The lipopeptide surfactin triggers induced systemic resistance and priming state responses in Arachis hypogaea L.

Abstract

Bioactive metabolites produced by multiple strains of Bacillus spp. stimulate plant defense responses. Among these, the cyclic lipopeptide surfactin was identified as an Induced Systemic Resistance (ISR) elicitor in different plant species. However, the underlying mechanisms involved in the ISR elicitation and the priming state costs in peanut plants (Arachis hypogaea L.) remain unknown. In this work, we demonstrated the ability of surfactin from B. subtilis to induce systemic resistance against Sclerotium rolfsii in peanut plants, and showed that this response involves key characteristics of priming-mediated resistance defense. Application of surfactin significantly reduced S. rolfsii disease incidence and severity on peanut plants, and an increased shoot and root dry weight was observed in surfactin pre-treated and pathogen challenged plants compared to non-treated challenged plants. In addition, peroxidase activity and phenolic compounds deposition underneath the fungal infection zone were significantly higher in surfactin pre-treated and challenged plants than in non-surfactin treated challenged plants. Collectively, results from this work indicate that ISR activity elicited by surfactin involves a priming defense state with low fitness-related costs, providing an enhanced protection against S. rolfsii in peanut plants.