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…

IMPACT OF THE WINES’ QUALITY ON THE WINE DISTILLATES’ ORGANOLEPTIC PROFILE

Brandy de Jerez (BJ) is a spirit drink made exclusively from spirits and wine distillates and is characterized by the use of casks for aging that previously contained Sherries. The quality and sensory complexity of BJ depend on the raw materials and some factors: grape variety, conditions during processing the wine and its distillation, as well as the aging in the cask. Therefore, the original compounds of the grapes from which it comes are of great interest (1 y 2) being in most cases the Airén variety. Their relationship with the quality of the musts and the wines obtained from them has been studied (3) and varies each year of harvest depending on the weather conditions (4).

Moderate wine consumption as part of a Mediterranean diet and lifestyle under debate

Moderate wine consumption – with the meals – represents one of the beneficial components of the traditional mediterranean diet (med diet) and a positive item in the med diet score [1,2, 3]. The med diet is considered one of the best diets in the world and the world health organisation (who) identified this eating pattern as an effective strategy to prevent non-communicable diseases (ncd), since it is associated with lower disease occurrence and all-cause mortality [4] . Numerous well-conducted epidemiological studies have also reported that light-to-moderate intake of wine/alcoholic beverages is not only related to a reduced risk of cardiovascular disease, but also to all-cause mortality.

CONSENSUS AND SENSORY DOMINANCE ARE DEPENDENT ON QUALITY CONCEPT DEFINITIONS

The definition of the term “quality” in sensory evaluation of food products does not seem to be consensual. Descriptive or liking methods are generally used to differentiate between wines (Lawless et al., 1997). Nevertheless, quality evaluation of a product such as wine can also relate to emotional aspects. As exposed by Costell (2002), product quality is defined as an integrated impression, like acceptability, pleasure, or emotional experiences during tasting. According to the ‘modality appropriateness’ hypothesis which predicts that wine tasters weigh the most suitable sensory inputs for a specific assess- ment (Freides, 1974; Welch & Warren, 1980), the nature of the quality definitions may modulate sensory influences.

Mitigating the effects of climate change on berry composition by canopy management

Primary and secondary metabolites are major components of grape composition and their balances define wine typicality

Innovative water status monitoring of white grape varieties with on-plant sensors

Context and Purpose. Climate change presents significant challenges to agricultural sustainability, particularly through the increasing frequency of drought and water scarcity.