Undaria pinnatifida (Harvey) Suringar aqueous extract activates potato defense responses against Phytophthora infestans

Abstract

Undaria pinnatifida is an invasive macroalga on the Argentinean coast and its use as a biostimulant was rarely investigated. The present work aimed to evaluate the effect of U. pinnatifida aqueous extract (AE) as an inducer of potato defense responses. Our results showed that AE protected potato plants against Phytophthora infestans infection. Application of AE by foliar spray (10% dilution), resulted in a significant reduction in disease severity. However, when antimicrobial activity was tested in vitro, a higher concentration of AE was needed to reduce P. infestans growth, showing hyphae morphological alterations and a reduction in the number of sporangia. These results indicate that AE at 10% induced defense responses in treated plants. The analysis of PR1 and IPII genes (Salicylic Acid and Jasmonic acid pathways markers, respectively), showed that the SA pathway would participate in the AE-induced resistance. Additionally, the accumulation of β-1,3-glucanase, guaiacol peroxidase activity, and changes in free polyamines were analyzed. An accumulation or enhanced activity was stimulated by AE. Moreover, the effect of AE treatment might be positive for the plant performance, since all the dilutions of AE tested showed an increment of chlorophyll content. These preliminary results strongly encourage further studies of the potential use of AE as an alternative tool for potato disease management using locally available seaweed in environmentally friendly conditions.