AgroPages-Agdia Launches 30 Minute DNA Test for <em>Xylella fastidiosa</em>-Agricultural news

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Agdia, Inc (Elkhart, IN) has commercialized a rapid and user-friendly DNA test kit, based on their AmplifyRP® XRT+ platform, for detection of Xylella fastidiosa (Xf).

Xylella fastidiosa (Xf) is the causal agent of multiple crop diseases including Pierce's disease in grape, citrus variegated chlorosis (CVC), almond leaf scorch disease (Figure 1) and olive quick decline syndrome. Severe Xf infections can decimate entire crops and cause enormous financial losses to growers.

The test is a real-time isothermal DNA amplification assay that utilizes recombinase polymerase amplification (RPA) technology. RPA facilitates rapid nucleic acid (DNA or RNA) amplification at a single operating temperature of 39°C using crude sample extracts. RPA can provide the same level of sensitivity and specificity as laboratory based PCR methods, but offers some clear advantages.

Figure 1: Xf symptoms on almond.

The total assay time is less than 30 minutes, including sample preparation. This is a stark contrast to PCR methods which can take hours or days to complete. PCR analysis must also be completed in a laboratory whereas AmplifyRP XRT+ can be performed on-site.

Agdia’s AmplifyRP XRT+ platform works similarly to the recently launched XRT platform in that the results can be obtained using a portable fluorometer. However, XRT+ provides greater flexibility because the test can alternatively be performed using a small portable heat block with results being visualized post-amplification on an Amplicon Detection Chamber. This allows end-users who don’t want to invest in a fluorometer an alternative method of running the test.

Figure 2: Real-time results on AmpliFire®

To run the test, an end-user first extracts their sample by adding it, along with extraction buffer, to a micro centrifuge tube that is provided in the kit. After the sample has been extracted a small volume is added to a solution that is used to rehydrate a lyophilized reaction pellet. Once the reaction pellet has been rehydrated it can be added to a portable fluorometer or a small heat block for 20 minutes. During this time, if present, Xf DNA will be amplified. If using the fluorometer results will automatically be displayed in real-time. Alternatively, if using a heat block, the reaction is added to an Amplicon Detection Chamber following the amplification step where results will be visible on a lateral flow strip.

Figure 3: Portable heat-block with post-amplification detection using Amplicon Detection Chambers.

Agdia’s AmplifyRP XRT+ kit for Xf includes 48 reactions and the necessary buffers to perform the test. If performing the test as a real-time assay, the end-user will need to purchase a portable fluorometer separately. Agdia claims the test is compatible with several commercially available fluorometers but recommends the AmpliFire® (Figure 2), manufactured by Douglas Scientific. The AmpliFire is battery operated and has a small footprint, making it possible to test in remote locations. Setup is simple because all the assay parameters are loaded into the AmpliFire using a barcode that is affixed to the test’s packaging. It also has a large, intuitive, touch screen interface that is used to initiate reactions and view results. More information on the AmpliFire can be found on Agdia’s website.

Alternatively, if the end-user runs the test as an end-point detection assay they will need to purchase Amplicon Detection Chambers (Figure 3), as well as a starter pack, separately. The starter pack includes a heat block (necessary for the amplification step) as well as pipettes, pipette tips, and a tube rack.