Analysis of ripening heterogeneity and anthocyanin accumulation changes in Vitis vinifera cv. Malbec berries in response to methyl jasmonate

Abstract

Methyl jasmonate (MJ) is a plant hormone involved in cellular signaling pathways triggering in response to biotic and abiotic stress. In grapevine berries it stimulates stilbenoid biosynthesis along with other secondary metabolites involved in defense processes. This response differs depending on berriesphenological and ripening stage; hence it is convenient to work with homogenous samples in order to properly assess this organ?s response. Berries ripen differently within the same plant; therefore a proper sampling procedure is very important. In a field sampling approach, soluble solids content (SSC) is a useful parameter to determine the ripening degree of a berry. Cordon trained Malbec vines were used to perform a ripening heterogeneity analysis by sampling berries along the whole plant and classifying them according to bunch?s distance from the main trunk and bunch?s section from top to bottom. Bunches furthest from the trunk were less ripen than the ones closer, and berries in the middle section of bunches were less variable than the ones on the top or bottom sections. Once determined the sampling section to be used, bunches were sprayed with 10mM MJ hydro-alcoholic solution and samples were taken at 0, 12, 24, 48 and 160 hours. Anthocyanin accumulation and profile was determined by HPLC-MWD. Sampling from bunches middle section resulted in a homogeneous SSC. MJ reduced total anthocyanin content significantly for hours 24, 48 and 160 compared to both alcoholic and water control samples. This reduction is most likely due to activation of stilbenoid biosynthesis pathway and the end use of precursor compounds common to both anthocyanin and stilbene synthesis. These results allow a better understanding of the effects of environment and viticultural practices, as well as MJ-mediated stresses, on Malbec´s anthocyanin metabolism.