Background and aims – Amaranthus cruentus, native to Mexico and Guatemala, has significant cultural, medicinal, and ornamental uses and growing agricultural relevance. However, little research has focused on its origin and domestication. To determine its domestication syndrome, we identified a set of domestication-linked traits in cultivated A. cruentus and compared them with its wild ancestor A. hybridus and with A. cruentus accessions from different regions. We assessed whether the domestication syndrome enables us (1) to differentiate between the wild and cultivated species and (2) to determine the level of domestication in populations of A. cruentus from different putative centres of domestication.

Material and methods – Populations of A. cruentus and A. hybridus were sampled from Mexico and Guatemala. Ten morphological traits related to vegetative stage, anthesis, and seed maturation were evaluated to identify patterns linked to domestication. PERMANOVA was used to analyse differences in traits between cultivated and wild populations.

Key results – Basal stem size, plant height, inflorescence length, and seed yield (total mass) differed significantly between A. cruentus and A. hybridus. Amaranthus cruentus had a broader range of seed and inflorescence colours. The Mexican accessions had taller plants, longer inflorescences, and greater seed yield than the Guatemalan.

Conclusion – The selected set of characters unambiguously distinguishes the wild A. hybridus from the cultivated A. cruentus, enables differentiation of domestication levels, suggesting that Mexican accessions are more domesticated than the Guatemalan.