Abstract
Aim: The objective of this work is to investigate the effects of early defoliation on cv. Chasselas under the temperate conditions of Switzerland, with particular attention to berry anatomical traits and wine sensory parameters.Methods and results: Defoliation (removal of 6 basal leaves + 6 lateral shoots per shoot) was completed during three developmental stages of grapevine, i.e., pre-flowering, late flowering and bunch closure, and at two intensity levels. The experimentation was performed repeatedly over four years. In addition to vintage effect, pre-flowering defoliation had a consistent impact on vine agronomic behaviour. The yield was highly affected by the technique (more than 30% loss). Earlier and more intense defoliation had more impact on yield, while post-berry-set defoliation had no effect on yield. Intensive defoliation also modified berry skin thickness and had a positive impact inhibiting Botrytis development. Wine composition and sensory analysis were not affected by the practice. However, pre-floral defoliation affected bud fruitfulness and vigour, i.e., trimming and pruning weights. This result noted a carryover effect that could affect vine sustainability under restrictive conditions.Conclusion: In the context of this study, pre-flowering defoliation seems to be an interesting practice to reduce vigour and control the high production potential of the cv. Chasselas. The intensity of early defoliation allows for the modulation of the impact on the yield in order to prevent excessive yield loss.Significance and impact of the study: Pre-flowering defoliation of the white cultivar represents a prophylactic solution to reduce both chemical entrants and bunch-thinning costs.
Highlights
Grapevine defoliation in the cluster zone is usually realized between berry set and bunch closure to create an unfavourable microclimate for cryptogamic diseases, such as Botrytis cinerea and powdery mildew (Zoecklein et al 1992; Percival et al 1994; Sternad Lemut et al 2015)
The leaf potassium concentration slightly increased and the chlorophyll index decreased under the pre-floral treatment (B). These results prove the presence of a carryover effect during the year following pre-floral defoliation, which confirms the warning results from other studies (Risco et al 2014 ; Uriarte et al 2012)
Pre-flowering defoliation resulted in major effects on vine physiology – i.e., reduction of berry set rate and yield, modifications in berry structure, reduction of vigour – and represents an interesting sustainable practice to control yield and enhance resistance to pathogens under the temperate climate of Switzerland
Summary
Grapevine defoliation in the cluster zone is usually realized between berry set and bunch closure to create an unfavourable microclimate for cryptogamic diseases, such as Botrytis cinerea and powdery mildew (Zoecklein et al 1992; Percival et al 1994; Sternad Lemut et al 2015). Grape growers are interested in pre-berry-set defoliation, which presents extra advantages under certain conditions This practice strongly affects berry set and berry number per bunch (Gómez et al 2012; Kotseridis et al 2012; Poni and Bernizzoni 2010; Sabbatini and Howell 2010). As a consequence, it limits the yield (Poni et al 2006; Palliotti et al 2012; Basile et al 2015) and induces tremendous modifications in berry structure, i.e. skin thickness and skin-to-pulp ratio, and in berry composition (total soluble solids, acidity, and polyphenols) (Palliotti et al 2012; Šuklje et al 2014; Komm et Moyer 2015; Verdenal et al 2017). No carryover effects could be observed because the vines had sufficient reserves (Acimovic et al 2016)
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