Maize Root Architecture and Development

Maize (Zea mays L.) is one of the most important crops in the world. Copious genetic and phenotypic resources facilitate its use as a model organism by researchers. However, the root system has long remained inconspicuous, despite its foundational role in key plant and plant-environment processes. Recent advances in phenotyping facilitate characterizations of roots in multiple environments, and through time. Of special interest is Root System Architecture (RSA) -- when and where a plant places its roots -- which dictates a plant’s ability to forage for often ephemeral and heterogenous resources in the soil. RSA is a highly complex, quantitative trait and little is known about the specific genes that control it. In order to characterize root phenotypes and their developmental changes, 27 lines representing maize genetic diversity (NAM Founders) were grown in Columbia, MO, USA in 2016. Root crowns were harvested at multiple time points, spanning 4 weeks after planting through tasseling. These roots were washed and imaged for 2D architecture analysis using Digital Imaging of Root Traits (DIRT). Samples from weeks 4, 7, and tasseling were also scanned for 3D architecture using X-ray Computed Tomography, in order to make comparisons about the information content of each method. Our analysis revealed time specific differences in root architecture traits as a function of genotypic diversity. 3D RSA traits computed from the X-ray CT provide additional information, such as root volume and solidity (density), that allow enhanced clustering of genotypes based on their RSA phenotypes. These experiments provide the first steps toward a more complete and biologically relevant view of maize RSA development during vegetative and reproductive growth.