Rapid visual detection assay for Bactrocera dorsalis (Hendel) using recombinase polymerase amplification and CRISPR/Cas12b

The oriental fruit fly Bactrocera dorsalis (Hendel) is considered as a quarantine pest in many countries and regions. Challenges remain in distinguishing this species with morphological similarities, especially in relevant development stages. In recent years, CRISPR/Cas12b genetic diagnostics has seen rapid advancements and offers an efficient tool for the identification of pathogens, viruses, and other genetic targets. Here we developed a new and rapid visual detection assay of B. dorsalis using recombinase polymerase amplification (RPA) and the CRISPR/Cas12b system. The system can detect different developmental stages of B. dorsalis within 30-35 min at 43 ℃ and the results are easily observed by the naked eye based on the color change in the tube during the reaction. The specificity and high sensitivity of this method was demonstrated, allowing for detection from 3.2 pg µL^{- 1} of DNA. With crude DNA, this diagnostic system successfully identified B. dorsalis by holding the reaction tubes in the hand. Our study demonstrates that RPA-CRISPR/Cas12b visualization system is effective to detect B. dorsalis rapidly and accurately. This approach can be applied for monitoring and identification of other pests in border and relevant locations, preventing biological invasions and ensuring pest control.