Abstract：
BACKGROUND: The characterization of genetic diversity and population differentiation for maize inbred lines from breeding programs is of great value in assisting breeders in maintaining and potentially increasing the rate of genetic gain. In our study, we characterized a set of 187 tropical maize inbred lines from the public breeding program of the Universidade Federal de Viçosa (UFV) in Brazil based on 18 agronomic traits and 3,083 single nucleotide polymorphisms (SNP) markers to evaluate whether this set of inbred lines represents a panel of tropical maize inbred lines for association mapping analysis and investigate the population structure and patterns of relationships among the inbred lines from UFV for better exploitation in our maize breeding program.
RESULTS: Our results showed that there was large phenotypic and genotypic variation in the set of tropical maize inbred lines from the UFV maize breeding program. We also found high genetic diversity (GD = 0.34) and low pairwise kinship coefficients among the maize inbred lines (only approximately 4.00 % of the pairwise relative kinship was above 0.50) in the set of inbred lines. The LD decay distance over all ten chromosomes in the entire set of maize lines with r2 = 0.1 was 276,237 kb. Concerning the population structure, our results from the model-based STRUCTURE and principal component analysis methods distinguished the inbred lines into three subpopulations, with high consistency maintained between both results. Additionally, the clustering analysis based on phenotypic and molecular data grouped the inbred lines into 14 and 22 genetic divergence clusters, respectively.
CONCLUSIONS: Our results indicate that the set of tropical maize inbred lines from UFV maize breeding programs can comprise a panel of tropical maize inbred lines suitable for a genome-wide association study to dissect the variation of complex quantitative traits in maize, mainly in tropical environments. In addition, our results will be very useful for assisting us in the assignment of heterotic groups and the selection of the best parental combinations for new breeding crosses, mapping populations, mapping synthetic populations, guiding crosses that target highly heterotic and yielding hybrids, and predicting untested hybrids in the public breeding program UFV.
RESULTS: Our results showed that there was large phenotypic and genotypic variation in the set of tropical maize inbred lines from the UFV maize breeding program. We also found high genetic diversity (GD = 0.34) and low pairwise kinship coefficients among the maize inbred lines (only approximately 4.00 % of the pairwise relative kinship was above 0.50) in the set of inbred lines. The LD decay distance over all ten chromosomes in the entire set of maize lines with r2 = 0.1 was 276,237 kb. Concerning the population structure, our results from the model-based STRUCTURE and principal component analysis methods distinguished the inbred lines into three subpopulations, with high consistency maintained between both results. Additionally, the clustering analysis based on phenotypic and molecular data grouped the inbred lines into 14 and 22 genetic divergence clusters, respectively.
CONCLUSIONS: Our results indicate that the set of tropical maize inbred lines from UFV maize breeding programs can comprise a panel of tropical maize inbred lines suitable for a genome-wide association study to dissect the variation of complex quantitative traits in maize, mainly in tropical environments. In addition, our results will be very useful for assisting us in the assignment of heterotic groups and the selection of the best parental combinations for new breeding crosses, mapping populations, mapping synthetic populations, guiding crosses that target highly heterotic and yielding hybrids, and predicting untested hybrids in the public breeding program UFV.
摘要：
背景：来自育种计划的玉米自交系的遗传多样性和种群分化的表征对于帮助育种者维持并潜在地提高遗传增益率具有重要价值。在我们的研究中,我们根据18个农艺性状和3,083个单核苷酸多态性（SNP）标记，对来自巴西联邦维萨大学（UFV）公共育种计划的187个热带玉米自交系进行了鉴定，以评估这组自交系是否代表一组热带玉米自交系进行关联作图分析，并调查UFV自交系之间的种群结构和关系模式，以便在我们的玉米育种计划中更好地利用。
结果：我们的结果表明，来自UFV玉米育种计划的热带玉米自交系中的表型和基因型变异很大。我们还发现，在玉米自交系中，遗传多样性较高（GD=0.34）和配对亲缘系数较低（仅大约4.00％的配对相对亲缘关系高于0.50）。在r2=0.1的整个玉米品系中，所有十个染色体上的LD衰变距离为276,237kb。关于人口结构，我们基于模型的结构和主成分分析方法的结果将自交系分为三个亚群，在两个结果之间保持高度一致性。此外,基于表型和分子数据的聚类分析将自交系分为14个和22个遗传差异簇，分别。
结论：我们的结果表明，来自UFV玉米育种计划的热带玉米自交系组可以包含一组适用于全基因组关联研究的热带玉米自交系，以剖析复杂数量性状的变异在玉米中，主要在热带环境中。此外,我们的结果将是非常有用的协助我们在杂种优势组的分配和选择最好的亲本组合为新的育种杂交，绘制人口图，绘制合成种群，针对高杂种优势和产量杂种的指导杂交，并在公共育种计划UFV中预测未经测试的杂种。
结果：我们的结果表明，来自UFV玉米育种计划的热带玉米自交系中的表型和基因型变异很大。我们还发现，在玉米自交系中，遗传多样性较高（GD=0.34）和配对亲缘系数较低（仅大约4.00％的配对相对亲缘关系高于0.50）。在r2=0.1的整个玉米品系中，所有十个染色体上的LD衰变距离为276,237kb。关于人口结构，我们基于模型的结构和主成分分析方法的结果将自交系分为三个亚群，在两个结果之间保持高度一致性。此外,基于表型和分子数据的聚类分析将自交系分为14个和22个遗传差异簇，分别。
结论：我们的结果表明，来自UFV玉米育种计划的热带玉米自交系组可以包含一组适用于全基因组关联研究的热带玉米自交系，以剖析复杂数量性状的变异在玉米中，主要在热带环境中。此外,我们的结果将是非常有用的协助我们在杂种优势组的分配和选择最好的亲本组合为新的育种杂交，绘制人口图，绘制合成种群，针对高杂种优势和产量杂种的指导杂交，并在公共育种计划UFV中预测未经测试的杂种。
