Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2003
Publication Date: 3/1/2003
Citation: JANISIEWICZ, W.J., LEVERENTZ, B., CONWAY, W.S., SAFTNER, R.A., REED, A.N., CAMP, M.J. CONTROL OF BITTER ROT & BLUE MOLD OF APPLES BY INTEGRATING HEAT AND ANTAGONIST TREATMENTS ON 1-MCP TREATED FRUIT STORED UNDER CONTROLLED ATMOSPHERE CONDITIONS. POSTHARVEST BIOLOGY AND TECHNOLOGY. Vol. 29, p 129-143. March 2003. Interpretive Summary: Fungicides have been applied to fruits after harvest to reduce amount of decay, but use of fungicides has been increasingly curtailed by development of pathogens resistance to many key fungicides and the public perception that they are harmful to human health and the environment. During the past fifteen years, biological control of postharvest diseases (BCPD) has emerged as an effective alternative. The pioneering biocontrol products based on beneficial bacteria and yeasts are commercially available, but they have some limitations, and can not be used under all circumstances. Those limitations may be addressed by a variety of ways, including combining BCPD with other alternative methods, which by themselves can not provide adequate protection but in combination with BCPD provide additive or synergistic effect. We combined hot air treatment (4 days at 38 C) with the beneficial yeast, Metchnikowia pulcherrima, treatment to control bitter rot (caused by Colletotrichum acutatum) and blue mold (caused by Penicillium expansum) on apples treated with ripening inhibitor 1-MCP. The yeast effectively controlled bitter rot, and in combination with the heat treatment controlled blue mold on apples. Heat alone controlled blue mold on fruit inoculated with the fungus up to 12 hours before heating, and the yeast provided a residual effect up to 4 months the duration of the experiment. 1-MCP enhanced fruit decay development but this negative effect was neutralized by the antagonist. If 1-MCP will be used commercially for extending shelf life of fruit, this will have to be weighed against its effect on stimulation of fruit decay.
Technical Abstract: In order to maximize control of fruit decay by alternatives to synthetic fungicides after harvest, various control strategies can be integrated. Treatment of fruit with antagonists is one of the most promising alternatives. This treatment, however, has little or no eradicative activity, which limits its use. Fruit treatment with hot air (at 38 C) for 4 days has eradicative but no residual activity against blue mold (caused by P. expansum) on apple, and 1-methylcyclopropene (1-MCP) is an ethylene receptor inhibitor which slows apple maturation and, presumably, extends action of natural defense mechanisms. An antagonist, M. pulcherrima T5-A2, was used in combination with heat and 1-MCP treatments to control bitter rot (caused by C. acutatum) and blue mold (caused by P. expansum) on `Golden Delicious' apples under controlled atmosphere (CA) conditions. 1-MCP treatment increased bitter rot and blue mold decays, but both of these decays were effectively controlled on 1-MCP treated apples by a combination of the antagonist and heat treatments. C. acutatum is a weaker pathogen than P. expansum, and bitter rot, even on the control treatments, developed only after 4 months in CA storage followed by 2 weeks incubation at 24 C. In contrast, nontreated fruit inoculated with P. expansum were completely decayed after 2 months in CA. The antagonist controlled bitter rot more effectively than blue mold, while blue mold was more effectively controlled by heat treatment. The use of 1-MCP on harvested fruit to inhibit maturation can predispose fruit to decay, but the alternatives to synthetic fungicides are capable of preventing this increase in decay.