Leaf chlorophyll content is a key indicator of plant physiological status in viticulture; therefore, regular evaluation to obtain data for nutrient supply and canopy management is of vital importance. The measurement of pigmentation is most frequently carried out with hand-held instruments, destructive off-site spectrophotometry, or remote sensing. Moreover, smartphone-based applications also ensure a promising way to collect colorimetric information that could correlate with pigmentation. In this study, four grapevine genotypes were investigated using smartphone-based RGB (Red, Green, Blue) and CIE-L*a*b* colorimetry and a portable chlorophyll meter. The objective of this study was to evaluate the correlation between leaf chlorophyll concentration and RGB- or CIE-L*a*b*-based color indices. A further aim was to find an appropriate model for discriminating between the genotypes by leaf coloration. For these purposes, fully developed leaves of ‘Chardonnay’, ‘Sauvignon blanc’, and ‘Pinot noir’ clones 666 and 777 were investigated with the Color Grab smartphone application to obtain RGB and CIE-L*a*b* values. Using these color values, chroma, hue, and a further 31 color indices were calculated. Chlorophyll concentrations were determined using an Apogee MC100 device, and the values were correlated with color values and color indices. The results showed that the chlorophyll concentration and color indices significantly differed between the genotypes. According to the results, certain color indices show a different direction in their relationship with leaf pigmentation for different grapevine genotypes. The same index showed a positive correlation for the leaf chlorophyll concentration for one variety and a negative correlation for another, which raises the possibility that the relationship is genotype-specific and not uniform within species. In light of this result, further study of the species specificity of the commonly used vegetation indices is warranted. Support Vector Machine (SVM) analysis of the samples based on color properties showed a 71.63% classification accuracy, proving that coloration is an important ampelographic feature for the identification and assessment of true-to-typeness.

To mitigate the potential drawbacks of late pruning, this study evaluated an alternative approach utilising the anatomical features of the umbrella trellis system, cane pruning, and apical dominance. Vine canes were tied at four distinct phenological stages: before budburst, at the 3-leaf, 5-leaf, and 7-leaf stages (BBCH 00, 13, 15, and 17, respectively). We hypothesised that exploiting apical dominance would allow distal buds to burst first; subsequent arching and tying of the cane would then trigger the burst of the remaining basal buds with a temporal delay. The effects of these treatments were evaluated based on leaf area index (LAI), canopy porosity and structure, fertility coefficients, and yield components, supplemented by must composition analysis at harvest and compared alongside a traditional late-pruned cordon-system evaluated under identical phenological timings. Our findings indicated that delayed tying treatments on umbrella-trained vines did not affect canopy structure, resulted in higher yields, greater average bunch weights, without inducing the negative side effects reported for late pruning cordon-trained vines. Regarding final must composition, the treatments produced minor and inconsistent variations, with no significant differences across most measured parameters at harvest.