Widespread use of legume green manures is limited by a lack of reliable varieties that meet the needs of farmers. Improving symbiotic N fixation (SNF) in open-pollinated legume species poses a challenge because normal methods used for assessing SNF conflict with breeding practices such as seed production and removing low-quality sires. We investigated methods for measuring symbiotic N fixation that are compatible with breeding practice for two major legume cover crops: hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.). We collected two nondestructive samples at the early-flowering stage (Meristem and Wedge) and a sample at seed harvest (Seed). Our objective was to determine which combination of measurements best predicted symbiotic N fixation (% N derived from atmosphere [Ndfa]) and total N content at 50% flowering. Our statistical approach accommodated the problem that target traits and seed measurements cannot be measured in the same individuals. Overall, the Wedge sample provided the best prediction for Ndfa at 50% flowering. The best predictions for total N plant^–1 came from combining vigor ratings with aboveground biomass at seed harvest. In addition to specific recommendations for legume cover crop breeding programs, we provide a flexible statistical method for studying relationships between traits that cannot be measured jointly.

中文翻译：

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估算绿肥育种计划中与农艺相关的共生固氮作用

由于缺乏满足农民需求的可靠品种，豆科绿肥的广泛使用受到限制。改善开放授粉豆科植物的共生固氮 (SNF) 是一项挑战，因为用于评估 SNF 的常规方法与育种实践（如种子生产和去除低质量种公牛）相冲突。我们研究了测量共生固氮的方法，这些方法与两种主要豆科覆盖作物的育种实践兼容：多毛紫云英 ( Vicia villosa Roth) 和深红色三叶草 ( Trifolium incarnatumL.）。我们在开花早期（分生组织和楔形）收集了两个无损样品，在种子收获时收集了一个样品（种子）。我们的目标是确定哪种测量组合最能预测共生固氮（来自大气的 N% [Ndfa]）和 50% 开花时的总 N 含量。我们的统计方法解决了无法在同一个人中测量目标性状和种子测量值的问题。总体而言，Wedge 样本在 50% 开花时提供了对 Ndfa 的最佳预测。总氮植物的最佳预测^–1来自将活力等级与种子收获时的地上生物量相结合。除了对豆类覆盖作物育种计划的具体建议外，我们还提供了一种灵活的统计方法来研究无法联合测量的性状之间的关系。