Dr. Richard T. Mayer, USHRL, ARS, USDA, Fort Pierce, Florida

Research is performed on plant-insect and plant-insect-pathogen interactions to either discover new forms of resistance or how to utilize existing forms of resistance against insects and pathogens. Pest insects include the citrus root weevil, the silverleaf whitefly, and aphids and diseases that may be vectored or facilitated by the insect, i.e., phytophthora, gemniviruses, etc. It is possible to boost plant defensive systems by application of elicitors. Several new environmentally friendly elicitor products have been developed that are now marketed. Plant defensive systems include enzymes and proteins, and chemical products resulting from their action. The levels of desired defensive materials in plants can be elevated by genetically engineering plants to overproduce the materials so that increased resistance results. Numerous genes from citrus have been identified and cloned that may serve to increase resistance. Several genetically enhanced/engineered plants have been produced that contain heightened levels of the materials; these plants are currently being evaluated for resistance against insect pests and pathogens.

Development of control methods for Diaprepes abbreviatus include projects on:

Use of larval digestive inhibitors to control soil populations of Diaprepes larvae.
Use of biological control agents especially microbials.
Identification of Diaprepes resistance factors in citrus.

Identification of citrus genes that can raise resistance to insect pests and pathogens include projects on:

Defensive proteins such as glucanases, chitinases, peroxidases, stress proteins, anti-phytopthora proteins, polygalacturonase inhibitor proteins, etc.
Isolation and characterization of proteins and genes involved in the phenylpropanoid pathway in citrus.
Isolation and characterization of proteins and genes involved in bioflavonoid metabolism in citrus.

Characterization of insect-host plant and insect vector-host plant-pathogen interactions include projects on:

Doostdar, H., and Mayer, R. T. Methods and compositions for controlling coleopteran infestations. U.S. Patent filed Dec. 11, 2000.

Doostdar, H., Burke, M. D., Mayer, R. T. Bioflavonoids: Selective substrates and inhibitors for cytochrome P450 CYP1A and CYP1B1. Toxicology. 144: 31-38. 2000.

Inbar, M., Doostdar, H., Mayer, R. T. Suitability of stressed and vigorous plants to various insect herbivores. OIKOS. Accepted Aug. 28, 2000.

Inbar, M., Doostdar, H., Gerling, D., Mayer, R. T. Induction of systemic acquired resistance in cotton by BTH has a negligible effect on Phytophagous insects. Entomologia Experimtalis et Applicata. Accepted Nov. 3, 2000.

Inbar, M., Doostdar, H., Leibee, G. L., and Mayer, R. T. The role of rapidly-induced plant responses in asymmetric interspecific interactions among insect herbivores. J. Chem. Ecol. 25:1961-1979. 1999.

McCollum, T. G., Doostdar, H., Niedz, R., Mayer, R. T., Burkhart, and McDonald, R. E. Biochemical and molecular characterization of a ß-1,3-endoglucanase from 'Valencia' orange callus. J. Plant Physiol. 155:16-23. 1999.

Inbar, M., Doostdar, H., and Mayer, R. T. The effects of sessile insects (whitefly nymphs) on leaf-chewing caterpillars. Environ. Entomol. 28: 353-357. 1999.

Inbar, M., Doostdar, H., Sonoda, R. M., Leibee, G. L., Mayer, R. T. Elicitors of plant defensive systems reduce insect densities and disease incidence. Chem. Ecol. 24:135-149. 1997.

Doostdar, H., McCollum, T. G., and Mayer, R. T. Purification and characterization of an endo-polygalacturonase from the gut of West Indies sugarcane rootstalk borer weevil (Diaprepes abbreviatus L.) larvae. Comp. Biochem. Physiol. 118B: 861-867. 1997.

Mayer, R. T., McCollum, T. G., McDonald, R. E., Polston, J. E., and Doostdar, H. Bemisia feeding induces pathogenesis-related proteins in tomato. In: Bemisia 1995: Taxonomy, biology, damage, control and management. (D. Gerling and R. T. Mayer, Eds.) Intercept Ltd., Andover, Hants, UK. pp. 179-187. 1996.

Mayer, R. T., McCollum, T. G., Niedz, R. P., Hearn, C. J., McDonald, R. E., Berdis, E. and Doostdar, H. Characterization of Seven Basic Endochitinases Isolated from Cell Cultures of Citrus sinensis (L.). Planta. 200:289-295. 1996.

Mayer, R. T., Shapiro, J. P., Berdis, E., Hearn, C. J., McCollum, T. G., McDonald, R. E., and Doostdar, H. Citrus rootstock responses to herbivory by larvae of the sugarcane rootstock borer weevil (Diaprepes abbreviatus L.). Physiologia Plantarum 94:164-173. 1995.

Doostdar, H., Shapiro, J. P., Niedz, R. P., Burke, M. D., McCollum, T. G., McDonald, R. E., and Mayer, R. T. A cytochrome P450 mediated naringenin 3'-hydroxylase from sweet orange cell cultures. Plant and Cell Physiology 36:69-77. 1995.