Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2004
Publication Date: 1/1/2004
Citation: Karabulut, O., Smilanick, J.L., Mlikota-Gabler, F., Mansour, M. Near-harvest applications of metschnikowia fructicola, ethanol, and sodium bicarbonate to control postharvest diseases of grapes. Plant Disease 87(11)1384-1389. Interpretive Summary: Postharvest decay of table grapes causes troublesome losses of the fruit during storage and marketing. An approach investigated to manage this problem was to apply substances to inhibit these pathogens to the grapes in vineyards before harvest. Significant reductions in the number of decayed table grape berries that developed after harvest during storage occurred when the yeast Metschnikowia fructicola, ethanol, or sodium bicarbonate, alone or in combinations, were applied to table grapes in the vineyard a day before harvest. Currently, harvested table grapes in California are treated with sulfur dioxide gas in sealed storage rooms to control postharvest decay. Vineyard applications of the products employed in this work could conceivably replace this practice in some locations, although regulatory issues associated with their practical commercial use have not been addressed.
Technical Abstract: The yeast Metschnikowia fructicola, ethanol, and sodium bicarbonate (SBC), alone or in combinations, were applied to table grapes 24 h before harvest to control the incidence of postharvest diseases. In four experiments, all significantly reduced the number of decayed berries caused by Botrytis cinerea, Alternaria spp., or Aspergillus niger after storage for 30 days at 1C followed by 2 days at 20C. In three experiments, a gray mold (caused by B. cinerea) incidence of 34.2 infected berries per kg among untreated grapes was reduced by Metschnikowia fructicola at 2 x1 07 cfu/ml, ethanol at 50% (vol/vol), or SBC at 2% (wt/vol) to 12.9, 8.1, or 10.6 infected berries per kg, respectively. Ethanol, SBC, and SO2 generator pads were similarly effective. M. fructicola effectiveness was not improved when combined with ethanol or SBC treatments. Ethanol and yeast treatments did not harm the appearance of the grapes, although M. fructicola and SBC left noticeable residues, and SBC caused some visible phytotoxicity to the rachis and berries. Ethanol applied at 50% (vol/vol) reduced epiphytic fungal and bacterial populations by about 50% compared to controls. M. fructicola persisted on berries during storage when applied alone or after ethanol treatments, whereas SBC reduced its population significantly.