Isolation and characterization of host recognition cues in corn roots for larvae of the western corn rootworm (Coleoptera: Chrysomelidae)
2013
Bernklau, E. J. | Hibbard, B. E. | Bjostad, L. B.
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 comprised of both polar and non-polar 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). GC-MS analysis determined that F-1 contained a blend of small sugars, diacids, amino acids and inorganic compounds. The non-polar 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 non-polar fractions or to F-1 alone. Methyl esterification of fraction B, followed by GC-FAME analysis, confirmed that fraction B was comprised of primarily lipids containing fatty acyl groups.
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