Genetic evaluation of root complexity in maize

Root architecture is strongly linked to plant survival under abiotic and biotic stress conditions. The objective of this study was to investigate the inheritance of the primary root system complexity in maize (Zea mays L.). For a total of 231 recombinant inbred lines (RIL) derived from the IBM (B73×Mo17) population multiple primary root systems were produced by applying a replicated alpha lattice experimental design. Digital images of each root system were taken at days four and eight after germination. For each root system image, the fractal dimension (FD) was computed. Significant differences between RILs were found in the FD calculated after four (FD1) and eight (FD2) days. For FD1 22 QTLs, for FD2 13, and for FD change over time (ΔFD) 12 QTLs were found on all ten maize chromosomes explaining between 24.6 and 46.8% of the phenotypic variation. Both parental inbreds contributed FD-increasing QTL alleles. FD1 and FD2 had five chromosomal BIN locations in common. Four unique QTLs were identified for the dynamics of root growth between days four and eight. Maize root mutants involved in root morphology were located in chromosomal BINs carrying QTLs for FD1 or FD2. This study demonstrated the usefulness of the IBM population as a maize community resource to investigate the genetic basis of root complexity in maize.