A HISTORY of NEMATOLOGY in CALIFORNIA (As of April, 2008)
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A HISTORY OF NEMATOLOGY IN CALIFORNIA (as of April, 2008) by Dewey J. Raski Professor Emeritus of Nematology University of California, Davis Ivan J. Thomason Professor Emeritus of Nematology University of California, Riverside John J. Chitambar Senior Plant Nematologist California Dept. of Food and Agriculture Sacramento and Howard Ferris Professor of Nematology University of California, Davis encouraged and aided by the cooperation of Professor of Nematology Edward P. Caswell-Chen University of California, Davis Professor of Nematology Harry K. Kaya University of California, Davis Professor Emeritus of Nematology Armand R. Maggenti University of California, Davis Professor of Nematology Steven A. Nadler University of California, Davis Professor Emeritus of Nematology Seymour D. Van Gundy University of California, Riverside Acknowledgments Our profound thanks to: Norman Jones - who provided most valuable help in translating and transfering major parts of the text from handwritten calligraphy to electronic media. Dan Rosenberg - for reviewing the section on the C.D.F.A. adding many changes and additions from his vast store of information and knowledge of that group’s genesis and growth. Patty Sorrels - for her constant and ready willingness to help Dr. Thomason process contributions as they came available and forwarding them to Dr. Ferris’s computer at U.C.D. Raski, Thomason, Chitambar and Ferris: Nematology in California 2 PREFACE Over the past several years it has become increasingly apparent that the nematologists who were the founding members of this science in California were missing a unique opportunity to reflect on and record the events of their careers that were part of the substance and achievements of nematology. Virtually all of the early researchers are already retired but may yet serve as direct contacts with the few even earlier pioneer nematologists and are still in communication with the current faculty and staff. Perhaps it would be appropriate here to point out and emphasize some facts pertinent to an account of the development and growth of nematology. Nematodes were mostly unknown as threats to agriculture until the early 1900s. Root-knot nematodes of the genus Meloidogyne were most frequently studied partly because they produced galls or swellings on the plant roots. This permitted observers to wash the roots clean, preserve them in fixative and collect specimens when convenient. The same was true for cyst forming nematodes, such as Heterodera schachtii, where the females formed durable cysts easily visible to the unaided eye. Only much later, beginning about the end of World War II, various collection techniques, especially wet-sieving and Baermann funnel methods brought to light myriad new and fascinating species in great numbers. But until then the administrators of universities and government agencies were literally uninformed about nematodes. The succeeding generations of students had no way to learn about them because there were no courses on nematology in all of U.S.A. For the next 50 years there was a sustained and remarkable surge in the attention given to nematodes affecting the agricultural industry. Major advancements were achieved in the taxonomy and classification of nematodes revealing many more species and genera of endoparasitic types (which penetrate the roots). To these were added a vast array of ectoparasitic types (which feed on the surface of roots). In addition, world-wide collections have added immensely to our knowledge of the diverse life histories and feeding mechanisms of nematodes, their great abundance and ubiquitous distribution in literally every imaginable biological niche. Nematodes represent far more than simply pathogens affecting agricultural crops. In fact they are one of the most successful forms of life on this planet surviving the hottest, driest soils; in the ice caps of the antarctic; in every water system, from fresh-water to marine. A single species, Caenorhabditis elegans, has emerged as an immensely important model organism for studying fundamental biological processes by scientists worldwide. All this is evidence that nematodes warrant far more attention and support to more fully understand all the potential values to be gained from studying such a rich fauna. Instead, Nematology at University of California, Davis (U.C.D.) was at one time subjected to pressures aimed at merger into other departments or elimination entirely from U.C.D. These pressures came as a consequence of local interpretations of policy changes set by the Office of Vice President of the University of California to reduce the proliferation of small departments or research centers, etc. To date Nematology at U.C.D. and the University of California, Riverside (U.C.R.) has resisted and survived these pressures, perhaps an understanding of the historical impetus and development of U.C. departments of Nematology will lead to renewed support and encouragement. Raski, Thomason, Chitambar and Ferris: Nematology in California 3 INTRODUCTION Nematodes are remarkable creatures for many reasons. They are found in virtually every imaginable habitat or biological niche. They are truly ubiquitous and worldwide in distribution and have developed a great range of unique life habits, feeding mechanisms, host ranges when parasitic, different means of surviving through unfavorable conditions and special adaptations for differing habitats. There are only a few records of nematodes dating as far back as biblical times and most of those were concerning parasites of humans and animals. There was good reason for this - other than a few animal parasites and a few marine species most nematodes are very small, slender and opaque in appearance and special techniques and equipment are required to separate them into clear water in order to find them. More importantly, nematodes are for the most part too small and slender to permit study of them in detail without benefit of magnification. It was the invention of the light microscope that finally enabled scientists to study microorganisms, including nematodes, in much greater detail than was possible earlier. Collectors found them to be numerous in a vast array of soil types, in freshwater and marine habitats, and in plant tissues both above and below ground. They are virtually everywhere in nature, including agricultural soils and crop plants. There was no information about life cycles of nematodes, their feeding mechanisms, or host ranges. However, the association of certain types or species with crop damage and/or poor yields soon became apparent to agriculturists. Nevertheless it wasn't until the late 1800s that their importance as a possible threat to agriculture began to be recognized in publications. I. EARLY PERIOD; LATTER HALF OF THE 19TH CENTURY. One of the first records of nematodes parasitic on plants was that of Kuhn (1858) reporting on the stem and bulb nematode, Ditylenchus dipsaci. Other notable publications included Schacht's work (1859) on sugar beet nematode, Heterodera schachtii, followed by Schmidt (1871) and Strubell (1888) on the same nematode. Cornu (1879) recorded work on root-knot nematode, Meloidogyne spp.; and De Man (1881) (Plate 1) on the lesion nematode, Pratylenchus spp. All of the above came from studies in Europe; awareness of nematode problems did not reach U.S. until after the turn of the century with one exception, a bulletin on root-knot nematode published by J. G. Neal in 1889. II. MID PERIOD; FIRST HALF OF THE 20TH CENTURY. These fifty years brought many advances to Nematology in the U.S. the most significant being the appointment of Nathan Augustus Cobb (Plate 2) in 1907 as Nematologist in the Bureau of Plant Industry of the U.S.D.A. Soon afterward a new Division of Nematology was established with Cobb as its first Director. Dr. Cobb was eminently successful in staffing his Division with many outstanding individuals who set high standards of excellence for research which has carried forward to the present time. Cobb himself was exceptionally prolific in a broad spectrum of nematode research including taxonomy, morphology, life habits and their effects on plants. In recognition of his leadership and many achievements, Cobb has been celebrated as the father of Nematology in the U.S. Raski, Thomason, Chitambar and Ferris: Nematology in California 4 Plate 1 Initially the work was concentrated in the east coastal regions but eventually spread throughout the U. S. E. A. Bessey made the first report of root- knot and sugar-beet nematodes in California in 1911. Another early record of nematodes in California involved the citrus nematode. That species was discovered by a Los Angeles County Agricultural Inspector who sent specimens to Cobb. Cobb described it as a new species and named it Tylenchulus semipenetrans in 1913. E. E. Thomas of the U.C. Citrus Experimental Station at Riverside, California demonstrated it to be injurious to citrus in 1928. Gotthold Steiner (Plate 3) was one of the first Nematologists to join Cobb in the Division and later became Director following the death of Dr. Cobb in 1932. A. L. Taylor (Plate 3) succeeded Steiner as Director of Division in 1956. B. G. Chitwood (Plate J. G. De Man Plate 2 3), renowned for his major contributions to nematode systematics and morphology, began his career with the U.S.D.A. in Washington, D. C. in 1928; later moved to Beltsville; still later joined the U.S.D.A Potato Cyst Nematode Laboratory in Hicksville, Long Island, N.Y. After leaving the U.S.D.A. he worked in Florida and finally in California. Jesse Christie (Plate 3) was stationed in Beltsville for part of his career but completed some of his most significant research while working in Florida. Gerald Thorne (Plates 4, 5) spent most of his career in Utah, his native state, where sugar beet cyst nematodes were a major agricultural pest. He made a number of visits to California assessing the importance of nematodes here and recommended various methods of control.