Legume-rhizobium symbiosis provides a sustainable nitrogen source for agriculture. Nitrogen fixation efficiency depends on both legume and rhizobium genotypes, but the implications of their interactions for plant performance in environments with many competing rhizobium strains remain unclear. Here, we let 399 Rhizobium leguminosarum complex sv. viciae strains compete for nodulation of 212 faba bean genotypes. We find that the strains can be categorised by their nodule occupancy profiles into groups that show distinct competitive interactions and plant growth-promoting effects. Further, we show that the diversity of strains occupying root nodules affects plant growth and is under plant genetic control. These insights provide a basis for re-designing rhizobium inoculation and plant breeding strategies to enhance symbiotic nitrogen fixation in agriculture.

豆科植物-根瘤菌共生为农业提供了可持续的氮源。固氮效率取决于豆科植物和根瘤菌基因型，但它们的相互作用对植物在具有许多竞争根瘤菌菌株的环境中性能的影响仍不清楚。在这里，我们让 399 根瘤菌 leguminosarum 复合物 sv.Viciae 菌株竞争 212 种蚕豆基因型的根瘤。我们发现，这些菌株可以根据它们的根瘤占有率概况分为几组，这些组显示出明显的竞争相互作用和植物生长促进作用。此外，我们表明占据根瘤的菌株的多样性会影响植物生长并受到植物遗传控制。这些见解为重新设计根瘤菌接种和植物育种策略提供了基础，以增强农业中的共生固氮。