Dual-Channel Colloidal Gold-Based Immunochromatographic Test Strip for Rapidly Differentiating Between Two Major Groups of Paracidovorax citrulli

Bacterial fruit blotch (BFB) caused by <i>Paracidovorax citrulli</i> is a severe threat to melon, watermelon, and other cucurbit crop production worldwide. The long-term adaptation of the pathogen to environmental conditions has resulted in substantial genetic diversity. In this study, we used <i>P. citrulli</i> strains from two groups as immunogens to obtain antibodies that were used to generate A.C1 and A.C2 colloidal gold immunochromatographic single test strips, which specifically identified group I and group II <i>P. citrulli</i> strains, respectively. We combined the A.C1 and A.C2 single test strips in a dual-channel plastic cartridge to construct a dual-channel colloidal gold immunochromatographic test strip able to distinguish between <i>P. citrulli</i> strains from two distinct groups. Test strip sensitivity reached 10⁶ CFU/mL under ideal conditions. Moreover, it was relatively stable, with no cross-reactions with strains of closely related genera. The dual-channel test strip developed in this study may provide farmers with a useful tool for managing BFB through the prompt implementation of quarantine procedures in the field.