Improving Grape Phenolic Content and Wine Chromatic Characteristics through the Use of Two Different Elicitors: Methyl Jasmonate versus Benzothiadiazole Yolanda Ruiz-García, † Inmaculada Romero-Cascales, † Rocio Gil-Muñ oz, ‡ Jose Ignacio Ferna ́ ndez-Ferna ́ ndez, ‡ Jose María Ló pez-Roca, † and Encarna Gó mez-Plaza* ,† † Food Science and Technology Deparment, Faculty of Veterinary Science, University of Murcia, Campus de Espinardo, 30071 Murcia, Spain ‡ Instituto Murciano de Investigació n y Desarrollo Agroalimentario, Ctra. La Alberca s/n, 30150, Murcia, Spain ABSTRACT: Benzothiadiazole (BTH) and methyl jasmonate (MeJ) have been described as exogenous elicitors of some plant defense compounds, polyphenols among them. The objective of this study was to determine whether the application of BTH or MeJ to grape clusters at the beginning of the ripening process had any effect on the accumulation of the main flavonoid compounds in grapes (anthocyanins, flavonols, and flavanols) and the technological significance of these treatments in the resulting wines. The results obtained after a 2 year experiment indicated that both treatments increased the anthocyanin, flavonol, and proanthocyanidin content of grapes. The wines obtained from the treated grapes showed higher color intensity and total phenolic content than the wines made from control grapes. The exogenous application of these elicitors, as a complement to fungicide treatments, could be an interesting strategy for vine protection, increasing, at the same time, the phenolic content of the grapes and the resulting wines. KEYWORDS: grape, wine, anthocyanins, tannins, flavonols, BTH, methyl jasmonate ■ INTRODUCTION Phenolic compounds are very important in crop plants and have been the subject of a large number of studies. Three main reasons can be cited for optimizing the level of phenolic compounds in crop plants: their physiological role in plants, their technological significance for food processing, and their nutritional characteristics. In plants, phenolic compounds contribute significantly to plant resistance against pests, pathogens, and environmental stress; they are effective as sun screens as well as antifeeding compounds; they may function as antioxidants and interact with growth regulators. 1 Moreover, some of them present antimicrobial activity and are involved in inducible resistance against pathogens, and their concentration in plant tissues may increase markedly as part of this resistance phenomenon. 2,3 This resistance process, mediated by the accumulation of endogenous salicylic acid (SA), a metabolite downstream of the biosynthetic pathway initiated by phenylalanine ammonialyase (PAL), is called systemic acquired resistance (SAR) and implies the induction of secondary metabolic pathways and the increased synthesis of products as a result of this metabolism, including phenolic compounds, 3,4 as a response to pathogen attack. In winegrapes, the technological importance of phenolic compounds, especially flavonoids, is well-known. They are responsible for the color of wines, especially anthocyanins (colored pigments responsible for the chromatic characteristics of red wines), proanthocyanidins (responsible for the long-term stability of red wine color), and flavonols (compounds that may influence wine color through copigmentation), and some other organoleptic properties such as astringency, bitterness, and body. Another important aspect that has been widely studied in recent years is the role of grape and wine phenolic compounds in the human diet. Many studies have suggested cardiovascular benefits, and some point to cancer chemopreventive activity and beneficial effects against other less prevalent but devastating illnesses, such as Alzheimer's disease and urinary bladder dysfunction. 5-8 Most of these beneficial functions may arise from their antioxidant action, which may occur through a combination of several distinct chemical events, including enzyme inhibition, metal chelation, hydrogen donation from suitable groups, and oxidation to a nonpropagating radical. 9-11 Taking all this into account and although genetic factors play an important role in the phenolic compound content of grapes, several approaches have been proposed for improving the phenolic content of crop plants, in general, and winegrapes in particular. Beside genetic transformation (forbidden in most countries), a wide range of factors is able to modify the grape phenolic content, including agronomic practices, clonal selection, and those stress factors that may trigger SAR establishment. 11 However, it has been demonstrated that SAR can also be induced or enhanced by the exogenous application of natural or synthetic compounds that may have powerful effects. 12 Received: July 22, 2011 Revised: December 7, 2011 Accepted: January 9, 2012 Published: January 9, 2012 Article pubs.acs.org/JAFC © 2012 American Chemical Society 1283 dx.doi.org/10.1021/jf204028d | J. Agric.Food Chem. 2012, 60, 1283-1290