This mold is the most significant source of post-harvest 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 post-harvest 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 post-harvest diseases. But yeasts that control post-harvest 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.

ARS is USDA's chief scientific research agency.