Screening Ancient Maize Relatives for Beneficial Endophytic Diazotrophs

Nitrogen is an essential plant macronutrient, and synthetic nitrogen fertilizer has become essential to modern agriculture. Despite the abundance of nitrogen gas in our atmosphere, plants cannot metabolize this form, and so instead rely on obtaining available forms of nitrogen from the soil. Diazotrophs are bacteria that can "fix" atmospheric nitrogen to plant bioavailable compounds and represent an attractive alternative to synthetic nitrogen fertilizer which is costly to growers and damaging to the environment. Therefore, this thesis examines the endophytic bacterial communities of wild maize relatives and ancient farmer landraces, to identify bacteria that fix nitrogen, secrete plant bioavailable forms of nitrogen, and/or otherwise increase plant tolerance to nitrogen starvation. The data suggests that the maize family has retained nitrogen fixing seed endophytes across 9000 years of evolution, human selection, and migration. Furthermore, the ancestor of all maize and ancient maize relatives host bacteria that confer tolerance to nitrogen starvation.