Genetic Characterization of Indicators for Diazotrophic Recruitment in Zea mays

Zea mays spp. mays (hereafter maize) landrace populations cultivated within indigenous communities of Mexico have been reported to be farmed using traditional cultivation practices without fertilizers or pesticides, and several fields have exhibited low NO₃- levels. Interestingly, certain landrace maize populations perform well under such conditions, and may reach heights greater than 5 m at maturity. Many such landrace populations are characterized by the presence of thick, abundant aerial roots that secrete significant quantities of root exudate (a.k.a. mucilage). This polysaccharide-rich exudate may play a vital role in recruitment of diazotrophic microbes to facilitate nitrogen fixation within said landrace populations. The studies summarized hereafter utilize natural ¹⁵N abundance within maize leaf tissues to infer nitrogen fixation activity [via symbiotic diazotrophic microbes] within various subpopulations of Zea mays. Furthermore, we present genetic data showing substantial introgression of the pre-domesticate Zea mays spp. mexicana into one of the landraces under study. With a pronounced aerial root morphology of its own, Z. mays spp. mexicana may be the ancestral source for aerial root development, mucilage production, and potential diazotrophic recruitment within modern maize. Conclusive evidence and genetic elucidation of diazotrophic recruitment in maize would have profound impacts on global maize production, with the potential to drastically reduce both production costs and harmful effects on the environment.