Rapid Visual Detection of on Lychees Using Recombinase Polymerase Amplification Combined with Lateral Flow Assay Based on the Unique Target Gene .

Downy blight, caused by , is a destructive disease that impacts lychee fruit throughout the pre-harvest, post-harvest, and transportation phases. Therefore, the prompt and precise identification of is crucial for the effective management of the disease. A novel gene encoding a Rh-type ammonium transporter, , was identified in through bioinformatic analysis in this study. Based on this gene, a coupled recombinase polymerase amplification-lateral flow (RPA-LF) assay for the rapid visual detection of was developed. The assay has been shown to detect accurately, without cross-reactivity to related pathogenic oomycetes or fungi. Moreover, it can be performed effectively within 15 to 25 min at temperatures ranging from 28 to 46 °C. Under optimized conditions, the RPA-LF assay could detect as low as 1 pg of genomic DNA in a 25 μL reaction system. Furthermore, the RPA-LF assay successfully detected in infected lychee samples within a 30 min timeframe. These attributes establish the RPA-LF assay as a rapid, sensitive, and specific method for diagnosing early; it is particularly suitable for applications in resource-limited settings.