Background: Epichloë endophytes provide many benefits to host plants, including enhanced insect resistance. Fungal alkaloids are usually thought to be responsible for the endophyte-conferred herbivore resistance. Nonetheless, the fungal alkaloid profiles and concentrations may vary considerably among grass-endophyte systems. This indicates that apart from fungal alkaloids, additional mechanisms such as endophyte-mediated host defense are likely contributed to endophyte-grass-insect interactions. In this study, we addressed this issue by investigating the effect of Epichloë on the defense responses of Achnatherum sibiricum against locusts.
Results: The results showed that Epichloë endophytes increased locust resistance of A. sibiricum in both choice and non-choice feeding experiments. In no feeding groups, endophyte infection increased the content of jasmonic acid (JA) and ethylene (ET), chitinase activity, and the biosynthetic gene expression of the relevant pathways. Endophyte infection also increased the content of total phenolics and condensed tannins. These indicators were negatively correlated with leaf consumption. In locust feeding groups, endophyte infection increased trypsin inhibitor activity. Exogenous application of phytohormones further proved that JA and ET reduced the consumption of A. sibiricum by locusts.
Conclusion: The present study showed that endophyte-conferred host defense was mainly constitutive, that is, the defense characteristics of host plants were mainly manifested in no feeding groups. Endophyte presence enhanced locust resistance of the host by activating the JA/ET signaling pathway, elevating chitinase activity and phenolic compounds content, thereby improving the defense ability of host plants. © 2024 Society of Chemical Industry.
Keywords: Achnatherum sibiricum; Epichloë; chitinase; phenolics; phytohormone; plant defense.
© 2024 Society of Chemical Industry.