Basal defoliation, salicylic acid and cyanocobalamin to ameliorate the physiological and biochemical characteristics of flood-irrigated ‘Crimson Seedless’ grapevines in a semi-arid Mediterranean climate

There is a high retail demand for ‘Crimson Seedless’ grape. Cluster shape, berry size, colour, and sugar contents influence the overall fruit quality and marketability. In many commercial vineyards of flood-irrigated clay soils under warm and humid semi-arid climates, adequate irrigation may lead to an enhanced fruit set that could potentially be associated with restricted berry growth, compact clusters, and poor berry colour and taste. To assess the role of some agronomic practices that may influence the canopy microclimate, and affect primary and secondary metabolites, seven treatments arranged in a randomised complete block design (RCBD) system with three replicates each (three vines per replicate) were applied as follow; the control (T1), 5-leaf basal defoliation at pre-bloom (BDPB) (T2), BDPB + foliar spray (FS) of 200 mg · L^–1 salicylic acid (SA) (T3), BDPB + FS of 20 mg · L^–1 cyanocobalamin (CCA) (T4), 5-leaf basal defoliation at full bloom (BDFB) (T5), BDFP + SA (T6) and BDFB + CCA (T7). Foliar applications were applied at 1) 2 weeks after the beginning of vegetative growth, 2) full bloom and 3) veraison stages. The analysis of variance (ANOVA), the principle component analysis (PCA) and the two-way hierarchical cluster analysis (HCA) indicated that BDPB (T2) generally has a better effect than that of BDFB (T5). The most pronounced effect on vegetative growth (shoot length and leaf area), photosynthesis activity (leaf chlorophyll and carbohydrate contents), fruit weight and dimensions, and total yield was observed in the case of T3, followed by T6, whereas concerning berry firmness, colour (anthocyanins) and sensory characteristics (soluble solids: acids ratio, total sugars and phenols), the most pronounced effect was observed in the case of T4, followed by T7.