Evaluation of Dahlia and Agave Fructans as Defense Inducers in Tomato Plants Against Phytophthora capsici

In agriculture, the use of fructans has gained relevance due to their ability to improve plant immunity and resistance to pathogens. However, many studies use high-purity fructans, which makes their application more expensive. In this work, the efficacy of two agave fructans, one food grade from Agave tequilana Weber var. Azul (FT) and the other obtained by semi-craft extraction from A. cupreata (FC) were evaluated in comparison with reagent-grade inulin from dahlia tubers. The effectiveness of their defense response against Phytophthora capsici infection in tomato (Solanum lycopersicum L.) was analyzed by evaluating defense mechanisms, including lignin deposition, hydrogen peroxide (H2O2) accumulation, and β-1,3-glucanase and peroxidase activity. The results indicated that foliar application of both fructans showed protection against infection, reducing disease incidence and severity. FT fructans at lower concentration (0.5 g/L) showed the highest protection, followed by FC, while dahlia inulin showed lower effectiveness. An early and progressive accumulation of H2O2 was observed in fructan-treated plants, in contrast to the late increase in untreated infected plants. Also, peroxidase activity was higher in the fructan treatments, suggesting a more efficient defense response. Although lignin deposition was not directly correlated with protection against P. capsici, fructans showed potential as resistance inducers. Given their low cost, easy extraction, and zero environmental impact, agave fructans represent a viable alternative for crop protection in sustainable agricultural systems. This study opens the door to their validation in the field and their application in other economically important crops, contributing to biological control strategies with less dependence on agrochemicals.