Exploring the Etiology of Berry Shrivel Ripening Disorder: Considerations of Biotic and Abiotic Factors

While there are several disorders affecting grapevine berry development, Berry Shrivel (BS, also known as Sugar Accumulation Disorder, SAD) is a significant problem for grape growers in California, the West Coast, and internationally. BS is particularly problematic because it is difficult to diagnose, and all available evidence suggests that onset of the disorder is simultaneous with veraison. Although BS has been studied previously, several lagging questions remain; principally the potential existence of an etiological agent (i.e. pathogen), but also suggestions that only parts of a vine are affected, and how widespread the effects of sugar accumulation are in affected blocks. In the first project year, our team demonstrated that sugar accumulation of berries is uniformly lower in BS-affected blocks in relation to control blocks by several degrees Brix; similarly, anthocyanin content was reduced based on grape juice color. While preliminary, these observations suggest that BS is not a ‘rare and random’ occurrence in affected blocks, and that whole vine is affected rather than just sections of the vine. In addition, a bioinformatic analysis of publicly available data suggests that BS is not correlated with the presence of a particular RNA virus. This research is ongoing because the preliminary data are limited to RNA viruses and must be expanded to include DNA or other microbes. Altogether, in its first year, this project has provided important insights into the nature of the BS disorder and highlights the significant knowledge gaps that remain in our understanding of the impacts of this disorder.