Monday, December 10, 2007 - 9:17 AM

Banded cucumber beetle (Coleoptera: Chrysomelidae) resistance in romaine lettuce: Understanding latex chemistry

Amit Sethi, amit7@ufl.edu1, Hans T. Alborn, halborn@gainesville.usda.ufl.edu2, Heather J. McAuslane, hjmca@ufl.edu1, Russell T. Nagata, nagata@ufl.edu3, and Gregg S. Nuessly, gnuessly@ufl.edu3. (1) University of Florida, Department of Entomology & Nematology, PO Box 110620, Gainesville, FL, (2) USDA, Agricultural Research Service, 1600-1700 SW 23RD DRIVE, Gainesville, FL, (3) University of Florida, Everglades Research and Education Center, 3200 East Palm Beach Rd, Belle Glade, FL

Many plants subjected to herbivore damage exude latex, a rich source of numerous biochemicals that play important roles in host plant resistance. Our previous studies showed that fresh latex from Valmaine, a resistant cultivar of romaine lettuce Lactuca sativa L., applied to artificial diet is highly deterrent to feeding by banded cucumber beetle, Diabrotica balteata LeConte, compared to the latex of a closely related susceptible cultivar Tall Guzmaine. We hypothesized that differences in latex chemistry between Valmaine and Tall Guzmaine contribute to the insect resistance of Valmaine. In our current study, latex from both Valmaine and Tall Guzmaine was dissolved in three water/methanol combinations and methylene chloride, then applied to diet and offered to beetles under no-choice situations. Valmaine latex extracted with water:methanol (20:80) strongly inhibited beetle feeding when applied to the surface of diet. Further clean-up of water:methanol (20:80) extract of Valmaine latex was done by passing it through C18 and cation-exchange resins. Subsequently, deterrent compounds were eluted by passing 0.5 M NaCl through cation-exchange resin. Isolation and identification of the deterrent compounds is being carried out using HPLC-MS of cation-exchange extract. Our studies suggest that latex ingredients play a key role in Valmaine resistance to D. balteata, and latex may be a source of bioactive compounds with a potential use in pest management.

Species 1: Coleoptera Chrysomelidae Diabrotica balteata (banded cucumber beetle)