Carbon Isotope Composition and the NDVI as Phenotyping Approaches for Drought Adaptation in Durum Wheat: Beyond Trait Selection

Abstract

High-throughput phenotyping platforms provide valuable opportunities to investigate biomass and drought-adaptive traits. We explored the capacity of traits associated with drought adaptation such as aerial measurements of the Normalized Difference Vegetation Index (NDVI) and carbon isotope composition (δ13C) determined at the leaf level to predict genetic variation in biomass. A panel of 248 elite durum wheat accessions was grown at the Maricopa Phenotyping platform (US) under well-watered conditions until anthesis, and then irrigation was stopped and plot biomass was harvested about three weeks later. Globally, the δ13C values increased from the first to the second sampling date, in keeping with the imposition of progressive water stress. Additionally, δ13C was negatively correlated with final biomass, and the correlation increased at the second sampling, suggesting that accessions with lower water-use efficiency maintained better water status and, thus, performed better. Flowering time affected NDVI predictions of biomass, revealing the importance of developmental stage when measuring the NDVI and the effect that phenology has on its accuracy when monitoring genotypic adaptation to specific environments. The results indicate that in addition to choosing the optimal phenotypic traits, the time at which they are assessed, and avoiding a wide genotypic range in phenology is crucial.

Plant phenotyping relevance

NDVIおよび炭素同位体組成を用いたバイオマス・干ばつ適応形質の推定性能と測定時期の影響を評価しており、表現型取得法の応用・技術評価が中心である。

Code and data availability

The paper's Supplementary Materials (hosted at the MDPI URL listed in allowed_urls) contain paper-specific phenotyping assets: Table S1 (flowering time/phenological stage data for the 248 accessions), Tables S2–S3 (linear regressions of biomass vs. NDVI and biomass vs. δ13C), and Figure S1 (image of the field trial at