Blue mold, caused by the fungus Penicillium expansum, is the scourge of
apple breeders and producers throughout the world, causing extensive losses
to stored apples.
As the familiar saying goes, one bad apple really can spoil the whole
bunch?good fruit stored in containers with decaying fruit often absorbs a
moldy odor and flavor.

In a survey of the New York market from 1972 to 1984, blue mold caused by
Penicillium expansum was the most damaging parasitic postharvest disease of
apples. Documented losses from blue mold and other postharvest diseases have
focused on the fate of apples in storage, in transit, and in markets, but
little information is available on the significant losses that can occur in
apples sold to restaurants and in groceries. Despite the severity of this
problem, apple breeders have not been able to evaluate new fruit varieties
for blue mold resistance because of the apple's gene pool.

A theory called "geography of genes" posits that breeders looking to create
mold-resistant apples should obtain breeding seeds, or germplasm, from the
fruit's geographic area of origin. The geography of genes theory has assumed
particular significance as fruits' natural habitats are quickly being
eliminated.

Based on this gene theory and looking for answers to the blue mold problem,
Wojciech J. Janisiewicz, a researcher at the U.S. Department of
Agriculture's Agricultural Research Service, undertook a study of a new
apple germplasm collection from the center of origin in Kazakhstan. The
germplasm represents a much broader gene pool and was evaluated for
resistance to blue mold. Apples were harvested from trees that were
propagated from budwood collected in Kazakhstan and from seedling trees
originating from seeds of the same trees as the Elite budwood or from other
wild seedling trees in Kazakhstan.

The objective of the study was to determine disease resistance to
postharvest blue mold decay among apples from the Kazakhstan germplasm
(Kazak) collection. According to Janisiewicz, "Our results indicate a
greater genetic diversity among the Kazak apple collection than among
cultivated apples, as evidenced by their broad range of fruit maturity,
quality, and disease resistance patterns. The immune and resistant
accessions may serve as a source of resistance in breeding programs and can
be useful in explaining the mechanism of resistance to blue mold in apples.
This may lead to the utilization of any identified high-resistance germplasm
in apple breeding programs using traditional or genetic engineering
approaches."

The complete study and abstract are available on the ASHS HortScience
electronic journal web site:
[hortsci.ashspublications.org]

About ASHS
Founded in 1903, the American Society for Horticultural Science (ASHS) is
the largest organization dedicated to advancing all facets of horticultural
research, education, and application. More information at
[www.ashs.org].

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