Eradication and diversity of potato spindle tuber viroid in dahlia in Japan

The potato spindle tuber viroid (PSTVd) was discovered to infect Japanese dahlia (Dahlia sp.) in 2009. Although the plants were asymptomatic, a comprehensive survey using RT-PCR and RT-qPCR revealed PSTVd occurrence areas spread across 15 out of 24 prefectures where the potentially PSTVd-infected seedlings were supplied. All dahlia plants that tested positive for PSTVd and their neighboring plants were removed from the field. The process of testing and removal of infected plants was repeated until the disease was completely eradicated in 2021. Phylogenetic analyses revealed a close relationship among the collected PSTVds, which suggests that the same PSTVd variant was widely disseminated primarily through infected seedlings and tubers in Japan.