An efficient hybrid breeding program defines and utilizes a few heterotic groups. Objectives of this study were to determine genetic diversity and alignment of South Africa maize inbred lines collection towards tropical and temperate testers. Forty-four maize inbred lines were genotyped with 56,110 single nucleotide polymorphism (SNP) markers. A total of 40 lines were crossed to two tropical and two temperate inbred line testers. Due to seed shortages, testcross hybrids containing 14 and 18 lines were used in 2014/2015 and 2015/2016 seasons, respectively. Genotypes and specific combining ability (SCA) effects of hybrids were significantly different (P < 0.05) for grain yield. There was a weak correlation between molecular genetic distances and both grain yield mean performance and SCA effects of hybrids, indicating that productivity of maize inbred lines could not be reliably determined based on molecular genetic distances. The SCA data classified these maize inbred lines into three heterotic groups with respect to both tropical and temperate testers. The study also indicated high level of diversity among the maize inbred lines, which was shown by both the dendogram and molecular genetic distances. The SNP marker data classified the inbred lines into 11 clusters that could be simplified into three major groups of normal maize endosperm and two groups of quality protein maize endosperm types. However, the SNP data indicated that maize lines were more aligned towards the tropical than temperate inbred testers. This information would be useful for simplifying heterotic classification of the lines with profound implications for breeding progress.

一个有效的杂交育种计划定义并利用了一些杂种优势群体。本研究的目的是确定南非玉米自交系收集对热带和温带测试者的遗传多样性和比对。44 个玉米自交系用 56,110 个单核苷酸多态性 (SNP) 标记进行基因分型。总共 40 个品系与两个热带和两个温带自交系测试者杂交。由于种子短缺，分别在 2014/2015 和 2015/2016 季节使用了包含 14 个和 18 个品系的测试杂交杂种。杂种的基因型和特定配合力（SCA）效应对籽粒产量有显着差异（P < 0.05）。分子遗传距离与杂种籽粒产量平均性能和SCA效应之间的相关性较弱，表明不能根据分子遗传距离可靠地确定玉米自交系的生产力。SCA 数据将这些玉米自交系分为热带和温带测试者的三个杂种优势组。该研究还表明玉米自交系之间的高度多样性，这通过树状图和分子遗传距离来显示。SNP标记数据将自交系分为11个簇，可以简化为三个主要的正常玉米胚乳组和两组优质蛋白质玉米胚乳类型。然而，SNP 数据表明玉米品系比温带自交试验者更倾向于热带。该信息将有助于简化对育种进展具有深远影响的品系的杂种优势分类。