Minor Components Play an Important Role in Interspecific Recognition of Insects: A Basis to Pheromone Based Electronic Monitoring Tools for Rice Pests

Abstract

Several lepidopteran species share the same pheromone blend consisting of (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-9-hexadecenal (Z9-16:Ald) at different ratios and active doses. In rice pest Chilo suppressalis, (Z)-11-hexadecenol, (Z11-16:OH) and octadecanal (18:Ald) were identified as minor components in the pheromone gland of female moths, and these components were previously not considered as part of the sex pheromone of C. suppressalis. Z11-16:Ald, Z9-16:Ald and (Z)-13-octadecenal (Z13-18:Ald) frequently trapped other lepidopteran species, such as rice pests Scirpophaga incertulas and Mythimna separate, corn and vegetable pests Helicoverpa armigera in the field, suggesting a lack of specificity in the pheromone blend. Our data showed that the minor component Z11-16:OH did not have a synergistic effect on the attractiveness of the blend to C. suppressalis; however, pheromone mixtures containing Z11-16:OH failed in trapping male H. armigera moths. We confirmed the identity and specificity of the C. suppressalis sex pheromone and demonstrated that Z11-16:OH plays a key role in the reproductive isolation of C. suppressalis, M. separata, and H. armigera moths, and a similar role of Z9-18:Ald in that of S. incertulas and C. suppressalis. This phenomenon could be more widely applicable to interspecific interactions in the pheromone communication between insects, which is crucial to developing the electronic automatic counting device for automatically monitoring the pest population by pheromone trapping based on its species specificity.

A major locus controls a biologically active pheromone component inHeliconius melpomene

“…Male moth pheromones follow this wide distribution of chemical classes, with only a few species using fatty acid derived compounds, most notably Heliothis virescens which uses octadecanol, hexadecanol, and related compounds but not the respective aldehydes such as octadecanal (Conner & Iyengar 2016). In contrast to H. melpomene , we have failed to discover any physiologically active pheromones in H. cydno , perhaps because a minor component or components not tested here is biologically active (McCormick et al 2014; Chen et al 2018). Attempts to identify the H. cydno pheromone using GC-coupled electroantennographic detection were unfortunately unsuccessful due to technical issues with the setup, and thus the H. cydno pheromone remains undescribed.…”

“…As a fully saturated unbranched compound, octadecanal is unusual in being unrelated to known female pheromone types in moths, which largely use unsaturated or methylated hydrocarbons with or without terminal functional groups (Löfstedt et al 2016). The activity of octadecanal as a pheromone, however, has been tested behaviorally or electrophysiologically in eight species of Lepidoptera across a variety of families (Tatsuki et al 1983; Cork et al 1988; Tumlinson et al 1989; Ho et al 1996; McElfresh et al 2000; Yildizhan et al 2009; El-Sayed et al 2011; Pires et al 2015; Chen et al 2018). Only in Cerconota anonella (Pires et al 2015), and now in Heliconius melpomene , has some electrophysiological and behavioral activity been seen.…”

“…Darragh et al 2019b), identifying which components of these complex chemical bouquets are responsible for pheromonal communication is a considerable challenge. This is particularly true as even minor compounds can have major effects (McCormick et al 2014; Chen et al 2018). Determining pheromone bioactivity requires screening compounds via physiological activity followed by behavioral verification, and in many cases pheromone bouquet composition is known but the bioactive components remain unidentified.…”

A major locus controls a biologically active pheromone component inHeliconius melpomene

“…; Chen et al. ). Attempts to identify the H. cydno pheromone using GC‐coupled electroantennographic detection were unfortunately unsuccessful due to technical issues with the setup, and thus the H. cydno pheromone remains undescribed.…”

“…; Chen et al. ). Determining pheromone bioactivity requires screening compounds via physiological activity followed by behavioral verification, and in many cases pheromone bouquet composition is known but the bioactive components remain unidentified.…”