Antifungal Activity of Guayule Resin and Satureja Essential Oils Against Fusarium oxysporum in Borago officinalis

Latorre Pastor, Guayente; Julián Lagunas, Carmen; González García, Vicente; Mallor Giménez, Cristina; Niza González, Enrique; García Martínez, María de las Mercedes; González Navarro, Emilio José; Zalacain Aramburu, Amaya; Carmona Delgado, Manuel

Antifungal Activity of Guayule Resin and Satureja Essential Oils Against Fusarium oxysporum in Borago officinalis

2023

Guayule (Parthenium argentatum Gray) is a shrub with many interesting potential activities, different from their actual rubber exploitation. Guayule resin has already shown activity against fungi that cause damage to wood, so the aim of this work was to test the activity of guayule resin against Fusarium oxysporum Schltdl., a soil-borne fungus that causes losses of up to 80% in the borage (Borago officinalis L.) crop. Up to know there isn´t any effective treatments and it is becoming a huge problem for farmers in northern Spain. First, guayule resin was formulated in water in three different forms: resin alone, and resin with essential oils of savory (Satureja montana L.) in a 1:0.25 and 1:1 ratio (resin/savory). The activity was test by a minimum inhibitory concentration (MIC) assay carried out for 10 days to determine the effective dose for mycelial growth inhibition, and by a conidial germination inhibition assay carried out with the same battery of formulations. Guayule resin formulation alone proved to be very effective in inhibiting mycelial growth of F. oxysporum, with a reduction rate of >70% for all concentrations lasting up to 10 days. Resin formulations with savory essential oils proved to be less active, with growth reduction rates <30% at higher concentrations, and no inhibition at lower concentrations. On the other hand, none of the guayule formulations produced inhibition of conidial germination. Results showed that guayule resin could be an effective tool for the integrated management of pathogenic fungi such as F. oxysporum in B. officinalis crop, not to prevent the infection, but to cure it or minimize its harmful effects.

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