Behavioral and electrophysiological dose-response relationships in adult western corn rootworm (Diabrotica virgifera virgifera LeConte) for host pollen amino acids

A strong correlation is shown between taste cell inputs and phagostimulatory outputs with predominant dietary pollen amino acids for western corn rootworm, Diabrotica virgifera virgifera. Behavioral and electrophysiological dose-response profiles in adult beetles are presented for five major free amino acids in host pollens. Differential responses were found with strongest phagostimulation and sensory response elicited by L- alanine and L-serine, followed in order by L-proline and β-alanine. y- Aminobutyric acid gave the weakest and most sporadic response. ED₅₀ values for phagostimulation and chemosensory input were 28.3 nmol/disk and 13 mM, respectively, for L-alanine and 17 nmol/disk and 11 mM, respectively, for serine. Threshold values for the responses were approximately 1-2 mM. These behavioral and chemosensory dose-response ranges correspond closely to levels of free amino acids present in host plant pollens. Use of these response values in development of a pollen chemosensory code for western corn rootworm feeding is discussed.