Abstract
SummaryHerbivorous insects use olfactory cues to locate their host plant within a complex olfactory landscape. One such example is the European grapevine moth Lobesia botrana, a key pest of the grape in the Palearctic region, which recently expanded both its geographical and host plant range. Previous studies have showed that a synthetic blend of the three terpenoids, (E)‐β‐caryophyllene, (E)‐β‐farnesene and (E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT), was as attractive for the moth as the complete grape odour profile in laboratory conditions. The same studies also showed that the specific ratio of these compounds in the grape bouquet was crucial because a percentage variation in any of the three volatiles resulted in almost complete inhibition of the blend's attractiveness. Here, we report on the creation of stable grapevine transgenic lines, with modified (E)‐β‐caryophyllene and (E)‐β‐farnesene emission and thus with an altered ratio compared to the original plants. When headspace collections from these plants were tested in wind tunnel behavioural assays, they were less attractive than control extracts. This result was confirmed by testing synthetic blends imitating the ratio found on natural and transformed plants, as well as by testing the plants themselves. With this evidence, we suggest that a strategy based on volatile ratio modification may also interfere with the host‐finding behaviour of L. botrana in the field, creating avenues for new pest control methods.
Highlights
Terpenoids constitute the biggest class of plant metabolites involved both in primary (Croteau et al, 2000) and secondary metabolism (Zwenger and Basu, 2008)
All terpenes formally derive from the C5 isomers isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), whose biosynthesis can take place in plants via two distinct pathways: the mevalonate pathway (MVA) in the cytoplasm and the MEP/DOXP pathway in the chloroplast (Rohmer, 1999)
In the last step of the pathway, precursors are converted to terpenes by terpene synthase (TPS) enzymes, which are usually coded by gene families of 20–150 members in each species (Chen et al, 2011)
Summary
Terpenoids constitute the biggest class of plant metabolites involved both in primary (Croteau et al, 2000) and secondary metabolism (Zwenger and Basu, 2008). Terpenes have many ecological roles, such as direct and indirect defence against pathogens and insects (Hasegawa et al, 2010; Heiling et al, 2010; Huang et al, 2012; Unsicker et al, 2009), attraction of pollinators (Dudareva and Pichersky, 2000) and mutualistic fungi (Ditengou et al, 2015), as well as being used as signals for plant-to-plant communication (Arimura et al, 2000) As semiochemicals, their emission is often exploited by phytophagous insects, which use them as kairomones to recognize and locate their host plants (Bruce et al, 2005).
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