Beating Back Blue Mold
For many an apple, without protection after harvest, the stage is set
for an uneaten end. When an apple is injured, fresh fruit flesh turns
soft, brown, and watery. Older lesions are sometimes invaded by a white
fungus that eventually produces bluish-green spores. All this ends in
a confluence of musty odors and lesions covered by fluffy fungal bodies.
The actor in this drama is Penicillium expansum, otherwise known
as blue mold. It's the most significant cause of postharvest decay of
stored apples in the United States. Losses from postharvest decay could
be as high as 25 percent of the world's harvested fruits.
Farmers use a variety of methods to control such costly decay of fruits
and vegetables. Fungicides are a common treatment to suppress postharvest
decay organisms. But in keeping with the goal of farmers to reduce dependence
on synthetic chemicals, Agricultural
Research Service scientists have been working on developing biological
controls as environmentally benign alternatives.
Biological products, such as friendly yeasts or bacteria, work by consuming
nutrients in fruit and vegetable wounds that would otherwise allow rot-causing
fungi to thrive. There is much interest in using normally occurring
antagonistic microorganismsdecay-curbing yeasts and bacteriaas
effective alternatives to fungicides.
Wojciech Janisiewicz, with ARS' Appalachian Fruit Research Station
in Kearneysville, West Virginia, has filed a patent for a novel biocontrol
agent aimed at neutralizing blue mold.
Janisiewicz isolated a yeast, Metschnikowia pulcherrima, that
occurs naturally on buds, flowers, and fruits of apple trees. M.
pulcherrima is one of several yeast species that exhibit strong
antagonistic activity against postharvest decays of pome fruits, such
as apples and pears.
Janisiewicz showed M. pulcherrima to be highly effective as
an antagonist against blue moldeven at cold-storage temperaturesa
feature of major importance to produce-warehouse operators.
The lab is now looking for a company to work with to mass-produce M.
pulcherrima for commercial use.By Rosalie Marion Bliss,
Agricultural Research Service Information Staff.
"Beating Back Blue Mold" was published in the August 2003 issue of Agricultural Research magazine.