Genome composition changes due to long term selection by soybean breeders

大豆品种的持续改良依赖于亲本之间足够的遗传变异来产生一个个体群体，在这个群体中有足够的表型变异来改善感兴趣的性状。由于表型变异与遗传多样性呈正相关(Moose和Mumm，2008)，因此大豆育种计划保持足够的遗传多样性水平对于特定性状的持续遗传获得是很重要的。此外，为利基市场开发大豆品种是加拿大大豆育种者的一个重要目标。这就要求种质资源不仅要有产量等性状的遗传多样性，而且要有食品级特性或营养成分等增值性状的遗传多样性。基因组技术的最新进步为研究一个物种的全基因组变化提供了前所未有的能力。通过将这些技术应用到育种计划的系谱中，可以研究由于长期育种人员选择而导致的大豆基因组的特定变化。首先，通过对家系成员进行基因分型，可以表征世代育种活动中遗传多样性的变化。其次，可以跟踪染色体的传递，并确定等位基因组成在世代和选择周期中的变化。 除了选择的整体效果外，还可以使用分子工具检测被称为“选择签名”的特定基因组变化。正如以前的一些研究表明的那样，这些选择签名似乎经常出现在控制农艺重要性状的基因组区域。这项研究的目标是：1)确定由于长期育种家选择而导致的大豆基因组的变化；2)开发基于分子的策略，以促进具有最大遗传潜力的新的和改良的大豆品种的开发，用于公共和私人大豆育种计划。

Continued improvement of soybean varieties relies on sufficient genetic variation between parents to produce a population of individuals in which there is enough phenotypic variation to improve traits of interest. As phenotypic variation is positively associated with genetic diversity (Moose and Mumm 2008) it is important for a soybean breeding program to maintain a sufficient level of genetic diversity for continued genetic gain of a particular trait. In addition, developing soybean varieties for niche markets is an important objective for Canadian soybean breeders. This requires germplasm sources to have genetic diversity not only for traits such as yield, but also value-added traits such as food grade properties or nutraceutical compounds. The recent advancements in genomic technologies allow for unprecedented capabilities when investigating whole-genome changes to a species. By applying these technologies to pedigrees of a breeding program, the specific changes in the soybean genome due to long-term breeder selection can be studied. First, by genotyping the members of a pedigree, the changes in genetic diversity over generations of breeding activity can be characterized. Secondly, the transmission of chromosomes can be tracked and changes in allelic composition over generations and selection cycles can be determined. In addition to the overall effects of selection, specific genomic changes known as "signatures of selection" can be detected using molecular tools. As a number of previous studies have shown, these selection signatures appear to be frequent in genomic regions controlling traits of agronomic importance. The goal of this research is to: 1) determine the changes in the soybean genome due to long-term breeder selection and, 2) develop molecular-based strategies that can be applied to facilitate the development of new and improved soybean cultivars with maximum genetic potential to be used in a public and private soybean breeding program.