Rapid Detection of the Strawberry Foliar Nematode Aphelenchoides fragariae Using Recombinase Polymerase Amplification Assay with Lateral Flow Dipsticks.

Rapid and reliable diagnostic methods for plant-parasitic nematodes are critical for facilitating the selection of effective control measures. A diagnostic recombinase polymerase amplification (RPA) assay for Aphelenchoides fragariae using a TwistAmp ^® Basic Kit (TwistDx, Cambridge, UK) and AmplifyRP ^® Acceler8 ^® Discovery Kit (Agdia, Elkhart, IN, USA) combined with lateral flow dipsticks (LF) has been developed. In this study, a LF-RPA assay was designed that targets the ITS rRNA gene of A. fragariae. This assay enables the specific detection of A. fragariae from crude nematode extracts without a DNA extraction step, and from DNA extracts of plant tissues infected with this nematode species. The LF-RPA assay showed reliable detection within 18-25 min with a sensitivity of 0.03 nematode per reaction tube for crude nematode extracts or 0.3 nematode per reaction tube using plant DNA extracts from 0.1 g of fresh leaves. The LF-RPA assay was developed and validated with a wide range of nematode and plant samples. Aphelenchoides fragariae was identified from seed samples in California. The LF-RPA assay has great potential for nematode diagnostics in the laboratory with minimal available equipment.