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Title: Restoring a Maize Root Signal That Attracts Insect-killing Nematodes

Author
item DEGENHARDT, JOERG
item HILTPOLD, IVAN
item HOLLNER, TOBIAS
item FREY, MONIKA
item GIERL, ALFONS
item GERSHENZON, JONATHAN
item Hibbard, Bruce
item ELLERSIECK, MARK
item TURLINGS, TED C J

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2009
Publication Date: 8/4/2009
Citation: Degenhardt, J., Hiltpold, I., Hollner, T.G., Frey, M., Gierl, A., Gershenzon, J., Hibbard, B.E., Ellersieck, M.R., Turlings, T. 2009. Restoring a Maize Root Signal That Attracts Insect-killing Nematodes. Proceedings of the National Academy of Sciences. 106:13213-13218.

Interpretive Summary: When attacked by insects, plants emit volatiles that can serve as foraging cues for natural enemies of herbivorous insects. It has been proposed that the emissions of these volatile signals can be manipulated to improve crop protection. The western corn rootworm is the most important insect pest of corn in the United States and is becoming a more important pest in parts of Europe. Recently, an entomopathogenic nematode species that can control the western corn rootworm was documented to be attracted by a chemical released by ancestral corn and European lines when under rootworm attack, but not most American varieties. To restore nematode attraction, a non-producing corn line was transformed to release this nematode attractant. In rootworm-infested field plots in which we released nematodes, transformed plants received significantly less root damage and had 60% fewer adult beetles emerge than isogenic lines. This demonstration that plant volatile emissions can be manipulated to enhance the effectiveness of biological control agents opens the way for a novel ecologically sound pest control strategy.

Technical Abstract: When attacked by insects, plants emit volatiles that can serve as foraging cues for natural enemies of herbivorous insects. It has been proposed that the emissions of these volatile signals can be manipulated to improve crop protection. Here we demonstrate the full potential of this strategy by restoring the emission of a specific belowground signal emitted by insect-damaged maize roots. This signal, the sesquiterpene (E)- ß-caryophyllene, is highly attractive to the entomopathogenic nematode Heterorhabditis megidis. (E)-ß-Caryophyllene is emitted by ancestral maize and European lines, but most American varieties have lost this ability and do not attract the nematode, which is much less effective as a control agent of the larvae of the western corn rootworm, Diabrotica virgifera virgifera, a ferocious root pest. To restore nematode attraction, a non-producing maize line was transformed with a caryophyllene-synthase gene from oregano, resulting in constitutive emissions of (E)-ß-caryophyllene. In rootworm-infested field plots in which we released nematodes, transformed plants received significantly less root damage and had 60% fewer adult beetles emerge than isogenic lines. This demonstration that plant volatile emissions can be manipulated to enhance the effectiveness of biological control agents opens the way for a novel ecologically sound pest control strategy.