Some highly innovative techniques aimed at delaying ripening or, in any case, at obtaining a non-early-ripening product, are represented by the application of growth regulators. Some of these are plant hormones or phytohormones, organic substances synthesized by plants. They have a strong action on the plant metabolism and control growth, or other physiological functions of the plant, and, being active at very small concentrations, their effect can be felt event far away from the production centers, where they arrive transported by the translocation current of the solutes.

In the scientific/technical literature there are evidences of various growth regulators.

• Treatments, in pre-veraison, with auxins (naphthalenacetic acid), which are hormones known to have an anti-senescence action. The results obtained relate to ripening, which is more synchronous within the same bunch and delayed for about 10 days, preserving the sugar content and the final colour intensity. In further experiments, the use of other auxins resulted in a delayed increase in the grape weight and in the accumulation of anthocyanins.
• Treatments with brassinazole, an inhibitor of the biosynthesis of brassinosteroids, showed a clear retarding action on grape ripening.
• The synthetic cytokinins CPPU (N-2-chloro4-pyridinyl-N'-phenylurea) and TDZ (Thidiazuron), applied on different vines after fruit set, with berries having a diameter of 6-7 mm, were able to increase the average weight of the bunches and berries, to reduce sugar concentration, pH and the colour of the berry, as well as to increase total acidity.
• The slowing down of grape ripening can be also achieved by applying 1-MCP (methylcyclopropene) which is a specific inhibitor of ethylene receptors. Even compounds that release ethylene, such as CEPA (2-chloroethylphosphonic acid) can be effective in delaying ripening, if applied in the early stages of grape development. In Vitis vinifera, contrary to what happens in climacteric fruits, the compounds that release ethylene, such as Ethrel, are capable of delaying ripening following a probable increase in the concentration of auxins in the grapes in the pre-ripening phase [1, 2].

The number of experimental researches on these substances in viticulture is not very high. Consequently, the partial information on the regulation of physiological processes and the uncertainty of the results, due to the variability of soil and climatic conditions, and to the different genetics of the cultivar, severely limit the application of growth regulators. This fact prompts us to be cautious and recommends new experiments in different viticultural contexts, before its actual application in the vineyard [3].

By Stefano Pedò, Fondazione Edmund Mach (I)

Related documents

• https://www.soihs.it/ItalusHortus/Review/Review%2017/Palliotti.pdf
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153680/
• http://www.italushortus.it/phocadownload/review/review_16/02.bonghi.pdf