Berry shrivel: physiological, compositional and anatomical consequences affecting berry development in Vitis vinifera L.

Geoffrey Earle Hall

In premium wine production, grape quality is arguably the most important factor in determining the wine’s character. In recent years, quality has been under attack by a grapevine (Vitis vinifera L.) disorder known as berry shrivel (BS). Symptoms of BS include low sugar accumulation, low pH, poor color development, and visible shriveling of ripening berries; all of which are not desirable fruit characteristics. Therefore, BS affected fruit is often removed from the vineyard at an extreme cost to the grower. BS symptoms are often closely related with another well known shriveling disorder named bunch-stem necrosis (BSN). As the name states, BSN develops necrotic lesions on the rachis, which is often used as the key distinction between the two disorders. Various experiments using both field and potted vines were conducted in order to elucidate the key physiological, anatomical and compositional factors involved in the development of BS. BS compositional symptoms commenced immediately following veraison (i.e. inception of ripening), while BSN developed weeks later. Reduced sugar and water import, presumably via phloem limitation, lead to examinations of BS, BSN, and healthy rachises. BS clusters experienced an increased susceptibility to rachis necrosis. Further, a correlation found between the degree of shriveled berries on a cluster and the severity of necrotic lesions suggested v BS clusters are not void of necrosis. Microscopic observation and quantification of cellular viability clearly showed a reduction of live cells in both BS and BSN rachises. Additional experiments were aimed at inducing BS symptoms by imposing environmental and nutritional stress on potted vines and fresh cut shoots. When exposed to cold nighttime temperatures, potted vines experienced photoinhibition and reduced partitioning of assimilates to clusters. Given BS and BSN’s low solute accumulation, berry shrinking, reduced rachis viability and susceptibility to necrosis, we suggested that the disorders may be linked. Further, we concluded that BS is a ‘symptom less’ (non-necrotic) version of BSN, in which limited assimilate transport into berries is facilitated by an inhibition of phloem function, imitating a girdling effect.

Berry shrivel: physiological, compositional and anatomical consequences affecting berry development in Vitis vinifera L.

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