Efficiency of chitosan application against Phytophthora infestans and the activation of defence mechanisms in potato

Late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating diseases that results in huge losses of potato crops worldwide. Chitosan as a defence elicitor can induce plant innate immunity against pathogen infection, but the efficiency and specific defence mechanism of chitosan against late blight in potato have not been elaborated. In this study, we demonstrated that the application of chitosan significantly enhanced potato resistance and reduced P. infestans infection in potted potato and in the field. Large-scale transcriptomic analysis suggested that chitosan preferentially activated several important pathways related to the plant defence response. Notably, we revealed that chitosan triggered pattern-triggered immunity responses in potato. Chitosan could trigger pattern recognition receptors to initiate intracellular signalling, and gradually amplify the immune signal. qRT-PCR verification showed that chitosan induced the expression of defence-related genes in potato. Moreover, treatment with chitosan result in Induced Systemic Resistance (ISR) in potato, including an accumu-lation of plant hormone salicylic acid, increase in the level of phenylalanine ammonia lyase activity anda content decrease of malondialdehyde. These findings help elucidate chitosan-mediated activation of the immune system in potato and provide a potential ecofriendly strategy to control potato late blight in the field. (c) 2021 Elsevier B.V. All rights reserved.