Inception, progression, and compositional consequences of the sugar accumulation disorder (SAD) Mark Krasnow Mark Matthews Ken Shackel
Sugar Accumulation Disorder (SAD) a.k.a. ‘Berry shrivel’ • Impeded sugar accumulation • Healthy appearing rachis • Poor color development (in red varieties) • Premature berry desiccation
Cabernet Sauvignon and Sauvignon blanc clusters displaying symptoms of SAD.
SAD Grapes displaying SAD have been seen: • Throughout California • In Oregon and Eastern Washington • In Europe (Austria)
Our work originated at the Oakville Experimental Vineyard With Cabernet Sauvignon vines that had consistently shown berry shrivel symptoms over several seasons Some clusters showed shrivel and others did not.
Sampling protocol: pre-symptom expression Likely to Shrivel vine Normal vine (Weekly 2-berry samples frozen and stored separately) Five clusters tagged for composition/firmness Ten clusters tagged for composition/firmness
Symptom expression Likely to Shrivel vine Normal vine “Healthy” clusters
Pooling 2-berry samples within/between vines Likely to Shrivel vine Normal vine Shrivel Pool (SAD)
Pooling 2-berry samples within/between vines Likely to Shrivel vine Normal vine “Likely to shrivel” (LTS) pool
Pooling 2-berry samples within/between vines Likely to Shrivel vine Normal vine Control pool
SAD symptom expression Krasnow et al. 2009 AJEV
First visible shriveling
Fluorescein Diacetate cell viability staining in fruit – Ken Shackel • Allows differentiation of living versus dead cells
Living cells Dead cells
SAD symptom development • SAD fruit has lower Brix, pH, and anthocyanin concentration than control fruit SAD clusters stop accumulating sugars weeks before visible symptoms • Cells die as symptoms become visible •Vine phenomenon - nonsymptomatic clusters on SAD vines develop similarly to SAD clusters
Is shrivel [SAD] the result of impaired phloem transport? Stopping sugar import by girdling the cluster should mimic SAD
Girdling experiments to mimic SAD Girdling was done with a knife above and below the peduncle to stop sugar transport to the berries.
Cabernet Sauvignon Girdled before veraison. Picture taken 103 DAA (63 DAG) Not girdled
Yes, girdling mimics SAD with respect to berry growth, sugar accumulation, and color development.
Crop Thinning Experiments Greenest clusters dropped at veraison Clusters dropped at set
Set Veraison thinned 0.3 a Site Unthinned 1.0 a thinned 0 a 2007 % SAD Stag’s Leap Sonoma 6.3 a 0.9 a 4.7 a Rutherford River 3.2 a 6.5 a 6.5 a
2008 % SAD --- same lack of thinning effect Thinning crop has not diminished incidence of SAD symptoms in remaining fruit.
2007 Budding Experiments Chip budding from normal to SAD vines and SAD to normal vines Normal buds SAD vine
30 vine sets (15 SAD, 15 healthy) were planted in: Oakville (1773 GDD) Davis (2069 GDD) Hopland (1937 GDD) Parlier (2469 GDD)
Normal SAD propagated vine propagated vine
Normal source SAD source
2009 Davis vine harvest data Harvest weight (g/vine) Sample Normal propagated (n=10) SAD propagated (n=11) Brix 442 a 25.7 a 372 a 17.6 b Similar results at all locations in 2010.
SAD: Source Brix 1B 18.8a 3B 17.3 b 5B 15.7 c 2B 15.0 c Controls: Source Brix 3A 22.0a 4A 21.9a 2A 20.5a Clonal propagation: 3 independent wood sources of control and 4 independent wood sources of SAD, all planted at 4 locations (OEV, UCD, KAC, and Hopland). Due to budget limitations, only the OEV and UCD vines now remain.
The 2003 budding experiments demonstrated that SAD is transmissable
2007 Budding experiments demonstrated that healthy buds grafted onto SAD vines develop SAD fruit
and that SAD is able to spread from grafted buds to affect an entire vine; And - there are consistent clonal differences
SAD and pathogens The SAD vines at OEV have been tested for the following pathogens by FPS •Leafroll viuruses •Fanleaf virus •Phytoplasmas •Tomato ringspot virus •Grapevine vitiviruses •Arabis mosaic virus All tests have yielded negative results, [or both SAD and healthy vines have given positive results] •Xylella fastidiosa •Rootstock stem lesion associated virus • Grapevine fleck virus • Rupestris stem pitting associated virus
Conclusions • Sugar accumulation stops prematurely
Conclusions • Sugar accumulation stops prematurely • Anthocyanin accumulation stops about same time as sugar accumulation
Conclusions • Sugar accumulation stops prematurely • Anthocyanin accumulation stops about same time as sugar accumulation •SAD symptoms may arise from impaired phloem flux, like leaf roll virus
Conclusions • Sugar accumulation stops prematurely • Anthocyanin accumulation stops about same time as sugar accumulation •SAD symptoms may arise from impaired phloem flux, like leaf roll virus •SAD is propagate-able & transmissible
Conclusions • Sugar accumulation stops prematurely • Anthocyanin accumulation stops about same time as sugar accumulation •SAD symptoms may arise from impaired phloem flux, like leaf roll virus •SAD is propagate-able & transmissible •SAD at Oakville is a vine phenomenon