Molecular characterization, construction of an infectious clone, and evaluation of banana cultivar susceptibility to banana bract mosaic virus from Taiwan

Banana production has suffered from Potyvirus musae (banana bract mosaic virus, BBrMV) in the Philippines and India; however, its occurrence and biological characteristics in Taiwan remain poorly understood. In this study, field surveys conducted between 2017 and 2018 identified 13 BBrMV-infected samples from commercial banana production areas in Taiwan. Among these, isolate F92 was successfully preserved by aphid transmission and used for further characterization. An infectious clone of BBrMV isolate F92 was constructed to establish a reliable inoculation system. In addition, poly(A) tail length was found to affect viral infectivity, and a longer poly(A) tail produced more consistent systemic infection. Using this system, the susceptibility of five banana cultivars commonly grown in Taiwan was evaluated. Most cultivars showed relatively mild symptoms and stable or declining viral accumulation, whereas the cultivar 'Rose' was more susceptible. This study reports the first infectious clone of BBrMV and provides a useful tool for evaluating cultivar susceptibility. Because BBrMV has not yet become widely established in Taiwan, these results may provide useful information for future disease management if the virus spreads in Taiwan.