Beauveria bassiana endophytic colonisation alters volatile profiles without affecting lacewing oviposition and is modulated by plant genotype

Abstract: Biological control strategies integrating entomopathogenic ascomycetes (EA) and
natural enemies are a key component for Integrated Pest Management (IPM) programs. Among EA, Beauveria bassiana has demonstrated efficacy against aphids, targeting them through integumentary contact, but also as a plant endophyte, colonising systemically the crop. This endophytic colonisation can alter the chemical ecology of the plant, influencing multitrophic interactions in the context of IPM strategies. Additionally, the degree of endophytic colonisation can vary among plant species and fungal strains, raising questions about possible variations among different cultivars of the same host plant species. Hereby, this study evaluates endophytic colonisation and its effects on the volatile profiles of three different melon cultivars (Cucumis melo L. cv. Galia, Futuro and Rinconete) by the AE B. bassiana. Colonisation rates ranged from 73.0 % to 85.0 %, showing the cv. Galia the highest percentage. Analyses revealed a core set of two volatiles (cis-3-hexenal and N,N-dimethyl-1-dodecanamine) common across all cultivars endophytically colonised by B. bassiana. Additionally, cultivar-specific VOCs such as cis-3-hexenol and β-phellandrene (cv. Galia), cinnamaldehyde and cinnamyl alcohol (cv. Futuro), and styrene and acetophenone (cv. Rinconete) were identified. Understanding these changes associated to the plant genotype is essential for optimising the behaviour of natural enemies within IPM programs. In a second experiment, the impact of colonisation on the multitrophic system involving melon cv. Galia, Aphis gossypii, and Chrysoperla carnea was assessed by olfactometer bioassays. Lacewings did not exhibit a distinct preference for any treatment. However, volatile analysis revealed quantitative differences in the volatile profile from B. bassiana-colonised plants and a different volatile response of these plants when they were infested by the aphids, which may influence other plant-insect interactions. This work underscores the potential of endophytic EA combined with other natural enemies in IPM programs.