Phenotypic diversity of root anatomical and architectural traits in Zea species

We characterized phenotypic variation for root traits in 256 Zea accessions, including maize landraces and Z. mays subsp. huehuetenangensis, mexicana, and parviglumis, Z. nicaraguensis, Z. perennis, and Z. luxurians. Anatomical traits included areas of the cross-section, stele, cortex, aerenchyma, and xylem, and number of cortical cells and cell files. Architectural traits included diameters of the nodal root system, individual crown roots, and the stem; numbers of seminal and nodal roots; biomass; and nodal root length and branching. Ranges for anatomical traits were similar for teosintes and landraces, except for aerenchyma and xylem areas, which varied more among landraces. Landraces had greater variation for architectural traits except for nodal root number and branching, and larger stele and xylem areas, longer and thicker nodal roots, wider nodal systems, and more seminal roots than teosintes. In contrast, teosintes were smaller, but had more nodal roots with greater branching. At a common plant size, teosintes would have greater mean values for all anatomical traits except for areas of the stele, xylem and aerenchyma. Landraces had greater scaled values for all architectural traits except for branching traits and crown root diameter. Cluster analysis divided accessions into eight root phenotypes. Phenotypic diversity for root traits in the genus Zea could be a valuable resource for improving stress tolerance in maize.