Characterisation of aphid antixenosis in aphid-resistant ancestor wheat,Triticum monococcum

Abstract

AbstractBACKGROUNDDue to the increasing presence of insecticide resistance across cereal aphid populations, new aphid management strategies, including the engineering of host resistance to aphids into commercial wheat varieties, are required. Previous studies have identified ancestor wheat,Triticum monococcumaccessions MDR045 and MDR049, with resistance against the grain aphid,Sitobion avenae. To test the hypothesis that resistance can be accounted for by antixenosis (reduced attractiveness of host plants)viathe release of repellent volatile organic compounds (VOCs), we explored the response ofS. avenaeto MDR045 and MDR049 followingS. avenaeherbivory, using behaviour and electrophysiology experiments.RESULTSIn four-arm olfactometry assays, alateS. avenaeshowed aphid-density dependent reduced preference to VOC extracts fromT. monococcumMDR045 and MDR049. By contrast, alateS. avenaeshowed aphid-density dependent increased preference to extracts from hexaploid wheat,T. aestivumvar Solstice andT. monococcumMDR037. Coupled gas chromatography-electroantennography (GC- EAG), using the antennae of alateS. avenae, located 24 electrophysiologically active compounds across all tested accessions. Synthetic blends created from 21 identified EAG-active compounds confirmed bioactivity of corresponding VOC extracts in four-arm olfactometry assays against alateS. avenae.CONCLUSIONOur data suggest that resistance ofT. monococcumMDR045 and MDR049 toS. avenaecan be at least partially accounted for by antixenosis, through antennal perception of specific repellent VOC blends induced byS. avenaefeeding behaviour.