Berry shrivelling is an important phenomenon that occurs through grape berry water loss due to the alteration of the fruit water budget when transpiration and potential water back flow to the plant exceeds the import of water into the berry through the phloem and xylem. Berry shrivelling can have a significant economic impact, reducing yields by up to ≥25% with consequences on berry composition and the resulting wine. Its occurrence and consequences are expected to increase due to predicted climate warming, shifting grape development, and ripening into warmer periods (i.e., heat waves).
Berry fresh mass loss is variable between
seasons, sites, and vineyards and it seems to be accelerated by higher
temperatures, water constraints and/or stress and excessive bunch sun exposure.
Berry shrivelling can occur, before (as early as bloom, affecting the ovaries)
or after veraison in red and white varieties.
A recent study on individual Shiraz berries
(Montpellier l’Institut Agro vineyard; vines trained in vertical shoot
positioning under fertirrigation) revealed interesting and original results comparing
normal to shrivelled berries in terms of fresh mass, °Brix, probable alcohol
and quantity of sugar per berry (mg/berry). The results clearly demonstrated
that the increase in probable alcohol/°Brix per berry (post plateau of berry
sugar loading) is not due to berry sugar accumulation during ripening but only
to berry water loss. This conforms with previous results on the same cultivar
(McCarthy and Coombe 1999; Rogiers et al., 2006; Rogiers and Holzapfel 2015).
Late ripening berry shrivel in Shiraz may begin
at around 90 days after flowering, but it is not evident every season. While
loss in mesocarp cell vitality and cell membrane integrity precedes the onset
of shrivel, the internal biochemical and physiological events that lead to
these developmental processes remain largely unknown. However, it was
demonstrated that hypoxia (low oxygen) in the berry mesocarp may contribute to
the onset of cell death (Xiao et al., 2018a). Previous studies have shown that
high temperature and dehydration can exacerbate the extent of cell death and
berry dehydration (Bonada et al., 2013; Xiao et al., 2018b), and this can be
ameliorated with shade covers (Caravia et al., 2016). It is interesting to note
that unlike seeded wine grapes, table grapes do not tend to undergo this late
ripening loss in cell vitality. Ultimately, berry shrivelling will affect grape
and wine composition and sensory profiles (Suklje et al., 2016).