Department of Agronomy and Plant Genetics, University of Minnesota, 411 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108, USA.
G3 (Bethesda). 2024 Sep 4;14(9). doi: 10.1093/g3journal/jkae154.
Intermediate wheatgrass (IWG) is a perennial grass that produces nutritious grain while offering substantial ecosystem services. Commercial varieties of this crop are mostly synthetic panmictic populations that are developed by intermating a few selected individuals. As development and generation advancement of these synthetic populations is a multiyear process, earlier synthetic generations are tested by the breeders and subsequent generations are released to the growers. A comparison of generations within IWG synthetic cultivars is currently lacking. In this study, we used simulation models and genomic prediction to analyze population differences and trends of genetic variance in 4 synthetic generations of MN-Clearwater, a commercial cultivar released by the University of Minnesota. Little to no differences were observed among the 4 generations for population genetic, genetic kinship, and genome-wide marker relationships measured via linkage disequilibrium. A reduction in genetic variance was observed when 7 parents were used to generate synthetic populations while using 20 led to the best possible outcome in determining population variance. Genomic prediction of plant height, free threshing ability, seed mass, and grain yield among the 4 synthetic generations showed a few significant differences among the generations, yet the differences in values were negligible. Based on these observations, we make 2 major conclusions: (1) the earlier and latter synthetic generations of IWG are mostly similar to each other with minimal differences and (2) using 20 genotypes to create synthetic populations is recommended to sustain ample genetic variance and trait expression among all synthetic generations.
中间冰草（IWG）是一种多年生禾本科植物，在提供大量生态系统服务的同时，也能生产出有营养的谷物。该作物的商业品种大多是通过少数几个选定个体杂交而产生的合成混合群体。由于这些合成群体的发展和世代推进是一个多年的过程，早期的合成群体由育种者进行测试，随后的世代则被释放给种植者。目前还缺乏对 IWG 合成品种内各世代的比较。在这项研究中，我们使用模拟模型和基因组预测来分析明尼苏达大学推出的商业品种 MN-Clearwater 的 4 个合成世代的群体差异和遗传方差趋势。在通过连锁不平衡测量的群体遗传、遗传亲缘关系和全基因组标记关系方面，4 个世代之间几乎没有差异。当使用 7 个亲本生成合成群体时，遗传方差会减少，而当使用 20 个亲本时，则可以最好地确定群体方差。对 4 个合成世代的株高、自由脱粒能力、种子质量和籽粒产量进行基因组预测，发现世代之间存在一些显著差异，但差异值可以忽略不计。基于这些观察结果，我们得出了 2 个主要结论：（1）IWG 的早期和晚期合成世代彼此之间非常相似，差异极小；（2）建议使用 20 个基因型来创建合成群体，以维持所有合成世代之间充足的遗传方差和性状表达。
