Precipitation before Flowering Determined Effectiveness of Leaf Removal Timing and Irrigation on Wine Composition of Merlot Grapevine.

Runze Yu,James A Kennedy,Sahap Kaan Kurtural,Matthew W Fidelibus

doi:10.3390/plants10091865

Abstract

Grapevine productivity, and berry and wine flavonoid concentration, depend on the interactions of cultivar, environment, and applied cultural practices. We characterized the effects that mechanical leaf removal and irrigation treatments had on the flavonoid concentration of ‘Merlot’ (Vitis vinifera, L.) grape berries and wines in a hot climate over two growing seasons with contrasting precipitation patterns. Leaves were removed by machine, either at prebloom (PBLR), or at post-fruit-set (PFLR), or not removed (control) and irrigation was either applied as sustained deficit irrigation (SDI) at 0.8 of crop evapotranspiration (ETc) from budbreak to fruit set, or regulated deficit irrigation (RDI) at 0.8 ETc from bud break to fruit set, 0.5 ETc from fruit set to veraison, and 0.8 ETc from veraison to harvest, of ETc In 2014, PFLR reduced the leaf area index (LAI) compared to control. The RDI decreased season-long leaf water potential (ΨInt) compared to SDI. However, in 2015, none of the treatments affected LAI or ΨInt. In 2014, berry flavonoid concentrations were reduced by PBLR as well as SDI. SDI increased the flavonoid concentrations in wine, and PFLR increased some wine flavonols in one season. No factor affected the concentrations of wine proanthocyanidins or mean degree of polymerization. Thus, mechanical PFLR and RDI may increase berry flavonoid accumulation without yield reduction, in red wine grapes cultivars grown in hot climates when precipitation after bud break is lacking. However, spring precipitation may influence the effectiveness of these practices as evidenced by this work in a changing climate.

Highlights

The San Joaquin Valley (SJV) of California is a major wine grape growing region of the United States
Red wine grapes from this region are generally priced lower than similar grapes from cooler growing regions because its climate, the high growing season temperatures and rapid growing degree day accumulation, favor high yields of fruit with relatively low berry flavonoid concertation at harvest
We previously studied the effects of mechanical leaf removal and water deficits on the anthocyanin content and profile of grape berries [3]

Summary

Introduction

The San Joaquin Valley (SJV) of California is a major wine grape growing region of the United States. In 2019, it produced 48% of the total wine grapes crushed in the state of California [1]. Wines made of SJV grapes are usually marketed as high volume, low-cost wines. The economics of this industry favor the development of production practices that minimize grape and wine production cost while maintaining or improving grape and wine quality. Mechanization of canopy management practices and the implementation of optimal irrigation practices can minimize labor costs and improve grape berry flavonoid concentration [2,3,4,5]

Methods

Findings

Discussion

Conclusion