Cesare Gessler was born in Ticino, Switzerland, in 1949. He received his diploma in agricultural engineering in 1974 and his Ph.D. degree in plant pathology in 1977 from the Swiss Federal Institute of Technology (ETH Zürich). Following post-doctoral work with Joseph Kuc at the University of Kentucky, he returned to ETH in 1981 to begin a career in plant pathology. He was granted the title of professor by ETH in 2006, a distinct honor in the Swiss university system, and was specifically nominated for his contributions in the areas of original research and service to his profession.
Gessler is internationally known and respected for his research in two important pathosystems: apple scab (Venturia inaequalis) and downy mildew of grapevine (Plasmopara viticola). Indeed, he is known as a leading researcher in Europe in both of these systems and the breadth and depth of his contributions are truly remarkable. In apple scab, Gessler’s work spans the gap from molecular genetics to practical epidemiology and organic practices for disease management. He was a pioneer in cloning resistance genes to V. inaequalis from wild apple and in producing a “cisgenic” Gala apple resistant to scab. This was both a technical advance, as woody plants are inherently less tractable than herbaceous, and a scientific advance because it demonstrated that a gene-for-gene system functioned in apple scab. Gessler furthermore recognized the significance of early discoveries of Weismann in 1931 regarding an obscure apple cultivar Boiken as evidence of pathogenic races in V. inaequalis. His careful and comprehensive follow-up studies not only generated much of our extant knowledge of the genetics of resistance in this pathosystem but also resulted in orchard-level demonstrations of race adaptation to apple cultivars, provided organic producers with a novel strategy of planting varieties with complementary resistance to manage scab, and provided the first hard evidence that races of V. inaequalis might ultimately adapt to the Vf gene, which served as a foundation of scab resistance in breeding programs worldwide, a prediction that was fulfilled soon afterwards.
Gessler has made notable contributions that have advanced our knowledge of grapevine downy mildew. Long considered exclusively as a classic polycyclic disease in which oospores played a transitory role, Gessler led an innovative and international research effort that called into question many of our assumptions regarding the epidemiology of this disease. Through development and creative use of microsatellite markers, Gessler and colleagues demonstrated a season-long contribution of oosporic inoculum to disease increase that often (and incongruously) outweighed the contribution of secondary inoculum. Many aspects of these pioneering studies were subsequently validated independently by other research groups in Europe and the United States. Gessler’s widely known tenacity in the face of opposition, his incessant questioning of his own findings and those of others, and his remarkable good humor throughout are hallmarks of his interactions with others and are an inspiration to his students, colleagues, and even his opponents.
Gessler has supervised 32 Ph.D. students to date. They are now widely dispersed and hold positions in research, teaching, and extension throughout Europe. Thus, his impact upon research has been greatly multiplied through exceptionally skilled mentoring. Many of these students played important roles in the above-described investigations. However, all contacted in the course of preparing this nomination agreed upon the pivotal role played by Gessler from the earliest conceptual stages of the work through publication and often beyond in helping with early career development. His accomplishments are all the more impressive when considered in light of his substantial teaching responsibilities not only at ETH but as an invited professor teaching epidemiology at other universities in and outside of Switzerland.
Gessler has greatly facilitated international communication, cooperation, and collaboration among those investigating diseases of apple and grapevine. He has been a leading participant and contributor in every International Workshop on Grapevine Downy and Powdery Mildew since 1991, and he hosted the fifth workshop in 2006 in Italy, where scientists from 13 countries participated. He has likewise for more than 20 years been an enthusiastic and productive member of the principal international scientific group dealing with research and extension on tree fruit diseases: the IOBC Working Group on Integrated Control of Pome Fruit Diseases, and again he has been one of the conveners of their meetings on several occasions. Gessler was the leading force in the early development of “Safecrop”: the Center for Research and Development of Crop Protection in San Michele, Italy, and served as the center’s scientific director from 2003 to 2007. He is an active and leading participant in annual meetings of European researchers and advisory personnel concerned with management of apple scab. His research is thoroughly vetted through early presentation by Gessler and a large contingent of graduate students and post-doctoral scientists from his lab at such international conferences. The degree to which his contributions (and often mere presence) stimulate creative discussions, move the science forward, and find applications in growers’ fields are widely appreciated by colleagues working in this area.
A notable service performed by Gessler for his profession has been the sometimes thankless task of engaging in discussions of genetically modified crops on the European continent, and he has often been willing to speak publicly as a proponent of limited uses of GMOs. His balanced critique of misapplications of such technology lent credibility to his support of selective and low-risk uses of GMOs to reduce environmental impacts of agriculture. Gessler has been quoted at length in newspapers throughout Europe, has made frequent appearances on European television, and has effectively and persuasively conveyed his views. For all of the aforementioned reasons, Gessler is thoroughly deserving of recognition as a fellow of The American Phytopathological Society.