Data from: Teosinte in Europe – searching for the origin of a novel weed

A novel weed has recently emerged, causing serious agronomic damage in one of the most important maize-growing regions of Western Europe, the Northern Provinces of Spain. The weed has morphological similarities to a wild relative of maize and has generally been referred to as teosinte. However, the identity, origin or genetic composition of ‘Spanish teosinte’ was unknown. Here, we present a genome-wide analysis of single-nucleotide polymorphism (SNP) data for Spanish teosinte, sympatric populations of cultivated maize and samples of reference teosinte taxa. Our data are complemented with previously published SNP datasets of cultivated maize and two Mexican teosinte subspecies. Our analyses reveal that Spanish teosinte does not group with any of the currently recognized teosinte taxa. Based on Bayesian clustering analysis and hybridization simulations, we infer that Spanish teosinte is of admixed origin, most likely involving Zea mays ssp. mexicana as one parental taxon, and an unidentified cultivated maize variety as the other. Analyses of plants grown from seeds collected in Spanish maize fields and experimental crosses under controlled conditions reveal that hybridization does occur between Spanish teosinte and cultivated maize in Spain, and that current hybridization is asymmetric, favouring the introgression of Spanish teosinte into cultivated maize, rather than vice versa.

近期出现了一种新型杂草，在西欧最重要的玉米种植区之一——西班牙北部省份造成了严重的农业损害。该杂草与玉米的野生近缘种形态相似，通常被称为类蜀黍（teosinte）。然而，‘西班牙类蜀黍’的分类身份、起源与遗传组成此前尚未明确。本研究对西班牙类蜀黍、同域分布的栽培玉米种群以及参考类蜀黍类群样本的单核苷酸多态性（single-nucleotide polymorphism, SNP）数据开展全基因组分析，并整合了已发表的栽培玉米与两个墨西哥类蜀黍亚种的SNP数据集。分析结果显示，西班牙类蜀黍并未与当前已认定的任何类蜀黍类群聚类在一起。基于贝叶斯聚类分析与杂交模拟实验，本研究推断西班牙类蜀黍属于混合起源，其亲本类群大概率为墨西哥类蜀黍亚种（Zea mays ssp. mexicana）与一个未被鉴定的栽培玉米品种。对从西班牙玉米田采集的种子培育的植株以及受控条件下的杂交实验开展的分析表明，西班牙类蜀黍与西班牙境内的栽培玉米确实存在杂交现象，且当前的杂交存在不对称性：更倾向于西班牙类蜀黍的遗传物质向栽培玉米渐渗，而非反向。