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Validation of a CANARY® multiplex testing platform for rapid identification of Ralstonia solanacearum

Abdelmonim Ali Ahmad: Department of Plant Pathology, Faculty of Agriculture, Minia University

<div><em>Ralstonia solanacearum (Rs) </em>race 3 biovar 2 (r3b2) is a bacterial plant pathogen listed by USDA-APHIS as a Select Agent. Accurate and rapid early detection, therefore, is needed for the efficient screening of imported plants to support exclusion of r3b2. PathSensors, Inc. in collaboration with USDA-APHIS and USDA-ARS has developed a high-throughput <em>Rs</em> diagnostic assay based on CANARY® (Cellular Analysis and Notification of Antigen Risks and Yields), an immune-based biosensor technology. Previous assay verification demonstrated that the assay had high specificity and sensitivity for <em>Rs</em> including r3b2 in inoculated zonal geraniums with very low false positive/negative rates and an analytical detection limit of 100 CFU for both r3b2 and non-r3b2 strains. In this study, a blinded third-party validation trial was conducted to simulate a real-world application of the assay. Water control and <em>Rs</em> r1b3 drench-inoculated zonal geranium stem samples were tested by the CANARY® assay and compared to plating followed by <em>Rs</em>-specific colony PCR (P-PCR). The CANARY® assay correctly identified <em>Rs</em>-inoculated samples, including early asymptomatic samples missed by P-PCR. This result suggests that the CANARY® assay has greater sensitivity which, combined with its speed and ease of use, makes it feasible for early detection screening of imported plants for the presence of <em>Rs</em> before further identification of r3b2 can be made.</div>