Development and implementation of an in vitro culture system for intact detached grape berries

Grape composition depends on the metabolites accumulated and synthesized during grape development. It is of paramount importance for grape growers because of its major role in shaping wine quality. Therefore, understanding the regulation mechanisms that control the accumulation of quality-related metabolites in grape is of both scientific and agronomical interests. The composition of grape berry at harvest is under complex regulation and can be affected by many factors (Conde et al., 2007). The study of the effects of these factors on berries still attached to intact plants can be highly challenging because of the large size of the plants, interplant, intercluster and interberry variability; and because it is complicated to precisely control the nutrients and hormones imported by the berries, and the environment. Therefore, in vitro cultured grape berries are a good model system, which better represents berry anatomy structure (skin and flesh) than grape cell suspensions and nevertheless largely reduces the system complexity compared to whole plant (Bravdo et al., 1990; Pérez et al., 2000; Gambetta et al., 2010). To this end, an in vitro culture system of intact detached grape berries has been developed by coupling greenhouse fruiting-cuttings production and in vitro organ culture techniques (Dai et al., 2014). The cultured berries are able to actively absorb and utilize carbon and nitrogen from the culture medium, and exhibit fruit ripening features such as color changing and softening. This in vitro system may serve to investigate the response of berry composition to environmental and nutrient factors