Identification of Zingiberenol and Murgantiol as Components of the Aggregation-Sex Pheromone of the Rice Stink Bug, Mormidea v-luteum (Heteroptera: Pentatomidae).

Mormidea v-luteum (Lichtenstein, 1796) feeds on commercial crops, such as rice and ryegrass, causing damage that slows growth and reduces productivity. With the aim of developing an eco-friendly control technique, we investigated the compounds involved in chemical communication in this species. The volatiles produced by a group of seven males or females allocated to different aerated glass chambers were collected for 24 h and analyzed by gas chromatograph/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy. The analyses showed six male-specific compounds, identified as two isomers of zingiberenol (compounds 1 and 2), three isomers of murgantiol (3, 5 and 6) and sesquipiperitol (4). Compounds 1 and 5 were the major components and were produced in a ratio of 6:4. The absolute stereochemistry of the two isomers of zingiberenol was established as (1S,4R,1'S)-1 and (1R,4R,1'S)-2 by chiral gas chromatography. Stereochemistry was not determined for all the other molecules. To confirm the attractiveness of these chemicals, bioassays were performed in a Y-tube olfactometer, first using crude extracts and, subsequently, synthetic compounds. Male volatiles were attractive to both sexes, demonstrating an aggregation pheromone. In bioassays with synthetic compounds, (1'S)-zingiberenol was highly attractive to both males and females. However, when (1'S)-murgantiol was tested, only females were attracted. Interestingly, when a mixture of zingiberenol and murgantiol isomers was tested, it was attractive to both sexes, with females more attracted to the mixture than to zingiberenol alone; males did not distinguish between treatments. Thus, the bioassay data suggest that the molecules have different functions in chemical communication of this species: zingiberenol acts primarily as an aggregation pheromone, while murgantiol plays a role as a sex pheromone.