Abstract
ABSTRACT: The effect of basal zone defoliation on vines influences yield and ripening depending on the phenological stage and its intensity. Early basal defoliation (EBD) was carried out at flowering on the autochthonous Vitis vinifera (L.) cultivar ‘Nerello mascalese’ grown on the eastern slopes of Mount Etna, Sicily. The effects were evaluated over a two-year period. In the first year, the canopy retained 67 % of its original leaf area after EBD and in the second year, 58 %. Compared with control vines, mid-day leaf water potentials in the EBD vines enjoyed higher water status throughout the growing seasons in both years. EBD had no significant negative effects on yield but did have significant positive effects on the levels of total polyphenols, total flavonols and total anthocyanins. Yield and its components are conditioned by a number of factors mainly linked to climate and to the vines’ general condition during berry growth and ripening. Even after two consecutive years of treatment, EBD does not have any negative effects on yield. However, EBD does have strong positive effects on berry quality attributes as a consequence of the following: greater exposure of the cluster to sunlight, higher vine water status and avoidance of high temperature stresses in the last phase of ripening during the analysis of anthocyanin.
Highlights
Nowadays, partial defoliation in the basal zone of the grapevine shoot is a common management practice used to control the microclimate in the cluster area
The solar radiation levels are somewhat high in both years
As for the physiological parameters, the vines subjected to Early basal defoliation (EBD) showed a better water status and higher levels of photosyntetic efficiency during berry growth and ripening and did not exhibit any reduction in yield
Summary
Partial defoliation in the basal zone of the grapevine shoot is a common management practice used to control the microclimate in the cluster area. This practice regulates the shade/exposure balance and the ratio of the older less photosynthetically active leaves to the younger more photosynthetically active leaves (Intrieri et al, 2008). Hunter and Visser (1988) suggested that excess vegetative growth is detrimental to interior-canopy microclimate as well as the photosynthetic rate of the entire vine This effect may not be strong because grapes have great resilience, showing compensatory increases in lateral growth and in the photosynthetic efficiency of younger leaves (Reynolds and Wardle, 1989). Effects of increased light exposure on berry flavonoids are unclear. Lemut et al (2013) found that increased light has a positive effect on flavonoid synthesis while others have reported decreased levels of these compounds (Spayd et al, 2002; Tarara et al, 2008; Pisciotta et al, 2013; Scafidi et al, 2018)
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