Antifungal efficacy of Aloe vera in vitro and its use as a preharvest treatment to maintain postharvest table grape quality

Aloe vera gel was added at several concentrations on potato dextrose agar (PDA) to test its efficacy on inhibiting mycelium growth of two common fungi responsible for fruit decay (Penicillium digitatum and Botrytis cinerea). For both fungi, the inhibition of mycelium growth rate increased with Aloe concentration, although to gain the same inhibition the necessary A. vera gel concentration was 3-fold higher for B. cinerea than P. digitatum. Overall, the dose of 250 mL L-1 led to 4- and 2-log reductions of mycelium growth for P. digitatum and B. cinerea, respectively. Based on these results, A. vera gel at 250 mL L-1 was applied as a preharvest treatment to table grape vineyards 1 or 1 and 7 days before harvesting. Fruit were cold-stored for 35 days and sampled weekly. Respiration rate and weight loss were significantly reduced in treated samples, while ripening parameters such as colour and fruit firmness were significantly delayed. Both mesophilic aerobics and mould and yeasts counts were significantly lower at harvest in treated samples, the effect being persistent during storage. At the end of the experiment, the percentage of rotted berries was significantly lower in treated than in control fruit. From these results it could be inferred that A. vera could be considered as a promising preharvest treatment to maintain table quality during postharvest storage. (C) 2010 Elsevier B.V. All rights reserved.