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Postharvest Pathology and Mycotoxins

Prevention of Black Spot Disease in Persimmon Fruit by Gibberellic Acid and Iprodione Treatments. A. Perez, Division of Postharvest Science of Fresh Produce, Agricultural Research Organization; R. Ben-Arie(2), A. Dinoor(3), A. Genizi(4), and D. Prusky(5). (2)(5)Division of Postharvest Science of Fresh Produce, Agricultural Research Organization; (3)Department of Microbiology and Phytopathology, Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12 Rehovot, Israel; (4)Department of Statistics, The Volcani Center, P.O. Box 6, Bet Dagan, Israel. Phytopathology 85:221-225. Accepted for publication 2 September 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-221.

Black spot disease (BSD) in persimmon fruit, caused by Alternaria alternata, develops primarily in the high humidity environment beneath the calyx. Three treatments with gibberellic acid (GA₃, 20 μg/ml) applied during fruit development at 30, 20, and 10 days before harvest, reduced decay more effectively than the single commercial treatment of GA₃ (50 μg/ml) applied 10 days before harvest. As a result of GA₃ treatment, the calyx of the fruit remained erect till harvest. The correlation coefficent between BSD under the calyx and calyx erectness was r = –0.72. Persimmon fruits treated with GA₃ in the orchard and stored at 0 C for 3 mo showed less fruit area becoming covered with black spot during storage compared with untreated fruit. Increasing the number of sprays from one to three resulted in a decreased infected area. Sprays of GA₃ also inhibited fruit softening, with a correlation coefficient of r = –0.63 between decayed area and fruit firmness. GA₃ at concentrations up to 200 μg/ml had no effect on fungal development in vitro and in vivo on inoculated fruits. GA₃ apparently affects decay development by enhancing resistance of the fruit. Preharvest treatment with GA₃ and the fungicide iprodione further reduced the percentage of fruits unmarketable due to BSD.