GiESCO 2019 banner
IVES 9 IVES Conference Series 9 GiESCO 9 GiESCO 2019 9 Disease‐induced alterations in the reflectance spectrum of grape leaves

Disease‐induced alterations in the reflectance spectrum of grape leaves

Abstract

Context and purpose of the study ‐ Phytopathogenic diseases impact the development and yield of grapevines, resulting in economical, social and environmental losses. Sick plants have their metabolism changed, leading to alterations in their reflectance spectra. Little is known on these alterations, and a better knowledge could be used in the development of sensors able to detect diseases through fast, non‐ destructive techniques. The present study was aimed at detecting spectral changes on the reflectance spectra of vines of cv. Cabernet Sauvignon, with early symptoms of downy mildew, powdery mildew, black‐ foot and Petri disease, describing the spectral domains where alterations are measurable with respect to healthy control vines. This information can be used to the development of low‐cost devices which can perform real‐time field measurements to early assessment of vineyard health status.

Material and methods ‐ Plants of Cabernet Sauvignon 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. The investigation began with discriminant analysis, which revealed that symptomatic plants are indeed separated from the control ones. Reflectance spectra were therefore further investigated and alterations on the shape of the spectra, characteristic of each disease, were looked for. 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.

Results ‐ A set of thresholds, which are 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% in reflectance with respect to healthy plants. The observed spectral deformations 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 are in general more useful, compared with measurements at 1900 and 2435nm.

DOI:

Publication date: June 22, 2020

Issue: GiESCO 2019

Type: Article

Authors

Pâmela PITHAN (1), Lucas GARRIDO (3), Diniz ARRUDA (1), Adriane THUM (1,2), Rosemary HOFF (3), Jorge DUCATI (1)

(1) Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970 Porto Alegre, Brazil
(2) Universidade do Vale do Rio dos Sinos, Av. Unisinos 950, 93020-190 São Leopoldo, Brazil
(3) Empresa Brasileira de Pesquisa Agropecuária, R. Livramento 515, 95701-008 Bento Gonçalves, Brazil

Contact the author

Keywords

Grapevine diseases, leaf reflectance, spectroradiometry, disease detection

Tags

GiESCO 2019 | IVES Conference Series

Citation

Related articles…

Shoot positioning: effect on physiological, vegetative and reproductive parameters

[English version below]

On a étudié durant deux saisons de croissance (2002/2003 et 2003/2004) l’effet de l’orientation vertical des rameaux sur les paramètres physiologiques, végétatifs et reproductifs dans la région de Stellenbosch dans un vignoble du cépage Merlot sur 99 R conduite à espalier et taillé a cordon coursonné. Les vignes étaient espacées 2.7 x 1.5 m. L’irrigation a été appliquée quand la baie avait la dimension d’un pois et a la véraison.

INFLUENCE OF THE NITROGEN / LIPIDS RATIO OF MUSTS ON THE REVELATION OF AROMATIC COMPOUNDS IN SAUVIGNON BLANC WINE

Production of volatile compounds by yeast is known to be modulated by must nitrogen. Nevertheless, various parameter of must quality have an impact on yeast fermentation. In this study we propose to evaluate the impact of nitrogen / lipids balance on a Sauvignon Blanc grape juice (Val de Loire).
Must was prepared from the same grapes at pilot scale. Three modalities were carried out: direct pressing, direct pressing with a pre-fermentation cold stabulation and pellicular maceration before pressing.

Efecto de distintos ambientes sobre las características físico – químicas y sensoriales del Montepulciano d’Abruzzo DOC

La región de Abruzzo está situada entre los Apeninos y el mar Adriático, limitando al norte con el río Tronto y al sur con el Trigno. Desde un punto de vista físico se divide en dos franjas

Application of a fluorescence-based method to evaluate the ripening process and quality of Pinot Blanc grape

The chemical composition of grape berries at harvest is one of the most important factors that should be considered to produce high quality wines. Among the different chemical classes which characterize the grape juice, the polyphenolic compound, such as flavonoids, contribute to the final taste and color of wines. Recently, an innovative non-destructive method, based on chlorophyll fluorescence, was developed to estimate the phenolic maturity of red grape varieties through the evaluation of anthocyanins accumulated in the berry skin. To date, only few data are available about the application of this method on white grape varieties.

Epigenetics: an innovative lever for grapevine breeding in times of climate changes

Climate change results in erratic weather conditions, which may lead for many crops including grapevine, to a reduced production and products of lower quality. Concerning grapevine, climate change results in shorter growing seasons and dates for budbreak, flowering and fruit maturity occur earlier in many regions. It also leads to an increase of various pests and diseases, as well as the vectors responsible for disease distribution.