Plant glucosinolate content increases susceptibility to diamondback moth (Lepidoptera: Plutellidae) regardless of its diet

Glucosinolates are plant defense compounds used in host-plant recognition by insects specialized on Brassicaceae, such as the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae). We tested whether there were differences in oviposition and larval survival among three strains of P. xylostella after more than 100 generations continuously reared on cabbage leaves, pea leaves, and wheat germ-casein artificial diet. Pea leaves and wheat germ-casein diet contain no glucosinolates. Tests were conducted with a total of 30 different plant species, and their glucosinolate contents were determined. Two-choice oviposition tests (comparing each plant species to Arabidopsis thaliana L.) and no-choice oviposition tests showed that, regardless of diet, total glucosinolate content and chemical complexity index for glucosinolates were positively correlated with oviposition preference, total oviposition, and larval survival in P. xylostella across the wide range of plants tested. Our research shows that long-term feeding on glucosinolate-free diet hardly affects oviposition preference and larval survival in P. xylostella. Our study also suggests that, even when comparing different plant species, glucosinolate content is likely to be associated with host-plant preference and host-plant suitability in P. xylostella. This indicates that crop varieties with high glucosinolate content are likely to be more susceptible to damage by P. xylostella than crop varieties with lower glucosinolate content. Additional implications of these findings for management of this important pest are discussed. This is the first time that a study includes oviposition preference, total oviposition, larval survival, and glucosinolate content across such a wide range of plant species