MSc Nina Dubach

08/2026

Supervision: Dr. Christine Pestalozzi and Prof. Klaus Schlaeppi

Abstract:

This Master thesis examines the effects of microbial benzoxazinoid metabolization on maize growth by studying the interactions between Zea mays, a major staple crop, and Sphingobium, an abundant maize root bacterium. To allow interaction studies in planta, a suitable gnotobiotic growth system was established for Zea mays, the Triple Pot system. Maize growth was assessed over time using a non-invasive plant growth measurement as well as destructive measurements upon harvest. Microbiological analyses were used to determine the capacity of Sphingobium to colonize the roots of Zea mays. Furthermore, metabolite analyses were performed to detect benzoxazinoid degradation products formed by maize root bacteria in vitro and in planta.

The findings of this thesis show that the Triple Pot system served as a suitable system to grow maize for up to 10 days under gnotobiotic conditions. Experiments using that system showed that maize growth was not significantly affected by the ability of Sphingobium to metabolize benzoxazinoids. Also the ability of Sphingobium to colonize the roots was not significantly affected by the level of benzoxazinoids exuded by different maize genotypes. In a synthetic community of abundant maize root bacteria together with Sphingobium, no evidence of the formation of alternative benzoxazinoid degradation products was found. By establishing a gnotobiotic growth system, this thesis provides a tool suitable for in planta experiments using Zea mays or similarly sized plants and contributes to a deeper understanding of how benzoxazinoids affect maize growth and root colonization.