Genetic diversity and population structure of native maize populations in Latin America and the Caribbean

Abstract

This study describes the genetic diversity and population structure of 194 native maize populations from 23 countries of Latin America and the Caribbean. The germplasm, representing 131 distinct landraces, was genetically characterized as population bulks using 28 SSR markers. Three main groups of maize germplasm were identified. The first, the Mexico and Southern Andes group, highlights the Pre-Columbian and modern exchange of germplasm between North and South America. The second group, Mesoamerica lowland, supports the hypothesis that two separate human migration events could have contributed to Caribbean maize germplasm. The third, the Andean group, displayed early introduction of maize into the Andes, with little mixing since then, other than a regional interchange zone active in the past. Events and activities in the pre- and post-Columbian Americas including the development and expansion of pre-Columbian cultures and the arrival of Europeans to the Americas are discussed in relation to the history of maize migration from its point of domestication in Mesoamerica to South America and the Caribbean through sea and land routes.

Diversity of Treegourd (Crescentia cujete) Suggests Introduction and Prehistoric Dispersal Routes into Amazonia

“…This route is linked to the coastal Guianas, an ancient area of exchange of Amazonian crops with Mesoamerica (Schultes, 1984). Molecular data of early maize (Zea mays) introduction into South America support dispersal from Mesoamerica through the Caribbean, spreading along the lowlands of the northeastern coast of South America to finally reach Amazon Basin through river systems (Freitas et al, 2003;Bedoya et al, 2017), although the oldest archaeological remains of maize are western (Bush et al, 2016). This route also agrees with pineapple dispersal from the Guianas, where it was domesticated and introduced into Mexico (Coppens D'Eeckenbrugge and Duval, 2009).…”

Genetic Structure, Core Collection, and Regeneration Quality in White Dent Corn Landraces

“…They were chosen from the Maize GDB database (http://www.maizegdb.org) using a genome coverage criterion (Supplemental Material S3). The selected SSRs have already been used by Dubreuil et al (2006), Cömertpay et al (2012), Warburton et al (2010), and Bedoya et al (2017) in studies of diversity and genetic structure of maize landraces and open‐pollinated varieties using DNA bulk sampling.…”

“…The raw data obtained in Peak Scanner were transcribed to Excel sheets and submitted to the program FreqsR (Franco et al, 2005) on the R platform (R Development Core Team, 2013) to determine the allele frequencies in each population calculated on the basis of peak heights (Franco et al, 2005; Dubreuil et al, 2006; Bedoya et al, 2017).…”

“…Although Uruguay is situated far from the center of origin of maize (9000 yr ago in Mexico and Mesoamerica; Bedoya et al, 2017), an indirect registry of maize was found in southeast Uruguay dating back 4100 yr (Iriarte et al, 2004). The white dent race of maize in Uruguay may come from diverse origins and numerous subsequent hybridization events (Paterniani and Goodman, 1977).…”

“…Microsatellites, or simple sequence repeats (SSRs), are codominant, robust markers well adapted to the analysis of DNA derived from pooled sampling (bulk strategy) (Reif et al, 2005a; Dubreuil et al, 2006). The bulk strategy, in which tissue from several individuals from an outcrossing population is bulked for genetic analysis, has been successfully implemented in several maize genetic diversity studies (Sharma et al, 2010; Warburton et al, 2010; Cömertpay et al, 2012; Bedoya et al, 2017), which revealed good correlation between bulk and individual samples in terms of estimated allele frequencies (Reif et al, 2005a). Bulking is an efficient approach, allowing the generation of useful datasets in a rapid and economical manner.…”