Disease Diagnosis In 60 Minutes?

Published online: Dec 03, 2001
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A Sunnyvale, CA, company working with Agricultural Research Service scientists has developed a portable, DNA-based device that will identify plant-disease organisms in less than 60 minutes.

Cepheid is working under a cooperative research and development agreement with the ARS in development of Smart Cycler, which connects to a laptop computer, and uses polymerase-chain reaction to replicate a target pathogen's DNA.

Two of the first major diseases now under going field and lab tests are potato brown rot and potato ring rot. A dozen or so other serious diseases such as citrus canker, bacterial wilt and Karnal bunt are also being tested.

The scientists are using their expertise in bacterial, fungal and viral genetics to design primers and probes targeting specific DNA sequences of several major plant pathogens. The primer's main job is to bind with a pathogen's DNA-if present in a leaf sample, for example-and prepare it for PCR amplification on the testing unit.

The amplified DNA also binds with the probe, emitting a fluorescent signal at the end of each PCR amplification cycle that's measure and displayed on the computer.

Users need only immerse infected tissue specimens in water for 20 minutes before placing a microliter sample of it into one of the unit's 16 reaction chambers for bacterial testing. No DNA extraction is necessary in this case.

This development could cut diagnostic lab waits for "real-time" recommendations on how best to curtail a crop-disease outbreak before it spreads.

Another use would be to check perishable plant materials at points of entry for exotic- plant disease organisms that would imperial domestic crops.