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Plant Physiologist
BLDG 001, Room 227, BARC-West
Beltsville, MD 20705
Phone: 301-504-5379; FAX: 301-504-6491

Summary of Research

Dr. Lydon is the Lead Scientist and contributes 100% to the Weed Biocontrol Project. Research goals are:

1) Enhance the efficacy and reduce the specificity of developed or potential microbial herbicides using recombinant DNA techniques. The biological activity of microbial herbicides are enhanced by genetically modifying biocontrol microorganisms with genes from bacteria required for phytotoxin production. Genes are introduced using recombinant DNA technologies. Transformed organisms are evaluated for phytotoxin production and resistance using screening procedures, bacterial bioassays, chromatographic techniques, spectrophotometric techniques, and enzymological and molecular methods. Selected transformants are compared with wild-type organisms for control of target weeds, related weed species, and their effect on crop plants. Markers for monitoring the dispersal of microbial weed biological control agents are developed using molecular genetic methodologies based on genes specific for the weed pathogens.

2) Determine the herbicidal potential of microbial, and to a lesser extent, plant metabolites. Investigate the physiological processes affected by those metabolites determined to be phytotoxic, establish site of action at the molecular level, and determine the molecular genetics of phytotoxin production. Natural products tested are extracted from producing organisms. Efficacy of natural phytotoxins is determined using bioassays and whole plant tests. Mode of action is determined using chromatographic techniques, spectrophotometric techniques, and enzymological methods. The genes required for the production of microbial phytotoxins are identified and isolated using Tn5 mutagenesis and related molecular biological techniques. To broaden the scope of this research, collaborations have been established with Dr. Robin Mitchell, Chemist and discoverer of the phytotoxins phaseolotoxin and tagetitoxin, Hort Research, Mt Albert Research Centre, Auckland, New Zealand and Dr. Ding Jin, Molecular Biologist and expert on RNA polymerase, Laboratory of Molecular Biology, NIC, NIH, Bethesda, Maryland.

3) Determine the potential of Aceria anthocoptes as a biological control agent of Canada thistle (Cirsium arevnese) and its role as a vector of plant diseases that impact Canada thistle. The host range of A. anthocoptes is determined by surveying existing populations of Cirsium species and by conducting host range tests with a range of Cirsium species under greenhouse conditions. Molecular genetic methodologies are developed to compliment morphological profiles of A. anthocoptes to increase the accuracy of the identification of the mite with respect to other eriophyid mites that may be harbored by Cirsium species.

Publications (1999-present)

Ochoa, R., E. Erbe, W.P. Wergin, C. Frye, and J. Lydon. 1999. The presence of Aceria anthocoptes (NALEPA) (ACARI: ERIOPHYIDAE) on Cirsium species in the United States. International Journal of Acarology 27:179-187.

Lydon, J. and S.O. Duke. 1999. Inhibitors of glutamine synthetase. In - Plant Amino Acids, ed. Singh, B., Marcel Dekker, Inc., New York, pp. 445-463. (Invited book chapter)

Lydon, J. and C.D. Patterson. 2001. Detection of tabtoxin-producing strains of Pseudomonas syringae by PCR. Letters in Applied Microbiology 32:166-170.

Baker, C.J., N.R. O'Neill, K. Deahl, and J. Lydon. 2002. Continuous production of extracellular antioxidants in suspension cells attenuates the oxidative burst detected in plant microbe interactions. Plant Physiology and Biochemistry 40:641-644.

Mills, D.J., C.B. Coffman, J.R. Teasdale, K.L. Everts, A.A. Abdul-Baki, J. Lydon, and J.D. Anderson. 2002. Foliar disease in fresh-market tomato grown in different bed strategies and fungicide spray programs. Plant Disease 86:955-959.

Bewick, T. and J. Lydon. Biological Control of Weeds - It's a Natrual. 2002. Weed Science Society of America, Biological Control of Weeds Committee, 8 pp. (Brochure).

Duke, S.O., B.E. Scheffler., D. Boyette, J. Lydon, and A. Oliva. 2003. Biotechnology for the control of weeds. In press. (Invited book chapter)