Rapid and Sensitive Detection of Fusarium oxysporum f. sp. cubense Tropical Race 4 Using a RPA-DETECTR Assay

Early and prompt detection of banana wilt pathogen Fusarium oxysporum f. sp. cubense (Foc), tropical race 4 (Foc TR4), causing global banana crop losses is crucial to curtail the disease spread, minimize damage and implement quarantine measures. We report the first successfully developed DNA Endonuclease Targeted CRISPR Trans Reporter (DETECTR) assay for the highly sensitive and specific detection of Foc TR4, validated across several isolates. Notably, specific crRNA spacer sequences and recombinant polymerase amplification (RPA) primers designed and evaluated for the DETECTR assay exhibited exceptional sensitivity, detecting Foc TR4 with genomic DNA as low as 0.005 ng, and demonstrated a very high specificity, and reproducibility. The RPA-DETECTR assay was validated using a diverse panel of samples, including both target and non-target pathogens confirming its robustness and reliability across different types of samples, ensuring practical application under varied conditions. In terms of throughput, the RPA-DETECTR assays enabled faster detection of Foc TR4 than other molecular diagnostics including PCR, quantitative PCR (qPCR) and droplet digital PCR (ddPCR) analyses, making this assay suitable for point-of-care (POC) detection of Foc TR4, and facilitating rapid decision-making and immediate response. This rapid detection capability is crucial in restricting any potential transboundary movement as part of ongoing disease management efforts.