Abstract Grain yield progress over 50 years of spring wheat breeding at the International Maize and Wheat Improvement Center (CIMMYT) was determined in field trials conducted during five crop seasons (2013–2017) at Norman E. Borlaug research station near Ciudad Obregon, Mexico. The trials included 30 varieties (24 bread wheat and 6 durum wheat) released between 1965–2014 and were sown under managed optimum, drought, and heat stress conditions. The optimum irrigated environment had 3 management systems, flat sowing with weekly drip irrigation (FDI), bed sowing with flood irrigation (BFI), and flat sowing with flood irrigation (FFI). The drought environment had 2 management systems, flat sowing with reduced irrigation (FRI) and flat sowing under severe drought stress (FSD). The heat stress environment was sown in beds (HFI) three months later than the normally sown irrigated and drought environments. The rate of grain yield progress was estimated relative to Sonalika released in 1965 and Mexicali C75 released in 1975 for bread and durum wheat, respectively. Grain yield progress per year for bread wheat was, 31.2 kg ha−1, 35.3 kg ha−1, and 24.7 kg ha−1 in irrigated environments FDI, BFI, and FFI, respectively. In the stress environments, bread wheat grain yield progress was estimated as 25.6 kg ha−1, 17.7 kg ha−1, and 18.1 kg ha−1 per year in FRI, FSD, and HFI, respectively. For durum wheat, the grain yield progress was estimated as 29.6 kg ha−1, 48.1 kg ha−1, 18.8 kg ha−1, and 29.8 kg ha−1, per year in FDI, BFI, FFI, and HFI, respectively. Trait linkage graph analysis using LASSO regularized graphical model estimated that biomass, harvest index, and grains per meter square (GNM) were linked to grain yield progress in all environments. Thousand kernel weight was associated with grain yield progress under optimum and heat stress conditions, whereas grain weight per tiller (GWT) associated with progress under drought. Results also show that the highest yielding varieties in each environment however, had different trait attributes, with some varieties having higher GNM and tillers per meter square compensating for low GWT, while others had high GWT to compensate for reduced GNM. In conclusion, CIMMYT’s wheat breeding program has continued to show progress in grain yield in different environments/management systems, and while certain traits have consistently improved over the years, the varieties developed have employed different trait strategies to achieve final grain yield.

中文翻译：

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CIMMYT 半矮化春小麦育种五十年：最佳、干旱和热应激环境下的粮食产量进展

摘要 国际玉米和小麦改良中心 (CIMMYT) 50 年春小麦育种的粮食产量进展是在墨西哥奥布雷贡城附近的 Norman E. Borlaug 研究站在五个作物季节（2013-2017 年）进行的田间试验中确定的。试验包括 1965 年至 2014 年间发布的 30 个品种（24 个面包小麦和 6 个硬粒小麦），并在最佳管理、干旱和热应激条件下播种。最佳灌溉环境有 3 种管理系统，每周滴灌平播 (FDI)、漫灌平播 (BFI) 和漫灌平播 (FFI)。干旱环境有两种管理系统，平播减灌（FRI）和严重干旱胁迫下平播（FSD）。热应激环境比正常播种的灌溉和干旱环境晚三个月播种在床上（HFI）。相对于 1965 年发布的 Sonalika 和 1975 年发布的 Mexicali C75，分别针对面包和硬粒小麦估算了谷物产量进步率。在 FDI、BFI 和 FFI 灌溉环境中，面包小麦每年的粮食产量进步分别为 31.2 kg ha-1、35.3 kg ha-1 和 24.7 kg ha-1。在胁迫环境中，FRI、FSD 和 HFI 中面包小麦籽粒产量进展估计分别为每年 25.6 kg ha-1、17.7 kg ha-1 和 18.1 kg ha-1。对于硬粒小麦，FDI、BFI、FFI 和 HFI 的谷物产量进展估计分别为每年 29.6 kg ha-1、48.1 kg ha-1、18.8 kg ha-1 和 29.8 kg ha-1。使用 LASSO 正则化图形模型的性状关联图分析估计，生物量、收获指数和每平方米谷物 (GNM) 与所有环境中的谷物产量进展相关。在最佳和热胁迫条件下，千粒重与谷物产量进展相关，而每分蘖粒重 (GWT) 与干旱条件下的进展相关。然而，结果还表明，每个环境中产量最高的品种具有不同的性状属性，一些品种具有较高的 GNM 和每平方米分蘖补偿低 GWT，而其他品种具有高 GWT 以补偿降低的 GNM。总而言之，CIMMYT 的小麦育种计划在不同环境/管理系统中继续显示出谷物产量的进步，虽然某些性状多年来一直在改善，