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New plum pox survey method aids detection.
(6/21/00)

New Research Speeds Detection of Plum Pox Virus

Agricultural Research Service scientists have developed new techniques that not only confirm the presence of plum pox virus (PPV) but also distinguish between severe and less virulent strains of the disease, their origin, and mode of transmission.

While stone fruits have been in the United States for centuries, PPV has not. Until late 1999, it was not known to occur in North America. Therefore, any PPV infestation represents a major quarantine concern to everyone involved in the $1.3 billion U.S. stone fruit industry.

Previously available serological and biological methods are sometimes not sensitive enough to detect PPV, are slow, and do not detect specific strains. The new tests were developed by scientists at the ARS Floral and Nursery Plants Research Unit in Beltsville, Md., led by John Hammond.

The new process uses a technique called polymerase chain reaction (PCR). PCR multiplies the molecules in a sample's nucleic acid, making enough DNA copies to be analyzed. ARS researchers developed PCR primers that initiate this process and are able to detect all PPV strains. Researchers then combined PCR with other biotech procedures that help researchers distinguish between different strains of PPV.

This allows researchers to more effectively track the origin of a PPV infection. If an orchard is found to be infected, the source might be from the mother trees used for tree propagation, by aphid transmission or via weed hosts of the virus.

Distinguishing between PPV types may help researchers find a correlation between a particular strain and its ability to infect a specific type of host plant. Some strains of PPV may infect a tree easily, while others can do so only with great difficulty. This also allows scientists to determine how long a tree has been infected, if any variants have developed, or if a tree has been infected numerous times from various sources. All of these are key to checking the spread of the disease and eradicating it from infected areas.

ARS is the chief scientific arm of the USDA.

Scientific contact: John Hammond, ARS Floral and Nursery Plants Research Unit, Beltsville, Md., phone (301) 504-5313, fax (301) 504-5096, jhammon@asrr.arsusda.gov.