Departamento de Genética, Escola Superior de Agricultura 'Luiz de Queiróz', Universidade de São Paulo (ESALQ-USP), Piracicaba, SP, Brazil.
Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, AM, Brazil.
Ann Bot. 2018 Mar 14;121(4):625-639. doi: 10.1093/aob/mcx190.
Amazonia is a major world centre of plant domestication, but little is known about how the crops were dispersed across the region. Manioc (Manihot esculenta) was domesticated in the south-western Amazon basin, and is the most important staple food crop that originated in Amazonia. Current contrasting distributions may reflect distinct histories of dispersal of bitter and sweet manioc landraces. To produce new insights into the evolutionary history of the crop, we investigated the contemporary genetic diversity and structure of bitter and sweet manioc along major Amazonian rivers.
The patterns of genetic structure and diversity of wild and cultivated sweet and bitter manioc with four chloroplast and 14 nuclear microsatellite markers were evaluated. Results were interpreted in terms of the crop's dispersal.
No phylogeographic patterns among rivers were detected, and genetic structure among rivers was confounded by the bitter-sweet divergence. However, differences in the distribution of nuclear diversity and somewhat distinctive patterns of genetic structure across rivers were observed within bitter and sweet manioc.
Various pre-Columbian and post-European conquest events in the history of Amazonian occupation may explain the absence of clearer patterns of genetic structure. However, the wide distribution of the most common chloroplast haplotype agrees with an early dispersal of manioc across Brazilian Amazonia. Furthermore, differences in genetic structure and in the spatial distribution of genetic diversity suggest that bitter and sweet manioc had distinct dispersal histories. Knowledge about how prehistoric and contemporary Amazonian peoples manage their crops is valuable for the maintenance and conservation of the impressive diversity of their native crops.
亚马孙地区是世界上主要的植物驯化中心之一，但对于该地区作物的传播方式知之甚少。木薯（Manihot esculenta）起源于亚马孙河流域西南部，是该地区起源的最重要的主食作物。目前分布的差异可能反映了苦木薯和甜木薯不同的传播历史。为了深入了解该作物的进化历史，我们调查了主要亚马孙河流域野生和栽培苦木薯和甜木薯的当代遗传多样性和结构。
利用四个叶绿体和 14 个核微卫星标记，评估了野生和栽培甜木薯和苦木薯的遗传结构和多样性模式。结果根据作物的传播进行了解释。
未检测到河流之间的系统发育模式，并且河流之间的遗传结构受到苦甜分歧的影响。然而，在苦木薯和甜木薯内观察到了核多样性分布的差异以及沿河流的遗传结构存在一些独特的模式。
在亚马孙地区的历史中，可能存在各种前哥伦布时期和欧洲征服后的事件，这些事件可能解释了遗传结构模式不明显的原因。然而，最常见的叶绿体单倍型的广泛分布与木薯在巴西亚马孙地区的早期传播是一致的。此外，遗传结构和遗传多样性的空间分布差异表明，苦木薯和甜木薯的传播历史不同。了解史前和当代亚马孙人民如何管理他们的作物对于维护和保护其本土作物的惊人多样性具有重要意义。
