Isolation and characterization of host recognition cues in corn roots for larvae of the western corn rootworm (Coleoptera: Chrysomelidae).
Behavioral bioassays were used to isolate compounds from germinating corn roots that elicit a host recognition response (tight-turning behavior) by neonate larvae of the western corn rootworm Diabrotica virgifera virgifera LeConte. When a behaviorally active extract of germinating corn roots was separated into an aqueous partition and a hexane partition, significantly more larvae (P < 0.05) responded to the recombined partitions than to either partition alone, demonstrating that the active material is a blend comprising both polar and nonpolar compounds. When the aqueous partition was separated with reverse-phase solid phase extraction, most of the behavioral activity was retained in the 100% water fraction (F-1). Gas chromatography-mass spectrometry analysis determined that F-1 contained a blend of small sugars, diacids, amino acids, and inorganic compounds. The nonpolar partition was separated on a silica column, and the resulting fractions were tested in combination with F-1 from the aqueous separation. More than 70% of larvae responded to the 100% acetone fraction (fraction B) in combination with F-1, and the response to this treatment was significantly higher than responses to the other nonpolar fractions or to F-1 alone. Methyl esterification of fraction B, followed by gas chromatographic fatty acid methyl ester analysis, confirmed that fraction B primarily consisted of lipids containing fatty acyl groups.
Department of Bioagricultural Sciences and Pest Management, Colorado State University, Campus Delivery 1177, Fort Collins, CO 80523, USA. ebernklau@lamar.colostate.edu
E J
EJ
Bernklau
USDA-ARS, University of Missouri, 205 Curtis Hall, Columbia, MO 65211, USA.
B E
BE
Hibbard
Department of Bioagricultural Sciences and Pest Management, Colorado State University, Campus Delivery 1177, Fort Collins, CO 80523, USA.
L B
LB
Bjostad
D000818:Animals; D002633:Chemotaxis; D001517:Coleoptera / Q000254:growth & development / Q000502:physiology*; D003463:Cues; D008401:Gas Chromatography-Mass Spectrometry; D007814:Larva / Q000254:growth & development / Q000502:physiology; D010936:Plant Extracts / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry* / Q000254:growth & development; D003313:Zea mays / Q000737:chemistry* / Q000254:growth & development
D010936:Plant Extracts