Out of America: tracing the genetic footprints of the global diffusion of maize

Abstract

Maize was first domesticated in a restricted valley in south-central Mexico. It was diffused throughout the Americas over thousands of years, and following the discovery of the New World by Columbus, was introduced into Europe. Trade and colonization introduced it further into all parts of the world to which it could adapt. Repeated introductions, local selection and adaptation, a highly diverse gene pool and outcrossing nature, and global trade in maize led to difficulty understanding exactly where the diversity of many of the local maize landraces originated. This is particularly true in Africa and Asia, where historical accounts are scarce or contradictory. Knowledge of post-domestication movements of maize around the world would assist in germplasm conservation and plant breeding efforts. To this end, we used SSR markers to genotype multiple individuals from hundreds of representative landraces from around the world. Applying a multidisciplinary approach combining genetic, linguistic, and historical data, we reconstructed possible patterns of maize diffusion throughout the world from American "contribution" centers, which we propose reflect the origins of maize worldwide. These results shed new light on introductions of maize into Africa and Asia. By providing a first globally comprehensive genetic characterization of landraces using markers appropriate to this evolutionary time frame, we explore the post-domestication evolutionary history of maize and highlight original diversity sources that may be tapped for plant improvement in different regions of the world.

Dissecting maize diversity in lowland South America: genetic structure and geographic distribution models

“…In contrast, no clear delimitation could be achieved among the landraces from the lowland regions of South America, adding further complexity to the testing of dispersal hypotheses. Over the years, studies of molecular diversity have referred to germplasm from the lowlands of South America by different names, such as Other South American maize [1], the Tropical Lowland group [8], the Lowland South American group [11], the South American Lowland, Bolivian Lowland and Costal Brazil groups [12], and the Middle South American group [13]. However, differences in geographical sampling between studies and the lack of integrative analyses make it difficult to assess whether these assemblages belong to the same gene pool and how they relate to each other.…”

Breeding Open-Pollinated, Hybrid and Transgenic Outcrossing Species

“…Today, maize is the most widely grown crop by country number and agro-ecozones, and shows a great culinary adaptation to diverse cultures worldwide. Microsatellite genotyping of hundreds of representative landraces plus a multidisciplinary approach combining genetic, linguistic, and historical data, led to reconstructing the likely patterns of maize diffusion throughout the world (Mir et al 2013). Landrace characterization with DNA markers may also reveal diversity sources that may be used in maize breeding.…”

Improved Representation of Biological Information by Using Correlation as Distance Function for Heatmap Cluster Analysis

“…Mexico is a centre of genetic diversity of maize and many other vegetative species [26]. Numerous Mexican corn varieties with different phenotypic prop-erties, such as grain colour, cob size, and biochemical profile are available in the gene pool [27].…”