QTL Identification in Backcross Population for Brace-Root-related Traits in Maize

The brace-root is a crucial part of the whole root system in maize and plays an important role in the maintenance of lodging resistance. In this study, a BC2F1 population with three replicates, derived from the cross between Yi17 (well-developed brace-root) and Yi16 (poorly developed brace-root) was used for quantitative trait locus (QTL) detection. The total lengths of the genetic linkage map for the three replicates were 659.6, 662.9 and 936.8 cM, respectively, and the average distances between adjacent markers were 3.43, 3.68 and 4.61 cM, respectively. In total, 21 QTLs were detected in the BC2F1 population. The detected QTLs were mainly located at bin 3.05 (four QTLs) and 8.04–8.05 (three QTLs). Bin 3.05 was first detected to be rich in QTLs for brace-root traits in all three replicates, and QTLs detected in bin 8.04–8.05 were consistent with our previous results in the F2:3 population. The QTLs qW3a and qVA3 were coincident QTLs; of these, qW3a was a major effect QTL. These results may provide important information for maize breeders to pyramid favorable chromosome fragments or QTL in breeding programmes targeted at well-developed brace-root materials.