Identification of genetic loci for flag leaf traits in wheat (Triticum aestivum L.)

The flag leaf size of wheat is an “ideotypic” morphological trait that plays a critical role in plant architecture and grain yield by providing photosynthetic assimilates in wheat. Although many of the genomics research studies covered the flag leaf traits, including flag leaf length (FLL), width (FLW), area (FLA), thickness (FLT), and volume (FLV), for a better understanding, this research used a recombinant inbred line (RIL) population derived from a cross between DH118 and Jinmai 919 to evaluate the genetic regions across six environments, including BLUP under both drought stress (DS) and well-watered (WW) conditions and analyze their correlation with traits related to grain yield. A total of 40 (QTL) quantitative trait loci controlling the five traits were detected across all environments, with phenotypic variance explaining (PVE) 5.09%-15.26%. Among them, 12 QTL were identified as stable, including two QTL for FLL, two for FLW, three for FLA, two for FLT and three for FLV, in which nine QTL were found to be validated in more than three environments through a double haploid (DH) population Jinchun 7 × Jinmai 919. The Qflw.saw-2A, Qfla.saw-2A, Qflv.saw-2A, Qflt.saw-2B, and Qflt.saw-3B were stated as novel due to not being reported by any of the previous research studies related to flag leaf traits. In addition, traits related to flag-leaf and grain yield were significantly correlated in both water regimes. These results provide a better understanding of the genetic basis underlying flag leaf traits. Also, target regions for fine mapping and marker-assisted selection (MAS) were identified and will be valuable for breeding high-yielding bread wheat.