Hex-3(Z)-enyl butyrate: a key volatile compound conferring resistance against Southeast Asian Thrips ( Thrips parvispinus ) in Capsicum spp

Abstract Chilli incurs substantial yield losses due to Thrips parvispinus (Karny) infestation, necessitating sustainable resistance breeding strategies. Understanding biochemical basis of resistance will help in exploring the candidate metabolites for indirect selection. LC–MS and GC–MS profiling of two resistant (IIHR-B-HP-79, IIHR 4550) and two susceptible (IIHR 3455, IIHR 4604) chilli accessions were performed. LC–MS profiling revealed Inositol with higher levels in susceptible accession IIHR 3455 (8.74 and 0.33 μg/g; VIP score: 2 and 2.5 under control and infested conditions respectively), indicating its role as a stress-induced metabolite rather than a marker for resistance. Secondary metabolites contribution to resistance was genotype-specific and may possibly be driven by complex interactions among these metabolites. Untargeted leaf volatile profiling revealed Hex-3(Z)-enyl butyrate as a significant volatile compound in the resistant accessions IIHR 4550 and IIHR-B-HP-79. Its high accumulation across two different species suggests that its production is not strictly species-specific. Validation of Hex-3(Z)-enyl butyrate through bioassays and olfactometer studies demonstrated reduced scraping damage percentage at 8 and 16 µL-L concentrations in leaf dip bioassays. Four-arm olfactometer studies indicated that Hex-3(Z)-enyl butyrate significantly affected T. parvispinus time spent and entries at 16 µL-L. Identified metabolites defences can serve as markers for breeding and also can be explored in pest management strategies.