Finding my way : Characterisation of maize roots volatiles that guide wireworms

Maize roots (Zea mays L.) can be damaged by various pests including soil-dwelling insects. Subterranean insects, often polyphagous, rely among other things on volatile organic compounds (VOCs) emitted by plant roots to locate and feed on them. Wireworms (Agriotes sp) are significant soil-dwelling pest in maize agriculture, as they feed on both roots and seedling crowns. Field surveys conducted in France have identified contrasted levels of attacks regarding maize varieties. In this study, our aim was to characterize the varietal odour profile of maize roots to better understand the VOCs driving the attraction of this pest. Six varieties were selected: three highly sensitivity to wireworm attacks; named Sens 1, Sens 3, Sens 4; and three tolerant varieties; namedTol1, Tol2, Tol 4. Plants (n = 4 per variety) were individually cultivated in a greenhouse using perlite substrate until reaching the four-leaves stage (BBCH14). This stage has been identified as the most vulnerable stage to insect attacks. Roots volatiles were collected using HiSorb sorbtive extraction, a high-sensitivity technique. Roots released a complex blend of 46 compounds from 9 chemical families, predominantly alcohols and aldehydes. Seven major compounds were consistently identified across all varieties: hexanal; 1-hexanol, 2-pentyl-furan; 1-hexadiene,3-ethyl-2-methyl; penten-3-one and aziridine 1-ehtenyl. Interestingly, sensitive and tolerant varieties were not different in terms of volatile organic compounds. Utilizing the HiSorb sorbtive extraction technique allowed us to identify a high diversity of compounds, even in low quantities. These findings suggest that roots odour profiles alone may not allow varietal discrimination by insects.