INFLUENCE OF CURING TIMES ON THE EFFECTIVENESS OF TREATMENTS WITH ACETIC ACID ON THE CONTROL OF P. DIGITA TUMON LEMONS

摘要

The restricted number of postharvest fungicides used in packing houses is leading to the selection of resistant strains of Penicillium digitatum (citrus green mould), one of the most common and serious pathogens during storage and marketing of lemons.Furthermore a growing concern for human health and a greater awareness for environmental conservation have multiplied the studies on new ecological technologies. Among the alternatives to synthetic postharvest fungicides, the use of acetic acid (classified as GRAS) together with a physical method such as curing, have led to encouraging results. In the present study is reported the combined use of curing, performed at reduced times compared to those reported to be effective, followed by acetic acid (AAC) treatments.Lemons of the variety "Limone di Massa" artificially inoculated with P. digitatum at a concentration of 10~4 spores/mL were cured for 0, 3, 6,12 and 24 hours and then treated with three different concentrations of AAC (25, 50 and 75 muL/L) for 15 min. Fruit was then stored at 20 °C and 80% relative humidity (RH) for 9 days, when the number of decayed fruits was monitored. The same combined treatments were also carried out on naturally infected lemons, stored for 6 or 8 weeks at 5 °C and 90% RH. After9 days of storage the lowest percentage of infected wounds, in artificially inoculated fruit, was 0% after 6 hours of curing followed by AAC fumigation performed at 50 ui/L, while lemons untreated or cured for three hours showed the worst results with 71.4 and 61.9 % of rotted fruit respectively. In naturally infected lemons the best results were achieved with curing performed for 24 hours followed by AAC fumigation at 50 ul/L. In these cases the combined treatment reduced decay by the 91.0 and 66.5% after 6 or 8 weeks of storage respectively, if compared to untreated fruit. The weight loss was not affected by any of the treatments.These results show that a good control of green mould during storage could be achieved, on lemon fruit, by combining a reduced curing time of 24 hours to the effect of AAC. The best results were obtained after 6 week of storage even if a satisfactory control was observed after 8 weeks of storage.