Rapid detection of the rice false smut fungus Ustilaginoidea virens by lateral flow strip-based recombinase polymerase amplification assay

Rice false smut, caused by Ustilaginoidea virens, is a devastating disease that greatly reduces rice yield and quality.However, controlling rice false smut disease is challenging due to the unique infection mode of U. virens. Therefore,there is a need for early diagnosis and monitoring techniques to prevent the spread of this disease. Lateral flow strip-based recombinase polymerase amplification(LF-RPA) overcomes the limitations of current U. virens detection technologies, which are time-consuming, require delicate equipment, and have a high false-positive rate. In this study, we used a comparative genomics approach to identify Uv＿3611, a specific gene of U. virens, as the target for the LF-RPA assay. The designed primers and probe efffectively detected the genomic DNA(gDNA) of U. virens and demonstrated no cross-reactivity with related pathogens. Under optimal conditions, the LF-RPA assay demonstrated a sensitivity of 10 pg of U. virens gDNA. Additionally, by incorporating a simplified PEG-NaOH method for plant DNA extraction, the LF-RPA assay enabled the detection of U. virens in rice spikelets within 30 min, without the need for specialized equipment. Furthermore, the LF-RPA assay successfully detected U. virens in naturally infected rice and seed samples in the field. Therefore, the LF-RPA assay is sensitive, efficient, and convenient, and could be developed as a kit for monitoring rice false smut disease in the field.