Vigor thresholded NDVI is a key early risk indicator of Botrytis bunch rot in vineyards

Carolina Pañitrur-De La Fuente,Jean Pascal Goutouly,Hector Valdés-Gómez,Marc Fermaud,V.F Laurie,Y Mirabal,Cesar Acevedo Opazo,Jean Roudet,Nicolás Verdugo-Vásquez

doi:10.20870/oeno-one.2020.54.2.2954

Abstract

Botrytis bunch rot (BBR) is a major disease occurring in vineyards worldwide. Its control is still largely based on the use of synthetic fungicide sprayings at predetermined intervals, which often produces negative residues in grapes and wines that may affect the environment and/or human health. To rationalize BBR management, disease risk indicators were developed and evaluated in a set of field experiments carried out between 2010 and 2019 in France and Chile. Key indicators include early grapevine vegetative growth, i.e. ground-based normalized difference vegetation index (NDVI), and the potential berry susceptibility to Botrytis cinerea, which is driven by tannin content in the skin. Under these contrasting weather and cropping conditions, regression analyses, including weather information, showed a highly significant positive correlation between the early NDVI, measured at berry pea size stage, and BBR incidence or severity at harvest, whereas the opposite was demonstrated for tannin content in the berry skin measured at an early herbaceous fruit stage. The exponential relationship between the final disease severity and the early NDVI allowed us to identify a possible threshold NDVI value, i.e. between 0.5 and 0.6, under which the BBR severity should be lower or close to 5% at harvest (BBR tolerance threshold for wine quality).

Highlights

Botrytis cinerea is a polyphagous fungus that infects more than 1400 species of cultivated plants, including grapevines (Elad et al, 2016)
Airborne spores of B. cinerea can infect floral tissues and/or fruit pedicel and the pathogen remains in a latency state until veraison, the point when the susceptibility of grape berries to B. cinerea begins to increase (Pezet et al, 2003; Pezet et al, 2004; Elmer and Michailides, 2004; Deytieux-Belleau et al, 2009)
Climatic conditions In France, all growing seasons evaluated were characterized by humid and temperate conditions, which favored B. cinerea development

Summary

Introduction

Botrytis cinerea is a polyphagous fungus that infects more than 1400 species of cultivated plants, including grapevines (Elad et al, 2016). This necrotrophic pathogen, responsible for Botrytis bunch rot disease (BBR), can infect all the organs of the plant but mainly damages ripening berries. Airborne spores of B. cinerea can infect floral tissues and/or fruit pedicel and the pathogen remains in a latency state until veraison, the point when the susceptibility of grape berries to B. cinerea begins to increase (Pezet et al, 2003; Pezet et al, 2004; Elmer and Michailides, 2004; Deytieux-Belleau et al, 2009). Flowering is a key BBR epidemiological stage (Gonzalez-Domínguez et al, 2019), latent infections may establish at later stages throughout the season (Hill et al, 2014) and direct infections may play an important epidemiological role during berry maturation, when the ontogenic resistance of berries decreases (Elmer and Michailides, 2004; Deytieux-Belleau et al, 2009; Hill et al, 2014)

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