In potato (Solanum tuberosum) crops, fungicides are essential to protect against fungal pathogens, but their high toxicity drives the search for safer alternatives. Natural products with high antioxidant activity are presented as a viable option to mitigate pathogen damage and strengthen plant defense mechanisms.

The main aim of this study is to evaluate the antioxidant response in the foliar system of potato crops inoculated with Rhizoctonia solani and treated with a biofungicide based on colored pulp extract. The profiles and concentrations of phenolic compounds were evaluated by high-performance liquid chromatography with diode array detection (HPLC-DAD), and the antioxidant activity by chemical methods in the foliar part of potato crops subjected to eight treatments, including inoculation with the pathogen Rhizoctonia solani, commercial fungicides, and a nanoencapsulated extract (SNL) based on a colored pulp extract (FCP) with a potential biofungicidal effect, at two doses (20 and 40 mg L^-1).

Four phenolic compounds from the hydroxycinnamic acid and flavonol families were detected, where 5-caffeoylquinic acid and quercetin-rutinoside were the most abundant compounds. The highest concentrations of total phenols were detected in the treatment with applications of SNL-FCP at a dose of 20 mg L^-1, reaching a concentration of 33.69 mg g^-1. The antioxidant activity with the best response was detected by way of the CUPRAC method, when the same treatment was applied.

These results suggest that the application of the encapsulated extract does not significantly increase phenolic compound concentrations under pathogen inoculation, but it does regulate antioxidant activity, similar to the control without R. solani inoculation. Thus, the use of this encapsulated extract has potential beneficial effects for potato crops.

ACKNOWLEDGMENTS: ANID/FONDECYT 1230587 Project.