PARENT SESSION
Poster Session #62: Parasite-Host Interactions.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Does herbivory by whiteflies affect pathogen performance on tomato?

BOROWICZ, VICTORIA^*,1,2, ALBRECHT, UTE¹, POWELL, CHARLES³, MAYER, RICHARD¹, ¹ US Horticultural Research Laboratory, Ft. Pierce, FL² Illinois State University, Normal, IL³ University of Florida-IFAS CREC, Ft. Pierce, FL

ABSTRACT- Feeding by whitefly (Bemisia argentifolii) nymphs induces the same biochemical pathways induced by microbial pathogens and results in production of proteins associated with disease resistance. We asked if feeding by whiteflies reduces subsequent infection by three pathogens of tomato: powdery mildew (PM), bacterial spot (BS), and tomato mottle virus (TMV). Tomato plants were raised with whiteflies for 5 weeks beginning 19 days post germination or kept free of whiteflies. Two days after treatment with insecticide to kill all insects the plants were inoculated with water (control), BS, PM, or TMV. Phytochemical analysis prior to pathogen inoculation showed that whitefly treatment had significantly increased the activities of foliar chitinase and peroxidase, two pathogenesis-related proteins associated with disease resistance. Evaluation of pathogen growth 3 weeks after inoculation showed that whitefly feeding significantly reduced incidence of PM. However, TMV levels evaluated by ELISA were not significantly affected by whitefly feeding, and BS failed to grow regardless of whitefly treatment. Six weeks after inoculation with pathogens the activities of chitinase and peroxidase were still elevated in plants initially fed on by whiteflies but continuing pathogen infection had no effect on these enzymes. Our study suggests that whitefly herbivory can affect plant-pathogen relations but the effect may vary among pathogen types.

KEY WORDS: disease resistance, pathogenesis-related proteins, foliar herbivory