LSU AgCenter
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Name: Christopher Clark
Title: Professor
Department: Plant Pathology and Crop Physiology Department
Organization: LSU AgCenter
Address 1: LSU Campus 302 Life Sciences Bldg.
Address 2: Baton Rouge, LA 70803
Phone Number: (225) 578-1381
Fax Number:


Postdoctoral Research Associate, Department of Plant Pathology, North Carolina State University, Raleigh, NC, 1976-77

Doctor of Philosophy, Cornell University - 1976
Master of Science, Cornell University - 1973
Bachelor of Science, Cornell University - 1970

Areas of Specialization/Research
My primary responsibility is for research on diseases of sweetpotato. Currently, my efforts are concentrated in two areas, cultivar decline and postharvest diseases. Cultivar decline is caused by accumulation of viruses, other pathogens, and mutations in the vegetative material used to propagate sweetpotatoes. We have helped develop a program for producing virus-tested sweetpotato seed and are currently investigating the etiology and epidemiology of the aphid-transmitted potyviruses and whitefly-transmitted begomoviruses that occur in sweetpotato in the U.S. and the bacterial soft rot pathogen, Erwinia chrysanthemi. We are also actively participating in a multidisciplinary, multi-state project funded by USDA RAMP that aims to develop an advisory program that will enable farmers to reduce use of pesticides that are used to control soil insects and Rhizopus soft rot on sweetpotato.

In addition to teaching the graduate level course in phytobacteriology, I devote some time to identifying bacterial diseases and help other commodity programs with research on bacterial diseases. I also collaborate with Dr. Gregg Pettis in the Department of Biological Sciences on research on the basic biology and molecular biology of the sweetpotato Streptomyces soil rot pathogen, Streptomyces ipomoeae.
I am also interested in efforts to reduce and rapidly respond to introduction or emergence of new pathogens/diseases and am a representative to the Southern Plant Diagnostic Network (SPDN).
Professional Experience
Research Contribution: In addition to the work documented in the references below, over the last 25 years, the multidisciplinary sweetpotato breeding team in the LSU AgCenter has released several cultivars of sweetpotato that have had disease resistance. In addition to Beauregard, which is currently grown on over 80% of US acreage and in several other countries, releases have included: Eureka, Travis, Hernandez, and Bienville. We have also worked with the personnel at the Sweet Potato Research Station in Chase, LA to develop a virus-tested foundation seed program which has been providing farmers since 1999.

Teaching Experience:
I teach Plant Health 7011 – Phytobacteriology I am organizing a newly approved course, PLHL 8800 - Practicum in Plant Pathology Participated in the past in teaching PLHL 4013 - Diseases of Economic Crops The lab on bacterial diseases in PLHL 4000, General Plant Pathology

Committee Assignments (University, Experiment Station and Departmental):

AgCenter Faculty Council member (2003-2004)
Plant Pathology Course and Curriculum Committee member
Refereed Journal Articles
LaBonte, D., Clark, C., Villordon, A., Cannon, J., Hoy, M., Sistrunk, M., Freeman, E., and Roberts, G. 2004. Yield of four generations of virus-tested sweetpotato. HortTechnology 14:1 - 3.

Carroll, H. W., Villordon, A. Q., Clark, C. A., LaBonte, D. R., and Hoy, M. W. 2004. Studies on Beauregard sweetpotato clones naturally infected with viruses. Int. J. Pest. Mgmt. 50:101 - 106.

Lotrakul, P., Valverde, R. A., and Clark, C. A. 2003. Properties of a begomovirus isolated from sweet potato [Ipomoea batatas (L.) Lam.] infected with Sweet potato leaf curl virus. Revista Mexicana de Fitopatologia 21:128 - 136.

Zhang, X., Clark, C. A., and Pettis, G. S. 2003. Interstrain inhibition in the sweet potato pathogen Streptomyces ipomoeae: Purification and characterization of a highly specific bacteriocin and cloning of its structural gene. Appl. Environ. Microbiol. 69:2201 - 2208.

Villordon, A., Q., Cannon, J. M., Carroll, H. L., Franklin, J. W., Clark, C. A., and LaBonte, D. R. 2003. Sweetpotato 'Beauregard' mericlones vary in yield, vine characteristics, and storage root size and shape attributes. HortScience 38:1089 - 1092.

Souto, E. R., Sim, J. Chen, J., Valverde, R. A., and Clark, C. A. 2003. Properties of Strains of Sweet potato feathery mottle virus and Two Newly Recognized Potyviruses Infecting Sweet Potato in the United States . Plant Disease 87:1226 - 1232.

LaBonte, D. R., Cannon, J. M., Clark, C. A., Villordon, A. Q., Wilson, P. W., Hammond, A. H., and Story, R. N. 2003. 'Bienville' sweetpotato. Hortscience 38:473 - 474.

Holmes, G. J., and Clark, C. A. 2002. First report of Geotrichum candidum as a pathogen of sweetpotato storage roots from flooded fields in North Carolina and Louisiana Plant Disease 86:695.

Harrison, H. F., Peterson, J. K., Clark, C. A., and Snook, M. E. 2001. Sweetpotato periderm components inhibit in vitro growth of root rotting fungi. Hortscience 36: 927-930.

Book and Book Chapter Contributions

Clark, C. A., Valverde, R. A., Fuentes, S., Salazar, L. F., and Moyer, J. W. 2002. Research for improved management of sweetpotato pests and diseases: Cultivar decline. Pages 103 - 112 in; Ames , T., ed. Proc. 1st Internat. Symp. on Sweetpotato, Acta Hort. 583.

Lotrakul, P., Valverde, R. A., Clark, C. A., Hurtt, S., and Hoy, M. W. 2002. Sweetpotato leaf curl virus and related geminiviruses in sweetpotato. Pages 135-141 in; Ames , T., ed. Proc. 1st Internat. Symp. on Sweetpotato, Acta Hort. 583.

C. A., Hoy, M. W., Valverde, R. A., La Bonte, D. R., and Cannon, J. M. 2002. Effects of viruses on sweetpotatoes in Louisiana, USA. Pages 238-241 in; Nakatani, M., and Komaki, K., eds. Potential of Root Crops for Food and Industrial Resources, Proc. Twelfth Symp. Internat. Soc. Trop. Root Crops, Sept. 10-16, 2000.

Loria, R., Clark, C. A., Bukhalid, R. A., and Fry, B. A. 2001. III. Gram-positive bacteria. B. Streptomyces. Pages 236 - 249 in: Schaad, N. W., Jones, J. B., and Chun, W., eds. Laboratory Guide for Identification of Plant Pathogenic Bacteria, 3rd Edition. APS Press, The American Phytopathological Society, St. Paul , MN .

Clark, C. A., and Valverde, R. A. 2001. Viruses and sweetpotato cultivar decline in
Louisiana , USA . Pages 62 - 69 in; Nakazawa, Y., and Ishiguro, K., eds. International Workshop on Sweetpotato Cultivar Decline Study, Proceedings, Kyushu National Agricultural Experiment Station, Miyakonjo , Japan .

Valverde, R. A., Lotrakul, P., and Clark, C. A. 2001. Properties and variability of Sweetpotato leaf curl virus. Pages 82 - 84, in; Nakazawa, Y., and Ishiguro, K., eds. International Workshop on Sweetpotato Cultivar Decline Study, Proceedings, Kyushu National Agricultural Experiment Station, Miyakonjo, Japan.

Clark, Christopher. 2000. Sweetpotato black rot. Pages 992-992 in: Maloy, O. C., and Murray, T. D., eds. Encyclopedia of Plant Pathology. John Wiley & Sons, Inc.

Clark,C. A., and Moyer, J. W. 1988. Compendium of Sweet Potato Diseases. APS Press, St. Paul, MN. 74 pp.
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