**1. Introduction**

The genus *Vitis* comprises 60–70 species and the majority of cultivated varieties pertain to *Vitis vinifera* L. The most studied process in this species is berry development, since it has a direct economic impact for wine, fresh fruit, and raisin production [1]. Berry development consists of two sigmoidal growth periods with a lag phase in between. The first stage (phase I) is characterized by a rapid cellular division and cell enlargement, establishing the final number of cells in the berries. At the end of this period, the seed embryos and berries have been defined. This stage is accompanied by the accumulation of metabolites, such as malic, tartaric,

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and hydroxycinnamic acids; minerals; tannins; flavonols; and volatile compounds, all essentials for normal berry development. During the lag stage (phase II), berry growth markedly diminishes, the concentration of organic acids reaches their highest level, and berries start to lose the chlorophyll accumulated during phase I. Finally, ripening stage (phase III) begins with the berry softening or *véraison*, and a gradual increase in sugar content occurs. Moreover, aroma and flavor compounds are accumulated during this stage, and anthocyanin accumulation takes place in red varieties. Also, berries increase their size by cell expansion without cellular division [2–4].

**Figure 1.** Schematic representation of hormonal content in grape berry development stages. Changes in hormone levels are shown for auxins, abscisic acid, brassinosteroids, ethylene, gibberellins, and cytokinins at phases I, II, and III of grape berry development. Several studies have shown a main role for auxins, cytokinins, and gibberellins in early phases of development associated to cell division process and fruit set. At *véraison*, there is a marked increase in abscisic acid levels, essential for ripening-associated physiological changes. High levels of brassinosteroids at *véraison* and phase III are consistent with a ripening-promoting role for this hormone. Moreover, a peak in ethylene has been detected prior to *véraison* that suggests a role in the initiation of this stage. Recently, a possible role for cytokinin signaling in phase III has been reported, due to its high levels at maturation. Changes in sugar content are depicted in purple curve, with an increase around *véraison* and its maximum in full mature berries. *Véraison* is denoted by a dashed line. For more details, see the text.

All the developmental phases of grapevine berry and the metabolic changes associated with them are tightly controlled by complex interactions between environmental factors, such as temperature [5–7], light [8–10], UV-B radiation [11–14], and water availability [15, 16], and endogenous factor, such as phytohormones [17–21]. Classically, fruits have been classified into climacteric and non-climacteric, where the first ones correspond to tomatoes, bananas, avocados, apples, and others that show a marked peak of ethylene associated with an increase in respiration rate during the onset of ripening. In opposition, non-climacteric fruits such as strawberry, citrus, and grapevines do not exhibit this correlation between ethylene and respiration [22–24]. However, recent evidence has suggested an unexpected role for ethylene in non-climacteric fruits [25]. In this chapter, we will discuss the current understanding of hormonal influence over berry development in grapevine, from early processes to ripening stage. In particular, the role of auxins, abscisic acid, brassinosteroids, ethylene, gibberellins, and cytokinins and its complex interaction network will be analyzed according to classic evidences and recent advances based on transcriptomic and proteomic approaches. The hormone levels at different stages of berry development are summarized in **Figure 1**.
