Impacts of Pre-bloom Leaf Removal on Wine Grape Production and Quality Parameters: A Systematic Review and Meta-Analysis

Joshua VanderWeide,Steven R. Schultze,Stefano Poni,Chris Gottschalk,Paolo Sabbatini,Esmaeil Nasrollahiazar

doi:10.3389/fpls.2020.621585

Abstract

Wine grape (Vitis vinifera L.) is the most widely cultivated fruit crop in the world. However, the climactic characteristics in some growing regions are suboptimal for grape production, including short season length and excess precipitation. Grape growers can utilize an array of methods to mitigate these issues, including “early leaf removal,” a management practice involving the removal of leaves from selected basal nodes along shoots around bloom. This meta-analysis reviews the extensive literature on this practice, with specific regards to application at “pre-bloom” (PB). One hundred seventy-five publications on the topic of “early leaf removal” were identified using key terms and subsequently narrowed via eight data curation steps. The comparison between treated (PB) and control plants in these studies revealed two important results. First, PB lowered bunch rot disease (−61%), partially through reducing the compactness of clusters. Second, PB promoted a significant increase in fruit total soluble solids (°Brix, +5.2%), which was related to the increase in the leaf-to-fruit ratio. Furthermore, cultivar and rootstock were found to have a large influence on the success of PB, while the contribution of climate was smaller. In conclusion, PB significantly lowers yield and bunch rot disease and increases °Brix, both of which improve grape and wine quality.

Highlights

Grapevines are among the most intricately managed food crops due to their sensitivity to external and internal factors, such as the environment and source–sink relations (Kliewer and Dokoozlian, 2005)
Given that disease pressure is higher in more humid climates, researchers in these regions sought to understand whether performing this practice earlier to alter cluster architecture could further reduce bunch rot disease
Future work with higher resolution data may yet reveal a stronger connection. This suggests the need for further investigation into our data set to more explicitly uncover the influence of climate and other categorical variables on the “success” of PB. This meta-analysis was conducted using 59 publications that describe the response of grapevines to pre-bloom leaf removal: an important grapevine canopy management technique

Summary

Introduction

Grapevines are among the most intricately managed food crops due to their sensitivity to external and internal factors, such as the environment and source–sink relations (Kliewer and Dokoozlian, 2005). Pre-bloom Defoliation and Grape Quality are utilized to align vine growth, vine development, and fruit ripening (internal factors) with environment conditions (external factors). One such practice is “leaf removal,” otherwise referred to as “defoliation” or “leaf thinning.”. Leaf removal is a technique that involves the removal of a select number of leaves that cover the fruiting region along shoots (Poni et al, 2006). This allows for a more open fruit-zone microclimate, which can lead to numerous production and fruit quality benefits

Methods

Results

Conclusion