Inversion of winter wheat yellow rust serious degrees by hyperspectral data

This paper focused on developing the appropriate spectral index to monitor yellow rust disease, which is relatively insensitive to species, canopy structures (such as leaf area index and leaf distribution angles), foliar inner structures, and soil condition variations. Firstly, canopy spectra and canopy chlorophyll concentration were acquired during growth duration, and the relationship between SPAD value and measured chlorophyll concentration was established. It indicated that the logarithmic relationship exists between TCARI/OSAVI and SPAD value, with a coefficient of determination R² = 0.7795 (n = 320). Therefore, the combined index (CCII) can be used to minimize the effects of LAI and no photosynthetic materials on the retrieval of chlorophyll concentration at canopy level. Secondly, The photochemical reflectance index (PRI) was chosen for disease index inversion by minimizing internal leaf structure effect, has and the linear negative relationship exists between the normalized photochemical reflectance index (NPRI) and disease index (DI), with a coefficient of determination R² = 0.8477 (n = 63), so the normalized photochemical reflectance index (NPRI) can be used to monitor the disease index of yellow rust