Grape quality assessment in vineyards affected by iron deficiency chlorosis using narrow-band physiological remote sensing indices

Abstract

The present study investigated the use of physiological indices calculated from hyperspectral remote sensing imagery as potential indicators of wine grape quality assessment in vineyards affected by iron deficiency chlorosis. Different cv. Tempranillo/110 Richter vineyards located in northern Spain, affected and non-affected by iron chlorosis, were identified for field and airborne data collection. Airborne campaigns imaged a total of 14 study areas in both 2004 and 2005 using the AHS hyperspectral sensor, which acquired 20 spectral bands in the VIS-NIR region. Field measurements were conducted in each study site to obtain leaf and grape physiological parameters potentially linked to wine quality. Simulations carried out with the rowMCRM radiative transfer model demonstrated the feasibility of estimating leaf chlorophyll a + b ( C ab) content using TCARI/OSAVI from AHS spectral bands. In addition to traditional structural vegetation indices (NDVI) and successful canopy-level chlorophyll indices (TCARI/OSAVI), other innovative physiological indices sensitive to changes in carotenoid ( Car) and anthocyanin ( Anth) content in leaves were assessed from the imagery. The rowMCRM model simulations were used to evaluate canopy structural effects on these physiological indices as a function of the typical row-structured canopy variables in vineyards (LAI, crown width, row distances, C ab content and soil background effects). Modeling results concluded that Car (Gitelson- Car2) and Anth (Gitelson- Anth) indices were highly affected by canopy structure ( C w, V s) and soil background ( ρ s). Field measurements of grape composition and quality were used to assess potential relationships with physiological indices sensitive to foliar pigment content ( C ab, Car and Anth). NDVI and TCARI/OSAVI indices yielded lower relationships for CIRG and IMAD must quality parameters than Car and Anth physiological indices. These results suggest that the increase in carotenes and anthocyanins due to drought, thermal damage or micronutrient deficiencies is a better indicator to detect phenolic ripening difficulties for vines affected by iron chlorosis than chlorosis detection. Therefore, the potential use of physiological remote sensing indices related to carotene and anthocyanin pigments demonstrates their importance as grape quality indicators in vineyards affected by iron chlorosis.