AbstractPlants use a wide array of secondary metabolites including terpenes as defense against herbivore and pathogen attack, which can be constitutively expressed or induced. Here, we investigated aspects of the chemical and molecular basis of resistance against the exotic rust fungusAustropuccinia psidiiinMelaleuca quinquenervia, with a focus on terpenes. Foliar terpenes of resistant and susceptible plants were quantified, and we assessed whether chemotypic variation contributed to resistance to infection byA. psidii. We found that chemotypes did not contribute to the resistance and susceptibility ofM. quinquenervia. However, in one of the chemotypes (Chemotype 2), susceptible plants showed higher concentrations of several terpenes including α‐pinene, limonene, 1,8‐cineole, and viridiflorol compared with resistant plants. Transcriptome profiling of these plants showed that severalTPSgenes were strongly induced in response to infection byA. psidii. Functional characterization of theseTPSshowed them to be mono‐ and sesquiterpene synthases producing compounds including 1,8‐cineole, β‐caryophyllene, viridiflorol and nerolidol. The expression of theseTPSgenes correlated with metabolite data in a susceptible plant. These results suggest the complexity of resistance mechanism regulated byM.quinquenerviaand that modulation of terpenes may be one of the components that contribute to resistance againstA. psidii.