Exploration of glaucous variation in a collection of wild diploid wheat Triticum urartu Thumanjan ex Gandilyan

Glaucousness is the visible opaque-white or bluish-green wax which appears in plant cuticles. Although W1 and Iw1 loci on chromosome 2B mainly play a role to determine glaucousness/non-glaucousness trait in polyploid wheat, in the chromosome 2A of polyploid wheat, the non-glaucous inhibitor locus has not been reported. We explored the glaucous phenotypes for leaf, spike and stem in 274 accessions of Triticum urartu Thumanjan ex Gandilyan (2n = 2x = 14, genome A(u)A(u)), the A genome progenitor of polyploid wheat. The 272 accessions of T. urartu were non-glaucous for leaf, spike and stem. It was thought that non-glaucousness of T. urartu played an important role for plant adaptation throughout the Fertile Crescent. However, PI 662236 was glaucous in leaves, leaf sheaths and spikes, whereas PI 662271 was glaucous on the leaves and leaf sheaths, but non-glaucous in the spikes. Prior to heading PI 662236 and PI 662271 mimicked T. urartu by showing glaucous leaves and leaf sheaths. The plant form and somatic chromosome number indicated that PI 662236 and PI 662271 were tetraploid Triticum dicoccoides (Korn. ex Asch. & Graebn.) Schweinf. (2n = 4x = 28, BBA(u)A(u) genome). The occurrence of T. dicoccoides in the collections of T. urartu demonstrated that even famous botanists can make mistakes in identifying grasses. However, these mistakes lead to finding two rare types of T. dicoccoides with occurrence of glaucousness. The majority of T. dicoccoides that are non-glaucous. The genotype of PI 662236 was assigned as iw1iw1iw3iw3 for glaucousness and that of PI 662271 was iw1iw1Iw3Iw3 for the inhibitors for non-glaucous spikes.

Automated summary

This study investigated the glaucousness in Triticum urartu and identified two rare glaucous types of Triticum dicoccoides, highlighting the importance of non-glaucousness in plant adaptation. The majority of T. dicoccoides are non-glaucous, but the discovery of glaucous variants suggests the potential for genetic diversity in glaucous traits among closely related species.