  Citation: Gutiérrez-Gamboa, G.; Guerrero-Méndez, M.; Araya-Alman, M.; Verdugo-Vásquez, N.; Valdés-Gómez, H.; Acevedo-Opazo, C. Sunscreen Based on Dicarboxylic Acid Salts Applications to Blueberries (Vaccinium corymbosum L.) Plants: Effects on Water Stress Tolerance and Productivity. Horticulturae 2022, 8, 95. https://doi.org/10.3390/ horticulturae8020095 Academic Editors: Begoña Miras- Moreno and Esther Novo-Uzal Received: 10 October 2021 Accepted: 11 January 2022 Published: 20 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). horticulturae Article Sunscreen Based on Dicarboxylic Acid Salts Applications to Blueberries (Vaccinium corymbosum L.) Plants: Effects on Water Stress Tolerance and Productivity Gastón Gutiérrez-Gamboa 1 , Mario Guerrero-Méndez 2 , Miguel Araya-Alman 3 , Nicolás Verdugo-Vásquez 4 , Héctor Valdés-Gómez 5, * and César Acevedo-Opazo 6, * 1 Escuela de Agronomía, Facultad de Ciencias, Universidad Mayor, Huechuraba 8580000, Chile; gaston.gutierrez@umayor.cl 2 Nutriprove, SA, Av. Linares 0410, La Granja 8780000, Chile; guerrero@nutriprove.com 3 Departamento de Ciencias Agrarias, Campus “San Isidro”, Universidad Católica del Maule, km 6 Camino Los Niches, Curicó 3340000, Chile; marayaa@ucm.cl 4 Centro de Investigación Intihuasi, Instituto de Investigaciones Agropecuarias (INIA), Colina San Joaquín s/n, La Serena 1700000, Chile; nicolas.verdugo@inia.cl 5 Facultad de Ciencias Agrarias, Universidad de Talca, 2 Norte 685, Casilla 747, Talca 3460000, Chile 6 Departamento de Fruticultura y Enología, Pontificia Universidad Católica de Chile, Av. VicuñaMackenna 4860, Macul 6904411, Chile * Correspondence: hevaldes@uc.cl (H.V.-G.); cacevedo@utalca.cl (C.A.-O.); Tel.: +56-99-7766-7799 (H.V.-G.); +56-99-849-0066 (C.A.-O.) Abstract: Background: Recently, antitranspirant or radiation-reflective products have been stud- ied in several crops to mitigate the negative effects of global warming in Mediterranean climates. Nevertheless, to our knowledge, there is a scarce availability of information studying their effects on blueberries and much less from applications of sunscreens elaborated based on a mixture of dicarboxylic acids. Methods: Controls and three treatments were performed in ‘Duke’ and ‘Star’ blueberries as follows: (i) control without water stress (T1 = 100% ETc); (ii) foliar application of sunscreen in plants without water stress (T2 = 100% ETc + sunscreen); (iii) water stress in plants without foliar application of sunscreen (T3 = 50% ETc); (iv) foliar application of the sunscreen in plants with water stress (T4 = 50% ETc + sunscreen). Stem water potential (Ψs), stomatal conductance (g s ), yield, berry weight and berry total soluble solids were determined. (3) Results: As expected, the decrease in irrigation frequency in water stress treatments (T3 and T4) allowed for a decrease in the water applied at 25% compared to non-stressed plants (T1 and T2). This resulted in an increase in the Ψs on the days closest to harvest in both varieties, decreasing g s in blueberries plants subjected to water stress conditions. Sunscreen applications to Duke plants subjected to water stress (T4) induced higher total berry soluble solids than the treatments performed in non-stressed plants (T1 and T2). Sunscreen applications to Star plants subjected to water stress (T4) promoted similar g s levels and did not affect total soluble solids concerning irrigated plants (T1 and T2). (4) Conclusions: The results suggest that the response to water stress to sunscreen application based on dicarboxylic acid salts depended on the cultivar. Therefore, despite the novelty of this research, it is necessary to perform long-term studies to establish accurate conclusions. Keywords: antitranspirants; global warming; highbush blueberry; Duke; Star 1. Introduction Blueberry consumption has increased globally over the last years, mainly due to its high antioxidant potential because of its richness in phenolic compounds [1]. North America is a traditional market in which more than half of the fresh blueberries produced is consumed and their demand has considerably increased in new markets, such as Europe and China [2]. Based on this, traditional and new growth areas across the globe have Horticulturae 2022, 8, 95. https://doi.org/10.3390/horticulturae8020095 https://www.mdpi.com/journal/horticulturae