During 1970 and 1971, I discovered that a devastating disease of potato plants is not caused by a virus, as had been assumed, but by a new type of subviral pathogen, the viroid. Viroids are so small — one fiftieth of the size of the smallest viruses — that many scientists initially doubted their existence. We now know that viroids cause many damaging diseases of crop plants. Fortunately, new methods that are based on the unique properties of viroids now promise effective control.
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- LOCAL LESION ASSAY
A technique to estimate the relative virus or viroid concentration, which involves rubbing variously diluted aliquots of a preparation onto leaves of a hypersensitive host plant that reacts to infection with the production of visible chlorotic or necrotic spots, the number of which is directly related to the virus or viroid concentration.
A pathogen that exists in vivo as an unencapsidated nucleic acid. The nucleic acid is a single molecular species RNA.
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Diener, T. Discovering viroids — a personal perspective. Nat Rev Microbiol 1, 75–80 (2003). https://doi.org/10.1038/nrmicro736
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