Theodor Otto Diener

Diener was born in Zurich, Switzerland on 28 February 1921.^[3][4] He served as aircraft mechanic for the Swiss Air Force in World War II^[5] He attended ETH Zurich, from which he graduated with Dr. sc. ETH degree in 1946.^[6] After graduation, he worked as research assistant at Swiss Federal Experiment Station for Viticulture and Horticulture in Wadenswil, Zurich,^[6] where on the first day, he discovered the first occurrence of a rust fungus on a cherry tree (Puccinia cerasi on the leaves) in more than 100 years.^[7]

In 1949, he emigrated to the United States, where, after a brief tenure at Rhode Island State College, he accepted a position as assistant plant pathologist at Washington State University's outlying Irrigation Experiment Station in Prosser, Washington,^[6] where he showed that pipecolic acid (an unusual amino acid) accumulates only in peach leaves with X-disease phytoplasma symptoms^[8] and that pipecolic acid causes X-disease phytoplasma symptoms.^[9]

Diener was married to Shirley Baumann and had three sons before they divorced. Diener was then married to Sybil Fox from 1968 until her death in 2012.^[10] Diener died at his home in Beltsville, Maryland on 28 March 2023 at the age of 102.^[10]

Diener published 2 books on viroids, 120 peer-reviewed articles, 53 chapters in books, and lectured on viroids worldwide.^{[citation needed]}

In 1959, Diener joined the US Department of Agriculture's Agricultural Research Service Pioneering Laboratory for Plant Virology at the Agricultural Research Service in Beltsville, Maryland,^[6] where he investigated the cause of the potato spindle tuber disease. This led to the unexpected discovery of the causative agent, a small RNA molecule, eighty times smaller than the smallest known viruses, for which he proposed the term viroid.^[11][12] Later, viroids were characterized as single stranded covalently closed circular RNA molecules occurring as highly base-paired rod-like structures.^[13] Viroids, together with viroid-like satellite RNAs have been officially endorsed by the International Committee on the Taxonomy of Viruses as a new order of subviral agents,^[14] which, in its 2014 publication, and as of 2024, encompassed Pospiviroid, Hostuviroid, Cocadviroid, Apscaviroid, Coleviroid genera of the Pospiviroidae family and Avsunviroid, Pelamoviroid, Elaviroid genera of the Avsunviroidae family.^[15]

In 1989, Diener hypothesized that the unique properties of viroids make them more plausible candidates as "living relics" of a hypothetical, precellular RNA world than are introns or other RNAs then considered as such.^[16] In 2016, Diener reevaluated his hypothesis, both reviewers agreed that Diener's hypothesis was still valid, but alternative hypotheses positing a more recent origin of viroids from cellular RNAs should also be considered.^[17]

• 1968: Campbell Award, American Institute of Biological Sciences
• 1969: Superior Service Award, U.S. Department of Agriculture
• 1973: Fellow Award; American Phytopathological Society
• 1975: Alexander von Humboldt Award, Alexander von Humboldt Society
• 1976: Ruth Allen Award: American Phytopathological Society^[18]
• 1977: Elected Member; U.S. National Academy of Sciences^[19]
• 1978: Elected Fellow, American Academy of Arts and Sciences
• 1979: Elected Andrew D. White Professor-at-Large, Cornell University
• 1980: Elected member, Leopoldina, German Academy of Sciences
• 1987: Wolf Prize in Agriculture, Wolf Foundation/State of Israel^[20]
• 1987: National Medal of Science, USA^[21]
• 1988: E.C. Stakman Award, University of Minnesota^[22]
• 1988: Distinguished Service Award, Potomac Division, American Phytopathological Society
• 1989: Inducted into Science Hall of Fame, Agricultural Research Service, U.S. Department of Agriculture^[23]
• 1989: Named Distinguished Professor, University of Maryland, College Park, MD
• 1994: Named Distinguished Professor Emeritus, University of Maryland, College Park, MD