White clover (Trifolium repens L.), an economically important forage legume in temperate pastures, provides quality herbage and plant-available nitrogen. Enhancing breeding efforts to improve dry matter (DM) yield and vegetative persistence will increase on-farm value of this forage. To increase genetic gain for such traits, breeding tools like genomic selection have proven to be highly valuable in other crops. However, its success relies on a sufficiently large training population and key fundamentals of selective breeding, that is, presence of additive variation. We investigated quantitative genetic parameters for spring DM yield and vegetative persistence in a white clover training population comprising 200 half-sibling (HS) families. This population was established in a replicated cattle-grazed, mixed-sward field trial at two contrasting locations and assessed for spring DM yield and stolon-related vegetative persistence traits over a 3-yr period. The additive variation and genotype × environment interactions, comprising the effects from year, season, and location were significant (P < .05) for most traits. Narrow-sense heritability for all traits ranged from low (.13; post-summer stolon branches) to high (.73; leaf size) and there was a positive phenotypic correlation (.28) between spring DM yield and stolon number. These results indicate that both spring DM yield and persistence can be concurrently improved through selective breeding in the current population. We also demonstrated that applying a high selection pressure produces the highest predicted genetic gain. There is, however, a trade-off between genetic gain and diversity in the population for the long-term success of a breeding program.

中文翻译：

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白三叶草训练种群干物质产量和营养持久性相关性状定量遗传参数的估计

白三叶草（Trifolium repensL.)，一种在温带牧场具有重要经济意义的豆科牧草，提供优质牧草和植物可利用的氮。加强育种工作以提高干物质 (DM) 产量和营养持久性将增加这种牧草的农场价值。为了增加这些性状的遗传增益，基因组选择等育种工具已被证明在其他作物中具有很高的价值。然而，它的成功依赖于足够大的训练人群和选育的关键基础，即加性变异的存在。我们调查了由 200 个同父异母 (HS) 家族组成的白三叶草训练种群的春季干物质产量和营养持久性的定量遗传参数。这个种群建立在一个复制的放牧牛群中，在两个对比地点进行混合草地田间试验，并评估春季 DM 产量和 3 年期间与匍匐茎相关的植物持久性状。加性变异和基因型×环境相互作用，包括来自年份、季节和位置的影响是显着的（P < .05) 对于大多数特征。所有性状的狭义遗传力范围从低（0.13；夏后的匍匐茎分枝）到高（0.73；叶片大小），春季干物质产量和匍匐茎数量之间存在正表型相关性（0.28）。这些结果表明，通过在当前种群中进行选择性育种，可以同时提高春季 DM 产量和持久性。我们还证明，应用高选择压力会产生最高的预测遗传增益。然而，为了育种计划的长期成功，种群的遗传增益和多样性之间存在权衡。