Effects of Different Water Stress Levels, Heterogeneity, and Location on Berry Phytochemical Properties in an Organic and Conventional Vineyard (Vitis vinifera cv. Cabernet-Sauvignon)

Investigate the effects of water stress on grape berry heterogeneity and
composition in Cabernet-Sauvignon (Vitis vinifera L.) grapes under
different farming practices (organic and conventional) based on soil
structure and provide valuable information for the wine industry
regarding quality. The research was conducted in two vineyards, one
certified organic and the other following conventional practices. The
experiment, designed with Split-Plot Experimental Design based on
stress levels, was divided into two main plots, Organic and
Conventional, and each of these plots was further divided into two
subplots. The predawn leaf water potential results categorized the vines
into two groups: those with values lower than -8 MPa and those above -
8 MPa, which were labeled as Dryland-shallow soil and Baseland-deep
soil, respectively, based on the location and soil type. During the
harvest, grape clusters were collected and classified into three groups
based on berry diameter (10mm-12mm, 12mm-14mm, 14mm-16mm).
The results indicated that the 10mm-12mm berry size group generally
exhibited the desired characteristics across all evaluated criteria. The
total anthocyanin and total tannin content were higher in the 10mm-
12mm berries from vines experiencing moderate stress (Stress 1),
regardless of location. Additionally, the Dryland-shallow soil condition
showed higher tannin content. On the other hand, grapes from highstress
vines displayed lower antioxidant values. The total polyphenol
index content was higher in the organic vineyard. Based on the findings,
it was suggested that to obtain high phytochemical compounds from
Cabernet-Sauvignon grapes in the Tekirdağ region, cultivation should
be carried out under Dryland-shallow soil conditions, where the
predawn leaf water potential can drop as low as -0.8 MPa during the
period between veraison and harvest. Moreover, berries between 10 mm
and 12 mm might suit for this purpose.