Grape production in the Serra Gaúcha region, south of Brazil, is severily constrained by several diseases such as the decline and death syndrome caused grapevine trunk (fungal) diseases (GTDs) and the grapevine leafroll-associated virus (GLRaV). As pathogens induce changes in leaf tissue that modify the reflectance, the spectral signature of asymptomatic and symptomatic grapevine leaves infected by GTDs and GLRaV was analyzed to check whether spectral responses could be useful for disease identification. This work aims at (a) defining the spectral signature of grapevine leaves asymptomatic and symptomatic to GTDs and GLRaV; b) analyzing whether the spectral response of asymptomatic leaves can be distinguished from symptomatic; and (c) defining the most useful wavelengths for discriminating spectral responses. For such, reflectance of leaves in either condition collected in a “Merlot” vineyard during three growing seasons was measured using a spectroradiometer. Principal components and partial least square discriminant analyses confirmed the spectral separation and classes discrimination. The average spectra, difference spectra, and first-order derivative (FOD) spectra indicated differences between asymptomatic and symptomatic leaves in the green peak (520–550 nm), chlorophyll-associated wavelengths (650–670 nm), red edge (700–720 nm), beginning of near-infrared (800–900 nm), and shortwave infrared. Hyperspectral data was linked to biochemical and physiological changes described for GTD and GLRaV. Variable importance in the projection (VIP) analysis showed that some wavelengths allowed to differentiate the tested pathosystems and could serve as a basis for further validation and disease classification studies.

中文翻译：

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叶子高光谱反射作为检测与葡萄园衰退相关的疾病的潜在工具

巴西南部 Serra Gaúcha 地区的葡萄生产受到多种疾病的严重限制，例如由葡萄干（真菌）病（GTD）和葡萄卷叶相关病毒（GLRaV）引起的衰退和死亡综合症。由于病原体会引起叶片组织的变化，从而改变反射率，因此分析了被 GTD 和 GLRaV 感染的无症状和有症状葡萄藤叶片的光谱特征，以检查光谱响应是否可用于疾病识别。这项工作旨在 (a) 定义对 GTD 和 GLRaV 无症状和有症状的葡萄叶的光谱特征；b) 分析无症状叶片的光谱反应是否可以与有症状的叶片区分开来；(c) 定义最有用的波长以区分光谱响应。对于这样，使用分光辐射计测量在三个生长季节期间在“梅洛”葡萄园中收集的任一条件下的叶子的反射率。主成分和偏最小二乘判别分析证实了光谱分离和类别判别。平均光谱、差分光谱和一阶导数 (FOD) 光谱表明绿色峰（520-550 nm）、叶绿素相关波长（650-670 nm）、红色边缘（700- 720 nm)、近红外 (800–900 nm) 和短波红外的开始。高光谱数据与 GTD 和 GLRaV 描述的生化和生理变化有关。