Highlights on the Mechanism of <i>Eucalyptus camaldulensis</i> Dehnh. Psyllid Infestation: Insight From Its Relationship With the Chemical Composition of Essential Oil Through Computational Study

Glycaspis brimblecombei Moore is an invasive insect pest that primarily targets Eucalyptus species, with a particular preference for Eucalyptus camaldulensis. The mechanism of host selection involves the recognition of host volatiles by odorant binding proteins (OBPs), which play crucial roles in various insect behaviors, including intersexual communication, oviposition, and interactions with host plants. The objective of this study was to identify the phytochemicals responsible for this host preference. The chemical composition of the essential oil extracted from the infested leaves of E. camaldulensis Dehnh. was analyzed using gas chromatography-mass spectrometry, revealing a total of 66 compounds that accounted for approximately 97.218% of the total oil. The major components identified were p-Cymene (29.78%), β-Phellandrene (15.55%), and Crypton (9.34%). Among the 66 volatiles detected, nine compounds, including Farnesol, Nirolidol, (Z,Z)-Farnesal, (Z,E)-Farnesal, Valerenol, β-Cubebene, cis-Linaloloxide, trans-Linalool oxide, and L-Linalool, exhibited the lowest Gibbs free energy (ΔG) values, ranging from -7.74 to -6.84 kcal/mol and favorable interactions with the hydrophobic cavity of the OBP CcapOBP22. Molecular dynamics simulations indicated that the docked models with (Z,E)-Farnesal, cis-Linaloloxide, and β-Cubebene were flexible and stable. This study may inform future pest management strategies targeting G. brimblecombei.