Fine mapping TaFLW1 , a major QTL controlling flag leaf width in bread wheat ( Triticum aestivum L.)

Introduction Flag leaf width (FLW) is directly related to photosynthetic capacity and yield potential in wheat. In a previous study, Qflw.nau - 5A controlling FLW was detected on chromosome 5A in the interval possessing Fhb5 for type I Fusarium head blight (FHB) resistance using a recombinant inbred line population derived from Nanda2419 × Wangshuibai. Materials and methods Qflw.nau - 5A near-isogenic line (NIL) with the background of Mianyang 99-323 and PH691 was developed and evaluated. FLW inheritance was investigated using two F 2 populations developed from crossing the Qflw.nau - 5A NILs with their recurrent parents. One hundred ten and 28 recombinants, which included 10 and 5 types of recombinants, were identified from 2816 F 2 plants with Mianyang 99-323 background and 1277 F 2 plants with PH691 background, respectively, and phenotyped in field trials for FLW and type I FHB resistance. Deletion bin mapping was applied to physically map Qflw.nau - 5A . Results and conclusions The introduction of Wangshuibai Qflw.nau - 5A allele reduced the FLW up to 3 mm. In the F 2 populations, Qflw.nau - 5A was inherited like a semi-dominant gene, and was therefore designated as TaFLW1 . The FLW of the recombinant lines displayed a distinct two-peak distribution. Recombinants with wider leaves commonly have Mianyang 99-323 or PH691 chromatin in the 0.2 cM Xwmc492 - Xwmc752 interval that resided in the 5AL12-0.35–0.57 deletion bin, and recombinants with narrow leaves were Wangshuibai genotype in this interval. Phenotypic recombination between FLW and type I FHB resistance was identified, implying TaFLW1 was in close linkage with Fhb5 . These results should aid wheat breeders to break the linkage drag through marker-assisted selection and assist in the map-based cloning of TaFLW1 .