Eighty years of maize breeding alters plant nitrogen acquisition but not rhizosphere bacterial community composition
There is considerable interest in breeding for crop genotypes that harness rhizosphere microbial communities and processes in support of plant productivity. However, the extent to which past breeding efforts have altered plant rhizosphere traits and plant-microbe collaborations is unknown.
We evaluated twelve best-selling and widely adapted maize hybrids released between 1936 and 2011 for changes in rhizosphere bacterial community composition (BCC) and plant access to endogenous soil nitrogen. Plants were grown in replicated monocultures fertilized with 0, 85 or 170 kg N ha−1 and measured for yield, nitrogen uptake and source. Rhizosphere BCC and function was assessed through potential extracellular enzyme assays and 16S rRNA gene amplicon sequencing.
Grain yield and nitrogen uptake from soil pools increased with year of hybrid release at all fertilization levels. Rhizosphere BCC and enzyme activity also varied among hybrids. However, releases from the 1960s and 70s were most distinct, while early and late releases shared similar BCC and enzyme activity.
These results indicate that breeding has increased maize ability to acquire nitrogen from soil reserves, but has not resulted in a directional shift in rhizosphere bacterial community assembly. The variation observed among hybrids reveals the potential for future breeding efforts to influence rhizosphere traits.
KeywordsBacterial community Maize Microbiome Nitrogen use efficiency Plant breeding Rhizosphere
Bacterial community composition
maximum likelihood population effects model
nitrogen use efficiency
maize physiological stages: six-leaf
We thank Dr. Mark Cooper for advising on the selection of hybrids and Dupont-Pioneer for providing the germplasm used in this study. This work was supported by the USDA National Institute of Food and Agriculture, Hatch project no. NYC-145446 and the Agriculture and Food Research Initiative Competitive Grant no. 2015-67019-23588.
Compliance with ethical standards
Conflicts of interest
M.E.S.’s research program receives partial cost reimbursement from Dupont-Pioneer for evaluation of Dupont-Pioneer corn hybrids in public commercial corn silage tests.
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