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Edward Sylvester

IN MEMORIAM

Edward Sanford Sylvester

Professor of Entomology, Emeritus

UC Berkeley

1920 – 2009

 

Edward Sanford Sylvester died at age 89 on July 25, 2009, after a short illness. Ned, as most of his colleagues and friends called him, was on the University of California, Berkeley faculty for 41 years and served as a Berkeley graduate student researcher before that. He was an internationally renowned scientist in the field of insect transmission of plant viruses, specializing in aphids, the most numerous and important family of plant virus vectors. He also served many years as a departmental chair and as an associate dean. Upon retirement, he was honored with the Berkeley Citation.

 

Ned was born in Brooklyn, New York, on February 29, 1920, and liked to remind his friends and family that being born on a leap day meant he aged only one-fourth as fast as they. He grew up in Wyoming and Colorado and was living in Denver when he enrolled at Colorado State University to major in entomology. He met his future wife Marian on a blind date while a student. After the country’s entrance into World War II, he joined the U.S. Navy but contracted rheumatic fever and was discharged after six months. He entered the graduate program in entomology at Berkeley, under the guidance of Professor Julius Freitag, in 1944. He was appointed as an assistant professor and assistant entomologist in the California Agricultural Experiment Station in 1949. At this time, Berkeley had four vector entomologists and was clearly the leading center in the world for the study of insect-transmitted plant pathogens.

 

Ned’s early studies involved viruses transmitted by aphids, concentrating originally on viruses of sugar beets and potatoes. Such viruses could be very debilitating to these crops, which were very important during wartime, when he began his research as a graduate student. He was originally fascinated by viruses that were “nonpersistently transmitted” by aphids. After acquiring viruses from plants, aphids only retained the ability to transmit the viruses for a few hours, even for shorter periods if they fed actively. This trait led many to propose that the aphids simply carried the viruses on the surface of their mouthparts, from which the virus was rubbed. Ned demonstrated that the optimum time for both acquisition and for inoculation of these viruses by aphids was only from a few seconds to a few minutes for each event after the aphid began to probe the plant. His characterization of the important features of aphid transmission of this large group of viruses has endured for over 50 years. Ned was one of several vector scientists to challenge the conventional wisdom of the time, which held that this method of aphid transmission was a simple mechanical transfer of virus particles on aphids’ needlelike mouthparts. Recent molecular discoveries involving the transmission of nonpersistently transmitted aphid-borne viruses have provided convincing evidence of how this process is mediated. Indeed, viral particles are attached mostly to the tip of the aphid’s stylet-like mandibles, but involve highly aphid-specific molecular targets and molecular “helper components.” Ned spent his first sabbatical leave with Roy Bradley in New Brunswick, Canada, where he and Bradley established some of the first convincing evidence that the tip of the aphid stylets was essential to vector transmission. It was here also that he helped to develop the use of artificial membranes for aphid feeding, which led Tom Mittler and Rex Dadd at Berkeley to adapt this technique to using artificial diets to study aphid nutrition.

 

From nonpersistently transmitted viruses, Ned moved on to study persistently transmitted viruses. Aphids could continue to transmit these viruses for days to weeks (a typical aphid lifespan) after acquiring them by feeding on a virus-infested plant. Sylvester and his collaborators showed that some of these viruses not only circulated within the body of their aphid vectors but also multiplied in the aphid. Students today might be surprised to find that during the 1960s this was a controversial assertion. Sylvester developed an interest in how temperature affected vector transmission. He found, for example, that temperature was important to the rate of replication of viruses in aphids. This began an intimate involvement with the design and repair of growth chambers, with careful attention to temperature recordings.

 

Ned belonged to the first generation of entomologists to make extensive use of statistics, and he was among the first to apply these concepts to vector transmission studies. He was widely consulted within the department for advice on statistical analysis and experimental design. He was the first to apply these concepts to vector transmission phenomena such as the latent period (the time between acquisition of a pathogen and its first transmission by a vector) as a descriptive statistic rather than a singular value. Graduate students from America and abroad whom he mentored in aphid transmission of plant viruses went on to establish their own research programs on control of plant virus diseases. Thoroughness and rigor of experimental design and execution were certainly the hallmarks of Ned’s research, and this usually required very large numbers of experimental plants, and hence large growth chambers to house them. For three decades, Ned toiled to maintain large growth chambers and developed impressive abilities for diagnosing their eccentricities.

 

From 1962 until his retirement in 1990, Ned was assisted in his research by Jean Richardson, especially after he took on administrative roles as chair of the Department of Entomological Sciences (1979-1985) and later as associate dean for academic affairs in the College of Natural Resources (1986-1990). Jean was a microscopist, and Ned acquired an electron microscope that was installed next to his office in the basement of a greenhouse at the Oxford Tract. They published findings on Rhabdoviruses of weeds and of strawberries, transovarial passage of virus in aphids, and the effects of mixed infections of viruses in aphids. Aphids are unusual insects with complicated life cycles: sexual and asexual reproduction with the spontaneous appearance of sexual males, live births alternating with egg-laying, winged and wingless adults, and seasonal alteration of hosts from genus-specific trees to a multitude of herbaceous hosts. Ned insisted his devotion to this single family of insects was well justified. On the Berkeley campus, he was among the most diligent of workers, spending many hours on weekends and holidays to water plants or tend aphid colonies if the need arose, even after becoming a distinguished professor. Ned was proud to point out that the insect vector group, established at Berkeley with the arrival of H. H. P. Severin in 1916, was the oldest continually operating such group in the world. Only two such labs were older but no longer existed. Due in part to his efforts, this tradition at Berkeley still continues.

 

Ned’s second and last sabbatical leave was spent at the behest of the United Nations Food and Agriculture Organization on a rural experiment station near Albay in the Philippines in 1978, working on the mysterious cadang-cadang disease of coconuts.

Among Ned’s most treasured leisure moments were fly-fishing in the Sierras near Graeagle in the summer. He is survived by his wife Marian Uhl, son Steven, daughter Kathryn Jarrett, and grandson Eric Sylvester.

 

Alexander H. Purcell                                                                         2010                            

John E. Casida

David L. Wood

Thomas E. Mittler