|Authors: ||B. Bondada, M. Keller|
|Keywords: ||grape, bunch stem, dehydration, necrosis, ripening, shrivel, sunburn, Vitis vinifera|
In order to gain an insight into the origin and probable causes of various shrivel types developing during ripening of grape berries, it is important that one first perform an integrated analyses to understand structural and compositional anomalies of the afflicted berries.
The objective of this study was to analyze different kinds of shrivels that afflict grape (Vitis vinifera L.) berries during their growth and development by dissecting their morpho-anatomy and shriveling nature, and analyzing fruit composition.
Field-grown 'Cabernet Sauvignon' vines with a history of physiological disorders were monitored for the incidence of various types of shrivels.
These included: sunburn (SB), prolonged dehydration (PD), late-season bunch stem necrosis (LBSN), early bunch stem necrosis (EBSN), and SOUR shrivel (SS). Except for SB berries, the pericarp of all other afflicted berries evolved with distinct morphological (shriveling pattern) and compositional characteristics (sugars, acids, pH, anthocyanins, phenolics, nutrients). Common to all shrivel types was the loss of volume despite retaining an intact morphology of epicuticular wax that occurred as upright platelets excluding on the sun-exposed hemisphere of SB berries wherein its crystalline structure was transitioned into amorphous masses.
A chlorophyllous inflorescence framework persisted in all shrivel forms but in LBSN rachis in which the necrotic regions developed tylosis.
Unlike the translucent mesocarp of healthy, SB and PD berries, the mesocarp was collapsed in SS and LBSN berries, nevertheless all had well-developed seeds.
Overall, the integrated structural and compositional analysis of different shrivel types revealed a severe reduction in fruit quality of clusters afflicted with SS and therefore were not suitable for making wine.
In contrast, despite shriveling of the pericarp, clusters of SB, PD, and LBSN berries had several sought-after compositional attributes rendering them suitable for making certain style of desirable wines.
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