# Spatial Variability of Grape Berry Maturation Program at the Molecular Level
## 3 Results and Discussion  
### Vineyard Spatial Variability in Vigor and Quality Traits  
Spatial variability in the vineyard is related to changes in terrain and soil physical and chemical properties. These changes result in variable vine vigor throughout the vineyard. Fruit development requires a specific canopy volume range to complete the ripening program. Thin or excessive canopy volume might impair or block berry maturation, while--within a certain interval--small changes in the canopy volume can affect fruit quality [33]. Our work investigated a 12-hectare cv. Cabernet Sauvignon vineyard for its variability in vigor, yield, and berry composition during the 2017 growing season. The study was carried out by a remote sensing approach accompanied by ground measurements, which included detailed vine and berry characterizations in 14 different sampling blocks. NDVI was calculated and mapped from a multispectral image taken on 15 August 2017, 20 days after veraison (Figure 1a). The 14 blocks were grouped into three statistically different vigor classes based on their NDVI values: Low Vigor Class (LVC) included blocks 2, 3, and 5, which exhibited NDVI values ranging from 0.540 to 0.567; Medium Vigor Class (MVC) included blocks 1, 4, 9, 13, and 14 with NDVI values varying from 0.581 to 0.589; High Vigor Class (HVC) included blocks 6, 7, 8, 10, 11, and 12, which showed NDVI values varying from 0.603 to 0.635 (Table 1; Tukey test \(p<0.05\)). An NDVI class map was generated by interpolation of the block NDVI values and showed high vigor variability from the northeast to the southwest vineyard corner, in which the three LVC and four out of the six HVC blocks were located, respectively. The other two HVC blocks were situated on the east side of the vineyard, whereas all MVC blocks were distributed along the northwest-southeast axis (Figure 1b). The majority (10 out of 13) of vine and berry parameters were statistically different between LVC and HVC classes, whereas the MVC values were, in some cases, significantly different from one or the other vigor class (Table 1). Pruning weight and LAI are estimations of vine canopy size and have been reported as good indicators for plant vigor classification [10; 34]. These two parameters presented, respectively, 34.36 and 12.63% CV across the blocks and showed significantly higher values in HVC as compared to LVC. Usually, more developed canopies are associated with better water status than those at lower vigor. In our case, the \(\Psi_{\text{leaf}}\) measured indeed showed a higher averaged value in HVC (\(-0.80\) MPa) compared to LVC (\(-0.95\) MPa) and a relatively high CV of 17.45%. This indicates that vigor differences within the vineyard are related to variability in the plant water status, which could be dictated by dissimilarities in soil water availability. Sugar level (by TSS) and berry weight were monitored throughout ripening and showed differing berry maturation trends across the vineyard (Figure S1; Supplementary Dataset S1). HVC blocks had higher berry weight from post pea size and lower sugar level from veraison onward, compared to LVC blocks. These differences increased with the season progression to reach 9.52% and 5.4% CV for berry weight and TSS, respectively, at harvest, when the variation by vigor class was statistically significant (Table 1). In addition to bigger berries, HVC vines showed significantly higher yield at harvest as compared to LVC (12.38 and 4.99 kg/vine on average, respectively). Indeed, yield is the parameter that showed the highest variability across the vineyard block (41% CV), demonstrating the high impact of the non-homogeneous agronomic conditions of this vineyard on plant productivity. In line with the different fruit maturation trends observed in LVC and HVC, high compositional variability between berries from different vigor classes was detected at harvest (Table 1).