There is increasing interest in understanding how the microbial communities on roots can be manipulated to improve plant productivity. Root systems are not homogeneous organs but are comprised of different root types of various ages and anatomies that perform different functions. Relatively little is known about how this variation influences the distribution and abundance of microorganisms on roots and in the rhizosphere. Such information is important for understanding how root–microbe interactions might affect root function and prevent diseases. This study tested specific hypotheses related to the spatial variation of bacterial and fungal communities on wheat (Triticum aestivum L.) and rice (Oryza sativa L.) roots grown in contrasting soils. We demonstrate that microbial communities differed significantly between soil type, between host species, between root types, and with position along the root axes. The magnitude of variation between different root types and along individual roots was comparable with the variation detected between different plant species. We discuss the general patterns that emerged in this variation and identify bacterial and fungal taxa that were consistently more abundant on specific regions of the root system. We argue that these patterns should be measured more routinely so that localised root–microbe interactions can be better linked with root system design, plant health and performance.

人们越来越有兴趣了解如何操纵根部的微生物群落以提高植物生产力。根系不是同质的器官，而是由执行不同功能的不同年龄和解剖结构的不同根类型组成。关于这种变异如何影响根部和根际微生物的分布和丰度，我们知之甚少。这些信息对于理解根-微生物相互作用如何影响根功能和预防疾病很重要。本研究检验了与小麦 ( Triticum aestivum L.) 和水稻 ( Oryza sativaL.) 生长在对比土壤中的根。我们证明微生物群落在土壤类型之间、宿主物种之间、根类型之间以及沿根轴的位置之间存在显着差异。不同根类型之间和沿单个根的变异幅度与不同植物物种之间检测到的变异相当。我们讨论了这种变异中出现的一般模式，并确定了在根系特定区域始终更丰富的细菌和真菌类群。我们认为应该更经常地测量这些模式，以便局部根 - 微生物相互作用可以更好地与根系设计、植物健康和性能联系起来。