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Ensuring an Apple a Day

By Rosalie Marion Bliss
August 8, 2003

To help maintain bountiful supplies of the fresh apples consumers enjoy, the U.S. Department of Agriculture is seeking to patent a biocontrol yeast that makes life miserable for the apple nemesis known as blue mold.

This mold is the most significant source of postharvest decay of stored apples in the United States. Caused by the fungus Penicillium expansum, blue mold leaves a telltale sign of soft, watery, light-brown rot.

The patent application is based on work by Agricultural Research Service plant pathologist Wojciech Janisiewicz at the ARS Innovative Fruit Production, Improvement and Protection Laboratory at Kearneysville, W.Va. He isolated a yeast, called Metschnikowia pulcherrima, that occurs naturally on the fruits, buds and floral parts of certain apple trees.

M. pulcherrima is one of several yeast species that serve as a biological control against postharvest decay of pome fruits. These friendly yeasts work by consuming the nutrients on fruit and vegetable skins that allow rot-causing fungi to thrive.

Janisiewicz showed that M. pulcherrima is highly effective at consuming nutrients that otherwise would support blue mold growth on apples. Moreover, Janisiewicz found that the yeast is effective at cold-storage temperatures, a feature of major importance to produce-warehouse operators.

Fungicides have been a major treatment for fruits and vegetables to prevent postharvest diseases. But yeasts that control postharvest diseases have emerged as an effective alternative to fungicides.

The Kearneysville laboratory is now looking for a company with which to license or partner to mass-produce M. pulcherrima for commercial use.

Read more about this research in the August issue of Agricultural Research magazine.

ARS is USDA's chief scientific research agency.