A genomic journey across the past, present, and future of South American maize.

This article focuses on the complex evolutionary history, dispersal, adaptation, genetic diversity, and conservation of maize (Zea mays ssp. mays) in South America. Maize was domesticated from the wild teosinte Zea mays ssp. parviglumis in southwestern Mexico about 9,000 years ago and subsequently expanded rapidly across the Americas through at least two major migratory waves, giving rise to distinct genetic lineages: ancestral Andean, ancestral Lowland, and Pan-American. Recent genomic studies have revealed a significant contribution of another wild relative, Zea mays ssp. mexicana, through introgression primarily during the second wave, influencing maize adaptation and diversity. Adaptation to highland environments in Mesoamerica and South America appears to have occurred largely independently, with limited genetic convergence, while the adaptive processes in lowland South American maize remain underexplored. The article highlights the considerable morphological and genetic diversity of South American maize landraces, the existence of multiple microcentres of diversity, and the urgent need for expanded genomic and conservation efforts to safeguard this agrobiodiversity amid changing climates and agricultural practices.