Viroid Discoverer Theodor Diener Passes Away at 102

Theodor Diener, a Swiss-born scientist who spent three decades as a plant pathologist at the Agricultural Research Service, discovered the viroid, the tiniest known agent of infectious disease, while investigating potato spindle tuber disease. He determined that the cause was not a virus, as other scientists had speculated, but rather a new, far smaller pathogen — the viroid. A viroid functions in a manner similar to that of a virus, invading a cell and making it reproduce the viroid’s RNA. Dr. Diener’s discovery created “new avenues of molecular research into some of the most serious diseases afflicting plants, animals, and humans.”