2024 Chenin Blanc and SAD: Part One

Earlier this month I blogged about our grapes being affected with late bunch stem necrosis along with this disorder, we believe that our Chenin blanc also suffered from sugar accumulation disorder (SAD).
I found this reference online which may address the problems we saw last year. The artcle was written in 2024 and is a review entitled, "Berry shrivel in grapevine: A review considering multiple approaches".
It is an excellent and thorough review. One of the illustrations explained how the various grape ripening diseases are related.¹

The diseases shown in the diagram include the following:

• Berry shrivel (BS)
• Sugar accumulation disorder (SAD)
• Bunch stem necrosis (BSN)
• Late season dehydration (LSD)
• Berry splitting
• Sunburn

These disorders are all classified as grape ripening disorders. What we observed in our Chenin blanc was definitely a sugar accumulation disorder. Shortly after harvesting our Auxerrois and Chardonnay, we did a comprehensive sampling of the Chenin blanc and came up with 17 Brix. We noticed that while some of the Chenin had reached 20 Brix, many bunches were lagging behind and were only at 14 Brix. According to the review this sugar accumulation disorder (SAD) is also known as suppression of uniform ripening (SOUR).
The findings reported in this review stated that the lack of sugar accumulation maybe the result of cell death in the berries, most commonly around the central vascular bundles proximal to the seeds, and may or may not progress to the pedicel and rachis. The cause of this cell death remains unknown but leads to impaired sugar import into the berries.
The review then goes into the current science that might help us to understand the causes of SAD, to be continued in Part Two.
References:
1. Griesser M, Savoi S, Bondada B, Forneck A, Keller M. Berry shrivel in grapevine: a review considering multiple approaches. J Exp Bot. 2024 Apr 15;75(8):2196-2213. doi: 10.1093/jxb/erae001. PMID: 38174592; PMCID: PMC11016843.