Is it possible to approximate the technological and phenolic maturity of grapes by foliar application of elicitors?

E.P. Pérez-Álvarez¹, E. Baroja1, G.B. Ramírez-Rodríguez², J.M. Martínez-Vidaurre¹, J.M. Delgado-López², P. Rubio-Bretón¹, T. Garde-Cerdán¹,
1 Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de La Rioja, Universidad de La Rioja). Logroño, Spain.
2 Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada. Granada, Spain

Email contact: teresa.garde[@]icvv.es

AIM: The increase in the temperature and the more severe water stress conditions, trends observed in recent years as a consequence of climate change, are leading a mismatch between the technological and phenolic maturity of grapes [1]. As a strategy to face this situation, the use of apatite (Ap) nanoparticles as nano-transporters of the elicitor, methyl jasmonate (Ap-MeJ), is proposed. Elicitors are compounds that, when applied to plants, activate their defense mechanisms, increasing the synthesis of secondary metabolites, mainly phenolic compounds [2, 3]. To date, methyl jasmonate (MeJ) has been used conventionally, but its "nano" application could improve its penetration into the plant, releasing it slowly, which would allow a reduction in the dose to be applied. Therefore, the objective of this work was to study the influence of foliar application of conventional MeJ and MeJ formulated in "nano" form on the composition of Tempranillo grapes during ripening.

METHODS: The experimental design was a randomized block design with three treatments, each in triplicate, with 10 vines per replicate. Foliar applications were carried out at veraison and 7 days later. In each application, 200 mL of solution was applied per plant, being the treatments: control (water), MeJ (10 mM) and Ap-MeJ (1 mM). Grape samples were taken at five points in time: one day before the first application (Fol1), one day before the second application (Fol2), fifteen days after the second application (Pre: pre-harvest), the day of harvest (Vend) and 15 days after harvest (Post: post-harvest). In each sample, the general parameters were determined using official methods [4]: ºBrix, pH, total acidity, glucose+fructose, malic acid, and total phenols.

RESULTS: The results obtained with the foliar application of MeJ as a tool to approximate the phenolic and technological maturity are promising. It has been observed that both, conventional MeJ and Ap-MeJ treatments, slightly reduced ºBrix of grapes and increased their phenolic content. Throughout ripening, the increase in phenolic compounds was mainly evident from pre-harvest to post-harvest, with a higher content in grapes treated with Ap-MeJ.

CONCLUSIONS: The application of MeJ could be an appropriate technique to mitigate the negative effects of decoupling in grape ripening related to the climate change. Moreover, the use of Ap-MeJ allows to optimize its dosage, contributing to a sustainable and economically viable viticulture.

References:

[1] Mira de Orduña, R. 2010. Climate change associated effects on grape and wine quality and production. Food Research International, 43, 1844-1855.

[2] Portu, J., Santamaría, P., López-Alfaro, I., López, R., Garde-Cerdán, T. 2015. Methyl jasmonate foliar application to Tempranillo vineyard improved grape and wine phenolic content. Journal of Agricultural and Food Chemistry, 63, 2328-2337.

[3] Portu, J., López, R., Baroja, E., Santamaría, P., Garde-Cerdán, T. 2016. Improvement of grape and wine phenolic content by foliar application to grapevine of three different elicitors: Methyl jasmonate, chitosan, and yeast extract. Food Chemistry, 201, 213-221.

[4] OIV. 2003. Compendium of Internationals Methods of Wine and Must Analysis. Paris: OIV.