Exploiting genotype × environment interaction (GEI) by specific selection for well-defined subregions could contribute to more productive and sustainable cropping systems. This case study aimed to verify this hypothesis by assessing actual genetic gains from phenotypic and genotypic selection for alfalfa (Medicago sativa L.) biomass yield in two subregions of northern Italy with contrasting GEI pattern (subregion A, featuring sandy-loam soil and no summer drought as a result of irrigation; subregion C, featuring silty-clay soil and summer drought resulting from rainfed cropping). Selection and test environments were mainly represented by four managed environments created by the factorial combination of the relevant soil types and drought stress levels. Genotypic selection depended on yield responses of 90 half-sib families in the environment representing each subregion (specific adaptation) or across these environments (wide adaptation); phenotypic selection for wide or specific adaptation was stratified for single plants in different environments. Half-sib family data indicated modest genetic correlation between subregions (r_g = 0.56). Biomass yield data of six selections and six cultivars or landraces providing their genetic base revealed at least twofold greater yield gains for specific adaptation over wide adaptation for phenotypic or genotypic selection, with a minimum within-subregion advantage of 43%. On average, genotypic selections displayed over 10-fold greater yield progress than phenotypic selections. Adaptation strategies had negligible impact on seed yield and leaf-to-stem ratio of the selections. Experiment data from seven agricultural environments highlighted the importance of breeding for specific adaptation to achieve yield progress over locally top-performing commercial varieties. Circumstances that support a specific-adaptation strategy were discussed.

中文翻译：

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区域适应性利用的育种收益：苜蓿案例研究

通过对明确定义的次区域的特定选择来利用基因型 × 环境相互作用 (GEI) 可以有助于提高生产力和可持续的种植系统。本案例研究旨在通过评估苜蓿 ( Medicago sativa)表型和基因型选择的实际遗传收益来验证这一假设。L.) 意大利北部两个具有对比的 GEI 模式的子区域的生物量产量（子区域 A，以沙壤土为特征，灌溉没有夏季干旱；子区域 C，以粉质粘土和雨育作物导致的夏季干旱为特征） . 选择和测试环境主要由四个管理环境代表，这些环境由相关土壤类型和干旱胁迫水平的因子组合创建。基因型选择取决于 90 个半同胞家族在代表每个子区域（特定适应）或跨这些环境（广泛适应）的环境中的产量反应；广泛或特定适应的表型选择针对不同环境中的单个植物进行分层。半同胞家族数据表明亚区之间存在适度的遗传相关性（r_g = 0.56）。六个选择和六个提供其遗传基础的栽培品种或地方品种的生物量产量数据显示，特定适应的产量增益至少是表型或基因型选择的广泛适应的两倍，最小的亚区域内优势为 43%。平均而言，基因型选择显示出比表型选择高 10 倍以上的产量进展。适应策略对种子产量和选择的叶茎比的影响可以忽略不计。来自七个农业环境的实验数据强调了进行特定适应育种的重要性，以实现比当地表现最佳的商业品种更高的产量。讨论了支持特定适应策略的情况。