Theodor O. Diener
Wolf Prize Laureate in Agriculture 1987
The Agriculture Prize Committee for 1987 unanimously decided that the Wolf Prize in Agriculture be awarded to:
Theodor O. Diener
Plant Protection Institute
Agricultural Research Service
Beltsville, Maryland, USA
“for his discovery and pioneering fundamental research on viroids, the smallest subviral pathogens, and his applied work on viroid detection in crops.”
His fundamental and applied studies have firmly established the existence of viroids, a new group of subviral pathogens.
Dr. Diener discovered that the pathogen causing potato spindle tuber disease is not a virus, as previously believed, but a much smaller, free RNA molecule, which he named viroid. The discovery by Diener and his colleagues of other viroids affecting various cultivated plants such as chrysanthemum stunt, coconut cadang-cadang and planta macho viroid of tomato soon followed; so that today viroids are considered to be an important group of disease agents affecting potatoes, tomatoes, citrus, avocado, etc. His pioneering studies on isolation and purification showed inequivocally that viroids have a unique molecular structure, different from any other pathogen. Dr. Diener found that viroids replicate without helper virus; that viroid-complementary DNA, produced by insertion into bacteria, are themselves infectious and that the RNA transcribed in potato cells is identical with the viroid. Cloned viroid-specific cDNAs were also developed by him for novel diagnostic tests.
Dr. Diener’s work has direct application to the control of viroid diseases of many crops, as well as to the elucidation of the unique biological and molecular properties of these small disease agents.