Departamento de Genética, Universidade de São Paulo, Escola Superior de Agricultura Luiz de Queiroz, Piracicaba, SP, 13418-900, Brazil.
Universidad Tecnológica del Uruguay, Durazno 97000, Uruguay.
Ann Bot. 2022 May 12;129(6):737-751. doi: 10.1093/aob/mcac049.
The lowlands of South America appear to be remarkably important in the evolutionary history of maize, due to new evidence that suggests that maize dispersed from Mexico and arrived in this region in a state of partial domestication. This study aimed to identify dispersal patterns of maize genetic diversity in this part of the continent.
A total of 170 maize accessions were characterized with 4398 single nucleotide polymorphisms (SNPs) and analysed to determine if maize dispersal was associated with types of endosperm and indigenous language families.
Four genetic groups were identified in the discriminant analysis of principal components and five groups in the cluster analysis (neighbour-joining method). The groups were structured according to the predominance of endosperm types (popcorn, floury, flint/semi-flint). Spatial principal component analysis of genetic variation suggests different dispersal patterns for each endosperm type and can be associated with hypotheses of expansions of different indigenous groups.
From a possible origin in Southwestern Amazonia, different maize dispersal routes emerged: (1) towards Northern Amazonia, which continued towards the Caatinga and south-eastern Atlantic Forest (Floury); (2) towards Southern Brazil, passing through the Cerrado and Southern Atlantic Forest reaching the Pampa region (Floury); and (3) along the Atlantic Coast, following Tupi movements originating from two separate expansions: one (Tupinamba) from north to south, and the other (Guarani) in the opposite direction, from south to north (flint, floury and popcorn).
由于新的证据表明玉米从墨西哥扩散而来，并在部分驯化的状态下到达该地区，南美洲的低地在玉米的进化历史中似乎显得非常重要。本研究旨在确定该大陆这一地区玉米遗传多样性的扩散模式。
共对 170 份玉米品系进行了 4398 个单核苷酸多态性（SNP）的特征分析，以确定玉米的扩散是否与胚乳类型和土著语系有关。
在主成分判别分析和聚类分析（邻接法）中分别鉴定出 4 个和 5 个遗传群。这些群体是根据胚乳类型（爆米花、粉质、硬质/半硬质）的优势来构建的。遗传变异的空间主成分分析表明，每种胚乳类型的扩散模式不同，这可能与不同土著群体扩张的假说有关。
从亚马逊西南部的一个可能起源地，出现了不同的玉米扩散途径：（1）向亚马逊北部扩散，然后继续向卡廷加和东南大西洋森林扩散（粉质）；（2）向巴西南部扩散，穿过塞拉多和南大西洋森林，到达潘帕地区（粉质）；（3）沿着大西洋海岸，沿着图皮人从两个独立的扩张而来的运动方向扩散：一个方向（图皮纳姆巴）从北向南，另一个方向（瓜拉尼）从南向北（硬质、粉质和爆米花）。
