The effect of phagostimulant mixtures on deterrent receptor(s) in two crucifer-feeding lepidopterous species

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Abstract
Sinigrin was incorporated in varying concentrations into four background mixtures. One background mixture contained potassium chloride (KCl) and no stimulatory sugar or sugar alcohol, two backgrounds contained KCl and a single sugar or sugar alcohol (sucrose or inositol, respectively), and the fourth background contained KCl and both sugar and sugar alcohol (sucrose and inositol, respectively). The lateral sinigrin-sensitive cell of Mamestra configurata was suppressed by phagostimulants at a low sinigrin concentration range. Electrophysiological suppression of sinigrin-sensitive cells in both the lateral and medial sinigrin-sensitive cells of Trichoplusia ni was effective at a low to high sinigrin concentration range. Independent of sinigrin concentration, it appeared that inositol, sucrose, and their combination, equally suppressed the lateral sinigrin-sensitive cell of M.configurata and a combination of both inositol and sucrose suppressed the lateral and medial sinigrin-sensitive cells of T. ni . There was an interaction between inositol and sucrose; inositol did not suppress or enhance the response to sucrose of the sucrose-sensitive cells in either species, but sucrose suppressed the response of the medial M. configurata inositol-sensitive cell to inositol. Inositol and sucrose backgrounds were effective in suppressing responses to potassium chloride in M. configurata , but not in T. ni . These sensory-based mixture effects, all of which were suppressive, are used to propose mechanisms for the ameliorating effect of inositol and sucrose on the feeding deterrent action of sinigrin.