Terroir 2020 banner
IVES 9 IVES Conference Series 9 International Terroir Conferences 9 Terroir 2020 9 History and innovation of terroir 9 Spectral characterisation of fungal diseases on Vitis vinifera leaves

Spectral characterisation of fungal diseases on Vitis vinifera leaves

Abstract

Aims: The aims of this study were to (1) detect alterations in the reflectance spectra of vines with fungal diseases, (2) map these alterations, and (3) determine the best wavelengths which may be used as early indicators of fungal diseases in vines.

Methods and Results: Cabernet Sauvignon vines grown in pots and kept in a greenhouse were inoculated with the pathogens causing mildew, powdery mildew, black-foot and Petri disease. In early stages of disease development, reflectance measurements were performed using a FieldSpec 3 spectroradiometer, which were compared with data from healthy plants. Additional measurements were performed with chlorophyll meters. The investigation began with discriminant analysis, which revealed that symptomatic plants are indeed separated from the control ones. Reflectance spectra were therefore further investigated, looking for alterations on the shape of the spectra, characteristic of each disease. The disease descriptors were based on ratios between spectral features internal to a spectrum, a procedure which allowed the derivation of parameters intrinsic to each disease. A set of thresholds, defined as the intensity ratios of reflectance at selected wavelengths, was derived for the studied diseases. The selected wavelength ratios were 443/496, 443/573, 443/695, 443/1900, 496/573, 496/695, 516/1900, and 1900/2435 (values in nanometers), for which the spectra from symptomatic plants present shape changes of as much as 20% with respect to healthy plants.

Conclusions:

Spectral deformations were observed for the studied fungal diseases; they are larger for black-foot and powdery mildew, but some wavelength ratios are also indicators of downy mildew and Petri disease. Data from near-infrared in general carry more information compared with measurements at 1900 and 2435nm.

Significance and Impact of the Study: Since little is known on alterations of the reflectance spectra of vines, a better knowledge could be used in the development of sensors able to detect diseases through fast, non-destructive techniques. Early disease detection can lead to preventive actions which potentially can mitigate losses in grape yield and quality.

DOI:

Publication date: March 23, 2021

Issue: Terroir 2020

Type: Video

Authors

Pâmela A. Pithan1, Jorge R. Ducati1*, Lucas R. Garrido2

1Remote Sensing Center, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970 Porto Alegre RS, Brazil
2Centro Nacional de Pesquisas em Uva e Vinho, EMBRAPA, Bento Goncalves RS, Brazil

Contact the author

Keywords

Grapevine diseases, leaf reflectance, spectroradiometry, disease detection

Tags

IVES Conference Series | Terroir 2020

Citation

Related articles…

Viticultural heritage in mountain territories of Catalonia: prospecting in the region of Osona, northern Spain

The recovery of ancestral or minority vine varieties has been gaining great interest in recent years, among other reasons because it is likely that some of these varieties, due to the fact that they are found in relict areas, have a greater potential for adaptation to external factors (biotic or abiotic) and can minimize the effects that climate change is causing in viticulture. Varieties that can be grown at altitude are currently being sought to combat rising temperatures and prolonged extreme drought conditions. In Catalonia, the Pyrenean expansion of vineyard cultivation is documented from the 10th century and has been related to the “small climatic optimum” (9th-12th centuries) and also to seigniorial power.[1] But different adverse climatic periods and the arrival of Phylloxera by the late 19th century made many of these crops disappear.[2]

Role of Harvesting Time/Optimal Ripeness in Zone/Terroir Expression

La maturité optimale est définie en fonction du style de vin désiré, qui est fonction du marché. Le sol et le climat ont un effet sur la typicité des vins. Le niveau qualitatif des raisins et des vins, et le potentiel pour obtenir différents styles de vin est déterminé par l’association des caractéristiques naturel du terroir et les technologies mises en

La Région Délimitée du Douro et le Vin de Porto — un terroir historique —

The viticulture of the Douro Delimited Region, one of the heirs of ancestral viticulture, traditionally empirical and of quality, while integrating modernity and contemporary tools, respects and has always present the principles on which it was developed.

Wine tannins: What place for grape seed?

Phenolic compounds are among the most important quality factors of wines. They contribute to the organoleptic characteristics of wine such as colour, astringency, and bitterness. Although tannins found in wine can come from microbial and oak sources, the main sources of polyphenols are skin and seed from grapes. Yet, the link between grape seed phenolic content and wine composition, or even the link between seed maturity stage and wine composition are poorly studied. This work describes and explains the seed tannins kinetics release in wine, but also the impact of seed maturity stage on seed tannins extractability.

Effect of Yeast Derivative Products on Aroma compounds retention in model wine

For many years, enological research has developed commercial formulates of yeast derivatives as stabilizing agents and technological adjuvants in winemaking. These products are obtained from yeast by autolytic, plasmolytic, or hydrolytic processes that liberate many macromolecules from the yeast cell, principally polysaccharides and oligosaccharides and most specifically mannoproteins that are well known for their ability to improve tartaric stability and to reduce the occurrence of protein hazes (Ángeles Pozo-Bayón et al., 2009; Charpentier & Feuillat, 1992; Morata et al., 2018; Palomero et al., 2009).