Host ranges and seed transmission of Tomato planta macho viroid and Pepper chat fruit viroid

Host ranges of Tomato planta macho viroid (TPMVd) and Pepper chat fruit viroid (PCFVd) were investigated across 32 species representing 10 genera, including horticultural plants that are frequently imported in large numbers by Japan. Plants were infected by mechanical sap inoculation, and viroid presence was checked using reverse-transcription polymerase chain reaction and back-inoculation of tomato. Among the 32 species, 16 and 15 were susceptible to TPMVd and PCFVd, respectively; most belonged to Solanaceae, and symptoms were only observed in tomato, potato, green pepper, and Solanum muricatum. Seed transmission of TPMVd and PCFVd was carried out using seeds obtained from infected tomato, Capsicum annuum, and Petunia x hybrida plants, and from a series of crosses involving healthy or infected Petunia x hybrida parental material. The seed transmission rate of TPMVd was 0-4.4% in tomato and 17.5 or 43.3% in Petunia x hybrida, while that of PCFVd was 0-1.4% in tomato and 0 or 16.8% in Petunia x hybrida. Seed transmission via the viroid-infected pollen parent or infected seed parent was investigated in Petunia x hybrida; rates were 91.8% and 100% for TPMVd and 69.2% and 65.3% for PCFVd, respectively. These data indicated a risk of unexpected worldwide viroid spread via international trade of asymptomatic plants and viroid-infected seeds and pollen.