Data from: Introgression from modern hybrid varieties into landrace populations of maize (Zea mays ssp. mays L.) in central Italy

Landraces are domesticated local plant varieties that did not experienced a deliberate and intensive selection during a formal breeding programme. In Europe, maize landraces are still cultivated, particularly in marginal areas where traditional farming is often practised. Here, we have studied the evolution of flint maize landraces from central Italy over 50 years of on-farm cultivation, when dent hybrid varieties were introduced and their use was widespread. We have compared an 'old' collection, obtained during the 1950s, before the introduction of hybrids, and a recent collection of maize landraces. For comparison, a sample of maize landraces from north Italy, and of improved germplasm, including hybrids and inbred lines were also used. A total of 296 genotypes were analysed using 21 microsatellites. Our results show that the maize landraces collected in the last 5-10 years have evolved directly from the flint landrace gene pool cultivated in central Italy before the introduction of modern hybrids. The population structure, diversity and linkage disequilibrium analyses indicate a significant amount of introgression from hybrid varieties into the recent landrace populations. No evidence of genetic erosion of the maize landraces was seen, suggesting that in-situ conservation of landraces is an efficient strategy for preserving genetic diversity. Finally, the level of introgression detected was very variable among recent landraces, with most of them showing a low level of introgression; this suggests that co-existence between different types of agriculture is possible, with the adoption of correct practices that are aimed at avoiding introgression from undesired genetic sources.地方品种（landrace）指未在正式育种计划中经历刻意且高强度选择的驯化本土植物品种。在欧洲，玉米地方品种仍有种植，尤其在传统农耕盛行的边缘地区。本研究针对意大利中部硬质型玉米地方品种，在马齿型杂交玉米品种引入并得到广泛推广的50余年间的农田种植演化过程展开分析。我们对比了杂交品种引入前的1950年代采集的"早期"种质资源，与近期采集的玉米地方品种样本；同时纳入意大利北部的玉米地方品种样本，以及包含杂交品种与自交系在内的改良种质作为对照。本研究共利用21个微卫星（microsatellites）标记对296份基因型材料进行分析。结果显示，近5至10年间采集的玉米地方品种，直接起源于现代杂交品种引入前意大利中部种植的硬质型地方品种基因库。群体结构、遗传多样性与连锁不平衡（linkage disequilibrium）分析表明，杂交品种向近期地方品种群体发生了显著程度的基因渐渗（introgression）。未观测到玉米地方品种存在遗传侵蚀（genetic erosion）现象，这说明地方品种的原位（in-situ）保存是保护遗传多样性的有效策略。最后，不同近期地方品种间的基因渐渗水平差异显著，多数样本仅表现出低水平的基因渐渗；这提示，通过采用规避非预期遗传来源基因渐渗的合理耕作措施，不同农业类型间的共存是可行的。