Phenotyping High-Throughput Platforms for Drought Tolerance in Nigerian Sorghum: Canopy Temperature, NDVI, and Yield Under Water Stress

This study develops and validates high-throughput phenotyping platforms for drought tolerance in Nigerian sorghum germplasm, specifically evaluating unmanned aerial vehicle-mounted thermal and multispectral sensors for non-destructive assessment of canopy temperature, vegetation indices, and their relationships to yield under water stress. Improving drought tolerance in Nigerian sorghum requires high-throughput phenotyping tools that can efficiently characterise large germplasm collections for stress response traits, overcoming the bottleneck of labour-intensive ground-based measurements. UAV-mounted remote sensing platforms offer a promising high-throughput approach, but their validation for Nigerian sorghum in field conditions has not been conducted. This study uses a UAV platform equipped with a thermal infrared camera and multispectral sensor with five spectral bands to characterise canopy temperature depression, NDVI, GNDVI, and NDWI responses in a panel of 240 Nigerian sorghum genotypes grown under irrigated and water-stressed field conditions at IAR Samaru and University of Maiduguri research stations over two seasons. UAV-derived phenotypic data are validated against ground-truth measurements of leaf temperature, leaf water content, stomatal conductance, and end-of-season grain yield. Genetic parameters for UAV-derived traits are estimated using mixed model analyses. Findings reveal strong correlations between UAV-derived canopy temperature depression and stomatal conductance, validating the thermal sensing approach for stomatal response characterisation under Nigerian field conditions. Broad-sense heritability for canopy temperature depression under stress is 0.72, demonstrating its suitability as a selection trait. The study recommends UAV-based high-throughput phenotyping integration into the IAR sorghum breeding programme.

Keywords: high-throughput phenotyping, drought tolerance, sorghum, UAV, Nigeria.