Despite the breeding efforts by many institutions, maize (Zea mays L.) productivity in sub‐Saharan Africa is still low. A limited number of productive maize hybrids have been developed partly due to a lack of knowledge on the diversity and heterotic relationship of the germplasm, especially in public breeding programs. Understanding the extent of diversity, structure, and heterotic grouping of available maize germplasm originating from different breeding programs is important to enhance long‐term genetic gain in hybrid maize breeding programs by optimizing heterotic pools using modern breeding tools. Information about the genetic structure of the available germplasm could help breeders design effective breeding strategies to improve yield. This study was conducted to determine the genetic diversity, population structure, and heterotic alignment among 187 elite maize inbred lines from the IITA (International Institute of Tropical Agriculture) and CIMMYT (International Maize and Wheat Improvement Center) maize breeding programs. The inbred lines were genotyped with 9857 Diversity Array Technology sequencing based single nucleotide polymorphism markers. Hierarchical clustering revealed three major groups, with some subgroups consistent with the selection history, and pedigree of the inbred lines. Three broad groups were detected: two consisting of CIMMYT lines and a mixed group consisting of both CIMMYT and IITA inbred lines. The STRUCTURE analysis revealed six subpopulations (fixation index value = 0.58), which depicts a moderate genetic diversity among the materials. Population 2 comprises the highest number of genotypes (102) from both programs. More than 89% of the elite lines had homozygosity exceeding 95%, with the remaining lines requiring further inbreeding through repeated self‐pollination. There was inconsistency in the predetermined heterotic groups' alignment between CIMMYT and IITA elite inbred lines. Analysis of molecular variance revealed that 96% of the total variation was accounted for by differences within groups, with the remaining 4% representing the variation between groups. This suggests that the two programs can benefit from germplasm exchange for the improvement of maize productivity.

中文翻译：

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适应撒哈拉以南非洲的 CIMMYT 和 IITA 玉米自交系的遗传多样性和优势排列评估


尽管许多机构做出了育种努力，但撒哈拉以南非洲的玉米 （Zea mays L.） 生产力仍然很低。开发出数量有限的高产玉米杂交种，部分原因是缺乏对种质多样性和关系的了解，尤其是在公共育种计划中。了解源自不同育种计划的可用玉米种质的多样性、结构和优势分组的程度，对于通过使用现代育种工具优化库来提高杂交玉米育种计划的长期遗传增益非常重要。有关可用种质的遗传结构的信息可以帮助育种者设计有效的育种策略以提高产量。本研究旨在确定来自 IITA（国际热带农业研究所）和 CIMMYT（国际玉米和小麦改良中心）玉米育种计划的 187 个优质玉米自交系的遗传多样性、种群结构和优势排列。使用基于 9857 Diversity Array Technology 测序的单核苷酸多态性标记对自交系进行基因分型。分层聚类揭示了三个主要群体，其中一些亚群与自交系的选择历史和系谱一致。检测到三大类群： 两个由 CIMMYT 系组成，一个混合组由 CIMMYT 和 IITA 自交系组成。STRUCTURE 分析揭示了 6 个亚群 （固定指数值 = 0.58），这描述了材料之间的中等遗传多样性。群体 2 包含两个计划中数量最多的基因型 （102）。 超过 89% 的优良品系的纯合性超过 95%，其余品系需要通过重复自花授粉进一步近亲繁殖。CIMMYT 和 IITA 精英自交系之间预定的优势群体排列不一致。分子方差分析显示，总变异的 96% 是由组内差异引起的，其余 4% 代表组间差异。这表明这两个项目可以从种质交换中受益，以提高玉米生产力。