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New Test to
Improve Plum Pox Monitoring in Stone Fruit
By Jan Suszkiw
October 3, 2003
Monitoring the spread of the plum pox
potyvirus in stone fruit crops could get a lot easier with a new, genetic
fingerprinting test developed by Agricultural Research Service scientists.
Plant pathologist Bill Schneider and colleagues in the
ARS Foreign Disease-Weed
Science Research Unit at Fort Detrick, Md., developed the test to expedite
year-round plum pox monitoring in and around Pennsylvania's Adams, Cumberland,
Franklin and York counties--the only U.S. sites where the stone fruit disease
is known to occur.
The aphid-borne disease causes acidity, unsightly rings and other defects
that diminish the quality of peaches and other stone fruit. Plum pox
poses no consumer danger, but it casts a threatening cloud over the economic
well-being of the nation's $1.8 billion stone fruit industry.
As part of an eradication effort, Pennsylvania researchers collect thousands
of leaf samples annually from commercial orchards, nurseries and other sites
for analysis in diagnostic labs. But plum pox only shows up at certain times of
the year, and in certain parts of a host tree, which complicates the process.
During the summer, for example, viral counts plummet as temperatures hit 84 and
90 degrees Fahrenheit. When that happens, antibody-based tests, such as the
Enzyme-Linked Immunosorbent Assay (ELISA), can yield misleading results. Other
methods are time-consuming and labor-intensive.
The new, ARS-developed test uses real-time polymerase chain reaction (PCR),
a chemical procedure that mass-produces copies of specific genes or gene
fragments so they can be identified. With real-time PCR, the targeted gene
becomes detectable as it's being multiplied. In this case, the gene is for a
specific protein that makes up the outer coat of the virus. Scientists
generally can determine whether the protein is in a sample in about six
hours--and if so, they can learn how much virus is in the sample. The ELISA
methods, by comparison, take about a day.
A longer article about this research appears in the September issue of
Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.