Yeast combats apple mould

The US Department of Agriculture says it is seeking to patent a biocontrol yeast that fights the apple nemesis 'blue mould', a fungus which leaves a telltale sign of soft, watery, light-brown rot.

Caused by the fungus Penicillium expansum​, this mould is the most significant source of postharvest decay of stored apples in the United States, according to the ARS.

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, West Virginia. 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 - apples and pears. These 'friendly' yeasts work by consuming the nutrients on fruit and vegetable skins that allow rot-causing fungi to thrive.

Janisiewicz claims to have shown that M. pulcherrima​ is highly effective at consuming nutrients that otherwise would support blue mould growth on apples. Moreover, Janisiewicz noted that the yeast is effective at cold-storage temperatures, an important feature to produce-warehouse operators.

Fungicides have until now been a major treatment for fruits and vegetables to prevent postharvest diseases, but as producers try to reduce reliance on synthetic chemicals yeasts have emerged as an effective alternative, says the ARS.

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

For further information, see the ARS website​.