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…

IDENTIFICATION AND LEVELS OF PHENOLIC COMPOUNDS (TANINS, ANTHO-CYANS) IN RED VARIETAL WINES (PROKUPAC AND BLACK TAMJANIKA) FROM SERBIA

The phenolic compounds of red wines represent a source of numerous benefits for human health, which is why they are a constant subject of scientific research. Winemaking in Serbia has a growing economic significance, with particularly autochthonous varieties included [1]. This research identifies and quantifies phenolic compounds of Serbian red varietal wines of Prokupac and Black Tamjanika varieties. Quantification of the level of phenolics has been conducted, including molecular tannins [(+)-catechin, (-)-epicatechin, procyanidin dimers B1, B2, B3, B4], molecular anthocyanins, and the mean degree of polymerization of tannins by HPLC by UV detection, total antioxidant capacity via spectrophotometric methods and chromatic characteristics via CIELAB.

The sea breeze: a significant climatic factor for viticultural zoning in coastal wine growing areas

La brise de mer est un facteur climatique important pour le zonage viticole des régions viticoles côtières car l’accélération du vent qui lui est associée l’après midi ainsi que l’augmentation de l’humidité relative et la réduction de la température concomitantes sont significatives pour le fonctionnement de la vigne et, par conséquent, la qualité du raisin et du vin

The role of climate/soil of different zones/terroirs on grape characteristics

According to the different concern of the ‘traditional’ and the ‘new’ wine-producing Countries, a variable importance is recognized to the climate/soil and to grapevine cultivars as factors affecting the wine quality. However, the viticultural experience can state that, within each area, climate and soil plays an incontestable role in affecting grape quality, and consequently wine quality, as well as the genetic characteristics of the cultivar.

New highlights of polyphenols from red wine to counteract ocular degenerative diseases

More recently, studies have shown that polyphenols could also prevent or improve vision in patients with ocular diseases and especially age-related macular degeneration (AMD) which is an eye disease characterized by damage to the central part of the retina, the macula, and that affects millions of people worldwide. Despite therapeutic advances thanks to the use of anti-vascular endothelial growth factor (VEGF), many resistance mechanisms have been found to accentuate the visual deficit.

Grape texture characteristics are linked to one major qtl

Berry texture and berry skin mechanical properties have high agronomic importance, related to quality and marketing requirements of wine, table and raisin grapes.