Mendoza-Suárez Marcela, Andersen Stig U, Poole Philip S, Sánchez-Cañizares Carmen
Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark.
Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
Front Plant Sci. 2021 Aug 19;12:690567. doi: 10.3389/fpls.2021.690567. eCollection 2021.
Biological nitrogen fixation by -legume symbioses represents an environmentally friendly and inexpensive alternative to the use of chemical nitrogen fertilizers in legume crops. Rhizobial inoculants, applied frequently as biofertilizers, play an important role in sustainable agriculture. However, inoculants often fail to compete for nodule occupancy against native rhizobia with inferior nitrogen-fixing abilities, resulting in low yields. Strains with excellent performance under controlled conditions are typically selected as inoculants, but the rates of nodule occupancy compared to native strains are rarely investigated. Lack of persistence in the field after agricultural cycles, usually due to the transfer of symbiotic genes from the inoculant strain to naturalized populations, also limits the suitability of commercial inoculants. When rhizobial inoculants are based on native strains with a high nitrogen fixation ability, they often have superior performance in the field due to their genetic adaptations to the local environment. Therefore, knowledge from laboratory studies assessing competition and understanding how diverse strains of rhizobia behave, together with assays done under field conditions, may allow us to exploit the effectiveness of native populations selected as elite strains and to breed specific host cultivar-rhizobial strain combinations. Here, we review current knowledge at the molecular level on competition for nodulation and the advances in molecular tools for assessing competitiveness. We then describe ongoing approaches for inoculant development based on native strains and emphasize future perspectives and applications using a multidisciplinary approach to ensure optimal performance of both symbiotic partners.
豆科植物共生固氮是一种环保且低成本的替代方法，可用于豆科作物中化学氮肥的使用。根瘤菌接种剂常作为生物肥料使用，在可持续农业中发挥着重要作用。然而，接种剂往往难以与固氮能力较差的本地根瘤菌竞争根瘤占据，导致产量低下。通常选择在受控条件下表现优异的菌株作为接种剂，但与本地菌株相比，根瘤占据率很少被研究。农业周期后在田间缺乏持久性，通常是由于共生基因从接种菌株转移到归化种群，这也限制了商业接种剂的适用性。当根瘤菌接种剂基于具有高固氮能力的本地菌株时，由于它们对当地环境的遗传适应性，它们在田间通常具有优异的表现。因此，来自评估竞争的实验室研究的知识以及了解不同根瘤菌菌株的行为方式，再加上在田间条件下进行的试验，可能使我们能够利用被选为优良菌株的本地种群的有效性，并培育特定的宿主品种 - 根瘤菌菌株组合。在这里，我们回顾了目前在分子水平上关于结瘤竞争的知识以及评估竞争力的分子工具的进展。然后，我们描述了基于本地菌株的接种剂开发的现行方法，并强调了使用多学科方法确保两个共生伙伴最佳性能的未来前景和应用。
