Volatilomics of Capsicum pubescens Plants Infested by Solenopsis geminata: Unraveling the Role of Oleic and Palmitic Acids in Plant-Fire Ant Interaction

Abstract

Solenopsis geminata is an aggressive pest of manzano pepper (Capsicum pubescens) crops. Herein, we report on the volatilomics profiling of manzano pepper plants obtained during S. geminata infestation by solid-phase microextraction coupled with gas chromatography-mass spectrometry. As a result, 68 volatile organic compounds were identified from ants, non-infested plants, and infested plants, including terpenes, esters, steroids, aldehydes, phenylpropanoids, and fatty acids. As a remarkable finding, oleic and palmitic acids were the main compounds released during ant infestation. These fatty acids were evaluated as biocidal or repellent agents under in vitro and in situ conditions. From these experiments, the biocidal effect of palmitic acid was more potent (median lethal dose [LC₅₀], 0.97 mg/cm²) than that of oleic acid (LC₅₀, 5.03 mg/cm²) on S. geminata workers. Nevertheless, only oleic acid had a repellent effect under in situ conditions (p < 0.01). Our results represent new insights into the role of both fatty acids in manzano pepper defense mechanisms.