The flag leaf serves as the primary photosynthetic organ in wheat, and its size is significantly correlated with wheat yield. The mapping of QTLs associated with flag leaf size and the development of closely linked molecular markers holds substantial significance for enhancing wheat yield potential. In this study, a genetic linkage map consisting of 11,583 markers was constructed by the Wheat55K SNP Array, and the quantitative trait loci (QTLs) for flag leaf length (FLL), width (FLW), area (FLA), and length/width ratio (FLR) were mapped across six experimental environments. A total of 97, 273, and 32 QTLs were mapped using the ICIM-BIP, ICIM-MET, and ICIM-EPI methods, respectively. Five QTLs, Q.Fll.sau-2D.1, Q.Flw.sau-1B.2, Q.Flw.sau-4B, Q.Fla.sau-4B.3, and Q.Flr.sau-2D.3, explained 15.97%, 15.28%, 10.81%, 11.00%, and 11.09% of the phenotypic variation on average and were considered major and stable QTLs for the FLL, FLW, FLA, and FLR, respectively. Three Kompetitive Allele-Specific PCR (KASP) markers, which are closely linked to these five QTLs, were designed. The genetic effects of these five QTLs were successfully confirmed in different populations. The pyramiding effect analysis revealed that the stable QTLs mapped in this study can significantly alter flag leaf size-related traits as the number of pyramided loci increases. The parental lines were further genotyped using the 120 K SNP Array, followed by density enhancement of the genetic map for the initial mapping intervals. This significantly narrowed down the physical distance of the initial mapping intervals, and candidate genes within the refined physical intervals were screened. These QTL mapping results of flag leaf size-related traits and the closely linked KASP markers revealed in this study provide new resources for future wheat breeding.
Li et al. (Wed,) studied this question.