Graduate Exit Seminar - Tuny Amphonechit

Plan to join Tuny Amphonechit's graduate exit seminar on April 29, 2025, at 2:00 pm in Kottman Hall, Room 333 or via Zoom. Tuny will present, "Microbial Community Diversity Associated with N₂ Fixation in Zea mays Aerial Roots and Soil"

Abstract: Globally, nitrogen (N) is the most widely used fertilizer, with maize (Zea maize) using large amounts of N. Solutions are needed to reduce synthetic N fertilizer usage because of its negative impacts on the climate with its high energy manufacturing requirements and releases of greenhouse gases, and on the environment causing pollution of surface- and ground-water, driving eutrophication. Recent and preliminary research has shown that indigenous maize landraces of Mexico took up to 82% of its N from the atmosphere by diazotrophic bacteria residing in the mucilage of aerial roots. This provides an innovative solution for reducing N fertilizer requirements for maize, but little information is available about the microbial community of the mucilage or of the rhizosphere soil in these accessions. Therefore, the objective was to determine the diversity of the total bacterial community and bacteria possessing the nifH (nitrogenase) gene in mucilage and rhizosphere soil across wild, heirloom, Mexican landraces (from low, mid and upper elevations), and improved maize accessions. The research was done by planting these accessions at the OSU Waterman Farm and sampling soils and aerial roots during the prime maize growth stage. Rates of N₂ fixation of these accensions was done using the ¹⁵N Natural Abundance or Dilution methods. The stable isotope ¹⁵N tracing method was employed to detect the biological N₂ fixation in the mucilage; while the nifH gene and 16s rRNA gene amplicon sequencing techniques were used to identify N-fixing bacteria and the total bacterial community, respectively, in mucilage and soil. Microbial diversity was also determined with EL-FAME biomarker analysis. Results showed that neither EL-FAME biomarkers nor phylogenetic diversity in the rhizosphere soil were affected by maize accessions. However, aerial root mucilage from different maize accessions significantly influenced EL-FAME biomarkers for bacteria, total EL-Fame and fungi. In addition, Azsospirillum and Klebsiella emerged as the dominant bacteria groups in the nifH gene amplicon sequencing, with PCoA ordination using phylogenetic data (16S) showing distinct groupings or shifts in overall bacterial diversity based on the maize elevation category – indicating that each maize ascension has a unique microbiome in the aerial root mucilage.

Advisor: Dr. Richard Dick