Summary
A two-year field study of 60 Zea accessions found that some had 20–40% of their nitrogen derived from the atmosphere. Aerial-root traits changed more consistently across the domestication continuum than this measure of biological nitrogen fixation.
A bioRxiv preprint reports that biological nitrogen fixation varies among wild and cultivated relatives of maize, without following a consistent pattern from wild Zea through landraces to improved varieties. The researchers assessed 60 accessions in field experiments over two years under low-nitrogen conditions. Some accessions had 20–40% of their nitrogen derived from the atmosphere, while the number of nodes bearing aerial roots changed more consistently with the crop’s history of spread and improvement.
Biological nitrogen fixation (BNF) is the conversion of atmospheric nitrogen into forms that can be used by living organisms. Some Mexican maize landraces support BNF in the mucilage around their aerial roots, prompting questions about how widely the trait occurs across Zea and how it has changed through crop evolution.
What the study found
The study compared aerial-root traits and BNF capacity across the maize domestication continuum, including wild Zea, landraces from Mexico and South America, and improved varieties. The measure reported was the percentage of nitrogen derived from the atmosphere, or %Ndfa. Some accessions across these groups had elevated %Ndfa, ranging from 20% to 40%; some also had higher values than typical improved varieties.
The pattern differed for aerial roots. Wild Zea and Mexican landraces consistently produced more aerial root-bearing nodes. The authors report that spread and improvement appear to have significantly reduced the number of these nodes. Yet %Ndfa did not vary systematically across the domestication continuum. In other words, the visible root trait tracked crop history more clearly than the nitrogen-fixation measure did.
Why the variation matters
Synthetic nitrogen fertilizers support maize productivity, but their use carries environmental and economic costs. The persistence of substantial variation in %Ndfa across Zea groups suggests that the crop’s wider gene pool could offer material for research and breeding aimed at improving nitrogen-use efficiency.
The findings are a survey of variation, not a demonstration that a particular variety can replace fertilizer or reduce its use in farming. The field experiments were conducted under low-nitrogen conditions and covered 60 accessions. As a bioRxiv preprint, the study is also an early research report. Its central contribution is to show that BNF-related variation remains present across wild, traditional and improved Zea, even as aerial-root traits have changed during crop evolution.