and thiram, showed weak antifungal activities against B. cinerea in kiwifruit. The higher efficacy of DPA in kiwifruit compared to in vitro can be explained by the strong defense response triggered by DPA in kiwifruit.…”

“…It has been indicated that fungal pathogens are difficult to control in postharvest fruit as they can advance through the fruit mesocarp 36 . Fungicides typically show low diffusion capacities and remain in the fruit skin, allowing the advancement of the pathogens throughout fruit internal phases 36 .…”

“…It has been indicated that fungal pathogens are difficult to control in postharvest fruit as they can advance through the fruit mesocarp 36 . Fungicides typically show low diffusion capacities and remain in the fruit skin, allowing the advancement of the pathogens throughout fruit internal phases 36 . This could explain why strong antifungal compounds, such as prochloraz and thiram, showed weak antifungal activities against B. cinerea in kiwifruit.…”

“…The in vitro antifungal activity was measured according to methods previously reported. 36 B. cinerea was placed in the center of a Petri dish with PDA medium (pH 5) containing 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2 and 5 mM DPA. The dishes were incubated at 26 °C for 3 days.…”