Weed Technology 2010 24:182–184
Symposium Influence and Legacy of Raghavan Charudattan in Biological Control of Weeds Erin N. Rosskopf, James T. DeValerio, Mark S. Elliott, Yasser M. Shabana, and Camilla B. Yandoc Ables* Dr. Raghavan Charudattan has worked in the area of biological control of weeds with plant pathogenic fungi for nearly four decades. He has maintained his research program in this line throughout his career. The scientific discoveries and contributions that he has made have been recognized by his peers and demonstrated through his election as fellow of both the Weed Science Society of America and the American Phytopathological Society. The basic knowledge that he has contributed to our understanding of the fundamental biology of weed/pathogen interactions and his contributions in the areas of mycology, etiology, and natural products will have long-lasting effects. Equally important to the basic and applied research that he has conducted is his role as a mentor and colleague. Dr. Charudattan has contributed to the scientific development of more than 60 students, postdocs, and scientists from more than 20 countries. Dr. Charudattan has contributed to the establishment of biological control of weeds with pathogens as a permanent and highly productive area of weed control research. Key words: Biological control, pathogens, bioherbicides. El Dr. Raghavan Charudattan ha trabajado en el a´rea de control biolo´gico de malezas con los hongos pato´genos de las plantas por cerca de cuatro de´cadas. E´l ha mantenido su programa de investigacio´n en esta lı´nea a lo largo de su carrera. Los descubrimientos cientı´ficos y las contribuciones que ha hecho han sido reconocidas por sus colegas y se lo han demostrado a trave´s de su eleccio´n como miembro de la Weed Sciency Society of America y de la American Phytopathological Society. Los conocimientos ba´sicos con los que ha contribuido para nuestra comprensio´n de la biologı´a fundamental de las interacciones malezas-pato´genos y sus contribuciones en las a´reas de micologı´a, etiologı´a y productos naturales, tendra´n efectos duraderos. Igualmente importante a la investigacio´n ba´sica y aplicada que e´l ha realizado esta´ su papel como profesor y asociado. El Dr. Charudattan ha contribuido al desarrollo cientı´fico de ma´s de 60 estudiantes de post-doctorado y cientı´ficos de ma´s de 20 paı´ses. Tambie´n ha contribuido al establecimiento del control biolo´gico de malezas con pato´genos de un a´rea permanente y altamente productiva de investigacio´n.
We consider Dr. Raghavan Charudattan, known as ‘‘Charu’’ to his friends and colleagues, a true scientific scholar. He received all of his undergraduate and graduate training at the University of Madras in India, where he studied plant pathology and mycology. He was a postdoctoral research associate first at the University of California, Davis and then at the University of Florida, where he became an assistant professor of plant pathology soon after his arrival. Charu became a full professor in that department in 1983 and most recently served as the department chair prior to his retirement. He has consistently worked in the field of biological control of weeds, despite skepticism about the value of this research expressed by some colleagues, and he has done so with the highest level of scientific integrity and inquiry. He is an excellent mycologist and plant pathologist, DOI: 10.1614/WT-D-10-00004.1 * First author: Research Microbiologist, USDA, ARS, USHRL, 2001 S. Rock Road, Fort Pierce, FL 34945; second author: Agricultural Extension Agent, University of Florida/Institute of Food and Agricultural Science, Bradford County Cooperative Extension Service, 2266 N. Temple Ave., Starke, FL 32091; third author: Diagnostician and Senior Biological Scientist, University of Florida/ IFAS, Florida Extension Plant Disease Clinic, Building 78 Mowry Rd., Gainesville, FL 32611; fourth author: Program Manager, Weed Biological Control, University of Florida, Department of Plant Pathology, P.O. Box 110680, Gainesville, FL 32611; fifth author: Associate Program Officer, Board on Agriculture and Natural Resources, The National Academies, 680 Keck Center, 500 Fifth St. NW, Washington, DC 20001. Corresponding author’s Email: [email protected]
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and also is an outstanding plant taxonomist, ecologist, weed scientist, and plant physiologist. His interest in and knowledge of biological control, while focused on weed/plant pathogen systems, is very thorough in the areas of insects and plant diseases as well. He has an unique historical and progressive perspective on the development of these fields of study as well as a thorough understanding of agriculture and the socioeconomic importance of the work to which he contributes. He regularly is sought for consultation in many areas of study, often well outside his principal discipline. Charu has had remarkable vision with regard to the development of the field of biological control of weeds with plant pathogens. He saw the importance of investigating agents for use in both the classical approach with nonnative pathogens and the inundative approach using indigenous ones. The focus of his early work was on the use of pathogens for control of weeds in aquatic systems. The development of Fusarium culmorum for control of hydrilla (Hydrilla verticillata L. F. Royle) involved one of the most novel approaches to the epidemiology of a disease on a submerged weed (SmitherKopperl et al. 1998, 1999) and represents one of 11 biological control patents that Charu now holds (US patent #4,263,036). Later work on this weed led to the identification of Mycoleptodiscus terrestris as a potential biological control agent, which also was identified as a pathogen of Eurasian watermilfoil (Myriophyllum spicatum L.) (Verma and Charudattan 1993). Further work on this weed revealed that a
combination of pathogens (F. culmorum or Acremonium sp.) and the leaf-mining fly (Hydrellia pakistanae; Diptera: Ephydridae) caused increased weed damage in comparison with the damage caused by either agent alone (Shabana et al. 2003). Another aquatic weed that has been of considerable interest to Charu is water hyacinth [Eichhornia crassipes (Mart.) SomsLaub.] for which he and his group worked on developing Cercospora rodmanii as a commercial biological control agent. The waterhyacinth/Cercospora system provides examples of Charu’s vision of biological control as a science. This was one of the first systems used to look at the effects of combining a fungal plant pathogen with an insect or chemical herbicide (Charudattan 1986) agent. This also is a system to look at the potential benefit of multiple pathogens, applied in combination, over that of a single agent (Vincent and Charudattan 2000). Some of the first work using DNA sequence data for the characterization and differentiation of fungal plant pathogen species (specifically Cercospora spp.) intended for use in biological control was conducted by Charu and his students (Tessman et al. 2001). He and his student from Egypt developed a novel system using hydrophilic polymers for formulating Alternaria eichhorniae and A. cassiae, bioherbicide agents for water hyacinth and sicklepod [Senna obtusifolia (L.) H. S. Irwin & Barneby] (Shabana et al. 1997). When Charu began work on terrestrial systems, he developed very progressive strategies, with emphasis on the bioherbicidal approach. He was looking for pathogens to target weeds that were important to annual production systems and for which chemical herbicides proved unsuccessful. This vision of the niche for biological control in crop production systems led to work on pigweeds (Amaranthus spp.) and nutsedges (Cyperus spp.). His work with pigweeds led to the characterization and naming of a new genus-specific fungus (Phomopsis amaranthicola), again using DNA sequence information to support the new species designation (Rosskopf et al. 2000a,b). It was one of the first sets of trials investigating a biological control agent for use in organic production systems. Two additional patents were granted on this agent (US Patents #5,510,316 and #5,398,728) and it also was used as a model for investigating the effects of crop production chemicals on a biological control agent (Wyss et al. 2004). The approach of evaluating potential biological control agents with a very practical eye continued with the work on Dactylaria higginsii (US Patents #5,945,378 and #5,698,491), in which the research led to the demonstration of improved crop yield as a result of the application of the biological control agent (Kadir et al. 2000). The use of this pathogen in tank mixes with other crop production materials also was investigated (Yandoc-Ables et al. 2006). Another novel approach developed by Charu and his group was an integrated management system of purple and yellow nutsedge (Cyperus rotundus L. and C. esculentus L.) based on bioenhanced organic hays used as mulches (Shabana et al. 2009). Investigation of the ‘‘multiple pathogen strategy’’ continued, and Charu’s vision of providing benefit to production agriculture also continued when he applied this approach to weeds in Florida citrus and sugarcane production (Chandramohan and Charudattan 2001; Chandramohan et al. 2002,
2003). The same method was used in a novel approach to land reclamation, in which the potential biological control agent Bipolaris sacchari for management of cogongrass [Imperata cylindrica (L.) Beauv.] was tested in combination with plant competition from bahiagrass (Paspalum notatum Flugge), a desirable grass species (Yandoc et al. 2004). Although Charu’s career focused on the practical application of biological control, he also contributed significantly to basic science in both plant pathology and weed science. His most recent work represents the culmination of this philosophy. Charu and his colleagues discovered a Tobacco Mild Green Mosaic Virus (TMGMV) strain (Wetter 1986, 1989) that causes a rare lethal hypersensitive response in tropical soda apple (Solanum viarum Dunal). This led to his most recent patent (US Patent #6,689,718). The company BioProdex, Inc. was established, and focused on the launching of TMGMV as the biological control agent SolvinixTM. Throughout his career, Charu has recognized the importance of international collaboration for the advancement of the science of biological control. He has maintained productive collaborations in more than 15 countries and has served as an educator for many years. In addition to his formal teaching responsibilities as lecturer on microbial control of plant diseases and weeds, and his role in short courses in Florida, Brazil, Nicaragua, and Mexico, Charu has also supervised more than 60 degree-seeking students, postdocs, and visiting scientists from more than 20 different countries. He has been a remarkable mentor, not only scientifically, but also has served as a model of professionalism and outstanding character. Because of these remarkable qualities as scholar, visionary, collaborator, teacher, and mentor, Charu has also been recognized as a leader. He has been named as a fellow of both the American Phytopathological Society and the Weed Science Society of America, served as one of the founders and the coordinating editor for the journal Biological Control: Theory and Application in Pest Management, and served as the department chair for the Plant Pathology Department at the University of Florida. He has been honored with many guest professorships, and as a consultant to the Food and Agriculture Organization, the World Health Organization, and the National Academy of Sciences. He has been recognized for his achievements by the USDA Secretary of Agriculture; the Cooperative State Research, Education, and Extension Service; and by the Animal and Plant Health Inspection Service. Despite all of the remarkable contributions that he has made and the well-deserved recognition that he has received, Charu remains a humble person, committed to serving science and colleagues to the best of his ability. For those of us lucky enough to call him friend, the most valuable lessons that he has shared are personal ones, to put your family and friends first, to never take yourself too seriously, and to maintain your scientific curiosity. Finally, as one of his colleagues said of him, ‘‘Charu demonstrates that you can be successful and still be nice.’’ Charu has taught us to appreciate the individual with whom you have the privilege of working as much as the work itself, and to be generous with opportunities and acknowledgement. For all of these lessons and many more that yet have to be learned, we are grateful.
Rosskopf et al.: Influence and Legacy of Raghavan Charudattan
Literature Cited Chandramohan, S. and R. Charudattan. 2001. Control of seven grasses with a mixture of three fungal pathogens with restricted host ranges. Biol. Control 22:246–255. Chandramohan, S., R. Charudattan, R. M. Sonoda, and M. Singh. 2002. Field evaluation of a fungal pathogen mixture for the control of seven weedy grasses. Weed Sci. 50:204–213. Chandramohan, S., J. M. Shine Jr., M. J. Duchrow, E. N. Rosskopf, and R. Charudattan. 2003. A bioherbicide system to manage guineagrass (Panicum maximum Jacq.) in sugarcane in Florida. Sugar Cane Int. 22(2):28–30. Charudattan, R. 1986. Integrated control of watehyacinth (Eichhornia crassipes) with a pathogen, insect, and herbicides. Weed Sci. 34:26–30. Kadir, J. B., R. Charudattan, W. M. Stall, and T. A. Bewick. 2000. Effect of Dactylaria higginsii on purple nutsedge (Cyperus rotundus) interference with pepper (Capsicum annuum L.). Pertanika J. Trop. Agric. Sci. 23:83–88. Rosskopf, E. N., R. Charudattan, J. T. DeValerio, and W. M. Stall. 2000a. Field evaluation of Phomopsis amaranthicola, a biocontrol agent for Amaranthus spp. Plant Dis. 84:1225–1230. Rosskopf, E. N., R. Charudattan, Y. M. Shabana, and G. L. Benny. 2000b. Phomopsis amaranthicola, a new species from Amaranthus spp. Mycologia 92:114–122. Shabana, Y. M., R. Charudattan, J. T. DeValerio, and M. A. Elwaki. 1997. An evaluation of hydrophilic polymers for formulating the bioherbicide agents Alternaria cassiae and A. eichhorniae. Weed Technol. 11:212–220. Shabana, Y. M., J. P. Cuda, and R. Charudattan. 2003. Combining plant pathogenic fungi and the leaf-mining fly, Hydrellia pakistanae, increases damage to hydrilla. J. Aquat. Plant Manag. 41:76–81. Shabana, Y. M., E. N. Rosskopf, A. H. Abou Tabl, R. Charudattan, and W. Klassen. 2009. Integrated use of bioactive, green, and plastic mulches to suppress Cyperus rotundus and C. esculentus in tomato. WSSA Abstract No. 438, 2009 Annual Meeting.
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Smither-Kopperl, M. L., R. Charudattan, and R. D. Berger. 1998. Dispersal of spores of Fusarium culmorum in aquatic systems. Phytopathol. 88:382–388. Smither-Kopperl, M. L., R. Charudattan, and R. D. Berger. 1999. Deposition and adhesion of spores of Fusarium culmorum on hydrilla. Can. J. Plant Pathol. 21:291–297. Tessman, D. J., R. Charudattan, H. C. Kistler, and E. N. Rosskopf. 2001. A molecular characterization of Cercospora species pathogenic to waterhyacinth and emendation of C. piaropi Tharp. Mycologia 93:323–334. Verma, U. and R. Charudattan. 1993. Host range of Mycoleptodiscus terrestris, a microbial herbicide candidate for Eurasian watermilfoil, Myriophyllum spicatum. Biol. Control 3:271–280. Vincent, A. C. and R. Charudattan. 2000. Evaluation of a combination of two pathogens as a potential bioherbicide for Eichhornia crassipes [Mart.] SomsLaub. under field conditions. Page 217 in Proceedings of the Third International Weed Science Congress-IWSC, Foz do Iguassu, Brazil, June 6–11. Corvallis, OR: International Weed Science Society. Wetter, C. 1986. Tobacco mild green mosaic virus. Page 205–220 in M.H.V. van Regenmortel and H. Fraenkel-Conrat, eds. Plant Viruses, Vol. 2, The RodShaped Plant Viruses. New York: Plenum Press. Wetter, C. 1989. CMI/AAB Description of Plant Viruses, No. 351. Kew, Surrey, UK: Commonwealth Mycological Institute. 6 p. Wyss, G., E. N. Rosskopf, R. Charudattan, and R. Littell. 2004. Effects of selected pesticides and adjuvants on germination and vegetative growth of Phomopsis amaranthicola, a biocontrol agent for Amaranthus spp. Weed Res. 44:1–14. Yandoc, C. B., R. Charudattan, and D. G. Shilling. 2004. Suppression of cogongrass (Imperata cylindrica) by a bioherbicidal fungus and plant competition. Weed Sci. 52:649–653. Yandoc-Ables, C., E. N. Rosskopf, R. Charudattan, and R. L. Pitelli. 2006. Effect of selected pesticides on Dactylaria higginsii, a potential bioherbicide for purple nutsedge. Weed Technol. 20:255–260.
Received January 7, 2010, and approved February 5, 2010.