Amaranth, the ancient pseudocereal: a promising crop for climate-resilient agriculture and healthy diets

<i>Amaranthus</i> spp. are plant species native to America. They are widely cultivated in tropical and subtropical regions worldwide. Some species in this genus are considered dual-crops. Their seeds and leaves can be used for both human and animal consumption. Grain and leafy amaranth are gluten-free and rich in protein, unsaturated fatty acids, vitamins, minerals, and low glycemic index carbohydrates. Traditionally, it was grown as a pseudocereal grain, especially in Central and North America. However, cultivated amaranth species still show semidomesticated traits. These traits need to be improved with current agribiotechnological methods. In this review, the actual knowledge on this emerging crop is presented, including centuries of traditional breeding techniques. The journey from history to domestication and taxonomic characterization is summarized. Furthermore, aspects of the responses to abiotic and biotic stresses of this alternative and emerging crop are analyzed in the context of climate change. Finally, the application of new genetic transformation techniques and plant breeding strategies is discussed. This provides a global perspective on the future potential of this emerging crop. However, despite all the advances made with amaranth, future challenges remain in several areas: in scientific research, which requires the full applicability of agribiotechnological methods and knowledge of the molecular basis of pest resistance and stress tolerance; in agriculture, as the optimization of agronomic practices and post-harvest management; and in the market and industry, such as marketing techniques and policies.