Metabolomics reveals constitutive metabolites that contribute resistance to fall webworm (Hyphantria cunea) in Populus deltoides

Abstract

Constitutive chemical defenses play important roles in protecting trees against insects. Studying the constitutive chemical resistance of trees to insect would thus help control the pests and minimize the associated ecological and economic losses. Poplar is an ecologically and economically important tree species but has been greatly damaged by fall webworm (Hyphantria cunea) in China. Here we investigated H. cunea resistance in 7 poplar cultivars commonly planted in China by applying bioassays, and analyzed metabolic profiles of H. cunea -resistant and -susceptible cultivars. Substantial variation in chemical profiles between resistant and susceptible genotypes was detected. Ninety-two distinguishing metabolites were identified. Correlation analysis indicated that hydroxycinnamates, benzenoids and their derivatives significantly positively correlated with resistance against H. cunea, whereas sucrose, glutamic acid and myo-inositol showed negative correlations. Bioassays of H. cunea given an artificial diet supplemented with these compounds confirmed their effects but indicated that they each have different roles. Metabolite enrichment and gene expression analysis showed that phenylpropanoid biosynthesis in poplar is important for constitutive resistance against H. cunea. Induced experiment found that some of the constitutive resistance-related metabolites were induced by H. cunea indicating that these metabolites also play a role in induced resistance. This study provides further insight into the molecular mechanisms behind H. cunea resistance in poplar and suggests candidate metabolites that may serve as biomarkers for breeding of resistant poplar cultivars.