Genetic analysis of vertical root pulling resistance (VRPR) in maize using two genetic populations

Root traits are important in improving nutrient and water use efficiency. Vertical root pulling resistance (VRPR) has been shown to be closely related to root system characteristics in maize (Zea mays L.). In the present study, two genetic populations derived from the same parents, one containing 218 recombinant inbred lines (RILs) and the other containing 187 advanced backcross BC4F3 lines, were genotyped using 184 SSR markers and evaluated for VRPR, grain yield (GY), stover yield (SY), and nitrogen uptake (N-up) under field conditions over 2 years. Our aims were (1) to locate QTLs associated with VRPR, SY, GY, and N-up, (2) to determine whether QTL detection is consistent between the BC4F3 and RIL populations, and (3) to identify backcross lines harboring favorable VRPR QTLs for use in future breeding programs. Using composite interval mapping (CIM), 12 and 17 QTLs were detected in BC4F3 and RIL populations, respectively. An important QTL region in bin 6.02 within the interval umc1006-umc1257 was found to control VRPR, SY, and N-up in both populations. These favorable alleles were contributed by the large-rooted parent Ye478. A significant positive correlation was detected between VRPR, SY, and N-up, but not between VRPR and GY. Backcross lines harboring VRPR QTLs could be useful germplasm for developing near isogenic lines (NILs) and for map-based cloning of genes controlling root growth.