Geneviève Jeanne Défago was born in Val d’Illiez, Vallais, Switzerland. She studied natural sciences at the University of Lausanne and received a M.S. degree from the Swiss Federal Institute of Technology (ETH) in Zürich with majors in biology and biochemistry. Her Ph.D. dissertation was awarded the Silver Medal in 1967, the highest prize given by the ETH. From 1967 to 1969, she was a Canadian Research Council postdoctoral fellow at the Prairie Regional Laboratory in Saskatoon, where she studied the reproductive physiology of Pythium. In 1969, Dr. Défago returned to Zürich and was appointed head of the scientific staff at the ETH Institute for Special Botany. Since 1977, she has served as deputy director of the Phytopathology Department and was acting director from 1986 to 1988 and from 1996 to 1998. In 1990, in recognition of her leadership and service to the Institute for Plant Sciences, she was named professor by ETH on recommendation of the Senate. Dr. Défago has distinguished herself as an accomplished scientist, an instructor, an administrator, and a champion for international development in plant pathology.
Dr. Défago is widely regarded as one of the world’s leading biological control scientists. She has been a pioneer in the application of biotechnology to understand how biocontrol Pseudomonas strains work and how they can be improved. She was one of the first to demonstrate that the physical and chemical properties of disease-suppressive soils can determine their capacity to support antagonistic Pseudomonas. She isolated P. fluorescens CHA0 from a suppressive soil and characterized this strain’s unparalleled repertoire of biocontrol and growth-promoting mechanisms. Dr. Défago, in collaboration with Dr. D. Haas, was the first to clone gacA from CHA0, a key global regulatory gene for bacterial secondary metabolism.
Dr. Défago’s group was the first to implicate bacterial siderophore production in induced systemic resistance and to link classical PR proteins with bacteria-induced resistance. Her group developed molecular and biochemical techniques to show that the relative contribution of cyanide, various antibiotics, and siderophores to disease suppression depends upon both the host and the target pathogen.
Dr. Défago and her colleagues demonstrated that minerals such as zinc and copper can influence biocontrol effectiveness by modifying signal compounds from pathogens. They found that copper and zinc significantly improved biocontrol activity of strain CHA0 against Fusarium oxysporum f. sp. radicis-lycopersici in soilless tomato culture. Copper, but not zinc, had a direct effect on disease suppression. The improvement in biocontrol activity by zinc resulted not from the stimulation of antibiotic production, as initially thought, but rather in the reduction of fusaric acid produced by F. oxysporum f. sp. radicis-lycopersici. Fusaric acid at concentrations as low as 0.12 mg/ml repressed production of 2,4-diacetylphloroglucinol, a key biocontrol metabolite by strain CHA0.
Dr. Défago’s work has important applications for improving biocontrol of soilborne pathogens. Her group was among the first to use transgenic bacteria that overproduce antibiotics for improved biocontrol. She was one of the first to use mixtures of bacteria and fungi for enhanced biocontrol. Dr. Défago has had long-term collaborations with industry to develop better biocontrol strains for greenhouse crops. Her recent discovery of environmental signals, particularly pathogen toxins, that modulate bacterial antibiotic biosynthesis may streamline strain selection procedures and enable inoculants to be customized for better performance in specific environments.
Dr. Défago has made major strides to establish scientifically based assessment of inoculant biosafety. She has an active program to evaluate the impact and benefits of transgenic inoculants in the environment. She is vice president of the Swiss Biosafety Commission and an international consultant for establishing European guidelines.
Besides her biocontrol work, Dr. Défago is renowned for seminal work elucidating the role of sterols in the reproductive physiology of Pythium and the role of tomatine in plant defense, and for her early biochemical studies of fungal wilt toxins initiated under E. Gäumann and H. Kern. Incidentally, through Gäumann, Dr. Défago is a direct descendent of A. de Bary, founder of plant pathology. Currently, she has active research programs in biocontrol of bindweeds using pathogenic fungi and in control of postharvest problems in tropical yams. She has had numerous collaborations in Europe, North America, Asia, and Africa. She has coauthored many scientific publications.
Dr. Défago has long been regarded as an extraordinary instructor by her peers and students. Her teaching excellence was recognized as early as 1977 when she was awarded the title ‘venia legendi’ by the ETH natural sciences faculty. Currently, she teaches eight undergraduate and graduate plant pathology courses at ETH. Her intensive practical course in plant pathology for biology majors is credited for record enrollments of graduate students in plant pathology. She has developed special courses in Iran and Norway and has sponsored scientists from developing countries to work in her laboratories. She has directed many Ph.D. and M.S. students, and has served on numerous other Ph.D. committees in Switzerland and France. Her original thinking, balanced with a zest for life, has always empowered those she mentors to produce only their best efforts.
Dr. Défago has been a major force in European and international plant pathology for 3 decades. She was a founder and the first president of the Swiss Society for Phytomedicine, which brings together phytopathologists, entomologists, and weed scientists. She was a charter member of the European Foundation for Plant Pathology and has served on its Council since 1989. She has served on the board of the International Society of Plant Pathology since 1985 and is a member of the Steering Committee for the International Organization for Biological Control. She is an active member of APS, French Society of Phytopathology, German Society of Phytomedicine, Swiss Botanical Society, Swiss Microbiology Society, and the American Society of Microbiology. She is an editor for the European Journal of Soil Biology and a reviewer for U.S. and European grant boards. She has organized several international conferences and edited two proceedings on biological control.
