Nitrogen fixation in a landrace of maize is supported by a mucilage-associated diazotrophic microbiota
(A) Mucilage of various Sierra Mixe maize lines collected in Sierra Mixe or field-grown plants in Madison, USA, and of teosinte display strong acetylene reduction activity. (-, no acetylene; +, 10% acetylene). Asterisks indicate significant differences (*P < 0.05; **P < 0.01, Mann-Whitney test). (B) Nitrogen fixation in Sierra Mixe maize mucilage by 15N2 assimilation. Mucilage collected from Sierra Mixe maize grown in Sierra Mixe was incubated in gas-tight vials filled with 15N2 or 14N2 gas for 70 hours at 37 °C. 15N (atom % excess) was determined by IRMS. (C and D) H. seropedicae and A. brasilense display acetylene reduction activity when added to nonfixing mucilage, whereas the same mucilage supplemented with sterile medium (-) or the same bacteria without mucilage (-) do not. (E) Oxygen concentration at 8 mm inside of the mucilage. Means and standard errors are shown. Different letters indicate statistically supported groups (Kruskal-Wallis test). (Data at DOI: 10.6084/m9.figshare.6534545). IRMS, isotope-ratio mass spectrometry.