||E. M. Tsagris, A. E. Martinez de Alba, M. Gozmanova, and K. Kalantidis, “Viroids,” Cellular Microbiology, vol. 10, no. 11, pp. 2168–2179, 2008. DOI: 10.1111/j.1462-5822.2008.01231.x p. 2168 right column bottom paragraphPubMed ID18764915
||"Viroids are small, circular RNA pathogens, which infect several crop plants and can cause diseases of economic importance. They do not code for proteins but they contain a number of RNA structural elements, which interact with factors of the host." "Viroids have a size of ca 250–400 nucleotides. They infect several crop plants, causing symptoms of differential severity, which range from mild effects such as hardly visible growth reduction, up to deformation, necrosis or chlorosis and severe stunting (Singh et al., 2003)."