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Naturally occurring yeasts offer pathogenic protection for fruits.

Some naturally occurring yeasts may be useful for protecting stone fruits against pathogens that attack after the fruit is harvested. USDA-ARS scientists examined the microflora on the surface of plums to find potential biocontrol agents against brown rot.

Fruit surfaces are naturally colonized by a variety of microbes, including bacteria and yeast. Some of those native microorganisms have a beneficial effect on reducing fruit decay after harvest. Agency researchers have determined that the surfaces on plums are able to harbor several species of yeast that have potential for use as biological controls against the brown rot disease found on stone fruits.

Brown rot is caused by the fungus Monilinia fructicola. Worldwide, brown rot is the most important disease risk for stone fruits in warm, humid climates. It is the primary disease for which fungicides are applied to the fruit. The brown rot fungi cause a soft decay of fruits. A lot of information exists about the benefits of natural fruit microflora on grapes and apples. But for plums, the extent of the natural flora's potential for biological control of fruit decay remains largely unknown.

In a previous effort, the ARS scientists developed a bacterium normally found on apples into a commercial biological control product that can be used in place of fungicides to control pome fruit diseases. The product is also allowed in organic marketing.

Recently, the research team identified yeasts that naturally colonized plums from the early stages of their development until harvest. The scientists explored the potential of these yeasts for controlling postharvest brown rot, the most destructive disease of stone fruits.

Through multiple screenings, the scientists found yeasts with a range of biocontrol activities against M. fructicola, including several isolates that provided complete control on plums from decay caused by this fungus.

Two of the best control candidate species were Aureobasidium pullulans and Rhodotorula phylloplana. The researchers also have other yeasts and bacteria that were isolated from stone fruits that can provide very good control of postharvest fruit decay. These are available under an ARS Material Transfer Agreement to any party interested in developing them into a commercial product.

Developing these yeasts into commercial products will provide growers with an alternative approach for combating brown rot after harvest, and this alternative should be compatible with requirements for the rapidly growing organic market.

Further information. Wojciech Janisiewicz, USDA-ARS Appalachian Fruit Research Laboratory, 2217 Wiltshire Rd., Kearneysville, WV 25430; phone: 304-725-3451; email:

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Publication:Emerging Food R&D Report
Date:Jul 1, 2015
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