The complex evolutionary history of wheat has shaped its associated root microbial community. However, consideration of impacts from agricultural intensification have been limited. This study investigated how endogenous (genome polyploidization), and exogenous (introduction of chemical fertilizers) factors have shaped beneficial rhizobacterial selection. We combined culture -independent and -dependent methods to analyze rhizobacterial community composition and its associated functions at the root-soil interface from a range of ancestral and modern wheat genotypes, grown with and without the addition of chemical fertilizer. In controlled pot experiments, fertilization and soil compartment (rhizosphere, rhizoplane) were the dominant factors shaping rhizobacterial community composition, whereas the expansion of the wheat genome from diploid to allopolyploid caused the next greatest variation. Rhizoplane-derived culturable bacterial collections tested for plant growth-promoting (PGP) traits revealed that fertilization reduced the abundance of putative plant growth-promoting rhizobacteria (PGPR) in allopolyploid wheats but not in wild wheat progenitors. Taxonomic classification of these isolates showed that these differences were largely driven by reduced selection of beneficial root bacteria representative of the Bacteroidota phylum in allopolyploid wheats. Furthermore, the complexity of supported beneficial bacterial populations in hexaploid wheats was greatly reduced in comparison to diploid wild wheats. We therefore propose that the selection of root-associated bacterial genera with PGP functions may be impaired by crop domestication in a fertilizer-dependent manner, a potentially crucial finding to direct future plant breeding programs to improve crop production systems in a changing environment.

中文翻译：

---

农业集约化减少了小麦中假定的促进植物生长的根际细菌的选择


小麦复杂的进化史塑造了其相关的根部微生物群落。然而，对农业集约化影响的考虑有限。这项研究调查了内源（基因组多倍化）和外源（化肥的引入）因素如何影响有益的根际细菌选择。我们结合了培养独立和依赖的方法，分析了一系列祖先和现代小麦基因型的根际土壤界面上的根际细菌群落组成及其相关功能，这些小麦基因型在添加和不添加化肥的情况下生长。在对照盆栽实验中，施肥和土壤区室（根际、根面）是影响根际细菌群落组成的主导因素，而小麦基因组从二倍体向异源多倍体的扩展引起了第二大变异。对根平面衍生的可培养细菌集合进行植物生长促进（PGP）性状测试表明，施肥降低了异源多倍体小麦中假定的植物生长促进根际细菌（PGPR）的丰度，但在野生小麦祖先中却没有。这些分离株的分类表明，这些差异很大程度上是由于异源多倍体小麦中代表拟杆菌门的有益根细菌的选择减少所致。此外，与二倍体野生小麦相比，六倍体小麦中支持的有益细菌种群的复杂性大大降低。 因此，我们提出，具有 PGP 功能的根相关细菌属的选择可能会因依赖肥料的方式进行作物驯化而受到损害，这是指导未来植物育种计划以在不断变化的环境中改善作物生产系统的潜在关键发现。