研究目的
To detect yellow rust disease in wheat during different growth stages by analyzing hyperspectral reflectance and developing optimal spectral indices.
研究成果
The study successfully developed and validated optimal three-band spectral indices (PRI (570, 525, 705) for early-mid growth stage and ARI (860, 790, 750) for mid-late growth stage) for detecting wheat yellow rust disease. These indices showed high correlation (R2 up to 0.888) and classification accuracy (up to 93.2%), providing a non-destructive remote sensing technique for precision agriculture. Future work should extend to hyperspectral imagery for larger-scale monitoring and include shortwave infrared data.
研究不足
The study is limited to hyperspectral data in the 350-1000 nm range; changes in plant water content in the shortwave infrared region (1300-2500 nm) were not considered. The method may be less accurate in early growth stages due to spectral similarity between healthy and infected wheat. Generalizability to different wheat cultivars and environmental conditions needs further validation.
1:Experimental Design and Method Selection:
The study involved conducting field experiments at two sites (Beijing Xiaotangshan Precision Agriculture Experiment Base and Langfang Experimental Station) to collect canopy spectral reflectance data using an ASD FieldSpec spectrometer. The experiments were designed to include healthy and yellow rust-infected wheat samples across different growth stages (jointing, booting, anthesis, filling, milky ripeness). Statistical methods like linear regression and linear discriminant analysis (LDA) were used to analyze the data and develop spectral indices.
2:Sample Selection and Data Sources:
Wheat cultivars with varying resistance to yellow rust were selected (e.g., 'Jing 411', '98-100', 'Xuezao', 'Mingxian 169'). Samples were inoculated with yellow rust pathogen at different concentrations. Spectral measurements were taken at specific days after sowing (DAS), with sample sizes detailed in Table 2 of the paper.
3:List of Experimental Equipment and Materials:
ASD FieldSpec spectrometer (Analytical Spectral Devices, Boulder, CO, USA) with a 25° field-of-view fore optic, spectral range 350-2500 nm, resolution 3 nm (350-1000 nm) and 10 nm (1000-2500 nm). BaSO4 calibration panel for reflectance correction. Software: MATLAB for data processing, SPSS 20.0 for LDA analysis.
4:0 for LDA analysis.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Canopy spectral reflectance was measured at
5:3 m height above ground, between
00 and 14:00 under cloudless conditions. Each spectrum was measured 20 times and averaged. Disease index (DI) was assessed using the formula DI = (∑ x f) / (n ∑ f) * 100, where x is incidence level, n is highest severity gradient (n=8), f is number of leaves per severity degree.
6:Data Analysis Methods:
Correlation analysis to identify sensitive wavebands. Calculation of all possible three-band combinations in PRI and ARI forms. Linear regression to model relationships between indices and DI, with R2 as evaluation metric. LDA for classification accuracy, using leave-one-out cross-validation.
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