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

Abstract

The research was conducted in two vineyards, one certified as 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 greater than -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 found to be higher in the 10mm-12mm berries from vines experiencing moderate stress (Stress 1), regardless of their location. Additionally, the Dryland-shallow soil condition showed higher tannin content. On the other hand, grapes from high-stress 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, using berries with size between 10mm-12mm might be suitable for this purpose.