First report of potato spindle tuber viroid isolated from pepper seeds produced in Vietnam

Abstract

Potato spindle tuber viroid (PSTVd; genus Pospiviroid) was detected from pepper (Capsicum annuum) seeds produced in Vietnam, during an export inspection. The PSTVd isolate maintained its viability. To investigate the phylogenetic relationship between PSTVd-VN and other PSTVd variants isolated from other plants, the PSTVd isolate was classi ed into lethal and severe strains. Inoculated tomatoes (cv.Rutgers) caused severe stunting, with necrosis of the stems and leaf veins. Although the inoculated pepper plants were asymptomatic, the fruits were smaller than the healthy ones. To our knowledge, this is the rst report of PSTVd from pepper seeds produced in Vietnam. Full TextViroids are unencapsidated, single-stranded, circular RNA consisting of 246-401 nucleotides. Among plant pathogens, they are the smallest pathogens and belong to two families (Pospiviroidae and Avsunviroidae) (Flores et al. 2005). The genus Pospiviroid in the family Pospiviroidae consists of nine species, of which one is the potato spindle tuber viroid (PSTVd) (Full ICTV Report on the Genus Pospiviroid; https://ictv.global/report/chapter/pospiviroidae/pospiviroidae/pospiviroid).Although PSTVd was originally reported in North America, it has spread to Africa, Asia, Europe, and South America (Smith et al. 1997). In recent years, PSTVd has been identi ed in several countries, and new viroids are being continuously discovered (Kinoga et al. 2021;Matsushita et al. 2021;Sial and Khan 2018).PSTVd infects various host plants and causes stunting, leaf chlorosis, leaf epinasty, fruit distortion, and stem and leaf necrosis in tomatoes (Solanum lycopersicum) and potatoes (S. tuberosum) (Hadidi et al. 2003;Singh et al. 2003). Viroids spread mechanically through plant sap, grafting, and transmission through seeds and pollen (Matsushita et al. 2018). Among these, seed transmission is an important