Abstract: The duration and rate of grain filling determine the individual grain size, thousand-grain weight (TGW), and final grain yield. Several reports have focused on the physiological basis of grain filling in wheat (Triticum aestivum L.), but rare on the genetic mechanism and QTL mapping due to its complexity. To identify QTLs related to grain filling, the F_7:8 generation of 142 recombinant inbred lines (RILs) derived from the cross between Yu 8679 (large spike) and Heshangmai (small spike) were planted in four ecological environments in Beijing (2006 and 2007), Hefei (2007), and Chengdu (2007). Three agronomic traits including mean grain filling rate (GFR_mean), maximum grain filing rate (GFR_max), and TGW were evaluated. A genetic map comprising 170 SSR and 2 EST markers (Tx23-24 and Tx37-38) was constructed based on the 142 RILs. According to the genetic map and phe-notypic data, quantitative trait loci were identified for these agronomic traits using the composite interval mapping (CIM) method. A total of 54 QTLs located on chromosomes 1A, 1B, 2A, 2D, 3A, 3B, 3D, 4A, 4D, 5A, 5B, 6D, and 7D for the three traits were identified over four environments. Among them, 17 for GFR_mean, 16 for GFR_max, and 21 for TGW, accounted for variations of GFR_mean, GFR_max, and TGW by 7.17–20.83%, 6.31–15.95%, and 4.36–16.80%, respectively. Ten genomic sections involving chromosomes 1A, 1B, 2A, 3B, 4D, 6D, and 7D with “pleiotropic effects” were detected. These QTLs with pleiotropic effects are useful for understanding the relationship between grain filling and other related grain yield traits at gene level.

Key words: Wheat, Quantitative trait locus (QTL), Recombinant inbred lines (RILs), Grain filling rate, Thousand-grain weight