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In this article we will discuss about the antagonist preparation for post-harvest.
Once effective antagonists are identified for Post-harvest diseases of fruits and vegetables, methods must be found to prepare, store, and apply them commercially. Pusey (1988) conducted a pilot test applying Bacillus subtilis under simulated commercial conditions for the control of brown rot of peaches. They effectively incorporated the antagonist into wax normally used on the packing line.
Brown rot was effectively controlled by this procedure, but considerable variation was found in the control rendered by the different preparations of the antagonist. In applying antagonists to harvested commodities, consideration should be given to the compatibility of such applications with other Post- harvest treatments such as fungicides and antioxidants.
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Presently, antagonists have to be applied at relatively high rates to be effective against Post-harvest diseases. Research is needed on ways of potentiating antagonistic activity through additives such as nutrients, wetting agents, or spreader-stickers. The use of antagonistic microorganisms as a substitute for fungicides under these conditions presents some unique opportunities and challenges.
Fruits and vegetables receive treatments prior to storage as various as chilling to hot water dips. Also, some commodities, such as potatoes, are put through a curing process with elevated temperatures and humidity. The effect of such treatments on epiphytic microbes, including potential antagonists, should be investigated.
The composition of epiphytic microbial populations on harvested commodities entering storage may affect their storability and prestorage treatments can profoundly affect such populations. Pathogens vary in their adaptability to differing storage conditions.
The adaptability of pathogens and antagonists needs to be examined under the special environmental conditions encountered in controlled and modified atmosphere storages. In selecting an antagonist suitable for Post-harvest diseases need to look for well adapted survival and growth in wounds or on the produce surface under storage conditions and that have an adaptive advantage over specific pathogens.
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For example, Rhizopus stolonifer is more sensitive to low temperatures than many microorganisms; therefore, an antagonist well adapted to low temperatures might prove advantageous against this pathogen.
Another example is the advantage of a Candida oleophila strain in reducing the level of Penicillium expansum infection in nectarines under storage conditions, the effectiveness of the antagonistic yeast was not reduced by controlled atmosphere in storage.
Tronsmo and Dennis (1977) selected an isolate of Trichoderma that grew at lower temperatures and was therefore more effective than other isolates of Trichoderma in controlling Botrytis rot of strawberries in storage.
