Schirra, Mario and D'Aquino, Salvatore and Palma, Amedeo and Marceddu, Salvatore and Angioni, Alberto and Cabras, Paolo and Scherm, Barbara and Migheli, Quirico (2005) Residue level, persistence, and storage performance of citrus fruit treated with fludioxonil. Journal of Agricultural and Food Chemistry, Vol. 53 , p. 6718-6724. eISSN 1520-5118. Article.
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The potential of postharvest dip treatments with fludioxonil (FLU) (a synthetic analogue of the bacterial metabolite of pyrrolnitrin), in controlling postharvest decay caused by Penicillium digitatum and Penicillium italicum of citrus fruit was investigated in comparison with the conventional fungicide imazalil (IMZ). The ultrastructural changes of fruit epicuticular wax was investigated as a function of water dip temperature, and the possible role of these changes was related to residue accumulation under FLU treatment. Residues retained by fruit were determined as a function of fungicide concentration, dip temperature, and fruit storage conditions. Scanning electron microscopy analysis revealed that fruit dipping in water at 30 or 40 °C did not cause differences in cuticular wax’s ultrastructure in comparison to control fruit, while treatments at 50, 55, or 60 °C caused the disappearance of wax platelets, resulting in relatively homogeneous skin surface, due to partial “melting” of epicuticular wax. Residues of FLU in fruit treated at 20 or 50 °C were significantly correlated with the doses of fungicide applied. When equal amounts of fungicide were employed, the residue concentrations were notably higher (from 2.6- to 4-fold) in fruit treated at 50 °C than in fruit treated at 20 °C. The dissipation rate of FLU in “Salustiana” and “Tarocco” oranges was lower in fruit subjected to treatment at 50 °C. The minimal FLU concentration for almost complete decay control in artificially wounded fruit during 7-d storage at 20 °C was 400 mg/L active ingredient (ai) in fruit treated at 20 °C and 100 mg/L ai in fruit treated at 50 °C. Results on nonwounded Tarocco oranges subjected to 3 weeks of simulated quarantine conditions at 1 °C, plus 6 weeks of standard storage at 8 °C and an additional two weeks of simulated marketing period (SMP) at 20 °C revealed that almost complete decay control with FLU applications of 100 mg/L at 50 °C and 400 mg/L at 20 °C resulted in ca. 0.8 mg/kg FLU fruit residues, in agreement with results on wounded citrus fruit. When equal concentrations and temperatures were applied, FLU treatments were as effective as IMZ. In vitro trials showed a low sensitivity to FLU against P. digitatum and P. italicum isolates. MIC values for the complete inhibition of mycelium growth were ≥100 μg/mL, while ED50 values ranged from 0.1 to 1 μg/mL for P. digitatum and from 1 to >100 μg/mL for P. italicum.The latter result suggests that care should be taken to avoid exclusive application of FLU in a sustainable program for management of fruit decay. However, integrating fungicide application and hot water dip may reduce the possibility of selecting fungicide-resistant populations of the pathogen, by increasing the effectiveness of the treatment.
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