Spectral reflectance indices as a rapid and nondestructive phenotyping tool for estimating different morphophysiological traits of contrasting spring wheat germplasms under arid conditions

SALAH EL-HENDAWY; NASSER AL-SUHAIBANI; ABD EL-AZEEM SALEM; SHAFIQ UR REHMAN; URS SCHMIDHALTER

Spectral reflectance indices as a rapid and nondestructive phenotyping tool for estimating different morphophysiological traits of contrasting spring wheat germplasms under arid conditions

Authors: SALAH EL-HENDAWY, NASSER AL-SUHAIBANI, ABD EL-AZEEM SALEM, SHAFIQ UR REHMAN, URS SCHMIDHALTER

Abstract: The aim of this study was to investigate whether spectral reflectance indices could be used to estimate different destructive morphophysiological traits of a wide and diverse range of spring wheat germplasm in a rapid and nondestructive manner. A total of 90 spring wheat germoplasms were evaluated under water shortage by applying only three irrigations during the growing cycle of germplasm with the amount of water totaling 2550 m³ ha^-1. Ten selected spectral reflectance indices were related to the green leaf number per plant, green leaf area per plant, total dry weight per plant (TDW), grain yield per hectare (GY), leaf water content (LWC), leaf area index (LAI), and canopy temperature (CT). Significant genotypic variability was shown for all morphophysiological traits and the ten selected spectral reflectance indices. The broad-sense heritability of the normalized water index (NWI)-3, NWI-4, water band index (WBI), and normalized difference vegetation index (NDVI) was high to medium as reflected in the morphophysiological traits, while for other spectral reflectance indices it was low. The indices NWI-3 and NWI-4 proved to be better predictors for LWC, GY, and LAI than NWI-1 and NWI-2. Spectral indices based on combine visible and near-infrared wavelengths such as the NDVI, the ratio of WBI/NDVI, and the R₉₄₀/R₉₆₀/NDVI were viable options to estimate TDW, GY, and LAI, whereas the WBI and R1₀₀₀/R₁₁₀₀ had the best fit to LWC. The R₉₄₀/R₉₆₀ index failed to capture the genotypic variability in any morphophysiological traits. The LAI was more correlated to and had more direct effects on all agronomic traits than CT. The overall results indicated that it is indeed possible to apply spectral reflectance tools in wheat breeding programs to estimate the destructive morphophysiological traits and assess genotypic variability of a large number of germplasms in a rapid and nondestructive manner.

Keywords: Canopy reflectance, canopy temperature, leaf area index, morphophysiological traits, phenomics

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