Trait mapping differentiates loci influencing spike and flag leaf glaucousness in wheat

The bluish-white appearance of some plants, known as glaucousness, results from the scattering effect of visible light due to plant surface waxes. This adaptive trait can contribute to tolerance of abiotic stresses in wheat (Triticum aestivum L.) such as drought, solar radiation, and heat. In this study, we identified quantitative trait loci (QTLs) and marker-trait associations for flag leaf and spike glaucousness in two biparental populations and a panel of elite winter wheat lines. For all populations, spike and flag leaf glaucousness were visually scored on a 0-4 scale in multiple environments. Our QTL analyses and association mapping identified a significant locus on the long arm of chromosome 3A (QFlg.ncb-3A) in all populations, explaining up to 36.6 percent of phenotypic variation for flag leaf glaucousness. Further, in one biparental population we identified three QTLs associated with spike glaucousness, located on chromosomes 1B, 2A, and 4D (QSpg.ncb-1B, QSpg.ncb-2A, QSpg.ncb-4D) where they explained up to 22.8, 20.7, and 14.2 phenotypic variation, respectively. The QSpg.ncb-1B QTL is located within the t1RS·1BL translocation from rye (Secale cereale L.) and demonstrates how glaucousness variation can be associated with an alien introgression in wheat. Our results suggest that QFlg.ncb-3A is a primary determinant of flag leaf and, to a lesser extent, spike glaucousness in the evaluated germplasm. Collectively, our results expand the understanding of the genetic control of glaucousness in wheat flag leaf and spikes tissues, suggesting both unique and shared loci may underly the degree of glaucousness on the different plant parts.