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PLoS Biol. 2018 Aug 7;16(8):e2006352. doi: 10.1371/journal.pbio.2006352. eCollection 2018 Aug.

Nitrogen fixation in a landrace of maize is supported by a mucilage-associated diazotrophic microbiota.

Author information

1
Department of Plant Sciences, University of California, Davis, California, United States of America.
2
Department of Agronomy, University of Wisconsin, Madison, Wisconsin, United States of America.
3
Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, United States of America.
4
Genome Center, University of California, Davis, California, United States of America.
5
Department of Population Health and Reproduction, University of California, Davis, California, United States of America.
6
Instituto Tecnológico del Valle de Oaxaca, Oaxaca, Mexico.
7
Mars, Incorporated, McLean, Virginia, United States of America.

Abstract

Plants are associated with a complex microbiota that contributes to nutrient acquisition, plant growth, and plant defense. Nitrogen-fixing microbial associations are efficient and well characterized in legumes but are limited in cereals, including maize. We studied an indigenous landrace of maize grown in nitrogen-depleted soils in the Sierra Mixe region of Oaxaca, Mexico. This landrace is characterized by the extensive development of aerial roots that secrete a carbohydrate-rich mucilage. Analysis of the mucilage microbiota indicated that it was enriched in taxa for which many known species are diazotrophic, was enriched for homologs of genes encoding nitrogenase subunits, and harbored active nitrogenase activity as assessed by acetylene reduction and 15N2 incorporation assays. Field experiments in Sierra Mixe using 15N natural abundance or 15N-enrichment assessments over 5 years indicated that atmospheric nitrogen fixation contributed 29%-82% of the nitrogen nutrition of Sierra Mixe maize.

Conflict of interest statement

Howard-Yana Shapiro is affiliated with Mars, Incorporated, one of the research sponsors. Author Cristobal Heitmann was unable to confirm authorship or contributions himself, and this was carried out collectively by the other co-authors.

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