Increased diversity of beneficial rhizobia enhances faba bean growth. Increased diversity of beneficial rhizobia enhances faba bean growth

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 based on 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-根瘤菌共生可为农业生产提供可持续的氮源。固氮（nitrogen fixation）效率同时取决于豆科植物与根瘤菌（Rhizobium）的基因型，但二者的互作对存在多种竞争根瘤菌菌株环境下的植物生长表现的影响仍有待阐明。本研究中，我们选取399株豌豆根瘤菌复合群豌豆变种（Rhizobium leguminosarum complex sv. viciae）菌株，使其竞争212份蚕豆（Vicia faba）基因型的结瘤位点。研究发现，可根据菌株的根瘤定殖谱将其划分为不同类群，各类群展现出差异化的竞争互作模式与促植物生长效应。此外，我们证实根瘤内定殖的菌株多样性会影响植物生长，且该过程受植物遗传调控。上述研究成果为重新优化根瘤菌接种与植物育种策略、提升农业共生固氮（symbiotic nitrogen fixation）效率提供了重要理论依据。