Physiological and genetic drivers underpinning canopy development are associated with durum wheat yield in rainfed environments

Durum wheat (Triticum turgidum L. ssp. Durum) is largely grown in rainfed production systems around the world. New cultivars with improved adaptation to water-limited environments are required to sustain productivity in the face of climate change. Physiological traits related to canopy development underpin the production of biomass and yield, as they interact with solar radiation and affect the timing of water use throughout the growing season. Despite their importance, there is limited research on the relationship between canopy development and yield in durum wheat, in particular studies exploring temporal canopy dynamics under field conditions. This study reports the genetic dissection of canopy development in a durum wheat nested-association mapping population evaluated for longitudinal normalized difference vegetation index (NDVI) measurements. Association mapping was performed to identify quantitative trait loci (QTL) for time-point NDVI and spline-smoothed NDVI trajectory traits. Yield effects associated with QTL for canopy development were explored using data from four rainfed field trials. Four QTL were associated with yield in specific environments, and notably, were not associated with a yield penalty in any environment. Alleles associated with slow canopy closure increased yield. This was likely due to a combined effect of optimised timing of water-use and pleiotropic effects on yield component traits, including spike number and spike length. Overall, this study suggests that slower canopy closure is beneficial for durum wheat production in rainfed environments. Selection for traits or loci associated with canopy development may indirectly improve yield and support selection for more resilient and productive cultivars in water limited environments.